Acoustic reflectors and piston drivers

[jcx]

Originally Posted by gedlee

Hi Markus

Digging down deep for topics? I cannot imagine such a device working well. The B&O device didn't.

"Fluid mechanics" versus "ray tracing"!? Thats a new one. So "Acoustics" is now "Fluid Mechanics"? Well I guess that it always was, its just that Fluid Mechanics is mostly a static flow analysis and acoustics is a dynamic one where any static flow is ignored. So I guess that B&O is interested in the air currents arround the room and their effect on the sound?

I assume Moulton was referring to some Ansoft style multiphysics modeling, maybe compressibility, flow losses from the cavity, edges - I agree that Hemholtz, Diffraction, acoustic impedance may the more common/useful engineering aproximations - didn't you find anything in phase plug design that needed a little more than linear acoustic modeling?

maybe it was just meant to contrast real Acoustic modeling vs Ray Tracing

he does post polar response Moulton Laboratories :: A new loudspeaker design

[gedlee]

Originally Posted by Bill poster

Out of interest, do you mean the Sausalito lens?

Yes, correct. B&O did not renew the license. If it had been successful they certainly would have.

[gedlee]

Originally Posted by jcx

I assume Moulton was referring to some Ansoft style multiphysics modeling, maybe compressibility, flow losses from the cavity, edges - I agree that Hemholtz, Diffraction, acoustic impedance may the more common/useful engineering aproximations - didn't you find anything in phase plug design that needed a little more than linear acoustic modeling?

There is nothing of interest in loudspeaker design that cannot be done with standard linear acoustic modeling. Fluid dynamics, ala the full Bernoulli equations, are never necessary when static flow is ignored. Even in nonlinear acoustics, the static flow terms are ignored , but the dynamic nonlinearity of the air is retained. But nothing in "audio" requires this kind of analysis.

maybe it was just meant to contrast real Acoustic modeling vs Ray Tracing

he does post polar response Moulton Laboratories :: A new loudspeaker design

Yes, he does show polar responses - they prove my point. There is nothing "good" about them. This whole concept was ill-conceived and fell flat in the marketplace. I first saw it at Dave's studio way back before it was even a patent. It didn't interest me then and still doesn't now. We always say "time will tell!" - it did.

[markus76]

Here's my more or less random prototype:



Driver is a Visaton B200. The reflector angle is about 45° and its circumference matches that of the driver's cone.

0° to 90° in 10° steps - box without reflector/with reflector:





















Box only:



Box with reflector:

[jcx]

"...In my case I tend to dislike ported speakers because of port noise..."

[markus76]

Originally Posted by gedlee

Digging down deep for topics?

Next is the acoustic lense

Originally Posted by gedlee

I cannot imagine such a device working well.

What are the problems?

[Bill poster]

Originally Posted by gedlee

Yes, correct. B&O did not renew the license. If it had been successful they certainly would have.

Eh? Are we talking about the same thing? B&O bought the Patent(s) and split the Rights of usage; its been instrumental in turning Bang & Olufsen's fortunes around.

[weltersys]

Originally Posted by gedlee
Hi Markus

Digging down deep for topics? I cannot imagine such a device working well. The B&O device didn't.

Originally Posted by Bill poster

Out of interest, do you mean the Sausalito lens?

Soundsphere has been peddling the reflector “technology” since 1976.

Dispersion is usually specified with -6 dB points, note that the -6 dB point of the Soundsphere Model 110B from 3 kHz to 8 Khz is perhaps 7 degrees, while the Architects and Engineers Specifications states the vertical polar coverage shall be 180°.

They didn’t lie completely, the vertical polar coverage is around 180° at 250 Hz, of course a conventional speaker has nearly that dispersion that low too.

The B&O / Sausalito “lens” basically is a fancy looking version of a similar reflector, which offers very wide horizontal dispersion, but extremely narrow vertical dispersion.

The coverage pattern goes from roughly spherical at low frequencies to a disc shape at high frequencies.

As David Moulton wrote: “The full reasoning regarding why such performance is desirable is well beyond the scope of this paper. “

It is also beyond the scope of my imagination why such performance would be desirable .

As Earl Geddes wrote, “This whole concept was ill-conceived and fell flat in the marketplace. I first saw it at Dave's studio way back before it was even a patent. It didn't interest me then and still doesn't now. We always say "time will tell!" - it did. “

[Bill poster]

The Soundsphere looks like something Pedro from Napoleon Dynamite would want. Thats why it failed

[weltersys]

Originally Posted by Bill poster

The Soundsphere looks like something Pedro from Napoleon Dynamite would want. Thats why it failed

The Soundsphere fails as a speaker but survives as a business venture using PT Barnum’s “a sucker is born every minute” approach since 1976, they are selling to a new generation of suckers now .

The Soundsphere suffers from the same problem that the B&O / Sausalito lens has, wide horizontal dispersion, but extremely narrow vertical dispersion.

Of course, David Moulton seems to think that problem is a virtue .

One man’s meat is another man’s poison .