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Old 17th March 2008, 03:16 PM   #3211
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"Which Roger Waters CDs use Ambisonics?"

Amused to Death

Peter Gabriel

Up

The Waters disk is really good sounding with several wrap around effects. Kind of freaky when you hear stuff behind you and you know it's 2 channel. Great set-up disk. If your phasing is screwed up it all falls apart.

Rob
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Old 17th March 2008, 03:26 PM   #3212
smoerk is offline smoerk  Antigua and Barbuda
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Hi Rob,

great, I will listen to both CDs. Do you know if they are UHJ encoded?

Quote:
Originally posted by Robh3606
"Which Roger Waters CDs use Ambisonics?"

Amused to Death

Peter Gabriel

Up

The Waters disk is really good sounding with several wrap around effects. Kind of freaky when you hear stuff behind you and you know it's 2 channel. Great set-up disk. If your phasing is screwed up it all falls apart.

Rob
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Old 17th March 2008, 05:47 PM   #3213
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Looking at this I would say no but I don't know if it's up to date. Off hand I don't know. I would have to see what's in the liner notes with the disks.

http://members.cox.net/surround/uhjdisc/ambivari.htm

Rob
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Old 18th March 2008, 08:16 PM   #3214
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Default Bjorn Kolbrek's Horn Articles in AudioXpress


Just received my latest copy of Ed Dell's AudioXpress magazine (to think I started my subscription to Audio Amateur in 1970 - I have the Summer 1970 issue in my hands now, complete with the address of my college dorm!)

Bjorn Kolbrek has just written Part Two of the articles, and you can find Part One here. Here's the link to the Horn Section of Bjorn's website, along with a very interesting discussion (and measurements) of a 200 Hz Midrange horn.

My prejudice in favor of impulse response over PA-style controlled-directivity is pretty well known, so I welcome articles with hard data (no smoothing, thank you very much). This data only confirms the decision to NOT use horns in the frequency regions where resistive radiation no longer applies - it's the extreme HF (above 7~10 kHz) where diaphragm breakup, phase-plug diffraction, and problems with horn directivity all work together to degrade the impulse response.

What I want to avoid most of all is the contemporary theater and PA practice of 10+ dB of boost equalization in the region where the drivers, phase-plugs, and horns are coming apart - adding more power in the same region where distortion is rapidly rising, and impulse response is storing a lot of energy, seems a sure prescription for harsh and fatiguing sound.
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Old 18th March 2008, 08:26 PM   #3215
gedlee is offline gedlee  United States
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Default Re: Bjorn Kolbrek's Horn Articles in AudioXpress

Quote:
Originally posted by Lynn Olson

Just received my latest copy of Ed Dell's AudioXpress magazine (to think I started my subscription to Audio Amateur in 1970 - I have the Summer 1970 issue in my hands now, complete with the address of my college dorm!)

Bjorn Kolbrek has just written Part Two of the articles, and you can find Part One here. Here's the link to the Horn Section of Bjorn's website, along with a very interesting discussion (and measurements) of a 200 Hz Midrange horn.
Unfortunately, this paper is riddled with errors. I am waiting for part two to see if he clears any of them up before I write in my concerns.
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Old 18th March 2008, 08:31 PM   #3216
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The PDF is the same as the magazine article - I've read both. Very curious to hear your response on Part One and Two of the Kolbrek articles. (These PDF's load very slowly, by the way.) As far as I can see, Part Two concludes the Kolbrek series.

Dr. Geddes, thanks for your insightful comments on the many problems of conventional phase-plugs that you made over in the Geddes thread - much appreciated. Still puzzled why compression driver phase-plugs almost intentionally seem to be diffraction generators, whether they use traditional circumferential or Tangerine/radial slots.

There are many articles analyzing 2nd-harmonic air distortion based on calculations of throat diameter, yet the spaces inside a phase-plug are much, much smaller, not to mention right-angle turns where the sound from the "covered" part of the diaphragm enters the phase-plug slits. Surely these right-angle turns generate velocity noise.
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Old 18th March 2008, 08:36 PM   #3217
gedlee is offline gedlee  United States
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I just read part two and unfortunately he only added more errors to the batch.

There is, unfortunately, almost nothing written about horns that is correct. It is virtually all based on Websters Equation, which is completely wrong. When one realizes just how wrong Webster's equation is, and that it can't be used for any real device, you come away with the realization that only in the last few years have we come to really understand how horns work. Anything prior to that has to be viewed with extreme skepticism.

Lynne - thanks for that link to part two. I can write my rebuttal now.
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Old 18th March 2008, 08:41 PM   #3218
gedlee is offline gedlee  United States
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Default Re: Bjorn Kolbrek's Horn Articles in AudioXpress

Quote:
Originally posted by Lynn Olson

My prejudice in favor of impulse response over PA-style controlled-directivity is pretty well known, so I welcome articles with hard data (no smoothing, thank you very much). This data only confirms the decision to NOT use horns in the frequency regions where resistive radiation no longer applies - it's the extreme HF (above 7~10 kHz) where diaphragm breakup, phase-plug diffraction, and problems with horn directivity all work together to degrade the impulse response.

What I want to avoid most of all is the contemporary theater and PA practice of 10+ dB of boost equalization in the region where the drivers, phase-plugs, and horns are coming apart - adding more power in the same region where distortion is rapidly rising, and impulse response is storing a lot of energy, seems a sure prescription for harsh and fatiguing sound.

Lynne - I agree with your concerns, they are mine too, but if you look carefully at my data you will see that I have acheieved a very admirable impulse response WITH my waveguides. Your concerns are real, but your uneasyness about their solution is unfounded.

Once one understands the problem, and that prior work on honrs was mostly wrong, it becomes possible to design out the issue that you highlight. Bt you can't do it if you hold on to the older incorrect ideas as propagated in the works stated above.
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Old 18th March 2008, 08:46 PM   #3219
gedlee is offline gedlee  United States
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Quote:
Originally posted by Lynn Olson

Dr. Geddes, thanks for your insightful comments on the many problems of conventional phase-plugs that you made over in the Geddes thread - much appreciated. Still puzzled why compression driver phase-plugs almost intentionally seem to be diffraction generators, whether they use traditional circumferential or Tangerine/radial slots.

There are many articles analyzing 2nd-harmonic air distortion based on calculations of throat diameter, yet the spaces inside a phase-plug are much, much smaller, not to mention right-angle turns where the sound from the "covered" part of the diaphragm enters the phase-plug slits. Surely these right-angle turns generate velocity noise.
The reason for the "bad" phase plugs goes back to the Bob Smith work on them. He solved a non-existant problem and offered up as proof data that is completly ambiguous - proving nothing. But yet this "idea" persists.

As ALL of mine and others work on distortion perception has shown 2nd order nonlinearities are virtually inaudible. Hence there really isn't a concern over this factor.

In our AES paper we shown how nonlinear distortion in a compression driver was completely inaudible to some 30 subjects all the way up to the drivers thermal limit. In a 2" driver this is a whole lot of SPL. Lets face it nonlinear distortion in these devices is just not a factor. Diffraction, which exists in about 95% or the designs, is a very big factor.

And yes, I would never build a horn if I had to bend it. The problems out number the benefits.
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Old 18th March 2008, 09:54 PM   #3220
SunRa is offline SunRa  Romania
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Quote:
Here's the link to the Horn Section of Bjorn's website, along with a very interesting discussion (and measurements) of a 200 Hz Midrange horn.
The site seems to be down. (unavailable)

Mr. Olson,

Have you had the chance to listen the 18Sound drivers you purchased?
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