Re: Kludge's 2009 AES Show Awards

[Filevski]

On Oct 23, 2:50*am, (Scott Dorsey) wrote:
> Richard Crowley > wrote:
> >"Scott Dorsey" wrote ...
> >> WORST PAPER IN SHOW
> >> In "Simple Amplifier for Single Frequency Subwoofer," Vladimir Filevski
> >> uses a low pass filter and a detector to determine the instantaneous level
> >> of low frequency information in a signal, and uses that control voltage
> >> to modulate the 50 or 60 Hz AC power line and apply it to a subwoofer.
> >> It replaces whatever bass content is in the signal with a single frequency
> >> thump.
>
> >Unbelievable. Does AES have no standards left?
>
> The show papers are not peer-reviewed the way the journal articles are.
> They are selected based only on a review of the abstracts. *Consequently,
> there are a lot of interesting papers showing preliminary results of
> incomplete but promising research, which would never make it into the
> journal. *On the other hand, now and then there's one of these things.
>
> There are also occasionally some papers from abroad which I think get
> accepted because everybody knows that the author would never be able to
> attend the conference unless he was presenting. *I feel really sorry for
> the authors in this position but sometimes I feel sorry for the audience
> members too.
> --scott
>
> --
> "C'est un Nagra. *C'est suisse, et tres, tres precis."


These words of Mr. Dorsey might make wrong impression that the concept
of "Single Frequency Subwoofer" is my invention. In fact, the whole
concept of high efficiency/low Bl (low damping)/single frequency
loudspeaker with frequency mapped amplifier was invented by Mr. Ronald
M. Aart of Philips Research Labs from Eindhoven, Netherlands. His
paper was published in (surprise, surprise!) peer reviewed Journal of
the AES (R. M. Aarts, "High-Efficiency Low-Bl Loudspeakers", J. Audio
Eng. Soc. , vol. 53, pp 579-592, 2005 July/August).
Because Holland is abroad (respective to USA), Philips team could only
manage to present their paper at the AES convention in Europe (120th
Convention of AES, Paris, France, May 2006) and to make live
demonstration of their Single Frequency Subwoofer. Again, this second
paper (on the same subject of Single Frequency Subwoofer!) was
published in (surprise, surprise!) peer reviewed Journal of the AES
(R. M. Aarts, J. A. M. Nieuwedijk, O. Ouweltjes, "Efficient Resonant
Loudspeakers with Large Form-Factor Design Freedom", J. Audio Eng.
Soc., vol. 54, pp 940-953, October 2006).
My only crime was that I realised that I could simplify their
amplitude modulating amplifier, eliminating the single frequency
generator, the mixer and the whole power supply (no power
transformer!). There are some certain application where this low cost/
low fidelity Single Frequency Subwoofer (of Philips!) can find use.
Audiophile's home is not that place! Mine neither.

Vladimir Filevski

[Richard Crowley]

"Filevski" wrote ...
> There are some certain application where this low cost/
> low fidelity Single Frequency Subwoofer (of Philips!) can find use.
> Audiophile's home is not that place! Mine neither.

Amar would love it.

[Scott Dorsey]

Richard Crowley > wrote:
>"Filevski" wrote ...
>> There are some certain application where this low cost/
>> low fidelity Single Frequency Subwoofer (of Philips!) can find use.
>> Audiophile's home is not that place! Mine neither.
>
>Amar would love it.

It is very good to see Mr. Filevski here, and yes, he's entirely right
about all the previous art.

In fact, you could argue that this is just the natural extension of the
bandpass subwoofer... you're going from a narrow range to a slightly
narrower one.

Amar's _Acoustimass_ system is a dual-tuned bandpass box... it produces
two different notes. There is some psychoacoustic research showing
that this is more effective than just one in that sort of application.
Bose has actually put a lot of effort into figuring out just how little
bass bandwidth you can get away with before most people notice and it
would be really interesting to see that stuff published someday.

What I find so alarming is that this _is_ just the natural progression,
and I think it's a progression into a terrible direction. The problem
with this stuff is that sooner or later, somewhere we're going to have
to actually listen to it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[DrBoom]

On Nov 1, 6:56*am, (Scott Dorsey) wrote:

> Amar's _Acoustimass_ system is a dual-tuned bandpass box... it produces
> two different notes.

Having designed and built a number of vented bandpass enclosures for
car audio applications, I can state with some authority that this
isn't true.
With appropriate driver choices, you can tailor the response to have a
flat
passband, a lot of "gain"[1] at the lower and/or upper resonance
points,
or a ton of "gain" at a single resonance point. There are a lot of
choices in
between.

Phase response is all over the place, or, to put it another way, group
delays
range from "high" to "it's in the mail". I never did do a system with
one of
these enclosures that incorporated time alignment to compensate for
20ms+
group delays, but there's no reason to think it wouldn't work well.

Feel free to slag the Acoustimush fart boxes, but I don't think a
blanket
statement like "vented bandpass enclosures produce two notes" is
supported by the facts.

[1] Not really "gain", properly speaking, but it looks that way when
you
measure it.

[GregS[_3_]]

In article >, DrBoom > wrote:
>On Nov 1, 6:56=A0am, (Scott Dorsey) wrote:
>
>> Amar's _Acoustimass_ system is a dual-tuned bandpass box... it produces
>> two different notes.
>
>Having designed and built a number of vented bandpass enclosures for
>car audio applications, I can state with some authority that this
>isn't true.
>With appropriate driver choices, you can tailor the response to have a
>flat
>passband, a lot of "gain"[1] at the lower and/or upper resonance
>points,
>or a ton of "gain" at a single resonance point. There are a lot of
>choices in
>between.
>

I think Bose would go for the resonance and 2 notes.

Remember the BIG tube or cannon ?

There was a lot of info as one investigated the Bose tuning way back in Speaker
Builder magazine. The authors conclusions were basically saying not so great.
I have built many simple bandpass boxes, and they are pretty neat since you can
get different plots and gains as needed. First ones I used a lot of manual
calculations, then got hold of a program to do it. I think I still have a slide rule type of
calculator for double tuned boxes.

greg

>Phase response is all over the place, or, to put it another way, group
>delays
>range from "high" to "it's in the mail". I never did do a system with
>one of
>these enclosures that incorporated time alignment to compensate for
>20ms+
>group delays, but there's no reason to think it wouldn't work well.
>
>Feel free to slag the Acoustimush fart boxes, but I don't think a
>blanket
>statement like "vented bandpass enclosures produce two notes" is
>supported by the facts.
>
>[1] Not really "gain", properly speaking, but it looks that way when
>you
>measure it.

[Scott Dorsey]

DrBoom > wrote:
>On Nov 1, 6:56=A0am, (Scott Dorsey) wrote:
>
>> Amar's _Acoustimass_ system is a dual-tuned bandpass box... it produces
>> two different notes.
>
>Having designed and built a number of vented bandpass enclosures for
>car audio applications, I can state with some authority that this
>isn't true.
>With appropriate driver choices, you can tailor the response to have a
>flat
>passband, a lot of "gain"[1] at the lower and/or upper resonance
>points,
>or a ton of "gain" at a single resonance point. There are a lot of
>choices in
>between.

You _can_ widen it. But Bose didn't.... the resonances are really narrow.
The narrower they are, the more efficient the system is, and the closer it
is to one-note bass.

>Feel free to slag the Acoustimush fart boxes, but I don't think a
>blanket
>statement like "vented bandpass enclosures produce two notes" is
>supported by the facts.

I didn't say that any of them produced two notes, other than the Acoustmass.
I have seen some that only produced one note, others that were more
broadband.

I am sure you have made much wider bandpass boxes than Bose has, but I
bet your ultimate goal for the product was different than Bose's.

Note that the Acoustimass is mechanically somewhat different than the
conventional vented bandpass enclosure; it's actually two narrowly-tuned
cavities coupled together.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."