Gainphile

2011-10-26T22:39:00.000-07:00

Life-like reproduction of acoustic recording is my primary goal. To achieve this goal my loudspeakers must engage the room neutrally, allowing room reflections to be delayed replicas of direct sound. This requirement demands a controlled radiation of sound waves both on and off-axis (Constant Directivity).

Nearly all commercial loudspeakers; typically woofer-midrange-dome tweeter in box arrangements (example) are unable to meet this requirement. Hence I build my own.

An ideal polar response of a theoretical constant-directivity loudspeaker.
As you move to the sides of the loudspeaker, the sound level decreases uniformly
across the whole spectrum from 20-20khz. This is not achievable in practice (yet).

S15 Econowave DSP, a variant of popular box and waveguide/horn topology
like the Econowaves, JBLs, Gedlee or PiSpeakers. Excellent directivity down to 1khz (2π), which gradually transition to omni-directional (4π) at lower frequencies.

A normalised sonogram plot of S16 Constant Directivity Dipole Loudspeakers.
90° waveguide dispersion gradually transition to 120° dipole down to 20hz!
This is the closest to ideal.

With the advent of computer-based realtime analyzers, it is possible for amateurs to build such loudspeakers at relatively modest cost. All of these projects were built well under $1000 as complete systems including active 4-way analog or DSP crossovers and 8-channel amplifications.

Andi W.

Melbourne, Australia

S16 - Constant Directivity OB

An attempt to improve high-frequency directivity of Dipole loudspeakers. Based on S12, various combinations of tweeters, compression drivers, and waveguides were investigated.
more ...

S15 Econowave DSP:
A Constant Directivity Loudspeaker
Econowave is a cost effective controlled-directivity loudspeaker design. DIY Folks at AudioKarma had investigated numerous driver + waveguide combination which would achieve this goal successfully,

This is a fully-documented build with variations of drivers used. You can also purchase the DSP configuration file to speed up listening to your music!
more ...

S12 OB - Open baffle simplicity
A true open baffle with its simplicity (no h/w/u -frame etc.) I have observed that there is something about them which other variations simply can't match due to very uniform polar response.

They project very transparent, holographic soundstage.

A Dipole Bass Array below could be used to increase the absolute bass SPL of these loudspeakers using 8 additional woofers, effectively making them 4-way system.
more...

S9 Open Baffle Speakers

These were built to revisit the previous design which measured and sounded most natural and smooth. So much that the further effort to obtain dipole bass quantity had to be scrapped.

The wide, pistonic dispersion of small 5" drivers combined with narrow baffle allows very smooth and uniform polar response to 2.5kHz, which is almost one octave above the high xo frequency. The loudspeakers are actively driven using 6 separate amplifier channels and allows potential addition of woofers for more low-frequency output.
more...

S11 Desktop Open Baffle
These are open baffle speakers for the desktop. They are 2-way system with active crossover and eq circuitry. The woofers are Seas L21 and the tweeters are TangBand W3-1364. They are designed to produce 40Hz dipole bass.

The distance to rear wall is about 35cm. I could not hear any faults despite general requirements for dipole speakers to be away from walls. This could be due to the nearfield listening location and that the relative distance is more important than the absolute one. Comparing to my living room dipoles (which is 1m from rear wall), maybe a bit less soundstage, but that's really nitpicking. Phantom image is very scary, almost like the speakers making no sound and the music comes out of the wall. Listening to some classical recording I got goosebumps. If there is one best thing that stands out from them, it's the midrange.
more...

Concepts and Work in Progress:

S14 DSP - 4 Way Dipole Loudspeakers

In progress...

These are 4-way Open Baffle loudspeaker design with 3-way main panel and inverted W-Frame subwoofers.

Objectives:
- Low midrange distortions, by assigning separate drivers for low-mid and high-mid duties
- Low vibrations due to W-Frame subwoofer's opposing forces
- Small footprint and height

Challenges
- The 5" high-mid drivers may proven to be too small for the baffle width
- Designing 4-way crossover will be more complex due to phase interference
- Back to back dome tweeters' known limitation. "dipolar" response, instead of dipole

more...

S18 - DSP 3-way Econowave
An attempt for better midrange resolution of constant directivity design. I have concluded that large woofer used in typical CD design is not optimum for midrange reproduction.
more ...

Dipole Bass Array
An investigation to double the number of woofers in a dipole system, which would provide additional 6dB of maximum output.

Other successful projects:

LinkwitzLab Pluto Clone
A genius Omni-Directional speaker design by Sigfried Linkwitz. They sound as open as dipole speakers with some superiority in the imaging area. However my clone lacks the transparency and clean sound of the open baffle.

Cheap and accurate loudspeaker measurement tool
Never embark in loudspeaker projects without adequate measurement tool. The ears are not to be trusted. The good news is a set of measurement tool can be build for under $70, including the soundcard!

DIY Linux-based Audiophile media centre
My high-resolution music collection has been growing, mostly sourced from Vinyl/LP rips. They are superior than normal CDs which are recorded at 16/44.1kHz.

Off-the-shelf audiophile media center or server are very expensive (read: Linn DS is $15,000!). Comparable solution could be built for under $400, including the sound card and Laptop.

Other/Past projects:

S17 - Constant Directivity Dipoles
In this iteration I want real dipole radiation front and back, and uniform to very high frequencies. This can only be done with extemely short front-to-back distance.

The "tweeters" used are TangBand 3" full-range. They allow three things to happen:

- Dipole peak to occur very high in the frequency range, allowing constant directivity
- Very open rear chamber for good rear frequency response
- Low crossover frequency

more...

S13 OB
This was an unsuccessful attempt to use fullrange drivers as dipole tweeters. Constant directivity was achieved up to excellent 10khz, yet the system did not sound coherent.

S10 OB - Seas L21RNXPWhen I saw someone was selling a pair of Seas L21RNXP really cheap on ebay I couldn't resist having a go at rigid piston driver. The most interesting finding was that S9 and S10 sounds similar, albeit the difference in xo point, baffle width, and cone/driver material. I was therefore convinced sthat if the design goals are met (frequency response, polar response, etc.) then speakers would sound similar. I prefer the S9 above for cost and aesthetics as they are smaller.

S8 OB
Dipole speakers with 6x 10" woofers as their main strength. It gives great bass, but unfortunately the 5" P13WH midrange is acoustically to small for the 30cm baffle, and hence do not sound smooth. I have since went back to slim baffle as the S9. These speakers were presented at local Australian hifi hobbyist meeting (SNA).

S7 Open Baffle
Discovery of narrow baffles and their excellent polar response

S6 Open Baffle
Experiments with large 15" Eminence Alpha woofers. I have since learnt that better result would be obtained by smaller drivers.

S4 OB
Pushing 15" woofer in a 2-way dipole configuration. Many problems were encountered here.

Stealth, Stealth 2, and Stealth3Various attempts for a low-frequency extension desktop Open Baffle speakers. They were huge and not aesthetically pleasing.

First open baffle system
The genesis of my dipole speaker designs. It was passive and utilised wide baffles. Even with all the inperfection I felt this was the right direction. There is a youtube clip of them here.

Loudspeaker journey
Various undocumented speakers built in the past for fun, amusements, and curiosity

Linux-Based Media Centre using Ubuntu, MMS, and SoundBlaster Live! 24bit

Emerald Physics S2 Clone
Failed project to clone Emerald Physics' CS2, a refresingly new take on commercial loudspeaker design.

4-Channel Gainclone
My amplifier to driver the active dipole loudspeakers

What's New

2011-10-24T17:49:00.000-07:00

6/2/12 - Experimentation with Linkwitzlab Watson with S16/MSXT

4/2/12 - S15 : B&C DE250 andCelestion CDX1-1745 variants posted

3/2/12 - Production version of original S15 documented and posted. Visitors can also purchase the config file.

18/1/12 - Design of the rounded waveguide loudspeaker: S15R

1/12/11 - Update on S16 variant using Titanium tweeters DQ25SC16: S16/MSTi

18/12/11 - Waveguide and Celestion compression driver GTG in Visits and GTGs

1/12/11 - Posted basic measurement data for recently built S16/MSXT

27/11/11 Melbourne audio round-trip GTG. Also report at SNA.

18/11/11 - Major cleanup and progress on the Garage Audio Room

6/11/11 - Synergy Horn GTG

1/11/11 - Completed S16/MS

31/10/11 - Site visits passed 100,000

30/10/11 - Building S16/MS

26/10/2011 - Added report of "The Australian Audio and AV Show" Visits and GTGs

25/10/2011 - What's New page created

Garage Audio Room, the "Gaincave"

2011-06-13T17:34:00.001-07:00

Before (13 June 2011)

Latest progress (18 Nov 2011)

Goal:
To construct a dedicated Audio room with sensible acoustics and aesthetics for under $500.

This is a journey in constructing a dedicated listening room. The room is a 1-car garage which needs major cleanup.

Build discussions is at StereoNet Australia.

13/6/2011
I tried playing the S9R dipoles in the garage. To my surprise it sounded very good despite tin roof and door. Later measurements revealed RT60 of 250ms, which is *more dead* than my living room (400ms). Looking at all the "junk" in the garage it will be a long journey, but acoustically it's very good already! Target room reverb for dipole loudspeakers are about 300ms - 500ms.

18/11/2011
Major cleanup and update
- Curtains
- Lighting and automatic turn-on sensor

Cost tracking

Heater - $60
Curtain accessories - $110
Downlight kit - $40
Automatic light sensor - $15
===
Total so far = $225
Target max = $500

S18 - DSP 3-way Econowave

2011-04-26T23:36:00.000-07:00

Waveguide: Dayton round 8" wg
CD: Selenium D220Ti
Mid: Seas L21RNXP
Low: Eminence Beta 12" or Jaycar CW2119

Hopefully this will bring out the best traits:
- Constant directivity down to 1.5khz
- High resolution of metal cone midrange (main concern with S15 build)
- Thundering bass of 12" sealed woofer tuned to Q=0.5
- Proprietary 'Zog Red' colour

Compromise would be:
- not as high sensitivity (except if the mid is replaced with pro driver)
- might not as transparent as OB. Will have to build and see...
- more complex active xo as 3-way

S17 - Constant Directivity Dipoles

2011-02-21T18:38:00.000-08:00

While the S16 provides smooth directivity, they are lacking rear radiation. In this iteration I want real dipole radiation front and back, and uniform to very high frequencies. This can only be done with extemely short front-to-back distance.

Design

The "tweeters" used areTandBand 3" full-range. They allow three things to happen:

- Dipole peak to occur very high in the frequency range, allowing constant directivity
- Very open rear chamber for good rear frequency response
- Low crossover frequency.

Measurements

The directivity plot was measured indoor so there is room for improvement when I take it for outside measurement later.

Follow the discussion at DIYAudio.

These are respectable uniform dipolar radiation, impossible to achieve with traditional methods like back to back dome tweeters.

The tradeoff is high frequency resolution of the 3" fullrange drivers.

Visits and GTGs

2011-02-21T10:54:00.000-08:00

Social events are part of a hi-fi hobby and as an amateur enthusiast I had been very lucky to enjoy the company of friendly visitors and as a guest to others.

Visitors

Waveguide GTG IV - 18/12/2011
Roger and Paul visited to measure various Celestion drivers. The driver is an excellent match to Pyle Econowave waveguide. Results of measurements at DIYAudio

Melbourne audio round-trip GTG - 27/11/2011
Paul, Warren, Matt, and Mike visited as part of a round-trip GTG. We later then went to Craig's place to hear the Jazzman and then to Trevor's to hear the Zingali horns. Report here.

Olivier & Inken from 2pi-online.de - 29/3/2011
Dropped by from Germany on their Aussie holiday to listen to S16, S15, and Pluto.

Olivier posted his impressions of my speakers on his site. His observation and preference is very much similar to mine.

Waveguide shootout I - 16/1/2011
A group of waveguide type speakers enthusiasts got together in Bonbeach for the 1st round of shootout. We had various compression drivers and horns of various shapes and sizes from D220Ti, DE250, BMS, Econowave Pyle, Oblate-spheroid, etc.

Paul Spencer had written about this event in his blog, he clearly explain how to read sonogram plots, etc.

Dipole - Omni Show & Tell - 27/6/2009
Paul Spencer and I arranged GTG in Melbourne to present dipole and omni speakers. I had my s8 and analogue-driver Pluto clone, and Paul presented his Vifa based dipoles (with Rythmic subs).

At the end of the day the visitors were most impressed with Pluto clone!

Paul's visit

Selwyn's visit

JPHoward visit

GTGs (Get-Together) and EventsSynergy Horns GTG - 5/11/2011
Measurements and listening to various implementation of Unity Horns. We had Yorkville Unity by Tom Danley and Paul's DIY versions. They sounded great.

Report at StereoNet Australia.

The Australian Audio and AV Show
October 21st 2011

Roger's Unity Horns - 21/5/2011
My second visit listening to his Unity Horn system. These are extreme-SPL setup, the horns themselves are 100+db utilising compression drivers and 8 Misco midranges.

2x Unity Horns. Real ones from Tom Danley and only two in Australia (!)
2x 18" AE woofers, ported
2x 12" woofers in bandpass configuration
1x 18" Maelstrom, sealed

The system would easily power a hall and I don't have to mention the ease of which they play loud passages.

Linkwitz Orion - 25/2/2011
A very rare chance in Australia, this is my dream loudspeakers and are the reference for Dipole speaker design. Created by Sigfried Linkwitz himself their resolution and projection is very hard to match. The reason I don't have them is the lack of $14000 (or $4000 DIY) to own one.

Ching Chung's system (Switzerland) - 22/9/2010
Ching Chung is a collector of "ultra-fi". These are esoteric and very expensive equipments. Among his collections are Halcro amplifiers ($120,000+ !), Cary amps/pre, and various loudspeakers from Martin Logans to Cain-Cain fulrange horns which he likes most.

Waveguide GTG II at Paul Spencer's - 5/3/2011
This was the second get together between waveguide enthusiasts. This time we had more waveguides, compression drivers and even a plasma tweeter!

Read the results here on Paul's blog.

DSP GTG part II at Roger's - 5/12/2010
This time I constructed an instant-switching box. We could instantly switch between any two DSP units (both 4 channel inputs and outputs). This method is much more revealing and immediate than ABX blind test.

The reference speakers were Roger's very high resolution Unity Horns. Again, I felt I could not detect differences between DSP units although some prefers miniDSP.

DSP GTG part I at Keith's - 31/10/2010
We were very lucky in Melbourne to have a population of the following DSP crossovers to test:
- Behringer DCX2496 (Paul Spencer)
- Behringer DCX2496, modified (Cybermurphy's)
- Behringer CX2310 (Keith's)
- DEQX HDP-3 (Keith's)
- MiniDSP (Gainphile's)

The loudspeakers used were Acapella Violons powered by Cary monoblocks and SGR amplifiers. Some thought that MiniDSP is the best sounding, but I could not hear any difference between any of the units (with the exception of DEQX which did not operate properly).

Craig's Jazzman
Craig lives only 5 minutes from me, and offered free leftover stuffing from his Jazzman project. I had a listen to them. These are very intricately built speakers.

Very beautiful, very smooth sound and deep bass. We had great listen of Dire Straits and Muddy Waters LP.

Acapella Violon GTG at Keith's -
I enjoyed Keith's drop-dead gorgeous setup. A pair of Acapella Violon running actively with 4 (!) Cary monoblocs.

The dynamics and presentation was simply stunning! This was the first time for me to hear horns too.

Legend Tikandi & DEQX GTG

Tiono's System (Singapore) - 20/10/2010
He is my university colleague and avvid collector of vinyl. His system consists of Sonus Faber monitors, Adcom GFA amps, and REL subs. He particularly pay attention to intricate electonic details (as electrical engineers do!)

He has since replaced the loudspeakers with Magnepan planars.

Adam Tensor GTG at Michael's - 22/8/2009
A very enjoyable afternoon listening to a pair of Adam Tensor Delta. They had sand-filled enclosure. "The Prof" is also coffee connosieur and cycling fanatic. Showed us great pics of "Tour de France".

DEQX and Legend Tikandi - 20/6/2009
I travelled to Mark's beautiful house in Emerald to listen to a pair of Legend Tikandi. These Australian loudspeakers are using the venerable Seas Excel and Visaton Ceramic-coated aluminium tweeters. They are actively driven with DEQX DSP units.

Measuring Open Baffle loudspeakers

2011-01-09T19:24:00.001-08:00

A five-steps guide in great sounding Dipole loudspeakers

This is a simplified step-by-step instruction in measuring dipole loudspeakers. Dipoles are unique in that the rear radiation influence the front and this presents challenges.

Assumptions:

3-way with active crossovers and Linkwitz-Riley filter using MiniDSP as active crossover
You understand basic crossover, filters (LT, Notch, Shelves), able to configure MiniDSP
You have and understand basic acoustic measurement tools

Blue = measurement step
Orange = configuration step

Step 1 - Decide baffle width

It is a compromise between SPL and polar response and the general rule of thumb is baffle width should be narrower than 2x diameter of the midrange. Design the speakers so that the ear/listening height is between Midrange and Tweeters.

Step 2 - Measure the Midrange

Mount the Midrange to the baffle, take it outside, lift it up so the midrange is >= 2m above the ground, and:

Measure from 1m at Midrange axis
This will provide graph which shows the frequency, height, and Q of dipole peak.

Set the xo to compensate this using notch filter. Observe where the dipole rolloff starts, and compensate using +6db/oct lowpass shelving filter.

The lowpass of the midrange will depend on excursion demand. Typically 100-200hz is good. Set this as lowpass frequency of midrange xo.

Measure off axis from 0 deg to 90 deg, in 10deg increments.
This will provide graph which shows where the dipole behaviour ends. Typically between 1.5khz to 2khz. This will set the M-T crossover point.

If the crossover point is too low for the tweeter (normally because the baffle width is too wide), then the dipole would not sound natural. Change the baffle.

Example: Measurements
showing excellent dipole response up to 2k
after which its polar response varies.

Both of the above midrange measurements cannot be reliably done indoors even with gating etc. Measurements for tweeters and woofers can be done indoors as shown below.

Step 3 - Measure the Tweeters

Mount the tweeters and take the speakers inside if needed (outside is always better). Mount the rear tweeter and wire in reverse if you are using back-to-back domes. Set the tweeter high-pass xo as per value found from step 2.

Measure from 1m at listening axis (between M and T) and play pink noise or use impulse. Set tweeter level so that it is reasonably flat. Don't worry if it sounds too bright at this stage.

Reverse tweeter polarity and find the deepest null by setting delay values or all-pass filter of the tweeter. This is to time-align both drivers. Once found, reverse back the tweeter. Measurement should be perfectly flat now. Note that with LR2, the tweeter should be reversed.

Step 4 - Measure the Woofers

Mount the woofer and measure nearfield (1cm from cone). If it's W or H-frame measure from the opening plane. Observe the shape of the frequency response and decide the Fs and Q. From there obtain values for Linkwitz transform target F and Q. F=20hz with Q=0.5 is good depending on woofer's excursion capability.

Set the Linkwitz Transform using values above and measure again to confirm. Set also the +6b/oct dipole rolloff compensation starting from xo point down to target F.

Example: Dipole woofer measurement before (black) and
after (blue) LT filter is applied, showing F=20hz with Q=0.5.
Linkwitz transform is explained here.

Measure from 1m from listening axis between Midrange and Tweeter with pink noise. Reverse the woofer and find the deepest null by setting Woofer's delay. Reverse back and the Woofer and Midrange is now time-aligned.

Step 5 - Listen and adjust levels

Listen to the completed speakers in stereo. Observe bass level and set accordingly. Listen to tweeter level with various program material (acoustic recording). If simple dome tweeters are used, most likely it will be too bright due to uneven dispersion. Optionally set a global EQ using Linkwitz DSS filter (Shelving highpass with F=1.5khz, Q=1, attenuation= -1db). Observe and if it's still too bright, change the attenuation to -2 or -3db. Allow time between adjustments.

This part of the design does require subjective observations, but do not try to compare with sounds from other loudspeakers. Use live acoustic (non-amplified) performance as reference and memory from speech, talking, etc. is useful.

Note that smooth dispersion at tweeter region is a pinnacle of Dipole design. When they are smooth, a flat setting would be correct. Refer to "NaO Note" or my own "S16/MS"

Summary

Dipoles can be methodically built just like any other loudspeakers using tools widely available to amateurs/DIYers. The critical section is the midrange which requires freespace/outdoor measurements when anaechoic chamber is not available.

Note that measurements at listening position is not necessary. While it is intuitive to do so, one cannot correct deviations in time domain with amplitude correction.

to be continued ...

Advanced topics:
What then from here
Electrical vs. acoustic response
Difficulties with passive dipole loudspeakers
Fixing the achiless heel of typical dipole setup
Room analysis

Music

2011-01-01T19:29:00.000-08:00

Argentinian recording
http://www.jacquelinesigaut.com.ar

Jacqueline Sigaut is a visceral and expressive artist. Has become an outstanding representative of the new generation of repertoire tango.She proposed new poems and melodies, which are added the classic themes of Tango. Renewed without neglecting the genre's origins with a tribute to the great masters and, through his warm voice and heartfelt interpretation, provides an overview and current female tango.

.oOo.

Geoffrey Gurrumul Yunupingu (born 1970) is an Indigenous Australian musician, who sings in the Yolngu language. He was born in Galiwin'ku (Elcho Island), off the coast of Arnhem Land, Northern Australia about 350 miles from Darwin. He is from the Gumatj clan of the Yolngu and his mother from the Galpu nation.

.oOo.

A recording collaboration between Australian multi-instrumentalist James Morrison and renowned pianist/composer Joe Chindamo, 2x2 is a double disc release that features a selection of repertoire classics mixed with some originals spontaneously arranged and recorded in one session. Disc one has been recorded as a quartet and disc two as a duo.

.oOo.

With one laptop, 2 microphones and 12 instrumental tunes under his belt, David Ross Macdonald hobo’ed his way across Australia during the bush-fire ravaged summer of 2002 visiting some of the countries finest guitar builders.

After sitting down with each craftsman for coffee and conversation on all things guitar, Dave set up his microphones in the luthiers kitchens, living rooms or workshops, was handed a freshly minted hand crafted instrument and pressed ‘record’.

1 month, 12 guitars and 3000 miles later ‘Southern Crossing’ was completed and is an expose and homage to the spirit, craft and musical works of art those luthiers embody in their guitars.

.oOo.

S16 (M, MS, MSXT, MSTi) - Constant Directivity Dipoles

2010-12-09T06:06:00.000-08:00

The S16 being measured in free space condition.
Roger, Paul, and Daniel are seasoned loudspeaker enthusiasts and builders.

Melbourne 15/1/2011

Work in progress to improve high frequency directivity of S12.

Summary of Midrange and Tweeter variants:

S16 - 10/12/10
Seas L21, Dayton 10" wg, D220Ti compression driver
Also B&C DE250 compression drivers later on
S16/M - 27/9/11
M=Magnesium - Seas W22 woofers
S16/MS - 30/10/11
Symmetrical tweeter response - Seas W22, DX25 + Monacor WG300
S16/MSXT - 27/11/11
Replaced DX25 with XT25
S16/MSTi - 27/11/11
Replaced XT25 with Vifa DQ25SC16-04

Woofers:
Jaycar CW2119

Crossovers:
- Two MiniDSP 2x4 Kit
- Advanced 4-way xo plugin

Amplifiers:
8-Channel Sure Electronics Class D

Follow the build discussion at DIYAudio Forum.

Measurement Data:

Directivity plot, Native frequency response, 1m:

Directivity plot, Normalised to 0deg, 1m:

In-room frequency response (1m ungated), also with reversed tweeter.

Why the fuss ?

You can compare the directivity plots above with typical dome tweeter implementation:

S9 OB:

We see narrowing of loudspeaker polar response, followed by "tweeter blooming". This is an expected response as the tweeters would behave omni-directionally at transition frequency. Humorously known as the "Klingon bird of prey" polar response :)

Recently a combination of large woofer and waveguide are becoming very popular, similar to the S15 Econowave build. While these types of speakers can provide constant directivity down to 800-1khz, unfortunately they soon transition to omni-directional at lower frequencies:

S15 DSP:

Observation:

There is a certain correctness about the sound of speakers with such smooth directivity from 20Hz to 20khz. It is immediate and dynamic. However with any loudpeakers they have plus and minuses:
Strength:
Very dynamic presentation. Willing to play effortlessly at very high SPL. Sound is very 'direct' and make dome tweeters sound diffused in comparison. Very natural.

Weakness:
Lack of rear HF radiation (arguably ok or even necessary), some degree of horn and compression driver coloration make them not as smooth as dome tweeters. Flat dipole bass is unable to pressurize the room effectively below 40hz, although these can easily be substituted with H or W frame dipole radiators.

Room response analysis

Elias Perkonen kindly performed wavelet analysis of the in-room response of these speakers.

Native frequency response, left and right:

Normalised, left and right:

Longer time windows, 150ms and 300ms:

As comparison, here are the bark wavelets of Elias' Dipole Line Array, 20ms and 150ms:

Update 21/5/2011
ps. no rapture yet!

Tried Selenium D220Ti compression drivers with B&C DE250. These drivers use Poly cone material and have a smooth but 'mellow' sound. Read about my burst signal test investigation here. (note: update 22/9/11, I prefer the cheaper D220Ti as a more accurate transducer).

The polar response is excellent and comparable to D220Ti although mounting adapters have to be used.

Update 27/9/2011

S16/M
Replaced L21RNX/P with Seas Excel W22, Magnesium cone

The Excels are interesting. When I tap the cone interestingly they don't sound like typical metal drivers. They sound like polycones! Magnesium are lighter than aluminium and apparently Seas were able to make a thicker cone for the same weight, providing better damping.

Replacing the Aluminium L21RNX/P there were only 2 differences. The cone resonance peak (W22 is about 100hz higher) and region between 1khz-2khz. Frequency response-wise they track within 1-2db. It was also interesting to note the behaviour of the resonance. It's different. The Aluminium has periodic resonance after the main one, while W22 has only one major peak and drops after that. Both L21 and W22 have serious drop about 2khz and really the 1.5khz XO is really pushing it.

Sonics of S16/M

Now, after only minor adjustment, which is the metal cone notch I sat down and listen.... Tonally they are inseparable. They sounded very much the same. However the Excel have this specific character that is quite difficult to explain. Basically it sounded mellow and laid back, but with resolution and transparency. It projects refinement and practically makes any music with overtones sounds......beautiful?? They reminded me of the Orions.

I think, however that the Excels are lacking the gusto and immediate transients of the Aluminium L21 especially playing percussive instruments.

6/10/2011
Interesting approach to solve dipole tweeter directivity by roflynn. Using Scanspeak tweeters and Monacor Waveguide WG300

30/10/11
S16/MS
Building the 16/MS (magnesium, symmetrical)
The objective is to provide front-rear controlled directivity of tweeter region, with symmetry. This was not able to be done with Waveguide/compression driver combination.

To the rescue is Vifa DX25 loaded with Monacor WG300. The dispersion is respectable (not as good as 16/M) but more importantly the small dimension allows back-to-back setup.

The polar response is not as smooth as large waveguide in S16, but it is sufficient to match dipole's directivity of -6db @60deg. When moving around the speakers I could hear the level drops uniformly. It is the best compromise so far between directivity and front-rear symmetry.

0-90deg, 10deg increment, normalised.

27/11/11
S16/MSXT
Replaced DX25 with XT25 ring radiator. The benefit is elimination of 12khz null thanks to the phase plug. This version was shown at Melbourne round-trip GTG.

Deep reverse null showing excellent time alignment and phase tracking. Also displayed is the difference between DX25 and XT25 when loaded with the waveguide. The lack of phase plug caused ~12khz null with DX25.

28/12/2011

S16/MSTi

I wanted better HF resolution which only rigid/metal dome tweeters can provide. A quick experiment mounting a Titanium domeVifa DQ25SC16-04 to the Monacor waveguide resulted in good result. I removed the phase plug of these drivers.

When loaded with the waveguide a 10+dB peak appears. This is excellent as we can notch this peak and resulted in lower distorion (distortion figures of these drivers are already excellent). It also resulted in excellent phase tracking, despite the non-matching diameter between waveguide throat and the dome. To my surprise the lack of phase plug does not exhibit a dip in the response (that 18khz dip is inherent to the driver).

The smallish waveguide loses directivity at 2khz. The polar response is not as good as a proper 10" waveguide, but definitely much better than normal dome tweeter on a baffle.

I prefer the sonics of these drivers compared to XT25 and earlier DX25. They are very transparent and detailed. YMMV. (Update 8/1/2012: They are not nice visually. The dome is light-reflective and draws attention. I liked the black XT25 better and have reinstalled them).

Update 7/2/2012
Experimentation with Linkwitzlab "Watson"
http://www.diyaudio.com/forums/multi-way/206083-linkwitzlab-watson.html

S15 - Econowave DSP

2010-11-12T19:37:00.000-08:00

The Original S15 Econowave DSP
Eminence Beta 12a + Selenium D220Ti & Pyle WG
(C1-W1-CD1)

Econowave is a cost effective controlled-directivity loudspeaker design. DIY folks at AudioKarma had investigated numerous driver + waveguide combination which would achieve the optimum polar response using off-the-shelf products. Paul Spencer at SNA has written concisely on what it is.

Follow the history of this design at AudioKarma and DIYAudio forums.

Specifications
Topology: Active 2-way with pro-woofers and compression drivers
Radiation pattern: Monopole - Controlled Horizontal Directivity
Directivity: Omni-directional at lower frequencies, smooth transition to 90 deg beam at 1.2khz
Frequency response: 20hz - 17khz. Critically damped LF Q of 0.5
Sensititivity: ~92dB
Dimension (H, W, D): 57 x 37 x 33cm
Vertical lobe (Listening position) : Tweeter axis, toe'd in 5-10deg
Amplifiers: 4-Channels required (2x stereo amps)
Crossover: DSP (MiniDSP + 2way Advanced Plugin)

Cabinet construction

The cabinet is basically made from 33cm, 18mm MDF cutouts. The offcuts are glued into the inside panels to provide additional strength and rigidity. The finished speakers are very heavy.

Cabinet C1

Cabinet C2
(future design ...)

A handsaw was used and could not provide precise cuts. Hence the construction can be made square and flush effectively by ofsetting 0.5mm and sanding.

DSP Crossover Configurations

The DSP configuration is available below. Alternatively you can listen to your music quicker and ensured that they are accurate by buying the .xml configuration file. Please specify the variant (e.g. C1-W1-CD1) where applicable.
Note: do not forget to implement L-PAD for the tweeters.

Woofer DSP crossover

Woofer W1: Eminence Beta 12

Cabinet C1

XO: 1250hz, LR2
Crossover point is chosen by careful consideration of distortion, group delay, power handling, and polar response. See my investigation here on dispersion pattern of various xo points.
EQ1: Notch Filter
PEAK 618hz / -2.8db / 2.6Q
EQ2: Linkwitz Transform Biquad (LT)
LT: Select "Advanced", Copy and paste below, and click "Process".
biquad1,
b0=1.00329685429188,
b1=-1.99470503770825,
b2=0.991546613279961,
a1=1.99477083461872,
a2=-0.99477767066137
The woofer is equalised to F3=20hz with critically-damped Q of 0.5. This means -3db@40hz and -6db@20hz. Please note that these values are driver and cabinet volume-dependent. If you change the cabinet volume drastically or change the Woofer, then you need to recalculate and remeasure the transform. No you can't just punch in factory-provided TS parameters.

Read more about LT Biquad here and here, and also a calculator.

Raw woofer measurement (nearfield)
LT Biquad (simulation)
Woofer with LT, Notch, and XO (measured nearfield)
Green=raw, Black=Equalised woofer, Red=Target frequency response
EQ3: Baffle step compensation
HIGH-SHELF 206hz / -6db / 1Q
Baffle step consist of shelving highpass with -6db/oct gain. It compensate the transition from 4pi (omni-directional) to 2pi (forward radiating) of box speakers. Read about baffle step here.
Woofer response with Baffle Step (measured, nearfield)
Woofer response from 1m
Black=with baffle step
Ignore values of EQ4.. etc.
Attenuation, Phase, and Delay
With CD1: Attenuation 0, Polarity NORMAL, Delay: 0ms
With CD2: Attenuation 0, Polarity NORMAL, Delay: 0.06ms

Tweeter DSP crossover

CD1 (D220Ti)

Compression driver: Selenium D220Ti screw-on

Waveguide: JBL 1" thread-on Progressive Transition, Part# 338800-001, or Pyle Pro PH612, or Dayton clone. In Australia: DJCity YD-L033
Directivity pattern measured from 0-90deg, 10deg increments:

XO: 1250hz, LR2
EQ1: Waveguide loading notch
PEAK 1956hz / -4.8db / 2.6Q
Raw and equalised Compression Driver + Waveguide (from 80cm)
Green=raw, black=equalised.
Passive L-PAD
Passive L-PAD is used at the compression driver to provide main attenuation for woofer level matching. The benefit is that noise from Amplifier will also be reduced. The remaining few dB is adjusted from MiniDSP.
L-PAD: -11db using 5.6 Ω and 3.3 Ω 5w resistors
Attenuation, Phase, and Delay
With W1: Attenuation -5db, Polarity INVERT, Delay: 0.04ms
Measurement from 1m at Tweeter level
Ignore lower frequencies.

I have a quick iphone capture of these loudspeakers in youtube:
http://www.youtube.com/watch?v=SwSK8dmeqgU

CD2 (DE250)

Compression driver: B&C DE250 + DJCity adapter (photo)
The adapter needs to be enlarged to 1 inch, so better ones may be found from PartsExpress.
Waveguide: JBL 1" thread-on Progressive Transition, Part# 338800-001, or Pyle Pro PH612, or Dayton clone. In Australia: DJCity YD-L033
Directivity pattern measured from 0-90deg, 10deg increments:

XO: 1250hz, LR2
EQ1: Waveguide loading notch1
PEAK 3981hz / -4.1db / 1.2Q
Raw and eq notch 1 (measured 1m)
EQ2: Waveguide loading notch2
PEAK 1269hz / -3db / 1.5Q
Fully eq'd Tweeter (measured 1m)
Passive L-PAD
Follow the passive -11db LPAD configuration as CD1 above.
Attenuation, Phase, and Delay
With W1: Attenuation -5db, Polarity INVERT, Delay: 0ms (measured 1m)

CD3 (CDX1-1745)

Compression driver: Celestion CDX1-1745 (photo) + PE Adapter

Waveguide: As per CD1 and CD2 (Pyle)

I configured and listened briefly this compression driver at recent GTG and was pleasantly surprised as how similiar the frequency characteristic and sonics is compared to B&C DE250.

A longer-term experience and listening may be needed to confirm, but there were three of us who felt the same during that brief setup. We even set it up playing both drivers together left and right.

Please follow the exact configuration of CD2 (DE250) for this compression driver.

Optional variations

Crossover
Second-order Linkwitz-Riley crossover topology (LR2) was chosen for group delay, however you might want to play the loudspeakers at very high SPL continously. In this case a 4th order crossover providing 24db/oct slopes may be a better approach. This can be done by selecting Woofer and Tweeter crossover to LR 24db/oct and changing the Tweeter's Polarity to non-inverting.

Using Subwoofer

Subwoofers can greatly relieve the stress to the pro-drivers which has highish Fs. I would recommend at least a pair to minimise excitation of room modes. The optimum scenario is to cross with LR2 slope (Q=0.5) and this can easily be done by modifying EQ2 (LT) biquad values. For example, if you would like to cross with the Subs at 80hz the biquad values for the LT would be like this.

"Geddes" Foam Plug

Earl Geddess popularised and patented the 30ppi foam plug approach on his GedLee line speakers. Many users reported improvements in the sound quality. I also tried it and posted my experience. Read Paul's Blog on what type of foam and how to get them in Australia.

The foam will attenuate the high frequency. So you need to increase the tweeter level by 2dB.

Loudspeaker Toe-In

There is a view that these speakers are best listened at extreme toed-in angle, as much as 45degrees. It does seem to provide uniform coverage across listeners but with soundstage depth compromise. I find about 5-10deg off the normal triangle is satisfying.

Room response analysis

Elias Perkonen kindly performed wavelet analysis of the in-room response of these speakers.

Native frequency response, left and right:

Longer time windows, 150ms and 300ms:

Update 11/2/2011
Zilch (Evan) who is the champion of this design passed away. He will be sorely missed.
http://audiokarma.org/forums/showthread.php?t=350053
http://www.youtube.com/watch?v=WvNH23XfeVI

Update 3/2/12
Production version of original S15 documented and posted.

Update 4/2/12
B&C DE250 variant posted
Celestion CDX1-1745 variant posted

S14 DSP - 4 Way Open Baffle with DSP XO

2010-09-29T02:22:00.000-07:00

A work in progres ...

These are 4-way Open Baffle loudspeaker design with 3-way main panel and inverted W-Frame subwoofers.

Objectives:
- Low midrange distortions, by assigning separate drivers for low-mid and high-mid duties
- Low vibrations due to W-Frame subwoofer's opposing forces
- Small footprint and height

Challenges
- The 5" high-mid drivers may proven to be too small for the baffle width
- Designing 4-way crossover will be more complex due to phase interference
- Back to back dome tweeters' known limitation. "dipolar" response, instead of dipole

Drivers
Tweeters: Vifa DQ25 with phase shield removed. Back to back.
Mid-high: Fountek FW146 5" aluminium woofer
Mid-Low: Seas L21RNXP, 8" aluminium woofer
Subs: 4x Jaycar 10" Paper cone

Crossovers:
Two 2x4 MiniDSP Kit
Advanced 4-way crossover plugin

Amplifiers:
Sure Electronics ClassD 4*100 watt

Follow the design and testing process at HTGuide Forum.

Target frequency response of S14

S13 OB - Fullrange dipole tweeters

2010-02-20T00:40:00.000-08:00

The back-to-back dome tweeter used in typical dipole setup is the achiless heel of the system. The on and off-axis frequency response is not smooth.

Many diy-ers investigated alternative approaches for the problem. Basically to keep uniform dipole radiation to very high frequencies, the baffle needs to be either very small or naked drivers are used. Having a pair of Tangband fullrange speakers I experimented with them.

The resulting result is smooth polar response up to 10khz.

While it looked promising, after a while I felt the whole system did not sound coherent. I have not understood the reasons behind it but it is perhaps due to:

- The transition of baffle size
- The fullrange driver unable to deliver the resolution required for high frequencies

I have sinced moved back from this design. The full investigation can be read here.

S12 OB - Open baffle simplicity

2009-11-25T18:19:00.001-08:00

A true open baffle with its simplicity (no H/W/U -frame etc.) I have observed that there is something about them which other variations simply couldn't match due to very uniform polar response.

The tradeoff is absolute maximum bass output. A dipole bass array utilising a total of 8x 10" woofers could be added to overcome this limitation. Then the system effectively become a 4-way as well as requiring more space.

Follow the discussion at diyAudio forum here.

Also similar discussion at Stereo.Net Australia here.

Basic measurement data is available here.

System: Active, 3-way with response shaping and time alignment.
Tweeters: 4x Hivi K1
Midrange: 2x Seas L21 RNXP
Woofers: 4x Jaycar CW2119

System's strengths: Coherency, transparency, very spacious and natural-sounding.

System's weaknesses: Colorations due to L21's metal resonance harmonics are audible on certain material, outright bass output. Back-to-back dome tweeters are never ideal dipole radiators.

S12 Dipole Crossover

Click on the image on the left to see the functional diagram of the active crossover. The crossover can be quickly implemented if you have the budget to procure digital XO such as DCX2496. I use analog op-amps and prototyping board.

Much of the functions are clearly explained at Linkwitzlab website. What is unique is the need to compensate early rolloff of the Seas L21RNXP. The midrange exhibit some coloration due metal cone breakup harmonics and this would be the same even if you use the more expensive W22EX. It is not always audible and only appears in certain recording material.

Seas L21RNXP is an excellent unit aside from the normal metal resonance, however they have been discontinued. Seas L22RNXP is the drop-in replacement. Forget exotic drivers such as the W22, you may as well build the Orion. Why use metal cones then? Well the audible transparency of those drivers is unmatched. They are pistonic until that breakup arrives.

Hivi K1 tweeters exhibited very low distortion and excellent dispersion when crossed at 2.2khz or above with LR4. The tweeters can easily be substituted with something else, as long as the units have excellent distortion and dispersion. With those criteria it's hard to beat the cost of K1 ($12). Dispersion is very important, for example the popular Vifa XT25 would not sound as accurate due to poor dispersion. The venerable Seas 27TBFCG would be a good candidate and the cost is still somewhat reasonable. Better tweeters may allow you to cross lower and help reduce midrange breakup coloration, but not much. Ideally 8" metal cones like L21/22 or W22 should only be used below 800hz.

Construction

Building the S12 is straight-forward, however there are some important considerations.

The side panels are not to increase acoustic path length as normally done by dipoles with "wings". They are for structural reasons, and generally the narrower the better. Although they are very narrow indeed (4.2cm) the midrange section should not be obstructed. I have observed audible midrange coloration if the side panels are simply extended through the midrange height, although I do not see it in the measurement. This could be a very high Q resonance which are hidden by diffraction effects in measurements.

The cavity for rear tweeter must be blocked, otherwise it forms a resonator. Stuffing the cavity using polyfill only helped marginally. It has to be angled to minimise diffraction issue with the midrange.

Link to other designs

Updates:
16/4/2010

Removed comments and pictures about sealed bass, DX25
Added observation notes on strengths and weaknesses

Updates
:17/4/2010

Added Dipole XO diagram and Construction

Updates:
3/11/2010

Implemented DSP XO (MiniDSP.com)

2x MiniDSP kit
1x 4-Way Advanced Crossover

For a total of $210 this is a truly great value for money. Refer to my investigation which led me to this path. The quality is outstanding and they are sonically transparent. Be wary in using digital attenuation for driver level matching. I use trimpots instead.

XO points (acoustics):
W-M: 200hz, 2nd order
M-T: 2khz. 4th order
Built an 8-Channel Class D Amplifier to drive the loudspeakers.
Another value for money. Total build cost for this 8-channel amplifier is $160 (!). Even cheaper than chip based amplifiers and there is no soldering involved.

Dipole Bass Array

2009-11-16T21:14:00.000-08:00

Doubling the number of woofers provide further +6db of maximum output. Basically they are vertically-stacked W-Frame open baffle speakers. The arrangements allows the front baffles to be kept narrow.

Follow the discussion at LinkwitzLab forum here. There are some cosiderations that needs to be investigated carefully, for example the effect of gravity to cone acceleration.

S11 OB - Bookshelf open baffle with Seas 8" and Tangband Full-range

2009-09-19T17:54:00.000-07:00

Drivers: Seas L21RNXP & Tang Band W3-1346s (bamboo cone)
Frequency: 40Hz-20kHz. Designed to be listened near field (read: not much SPL).

Build process here.

The speakers are really small as seen above. Very pleasing.

About the bass... the optimum compromise between distortion, listening level, and excursion is 40Hz. That's pretty deep, dipole or not. The woofers are working reaaaaallly hard. Some 30Hz can be felt but not respectable. Below 30Hz is just asking for trouble. These metal cone makes horrible sound when bottomed. It's simply just physics and there is no way I could get more, except putting again a pair of 15" on my desk.

The problem down low is also related to materials. LP rips have those pesky subsonic rumble which drives the cone to excursion to maximum a lot quicker than the program material. A 2nd order highpass at 17Hz fixes that effectively at the cost of group delay. I could not hear it.

Aside from that the speakers makes really great bass, but you already know what dipole bass is all about. I think it's like a good espresso. Small in quantity but what comes out is pure. I have a Yamaha sub below the desk and while it can provide the extension to last octave, it degrades the quality of the whole system. I turn it off and perhaps will use it to watch movies.

The distance to rear wall is about 35cm. I did could not hear any faults. . Phantom image is realistic, almost like the speakers making no sound and the music comes out of the wall.

I have small clip taken using my mobile phone in YouTube.

S10 OB - Seas L21RNXP on Open Baffle

2009-09-05T13:30:00.000-07:00

After completing my last iteration, I really don't feel the need to experiment with different speakers / OB topology. Any improvements I thought, would come from the drivers themselves which unfortunately is about $$$, not engineering. I should also start to make a PCB and perhaps paint the speakers or something like that :)

But when I saw someone is selling a pair of Seas L21RNXP really cheap on ebay I couldn't resist having a go at rigid piston driver. The Seas drivers are beautiful indeed, and this is not even the magnesium series. They were old types of drivers but never used. The newer ones are L22RNXP.

What I would like to gain from this one are:

- Ability of the midrange to cross lower than P13WH. Let's say 120Hz, presumably better integration with the woofers.

- Transparency of rigid cone drivers. Is the claims true?

- Much higher SPL level

And some drawbacks I would expect/investigate:

- The need to cross the mid to tweeter lower, possibly straining the tweeter.

- Would the increase of baffle from 19cm to 24cm affect the polar response in a really bad way?

- Metal cone resonance

Build process is discussed at diyAudio. See interesting finding here. Measurement data available and discussed here.

S9 Open Baffle Speakers

2009-08-02T19:54:00.000-07:00

Early version of S9, circa July 2009

This build is to revisit the previous design which sounded most natural and smooth. So much that the further effort to obtain dipole bass quantity had to be scrapped.

Build process is discussed here.

Driver-baffle relationship is very important. If the inherent response is not smooth, no amount of EQ would result in natural sound.

The smoothness of this design can be summarised by differences of frequency response between on and off-axis measurements:

Update 23/8/2009
Finished dipole H-Frame woofers:

Update 10/10/2009
Tidy up the prototype XO

Update 14/6/2010

Updated active crossover topology

W-M : 300Hz, 2nd order

M-T: 2.1kHz, 2nd order

Update 17/1/2011
- Converted Analog XO to DSP
- Changed H-Frame to W-Frame subs
- Measurement from recent GTG:

Normalised plot at 0 degrees, showing directivity pattern. Here we can see that the back to back dome tweeter is the achilles heel of such setup:

Update 29/5/2011
- Converted analog XO to DSP (MiniDSP)
- Use W-Frame woofer configuration. This opens the possibility of stacking 4 woofers/side.

Update 8/6/2011
Completed S9R, an "R" or rigid-cone version of this project. Fountek FW146 + Vifa DQ25. The phase shield of the tweeter needs to be removed to avoid resonance and stored energy.

Non-normalised sonogram of S9R, 0 - 90° taken with 11° increments.
I moved these loudspeakers in to my future "audio room" here: http://www.youtube.com/watch?v=RnaTs8oK8tA.
The iPhone does not record bass well unfortunately.

S8 Open Baffle Speakers

2009-03-25T12:26:00.001-07:00

4x HiVi K1 Tweeters
2x Vifa P13WH-00-08
6x Jaycar 10" woofers

Fully dipole radiation. LF equalized using Linkwitz transform to -3db at 20Hz.

Build process here.

System compromises :
- 5" mid still acoustically too small for 30cm baffle, thus the first dip is 1kHz
- HiVi K1 can only crossed comfortably 1.8kHz upwards. A 1.4kHz tweeter like Seas Millenium would be nice. But at $350 each they're way out of my league.

Update 20/7
The first compromise, P13 being acoustically too small for 30cm baffle is more serious than I thought initially. I was unable to get smooth midrange response despite multiple stages of equalization/notch. I have since scrapped this design and returned to S7-styled baffle, yet with further improvements.

S7 Open Baffle Loudspeakers

2009-01-19T15:58:00.000-08:00

The S7:
- Fully dipole radiation from 35Hz - 20kHz
- Vifa P13WH midrange
- Eminence Alpha 15"
- Fully active 4th-order Linkwitz-Riley crossovers M-T at 1.5kHz
- 2nd order LR W-M at 300Hz
- Time aligned using phase correction
- Tri-amped using 3 pairs of LM3875 Gainclones

Follow the design process here.

Practical OB design practices

2009-01-18T04:03:00.000-08:00

What has been learnt. Slapping a full-range driver on a wide baffle just doesn't work, unfortunately.

Drivers

Operate all the drivers at their pistonic properties as much as possible. This is roughly below their beaming frequency which is 1/2 wavelength of the effective cone diameter (0.5 * 345 / diameter) where 345 is the speed of sound in m/sec.
Baffle size

- All dipoles will exhibit a dipole peak. The 1st peak can be tamed using notch filter, but the next peak-and dips are not. The idea is to use the response before and just above the dipole peak. The consequence of this is usually the need of tweeter which can be crossed low, at about 1.4kHz.

- The baffle size should be less than 2.2x effective midrange cone diameter. This way the dipole peak will be pushed higher in the frequency response, ready to be crossed with a tweeter. Using very wide baffle will push down the peak (more bass) but also put the peak-and-dip in tweeter crossover region.
Dipole peak equalization

- Get 1m gated impulse measurement. Then select using 10ms time window. Notice the 1st peak. (Edit: I have since trusted outdoor, ungated measurement more. Raise the speakers to at least 2m from the ground and measure from 1.5m).

- Obtain Fo, Q, and depth of the notch filter. This can be really easy using JohnK's spreadsheet , but not entirely required.

- Build the active notch filter. The components must be as close as possible, and better yet simulate them using Spice.
Time alignment

- Measure on-axis the woofer and tweeter, both at exact same distance from baffle surface e.g. 30cm. Measure using impulse response.

- Select same time start and time window, e.g. 5.5ms with window of 6ms. Compare the phase of the woofer and tweeter, obtain the degrees difference. Then calculate:

e.g. xo freq = 1500, difference = 43.6 degrees. Then:
For LR4 the difference should be 0
Phase = 43.6/360 = 0.1211
time = phase/xo = 0.1211/1500 = 0.0807ms
equal distance = speed of sound * time = 345 * 0.0807 = 27.855mm

then create the circuit based on equal distance.

Open Baffle (OB) Loudspeaker Articles

2009-01-17T04:47:00.000-08:00

Collection of well-written articles and investigations about Open Baffle Loudspeaker design:

Advanced Articles:

Measured Monopole and Dipole room response
By Elias:
I did some measurements with monopole and dipole bass in a room.
Particularly I try to pay attention to temporal behaviour since as I believe steady state measurements in this case are pretty useless when considering human perception. Also I try to match the measurement excitation signal to represent the final situation, that is music.
Music is no impulse nor steady state sinusoid, thus I'm using short tone bursts with shaped envelope. It will give quite good visuality to what is happening in the room due the reflections.
Monopole vs Dipole bass
Elias gives emphasis on temporal fidelity of the reproduced signal. Real music signal contains time domain energy variations that must be reproduced accourately before high fidelity is achieved. This is also true for bass.

Past Projects

2009-01-01T23:39:00.000-08:00

Various speakers I built in the past which I remembered to take pictures of, not in any particular order.

Why build so many speakers? Because only transducers and speaker topologies makes acoustical difference to a hifi sound. Not CD players, not DAC, not Amplifiers, and most definitely NOT cables!

S11 Bookshelf OB speakers.

S9 with H-Frame woofers

Two 10", Vifa P13, and tweeters in dipole configuration
Sufficient output for a desktop OB!
Sept. 2008

Same thing as above before painting

Building Pluto Clones.
May 2008

Trapezoid 3-way OB speakers.

One 10" woofer was not sufficient in terms of bass output

How would dipole-monopole hybrid sound like? In short...not good.
May 2008

Experiment with U-frame dipole woofer.
Good output but not so good sound, most likely due to distance to the wall.
April 2008

What the H-frame setup look from the front.

Trying out H-Frame baffle.

Also not too good due to distance to rear wall avoid dipole radiation pattern.
April 2008

Small dipole desktop speakers. Passive XO. There's no bass output.
March 2008

The small desktop dipole from the front.

The woofers are taken from $12 dicksmith bookshelves.
They eventually used in the Pluto clones.

My first amplifier build for almost 20 years of HiFi hibernation.
Oct. 2007

My first ever Active Crossover.
Dec. 2007

"Number One". First dipole speakers!
It was finished in Christmas eve of 2007.

Very simple crossover.

Number Zero. The first time I ever heard of dipole speaker was this one, and not even a pair. I knew right away that this is 'the way'.
Dec. 2007

The drivers were from kerbside rubbish and the baffle was from unused kitchen cabinet.

Eminence alpha 15" + $4 Jaycar midrange.
Nov. 2008

Investigation on influence of driver offsite (time alignment).
The experiment was failure as the resonances kept from actually making good judgement.
Oct. 2008

Eminence Alpha 15 + Jaycar mid + TangBand 3" as tweeters.

Eminence Alpha 15 + P13WH + Tangband 3-way

The "S9". Most refined OB I built.
Aug. 2009

The "S8". Bass output was great but the 30cm baffle is too wide acoustically for 5" P13WH
March 2009

Another pic of S8. It requires 10 separate amps, but I ended up using 6.

The "S7", the right progress for smooth polar response and revisited as "S9"
Jan. 2009

P13WH mounted on very narrow baffle.

S7 XO work in progress!

Eminence 15" measured to investigate if it's worth to clone the Physics CS2.
The answer was NO.
It was a very hot summer night.
Jan 2009

Experiment in horn-loading tweeters.

Eminence Alpha 15" + Horn loaded tweeters.

10" woofer + Tangband fullrange 3".

These were actually promising for future revisit to "Desktop OB"
Nov. 2008

Simple xo

Unpainted

I don't know why I have so much shots taken.

Investigation of omnipolar tweeter + Dipole mid and low.

Testing in the living room.
I went back between Omni and Dipole numerous times. Always ended up having the Dipoles as perferred speakers.

15" Eminence Alpha + P13WH Midrange + Tangband 3".
Big enough for a desktop system ;) ?

Ridiculous Audiophile Products

2009-01-01T21:38:00.000-08:00

The "Belt Pen"
http://www.belt.demon.co.uk/
review: http://www.positive-feedback.com/Issue1/beltpen.htm

As I said, I cannot discuss the scientific theory behind the pen, but here is a quote from the literature provided with it: "The P.W.B. ‘X’ Coordinate Pen has been induced with complex messages and when a human writes a message with the pen, the conditions on the object change in a similar way to the events in the ‘double slit’ experiment, in which the essential ingredient is the pure energy form of the photons and electrons which readily interact with the human observer."

S6 Open Baffle Loudspeakers

2008-12-30T15:48:00.001-08:00

The goal of this design is low-distortion. This means operating drivers within their pistonic range. This range can be determined by rule-of-thumb of 1/2 wavelength of drivers' diameter.

20-300Hz: Eminence Alpha 15"
300-1500Hz: Vifa P13WH
1500-20kHz: tbd (Vifa DX25, XT25, or DX27)

Actively crossed and tri-amped.

Follow this design tread at DIYAudio.

Update 20/1

This design had reached a plateau of performance when trying to equalize the midrange from 300Hz and above. Large baffle caused undesirable peak and dip which resulted in rough midrange. Baffle size should be no more than 2x cone diameter for smooth response. Refer to S7 for the final design to fix this issue.

S4 Open Baffle Loudspeaker

2008-12-05T04:36:00.000-08:00

These prototypes are further continuation of Stealth 2. Where is #3 you may ask? Well it was a prototype failure and skipped.

Eminence Alpha15A crossed 24db at 1kHz. Good tonality was achieved but both drivers especially the vurnerable TC20 are strained.

What I gained from these prototypes are 1) Excellent bass using the Eminence with correct shelving lowpass filters, 2) Eminence peaks and their appropriate notches, 3) The Alphas have surprisingly good upper frequency extension.

This measurement was taken from listening position, in-room. Ignore the SPL numbers as I did not calibrate them.

DIY Audiophile Media Center

2008-12-02T20:32:00.000-08:00

Update 22/9/11

Audacious 2.5
http://www.webupd8.org/2011/04/audacious-250-released-with-option-to.html

To Install:
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install audacious

and if encountering error:
rm -r ~/.config/audacious

For slow computers like mine (PIII running Ubuntu Lucid via USB 1 !!):
- Choose Output-Only (not Duplex) from Ubuntu Preference->Sound
- Select PulseAudio, 10000 buffer, and 16 bits from Audacious.

.oOo.

My music collection has been growing, and in a good way. About 250GB of which 70% are native 16/96kHz and 24/96kHz recording in lossless FLAC format. Mostly sourced from Vinyl/LP rips. They are superior than normal CDs which are recorded at 16/44.1kHz.

As on-the-shelf audiophile media center or server is very expensive (read: Linn DS is $15,000!) I want to have a media center to allow me sit back and enjoy the music without fiddling with laptop keyboard as now.

I tried many Linux implementation of media center and finally settled on MyMediaSystem. It is pretty, fast, and useful with little non-needed gimmicks. There are additional 'bonus' such as movie player, TV player, internet radio, and photo viewer.

This is what I did. The hardware are:

IBM Thinkpad T23
DAC: SoundBlaster 24 bit Live!
Ubuntu 10.04 or above
Remote: TBA

Resources:
Ubuntu
MMS installation how-to

Install Ubuntu then run updates.
Install Ubuntu Restricted extra (to be able to play mp3 etc.)
Add the following lines from Accessories > Terminal

sudo add-apt-repository ppa:mms-prodeia
sudo apt-get update
sudo apt-get install mms
sudo apt-get install mms-plugin-audio
Edit the AudioConfig file in /etc/mms/. From Terminal type:

sudo gedit /etc/mms/AudioConfig

edit this line (after mapping a drive as explained here)

audio_dir_no_watch = /media/wdtv/04. MEDIA/01. MUSIC
audio_player = AlsaPlayer

If the collection is on network drive like the example above, one needs to use smbmount as in this article here or here

That's it.

Note: The SoundBlaster Live needs to be selected as default from System >Preference > Sound. In the past, this was done using asoundconf (retired now)

The above option installs a minimalist version of the Media Center basically audio player and Internet radio.

My collection of 24/192kHz recording :)
note that this was old screenshot using Ubuntu 7.10

To share directory
Install smbfs: sudo apt-get install smbfs

Create mydriveconnect.sh and make it executable

#!/bin/bash
sudo mkdir /media/mydrive
# unmount previously-mounted drive
sudo umount /media/mydrive
sudo smbmount "//192.168.1.11/wdtv_data/04. MEDIA/01. MUSIC" /media/mydrive -o username=defaults,password=defaults

in case RW is desired, use uid and gid option:
sudo smbmount "//192.168.1.11/wdtv_data" /media/mydrive -o username=default,password=default,uid=999,gid=999

find out the uid using "id" command from terminal

TangBand W3-1364 3" Monitor

2008-11-10T03:56:00.000-08:00

This was a side project which turned out to be good. I had a pair of Tangband W3-1364S 3" full-range speaker and a pair of Dick Smith bookshelf monitor box lying around. It is the old version, but the new one looks similiar. I enlarged the tweeter hole to 7.5mm and closed the woofer with small mdf board.

Pluses:
- Coherent due to no crossovers
- Acceptably clean due to low distortion above 70Hz
- Midrange, vocal is warm and glorious. Very realistic
- Small size
- Easy to make

Drawbacks:
- Low efficiency
- Box signature unavoidable
- Box quality is poor
- High-frequency beaming

It's ok... if I really want to serious playback I go to my living room for the cannons.

I utilised Dick Smith 5" monitor bought at ebay auction for $10. With the Tangband bamboo driver it was a lucky match! Ignore the magnitude, it's not a 100db efficiency but observe the driver rolloff which is then extended to about 45Hz by the port tuning. In fact this loudspeaker low extension is fine and I don't feel the need for a subwoofer. In my 3x4m room they are loud enough. The TangBand is very flat, but my measurement was not ideal as it was taken in front of the grill and there are diffraction effects. Also the drivers are not flush-mounted (yet).

Harmonics distortion measurement at 50Hz shows reasonable H2 and H3 at 100 and 150Hz. Ignore that peak at 5kHz as it is my computer fan noise being picked up by the microphone. First audible signal is heard around 40Hz. There is no audible sound at 20Hz (as it should) and 30Hz.

More comprehensive distortion measurement. At around 70Hz the 2nd and 3rd harmonic distortion drops to about 1% level which explains the average cleanliness of the sound. Most of the time H2 dominates which is normal cellulose cone behaviour and gives somewhat warm sound. H2 or 2nd harmonics is more pleasant than 3rd. I drive them with little Dared MP5 amps.

Photo of the dicksmith box. It is not well-braced and that's next on my to-do list. The measurement is:

Width: 160mm
Height: 330mm
Depth: 230mm
(outside measurement, panel thickness is 12mm)

Port diameter: 50mm
Port length: 110mm, flared on the outside

Closeup of the TangBand W3-1364 3" speaker. The cone is made from bamboo fiber and the chassis is cast metal (!). Very well made. This driver is highly regarded albeit the cost. See full review at ZaphAudio and his measurement results.

The measurement lab. As usual everything here are prototypes, temporary, and utilise anything available in the garden shed :)

Update 23/12/08

- Added Baffle Step compensation (BSC): 1mH parallel with 8.2R and connected in series with the speaker. Theory and design is here.

- Few attempts to add more damping in the box resulted degradation in sound quality. Better left alone and live with the colorations.

Update 25/5/09

- Blocked the port to make them sealed-box speakers. The bass sounds more realistic, albeit less extension.

- I spotted a very nice build of similiar small TangBand family here: http://attlid.eu/p_swift.html

Cheap and accurate speaker measurement

2008-11-09T20:36:00.000-08:00

Never embark on a loudspeaker project without decent measuring tool. This is my set of tools to measure speaker performance. My criteria is simplicity and accuracy.

Sound Card
Soundblaster Live! 24 bit - $60
Software
ARTA. The demo is free and fully functional, except you cannot save files
Alternatives: HOLMImpulse, REW (Room EQ Wizard), Speaker Workshop. All free.
Microphone
DIY Panasonic WM-61A microphone - US$3
Alternative: Behringer ECM8000

To utilise the WM-61A is quite easy. Electret mics all needs "phantom power" and the circuit is something like this, just need a 9-volt battery, 2k2 Resistor, and 10uF Capacitor (non polar). Of course if you want the real deal you can create something like SL's measurement mic or something like this.

The output plugs to left channel if USB DAC's "Line-in". On stereo 35mm connector it's the pointy bit. Mic's ground is the one connected to the body.

The finished product! ... I use chopstick to make it more tasty.

Close-up pic of the WM-61A. They're only like $3 a piece but very flat!

Download and install ARTA from this website, it's quite easy to use. For more functionality such as enclosure design etc. You need to use Speaker Workshop which is free, but very difficult to setup. I actually tried and gave up.

What I like to measure using ARTA are:

1. Frequency response. Simply point the mic to the speaker, choose "FR1" and click the play button. There will be pink noise heard and graph should appear. Something like this. In this case there were two measurements - the yellow line shows bass reflex port response.

2. Harmonics distortion - When a speaker is fed a tone, let's say 40Hz it should only sound 40Hz right? Well unfortunately no. There will be other tones heard as well and these are called harmonics. Ideally the harmonics should be none. The harmonics came in multiplies so for 40 Hz. ther will be:

2nd harmonics - 80Hz
3rd harmonics - 120Hz
4th harmonics - 160Hz
etc...

People say that 2nd harmonics sounds more pleasant than 3rd and above. To measure these harmonics, choose "SA" or spectrum analyzer then configure the generator to sine wave at the required frequency.

3. Harmonics sweep - this is similiar to the above, only that it is performed in sweeps. To do this quit ARTA and in the start menu there will be a program called "STEPS". Similiar to ARTA, run this and you'd get this diagram. In the example below it is clearly shown that the driver being measured performs best above 70Hz, where its harmonics are low. This is TangBand W3-1364 and with distortion of around 1% like that it's quite impressive.

So when all has been measured will the speaker sound good? NO. I view these measurements as a guide only, a debugging tool. Tranducer performance is much more complex than the above measurements.

But those who do not measure, don't know.

Update 2/7/09

I imported quite a few of these mics, and people have been asking for them. I'm always happy to distribute to fellow diyers, but there is none left now. Please do not ask me to send you the mic. And btw. a group buy at diyAudio or SNA may be the way to go (and do let me know if you organise one!)

Stealth 3

2008-08-16T02:37:00.000-07:00

This is a work in progress:

- Eminence Alpha 15"
- Vifa Midbass and Tweeters => Replaced with bamboo fiber FR
- XO completed 23/9
- Time alignment completed 23/9
- Notches ...
- new Baffle ...
- PCB ...

Very low extension of dipole bass, reaching 20-30Hz at -3 dB

16/8/08

Stealth 2 OB Speakers

2008-07-28T16:49:00.000-07:00

28/6/08
This is the second iteration of original Stealth Open Baffle speakers. It is practically the same as Stealth OB, aside from additional woofers and obvious baffle size plus a bit better documentation ;). It is a culmination of my work/experimentation with various designs of loudspeakers.

Nothing can compare the naturalness and non-coloration of dipole bass, and the 4 x 10" woofers provide plenty of them. The system acts as dipole up to 6kHz which is considered very high.

How much bass? Well if you have system that goes down low enough and permit my digicam's distortions these clips may give some ideas :)
http://www.youtube.com/watch?v=x61YMdowJbQ
http://www.youtube.com/watch?v=Tb4KPk3WVx0

Baffle

The baffles are 45 x 60 x 18mm MDF. In Australia go to Mitre 10 and get the 1,200mm one and ask them to cut in half - simple. It cost about $15. I designed them to be placed on top of my study room table. If you want them on the floor simply do a taller baffle. The rule is very simple with OB: The bigger, the better.

I painted them flat-black and it looks good. It's how I got the "Stealth" name from as it does remind me of F117. Yes it also "dissapears" on good recording.

Bass

Once you hear dipole or open baffle bass, it is hard to "unlearn" the experience. One would instantly recognise what "box coloration" is and will be irritated by it. Unfortunately dipole bass is hard to produce due to cancellation.

This can be rectified by displacing more air and the way to do it is by adding more woofer, bigger woofers, and woofer selection. The woofer must have Qts value of 0.7 or more (which means less damping, smaller magnet, etc). This tends to be cheaper woofer too! The Stealth 2 uses 4x 10" woofers. They have Qts of 0.7 and cost only $29 from Jaycar.

Second step is to equalize it. The equalising circuit is very simple as shown below. It can be built using three op-amps such as TL072 ($1 a piece). The signal goes through 120Hz low-pass filter and then shelved at 6db/octave to compensate the cancellation. The signal phase is inverted so from the amplifier the cables must be swapped between positive and negative.

It uses regulated PSU using 7815 and 7915, something like this. Very easy to make.

29/7/08
Note: Revision 3. Changed passive xo to 1st order for phase coherence. This is after comparing the female voice with Linkwitz Pluto. The original schematics is still available here, also Rev1, Rev2

I'm too lazy to draw PCB and use a breadboard instead. Don't worry the electrons don't mind... That extra op-amp IC was just for experimentation with notch filter.

Mid & High

I am a follower of simpler-is-better philosophy so driver selection is critical for the Mid & High section. Simple full-ranger like Fostek, Lowther, or Visaton B200 is the obvious choice but they are expensive and hard to find in Australia. So I went with the following:

For midbass use P13WH-00-08 woofer which has very smooth rollof at 6kHz. This driver has been praised by many for it's natural rollof and don't require crossover at all. No crossover is the best thing after active crossovers. Additionally, since it goes up to 6KHz the system will behave as dipole up to that frequency range - which is very good.

Tweeter selection is no longer critical at 6khz. Tweeters usually become expensive when they need to deal with low-frequencies. Since the P13WH midbass can go up to 6kHz the tweeter can use Vifa TC20TD05-06.

As shown on the diagram above it is crossed passively using simple 1st order crossover. Since this tweeter sensivity is 90dB we need to attenuate it using -4db L-pad resistor circuit. Simple.

What can be improved

I have few measurements using ARTA but could not find anything offending the frequency response. Being dipole it's quite hard to nail down true response due to many factors. I simply find music recordings become very enjoyable and I can listen to it for hours and hours.

Try it. It is actually very hard to get things wrong with OB. As the masters say:

"It is difficult to screw up an open baffle speaker design to where it sounds worse than your typical box speaker. " - Sigfried Linkwitz

"Being that open baffles are so easy to design and construct, the crossover is by far the biggest hurdle." - Nelson Pass

But obviously I have my further desires :) ... like:

Bigger woofers. I wish I had bought 12" ones as there are still some space on the baffle. Or perhaps 2x 12" + 2x 10".
Perhaps a full-ranger instead of midbass+tweeter. It's difficult to place the tweeter at ear level -- if I have the money that is
what else... I don't know actually. Perhaps prettier baffles ...
Stealth 3 ? ... it will be 4x 15" Eminence Alpha with fullrange drivers for mid & high. If I have the room ! perhaps even a CS2 clone.

Physics CS2 Clone

2008-07-26T19:52:00.000-07:00

This is my journey to clone Emerald's Physics CS2.

There is a discussion on this topic at AudioCircle forum.

Bill of Material:

4 x 15-inch Eminence Alpha-15A Drivers,
perhaps could be substituted with DJCity B15-100. update: No, the quality is not that good.
2 x Selenium D220Ti-8 1" Titanium Horn Driver
2 x 12" Round Waveguide 1" Threaded -discontinued?
substitute ? DJCity waveguide
48 x 18.5 x 2.5-inch baffle
Behringer DCX2496, 1 kHz xover, 48 db/octave
substitute with Linkwitz analog filters?

Logistics and costs (Australia)

4x Eminence Alpha 15A : AUD400 - obtained 30/09/08
2x Selenium drivers :
2x 12" waveguides :
Behringer DCX2496 : AUD450.
Cheaper option is to build corresponding analog filters.
Panels :

30/9/08 - The woofers are ready...

2/1/09 - Project abandoned.

After running prototypes and crossing the Alphas to 1kHz with appropriate notch filter I am not convinced that running them that high is beneficial. While tonality is good and I was surprised of their resolution as 15" driver at that frequency, beaming is a real and audible problem. I since then pursue the design where drivers are used at their optimised 1/2 wavelength formula.

Linkwitz Pluto ... sewer pipe omni-directional loudspeakers

2008-05-14T18:00:00.000-07:00

Disclaimer:
Linkwitzlab is not affiliated with Gainphile Blog.

So many good things has been said about this Linkwitz experiment ...

One say it gets too uncomfortably close compared to Orion Dipole ($8,000 system!). I am curious to see how it will compare to my OB speakers.

Importing a pair of Auras is not an issue ($60), but the woofers are too expensive for me. So I substituted them with a pair of Dick Smith woofers laying around. The base uses paving block readily available in the garden. PVC pipes and rubber coupler are available in Bunnings (Australia).

As usual, breadboard implementation. Easy, no soldering. The electrons don't mind.

Halfway build. Very easy, very cheap. $50 worth of PVC from Bunnings.

Update 13/6/2008 - The Verdict

So I've been living with the Plutos for few weeks now. These are my impressions about this amazing little speakers.

First, it is very small and slender. Visually appealing and cocky. I ended up not painting the PVC pipes as the beige colour is very nice.
Bass is amazingly deep. But it does not have that dipole speed and transparency. Slam is better than dipole.
It sounds lively like a dipole. There is no "narrow" box sound.
However they are very prone to positioning. While initially were intended for small room, I found out that they are less tolerant too, which somewhat defeats the purpose. They ended up in my larger living room where they can "breathe" more freely. I found dipole is much more tolerant even in smaller rooms.
In summary they sound like something in between dipole and box speaker, with leaning towards dipole.

Update 11/11/08:

Schematics posted on request. This is the same schematics available at LinkwitzLab. The greyed ones are not necessary, assuming you have a pair of stereo amps. I also removed the green ones because it sounds better subjectively without those. The green ones are tweeter phase delay and woofer notch filter. I'm not saying I know better than SL, just what I hear in my setup and my room.

(c) LinkwitzLab

I added a shelving low-pass on the woofer circuit to give deep bass. But can't play too loud (it's loud enough for 5x6m room). No need for subwoofer. Use the non-inverting circuit.
(note: removed and replaced with Linkwitz Transform circuit in next update)

Small clip is available at YouTube. Pardon my digicam's limitations and the fact that they only take 30-second clips.

Update 16/2/09

Revisited the equalization, and modified the Linkwitz Transform down to 20Hz. See design and conclusion here. In short, the low-frequency is extended but room modes issues still exist and manifest in boomy room sound.

Update 8/09

A friend came over to hear the speakers. He was very impressed, in his own words "I didn't know speakers can image like that." Hence, he is currently building his Pluto2 (real one).

Damping is an interesting topic. This is my final damping fill using polyester fibers. There is also an extensive discussion about the topic here. Note that I am using readily-available Polyfill, not the more exotic acousta-stuff.

Update 27/6/09

The pluto "imposter" was demo'ed at SNA Melbourne get-together (GTG). This is one of the comments:

"Now those little Plutos with some tracks had no right to sound as good as they did.Especially with that vocal track by Angelique Kidjo "Blewu" Amazing what you can make with some dunny pipes!!" -Joz

Update 6/8/10

I am on business assignment for a few months in Switzerland. I brought the Pluto clones and their small footprint and light weight make them a great pair of travelling loudspeakers!

Update 2/1/2011

Directivity plot, indoor, normalised at 0 degrees.

The Pluto maintains omni-directional pattern until 4khz where it starts to transition to forward-directional. The transition is excellent with minor widening around 15khz.

Stealth OB

2008-05-07T21:20:00.001-07:00

Looks like stealth fighter. Can dissapear.

Cheap DACT attenuator (6 steps)

2008-04-28T19:29:00.000-07:00

Using 6-Pole, 2-Position, 1-gang rotary switch from dicksmith. Any brand will do and the more the pole, the better. The 2 position provide left and right channels.

Design the attenuation by using the online calculator something like this, using dB attenuation steps of 56-39-26-12-0:

So the theoretical R values from gnd to signal in ohms are:
gnd-79-482-1,945-10,053-3,7441-signal

But for nearest real value use:
gnd-75-470-1,800-10,000-(36,000+1,800)-signal

This is better than my blue-aps pots. Total cost $4.

Vifa P13WH upgrade (P13WH-00-08) midbass woofer

2008-04-17T05:36:00.000-07:00

Arguably the best midbass in existence. Impressive flat frequency response and cast magnesium frame. Some comments, review, and designs with this 5.25" midbass:

Linkwitz' mid test

Lynn Olson' Ariel

Esquire

North Acoustics Spirit

Marshall Leach

Tempest

Troels Gravesen test

SDS Okara

Daline Transmission Line

The Merrimac

My own S7 OB Speakers

Manufacturer's specification

LDSG review

Dipole bass

2008-04-07T20:20:00.000-07:00

To obtain the purest sound I got rid of the ported sub and use 10" woofer with fully equalised response to compensate OB frequency attenuation.

First attempt to use H-Frame was successful but I did not like it aesthetically. So I went back to plain OB.

H-Frame experiment. I did not like the looks and discarded this.

The final setup is tri-amped system with plain open baffle. Mid & high are actively crossed at 3.5kHz using 24db/oct linkwitz-riley filter. The woofer is crossed at 120Hz and equalised towards low frequency at 6db/octave.

http://www.youtube.com/watch?v=aNmZRxdRQr0

Mini dipole speakers

2008-03-11T17:51:00.000-07:00

Having owned a pair of dipole speakers I tried to get rid of my floorstander in the study room. I found the sound lacks the naturalness of simple open-baffle system.

I use a pair of DSE 5" bookshelf speakers and mount it on a 28x45cm baffle. Predictably the bass is lacking but I rather have a natural-sounding midrange than closed-sound of boxed speakers.

It doesn't look too bad as well. Some possible next experimentation to fix the bass are:
- dipole subwoofer
- active compensation circuit

I did try using normal subwoofer but it simply ruins the overall sound character.

Gainclone HUM, THUMP grounding problems - The solution

2008-03-04T18:01:00.000-08:00

http://www.diyaudio.com/forums/showthread.php?s=&threadid=118735

There are numerous resources on the internet to build a Gainclone. I have successfully built 4 of them without any dramas, except on one area: Hum and Thump. These can be minimal but in a very quiet night can be very disturbing. My latest build had hum audible at 10cm which is low enough - but not perfect.

Thump is a more serious issue for me. I use the gainclone to drive speakers actively, and without protection to the tweeter. Thump means bye-bye tweeters.

So I researched the issue for about 3 months and it was quite a character building experience . So many times spent trying, untangling wire, ecetera which cost me lots and lots of valuable listening and family time. It has too, cost me a speaker (a test one thankfully).So now that I finally have a "black amp" so quiet that you could hear your neighbour fart , let's write it down to help beginners and non-engineers like me.

First of all there are excellent resources about grounding. I will list a few which had greatly helped me in this endeavour:

1. Peter Daniel's layout
2. Digi01's post about multi-channel amp grounding
3. Nuuk's (decibel dungeons) grounding
4. RJM Audio binary star grounding
5. LM3875's datasheet, very good ground loop explanation

For each of the contributors above I thank them for their insight about the topic. There is however, a lack of real wiring diagram for a complete, multi-channel, and specially non-PCB Gainclone systems.

So to cut to the chase, here is the final wiring diagram of a 4-channel Gainclone. Have a look and you may get the idea immediately. It is not overly complicated but there are minute criticalities which I will try to explain later.

Critical #1
'Separation' of signal ground and output ground. Notice that in the drawing there is a small ground point for inputs per channel, and one big ground point for everyting else. I use the term 'separation' loosely here as they are not really separated in electrical sense. There is a connection between 680R with the input ground, but it is not the same with connecting that input ground to the big centre ground point! This was my first mistake - thinking that connection points are all the same (thinking they measure 0 resistance on the ohm meter anyway)

Critical #2
Run the ground connection separately using cable to each relevant ground point. Yes there is a temptation to 'tidy up' and just use one cable and "hop" to the final ground point - it just won't work. Now, this may be different if you are using PCB as it may have beed designed well with large ground area etched.

Critical #3
Use different size of wire. Smallest for input ground, medium for output ground, and a really big one for PSU ground. This relates to point 1, and we try to make the signal flow from input ground to PSU ground - not the other way. Electric signal runs like water to the path of least resistance, and we want that path towards the PSU. During my experiment I found that using the same wiring topology, but also same wire throughout caused hum and more annoyingly loud THUMP when the amp is turned off.

In this photo you can see that my PSU is integrated with the first pair of Gainclone (my second pair would be mounted on top of this). The big cable come from PSU's ground.

Critical #4
Isolate input RCA ground from the chassis. Enough said, we want to 'control' the flow of signals to each ground point, and chassis is definitely not it. It took me quite sometimes to find RCA terminal with good isolation, found it at Dick Smith for $4 each.

Critical #5
Move the signal cables AWAY from any mains/transformes cables. I noticed that putting the signal wire really close to the amp's switch and cables produced noticeable hum. Good practice is to put potentiometers at the back, as close to the input as possible and use some kind of extention like Peter Daniel's chassis. But as you can see above I don't have the luxury of space by cramming 4 amps into such small chassis. I found out CAT5 cables for signal wiring is both neat and easy to tuck away from the mains/transformer.

Not so critical in terms of hum is that 5ohms resistor to AC ground. Some will question the wisdom of doing this in terms of safety, but it does help. I will leave this to you with disclaimer that yes, it is much safer to directly connect AC ground to the chassis.

There you go, hopefully my experience will help many, and if you're an experienced engineer please let us know if there are any inaccuaracy about the concept of this diagram. Thanks.

Bi-amp / Active Crossover using Gainclone

2007-12-29T00:41:00.001-08:00

31/12/07 - Final setup using 4 LM3875 gainclones to drive a pair of two-ways speaker -- that's one amp per driver! It sounds so transparent like glass.

30/12/07 - Managed to cram 4 channels of 3875 amps into this little box. It's a two-tier setup. The whole system now sounds really great but I'm having problems with hum on the second pair of amp (pulling hair...). Also I don't know why the new pair runs hotter even though they are exact same design.

28/12/07 - Completed active crossover setup. Now I need a second pair of gainclones to make sure all frequency matched!

The active crossover is based on Rod Elliot design 'P09' with cutover freq. of 3.5kHz. Calculated C=39nF, R=820R

Foobar2000 + ASIO how-to

2007-12-17T14:46:00.000-08:00

To bypass Windows/OS signal processing use ASIO with Foobar. First install 'asio4all' (http://www.asio4all.com) then from 'asio4all offline setting' activate the sound device e.g. USB DAC.

Install Foobar ASIO plugin (http://www.foobar2000.org/components/index.html) by copying the. dll in foobar directory. Then from Foobar go to preferences > playback > output > asio virtual device .. create ASIO4ALL as new device.

Once the device is created go back to 'output' then select ASIO: ASIO4ALL as the output device.

Note:
ASIO4ALL does not resample (it is why we want to use it after all), so for playing 24bit recording on 16bit DAC go to Foobar2000's DSP and activate resampler (PPHS) with 16 bit target sampling rate.

Dared MP-5: Connecting to Ubuntu Linux

2007-12-08T23:21:00.000-08:00

Dared MP5 is using a generic TI/Burr-Brown PCM2702E DAC chip which is supported by Ubuntu Linux.

Simply plug in the USB and go to System > Preferences > Sound. Select 'USB Audio' in 'Sound Events' and 'Music and Movies' and click 'Test'. A test tone should confirm that it's working.

There is a catch. Although tests are ok, Ubuntu players (VLC, Totem, etc.) keeps using the PC loudspeaker instead of USB Audio. To fix this the following steps can be performed to set the default sound device:

Open Terminal from Applications > Accessories
run the command 'sudo asoundconf list', you need to enter admin password. On my IBMT23 I got back:

Names of available sound cards:
I82801CAICH3
PCM2702
Then run 'sudo asoundconf set-default-card PCM2702' followed by a reboot to test.

The same procedures can be used for other Ubuntu/Linux compatible DAC such as SoundBlaster Live!

http://youtube.com/watch?v=pm04EJdLOeg

Dipole / open baffle speakers

2007-12-06T17:39:00.000-08:00

Just when I was wrapping up my project, I mounted 10" woofer onto a piece of panel, and never looked back. A day later I completed a pair of dipole speakers (open baffle) using only pairs of very cheap speakers I found on the side of the road.... and it sings the most beautiful notes.

There is no 'box' feeling. Just instruments and air that "breathes". There is an inherent low-frequency tradeoff as it is not as loud, but when it does get there -- what a bass! I love it so much I don't know what's next for improvement.

Perhaps it is time to finally .... listen.

http://youtube.com/watch?v=StnJpUfQcZc

8/1/08 - Fixed crossover calculation:
cutover freq 2500Hz
woofer imp. 8 ohms, L stays 0.5mH,
tweeter imp. 4 ohms (2x parallel 8 ohms), C changed from 3.3uF, then 2x3.3uF, then to 15uF but later back to 10uF in parallel (sounds better)

Jensen SPX-7 review and modifications

2007-12-03T15:06:00.000-08:00

The Jensen SPX-7 speakers are impressively well built and braced. Each uses two 6" speakers and a 25mm softdome tweeters. The drivers looks and feels rigid and cosmetically beautiful. Although bearing a US name, these Jensens are assembled in Australia.

Upon connecting the speakers to my gainclone amps, I found the sonics are nice. The crossovers are then upgraded using Mundorf M-Cap Audiophiler capacitors with similiar 3.3uF value.

The Mundorf capacitors contributes in very transparent mids and highs.

Dared MP-5: Review and modification

2007-11-23T05:24:00.000-08:00

Also known as the Fatman iTube.

After listening to the Dared MP-5 tubed integrated pre-amp, I decided that I want to make a pre-amp out for the LM3875 gainclone I built earlier. My gainclone have more power and subjectively cleaner sound.

So I needed to tap the DAC + Tubed preamp stage of the Dared MP-5 as it does not have RCA out. Flipped the amp upside down and removed 4 screws to get access to the board, I noticed that the Dared MP-5 is using STI TDA7265 chip power amp.

Reading the datasheet from google search I found out that pin # 7 and #11 are the inputs, so this is where I want to tap the signal. Looking at the PCB they are clearly marked as L, R, and GND. Thanks to the designer!

I simply disconnected the RCA IN cables and run a jumper from chip's inputs to the RCA slot, thus making it RCA OUT.

Then it is a simple matter of connecting the made-up "RCA OUT" from Dared MP-5 to my gainclone. Initial impression is very positive. The sound is more 'airy' and definite 'layers' of sound which the LM3875 gainclone are renowned for. But I will critically listen to in the next few weeks.

Update 25/5/09:
After living with the amp for quite a long time I have come to the conclusion that it is a very good amplifier which requires no modification/addition. I am using it now to power a pair of fullrange TangBand speakers.

Dared MP-5: unpacking

2007-11-02T05:38:00.000-07:00

During my search for a proper DAC for my gainclone I stumbled upon the Dared MP-5. It is very unique in the way that it combines USB DAC, tube pre-amp, and a (supposedly) gainclone implementation. The DAC is an older version which is 48khz so it won't be able to decode SACD or any 96khz recording. The amp is also a 13w/ch version as supposed to 50 or 60 watt LM3875 gainclones. Nevertheless the tube preamp is really appealing and even without RCA out I think I can simply tap the potentiometer to create one.

The Dared MP-5 came delivered in a quite big box. I did not expect that and it was a good sign.

It came with literally everything needed to make music. Just plug in a PC and Speakers. It also came with a white cotton gloves and brush, and you'll soon know why ...

This amp is like a piece of jewellery. Fully polished and shiny I opt to lift it from the bottom to move it around. It is also bigger than I expected and is very solid.

At the front there is a power button with blue led indicator, usb port with indicator, a volume control, and a headphone jack. At the back there are RCA line-in, switch to select usb/RCA input, and speaker connectors. The tubes are protected using a flat-black cage and it looks fine. I see people take it off but I just don't bother with it.

Gainclone sound & review

2007-10-21T21:48:00.000-07:00

I run the Gainclone using a pair of Jensen SPX-7 speakers bought second-hand from eBay which are (surprisingly) very well built. Temporary source currently either my IBM Thinkpad X31 (WinXP) or my IBM T23 (Ubuntu) but a proper tubed-DAC is on the way.

The Gainclone is a very nice, musical-sounding amps. I needed to run it in for about 48 hours and then it is simply is very hard to fault. Very detailed and fast -- from high to lowest frequencies, it reveals many sounds I did not notice before. It is a very musical amp and makes listening very relaxed and enjoyable.

I enjoy a wide range of music using this amp, from the clarity of piano and tenor voice of Christian Willisohn in Hold on I'm waiting for you ... to Metallica's Lars Ulrich snare drums in Holier than thou.

The Gainclone delivers big time!

Gainclone built progress

2007-10-20T21:40:00.000-07:00

I decided I won't spend $300 for casing but if you search the term 'Gainclone' in Google images there are heaps of excellent design samples. Mine uses Jaycar $15 casing which looks nice and tidy for its price.

The toroid and amps circuit fit perfectly.

30/12/07 - Managed to cram 4 channels of 3875 amps into this little box. It's a two-tier setup. The whole system now sounds really great but I'm having problems with hum on the second pair of amp (pulling hair...). Also I don't know why the new pair runs hotter even though they are exact same design.

7/1/08 - Upgraded the pots using two 100k ohms linear ALPS blue velvets. Result is not much difference.

Gainclone assembly & testing

2007-10-19T21:13:00.000-07:00

I decided to put both 2 channels and their power supply circuits into one board. This will shorten all signal length.

The wiring is point-to-point. I forgot to take the picture underneath but it is quite tidy due to very simple design. The feedback resistors were directly soldered onto the chip's pins for the shortest distance possible.

The assembly took me the whole night but it was straightforward. I plugged in the power and after looking cautiously for smoke I plugged in the speakers and it made a nice sound. There was a problem though.

The Gainclone would make beautiful sound but after 30-40 seconds it would get into some kind of oscillation problem. The sound was like bbrbbbbrbb ... after some thoughts and investigation I pointed out grounding as the culprit. It was using one transformer with two 0-30 outputs. I changed the wiring as shown here and the problem was fixed.

Gainclone design

2007-10-18T20:39:00.000-07:00

Simplest and best-sounding DIY amp, based on LM3875 amp. This part list is based on Australian pricing.

The topology is drawn by Mark Houston (diyaudioprojects.com). Many great sample builds there.

A simple, unregulated power supply.