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Old 27th June 2012, 07:41 PM   #6481
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The acoustic suspension speaker is exceptional because the DRIVER has so much mechanical compliance, that it would not work without a small box to limit its resonant frequency. It also used an 'overwound' voice coil, and tight fibreglass stuffing.
The infinite baffle has been around 'forever' where people put loudspeakers in closet doors, and walls back in the old mono days. The loudspeaker used in an infinite baffle cabinet has normal mechanical compliance, and is what is commonly available.
Harry Olsen allegedly broke the patent, citing prior art.
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Old 27th June 2012, 07:42 PM   #6482
dvv is offline dvv  Serbia
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Originally Posted by simon7000 View Post
I would say "Bingo!" But as that may not translate properly, it means you win, you covered everything.

As long as your driver stages have the extra voltage to drive the outputs fully, you should get what you are looking for.

The downside is that when some designs done that way clip, they can have a nasty recovery and create messy noises which are easier to hear than a soft clip that is masked by harmonic distortion.

You should look at what happens to the stored charges during clipping, where they go and how things are restored. Most folks only analyze the linear behavior of their designs. If the amplifier is big enough and your source is only digital such as CD's then there is much less chance for clipping. If you play records then things such as record warp can actually cause the system to clip without you being aware of the source. Things just don't sound right.

There is also an issue with the initial attack of electronic music. As this is modulated by the inband musical energy you can again get LF clipping behavior.

Best of luck in your project.
Thank you, Simon.

I was also concerned with possible sudden draw of energy, because if one adds up what the voltage gain stage uses, which is about 4o mA all told, with what the predriver and especially the driver may require, one quickly realises that it's high time to upgrade the regulator stage from its original MJE 15030/15031 devices to full blown MJL 3281/1302.

I'm sure somebody will now tell me that I'm overdiong it again, that the regulator pass transistor actually dissipates not so much power, etc, but my view is that the transistors feeding the drivers must NEVER fall short of the largest possible demand of the drivers times at least 2, preferably 3. So, a 50W device will be fed by a 200W device.

What the hell, if you've got 'em, flaunt 'em.

Natch, my capacitors just went up in capacity as well.

Oh yes, don't worry about the expression "Bingo!", it's a worldwide game these days, we have it locally both as Anglo-American Bingo, and as Italian "Tombola". It's a state monopoly, gambling, a frequent event in many European countries, the current top prize as advertised on TV is €1.2 million, which is about US$ 1,500,000. Never was a player myself, but you can't help seeing the many TV ads.

On clipping - I see your point, but I'm going to have trouble with that. While I'm making a nominally 100/200/400 WPC into 8/4/2 Ohms, all my calculations show that I should expect around 170 WPC/8 Ohms before clipping. That's such a lot of power that I believe I shall never experience it in real life with my speakers, in my room.

On the other hand, I see your point as very valid, and I will investigate this using lab resistors - it's an important consideration.

My sources are digital (CD player/DAC and the PC) and analog (tuner, still in good, old analog transmission).

As for the rails, they should be +/- 56V for the current gain stages and +/-63V for everything preceeding them. Thus, even counting the unavoidable voltage drop across all stages, if clipping does occur, it will happen in the current gain stages bfore the rest.

I did this quite deliberately. The last thing I need is for the say input stage to clip, and then have the clipped signal firther amplified, that would be a disaster.

Last edited by dvv; 27th June 2012 at 07:44 PM.
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Old 27th June 2012, 09:39 PM   #6483
pinobot is offline pinobot  Netherlands
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Originally Posted by dvv View Post
Please explain the difference between infinite baffle and acoustic suspension.

I ask because I am not aware of any, it was as Nigel said a matter of copyrights, but as far as I am aware, both use exactly the same principle and calculations.

Henry Kloss, who later started up KLH and eventually Advent, had no copyright problems simply because he was the co-owner of the original patent.
For what i understand, with acoustic suspension Vbox is smaller than Vas.
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Old 27th June 2012, 11:50 PM   #6484
gpapag is offline gpapag  Greece
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Richard Small writing is very good in explaining.
Theory and calculations are the same.
Importance of some parameters change the way of thinking.

http://diyaudioprojects.com/Technica...I-Analysis.pdf

(traditional closed box systems=infinitive baffle)
(air-suspension principle=acoustic suspension)

George
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Old 28th June 2012, 12:22 AM   #6485
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Is anyone actively using and promoting a genuine Acoustic Suspention speaker today ? I am involved a bit with idler driven turntables . I would like to think an A S speaker is as different to the norm as idler is to belt . That is an interesting debate in itself . Good belt drive should have the torque of an idler . I suspect most belt designers reject the concept . It is much like tubes verse transistors . I got my 8 watt valve amp down to below 10 % distortion today for the first time ( never built one before ) . All I am awaiting is some Gu 50 to compare with KT 88 ( different base before you tell me ) . That did feel good . It is at 0.1 % at 1 Watt which pleases me with exponential harmonics . If it was transistor I would be crying . Funny thing is it has a very good bandwidth ( 13 Hz to 66 Khz - 3 dB ) . It does sound very much like my other amps which is a shock to me . It is almost like I have no other design in me regardless of what I start with . I have to say it has been very well behaved all the way through , almost leading me on to what to do next . I have to say some of what I read about valves by very simple experiment is not strictly true . I suspect many things never get tried because someone said it doesn't work . I love the way people repeat the stuff . You can not use a KT88 in place of a EL 34 or the other way around. Well you can . It happens that a compromise bias setting can be found that suits both . It has so little effect on the KT 88 as to be worth doing . I have had great fun swapping all my tubes . It happens that whether by luck or design many suit a 450 V HT and 490 R cathode resistor . A few watts either way doesn't matter . If so use transistors . Bias voltages are KT 88 40 V and EL 34 32.5 V , 82 mA . 66 ma . EL37 also . 6L6 GT was at it's limit . The KT 88 wins by a small margin . Quad Electrostatics have no bass is another repeated " fact " . They do if the room is large enough and they are given space ( try half way up the room if you can , they can touch the walls as the dispersion is OK with that, talking more 63's than 57's now ) . Bass guitar even if not too loud . I would say in fact they have excellent powerful bass . I was demonstrating some at a show in Germany , a man said where is the subwoofer ? My boss said , in the car park . That was with a 300 B amp ( Art Audio ) ! No bass and too inefficient . You know a 300 B amp and Quads can still have less than 0.2 % distortion at gentle levels ( where instruments are real size ) . How many 0.00001 % distortion amps and conventional speakers can match that in combination ? Listen to 78's on Quads , what a positive experience . Like a time machine .

Last edited by nigel pearson; 28th June 2012 at 12:47 AM.
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Old 28th June 2012, 06:38 AM   #6486
dvv is offline dvv  Serbia
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Quote:
Originally Posted by gpapag View Post
Richard Small writing is very good in explaining.
Theory and calculations are the same.
Importance of some parameters change the way of thinking.

http://diyaudioprojects.com/Technica...I-Analysis.pdf

(traditional closed box systems=infinitive baffle)
(air-suspension principle=acoustic suspension)

George
Thank you George, that's the explanation I was looking for.
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Old 28th June 2012, 06:49 AM   #6487
dvv is offline dvv  Serbia
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If memory serves, initial patents are good for 20 years, and you can renew them, not sure if it's 10 or 20 years. After that, it will not apply any more.

Ed Villichur and Henry Kloss patented acoustic suspension in the early 50ies, say 1953. If I'm right, then all their patent rights must have expired by 1993 worst case.

AFAIK, nobody does acoustic suspension today, and even the infinite baffle is as rare as wisdom teeth. Bass reflex rules supreme, challenged only by electrostatics.

On the other hand, circumstances have changed all around. In the early 70ies, most bass reflex speakers did sound "boomy" and did tend to accentuate the bass; it hasn't been so for many, many years, Thiele & Small helped that one out a lot, really a lot.

This reduces the risk of using bass reflex, while still keeping its good side, which is relatively greater efficiency in comparison with typical infinite baffle designs, even those which did manage greater sensitivity than most.

And I think most driver manufacturers have either completely stopped or greatly reduced their infinite baffle driver production runs. Some German companies still do it in a limited way, but that's about it.
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Old 28th June 2012, 08:47 AM   #6488
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I rather like ABR designs. KEF , Celestion and Klipshe Forte . A bass cone with no magnet in place of a port hole . Transmission-line looks ideal on paper . Sorry I never much liked IMF .

Shahinian Acoustics Ltd.
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Old 28th June 2012, 09:16 AM   #6489
gpapag is offline gpapag  Greece
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Originally Posted by dvv View Post
Thank you George, that's the explanation I was looking for.
If you liked this, your next step is this. (J.E Benson ISBN 0-7906-1093-0)

http://www.amazon.com/Theory-Design-...rds=0790610930

George
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Old 28th June 2012, 12:25 PM   #6490
Pano is offline Pano  United States
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Infinite Baffle and closed box aren't really the same thing, are they? Well, at least under about ~1000L for most drivers.
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