A Visit to Hear Vlad's System

Al M.

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Sep 10, 2013
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I think that Al should start making his exceptional listening and analytical talent available as part of a consulting service for a commensurate fee - it would be worth every penny. Time for a career pivot Al?

Thanks for the too kind comments, Vlad (thanks Phil as well), and I am not sure if I should give a serious answer. I'll try. Unfortunately, I make mistakes or omissions in my listening as well. For example, I would not have paid attention to the micro-dynamics if Ack would not have mentioned this area of reproduction in his report, which to his credit he did. The other thing is that we both share more or less similar tastes and perceptions, which makes communication easy. That would not always be the case with others.

More importantly, one thing is to listen and analyze the sound, another is to know what to do about it. I have some experience, but not nearly enough. To start with, an important distinction is to know what comes from the components themselves that cannot be changed without significant expense, and what comes from setup and room/speaker interaction that can actually be changed and thus improved with the same gear in place. That can be really tricky. Going from there, the question becomes how to change it. Or, if a component should be changed, which one and why, and to what? (This is an area of decision often riddled with uncertainties and mistakes.) And so on.

Regardless, I am in the fortunate position that I have an often exciting day job that I love, as a biochemist. I'll keep that until I retire, if I am able to do so in good health.
 
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MadFloyd

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May 31, 2010
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The assesment of panels suggests to me that the absorbers were providing a partial first reflection to the listener
So the thought here is that absorption still reflects?
 
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pjwd

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Jun 23, 2015
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So the thought here is that absorption still reflects?
Yes ... in anechoic chambers the foam is about 600mm deep to avoid reflection ... of course that is extreme but most absorbers act within a relatively narrow range ... a tighly woven fabric cover might reflect high frequency for instance
They also roll off at either end of range and this all adds up to different reflected sound . The better companys usually have specs.
Most diffusers range is limited to depth as well
 
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VLS

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Yes ... in anechoic chambers the foam is about 600mm deep to avoid reflection ... of course that is extreme but most absorbers act within a relatively narrow range ... a tighly woven fabric cover might reflect high frequency for instance
They also roll off at either end of range and this all adds up to different reflected sound . The better companys usually have specs.
Most diffusers range is limited to depth as well

FWIW the diffusers I use are the 4" GIK "Impression Pro Series" (https://www.gikacoustics.com/product/impression-4inch-bass-trap-diffusor-absorber/), which, according to the company have an absorption profile shown below. (Although I don't entirely understand how it's possible to have absorption > 1.0, since, as I understand it, a value of 1.0 Sabins means all energy is absorbed ... https://en.wikipedia.org/wiki/Sabin_(unit) ).

According to GIK, the thickness mostly affects the absorption of the low frequencies, not so much the high frequencies ("The depth or thickness of the panels depends on the amount of low-frequency absorption desired. The thickness of the panel dictates the lower limit of absorption. As thickness increases, the amount of low frequency absorption increases as well. The thicker the panel, the greater the absorption.")

diffusor.png
 

pjwd

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Jun 23, 2015
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FWIW the diffusers I use are the 4" GIK "Impression Pro Series" (https://www.gikacoustics.com/product/impression-4inch-bass-trap-diffusor-absorber/), which, according to the company have an absorption profile shown below. (Although I don't entirely understand how it's possible to have absorption > 1.0, since, as I understand it, a value of 1.0 Sabins means all energy is absorbed ... https://en.wikipedia.org/wiki/Sabin_(unit) ).

According to GIK, the thickness mostly affects the absorption of the low frequencies, not so much the high frequencies ("The depth or thickness of the panels depends on the amount of low-frequency absorption desired. The thickness of the panel dictates the lower limit of absorption. As thickness increases, the amount of low frequency absorption increases as well. The thicker the panel, the greater the absorption.")

View attachment 79123
Thats a perfect example of why the reflected sound does not corelate with direct. Simplisticly you subtract that plot from the sound that hits the panel ... presume they are a diffuser as well so effectivly some hf sound not absorbed will be scattered, dropping level and changing phase. All works really well to calm down a room but theoretically not ideal at first relection point.
That 1.2 sabins / unit is probably a function of how they measured it ... but it gives a good picture of what it does
 

pjwd

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Jun 23, 2015
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Interesting - why is that?
The refelected sound is not the same as direct sound because of subtractions of absorbed sound and phase altered scattered sound so it creates a "smear" of the two at the listening point .. particularly if within 8 -10ms according to the gurus . If the device reflects the altered sound away from the listener then it should be fine. There is no doubt all these products can help to varying degrees but they may not be ideal if flat on the wall . I have found that reflecting sound away from the listening point to be the best option and some diffusers may do that (depending on the dispersion pattern ) .. in some cases the second reflection can also be an issue
 

VLS

Active Member
Mar 7, 2019
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The refelected sound is not the same as direct sound because of subtractions of absorbed sound and phase altered scattered sound so it creates a "smear" of the two at the listening point .. particularly if within 8 -10ms according to the gurus . If the device reflects the altered sound away from the listener then it should be fine. There is no doubt all these products can help to varying degrees but they may not be ideal if flat on the wall . I have found that reflecting sound away from the listening point to be the best option and some diffusers may do that (depending on the dispersion pattern ) .. in some cases the second reflection can also be an issue

Ah, OK. I have them angled so the reflected sound from both speakers is directed away from the listening position, as well as away from the side walls.
 

pjwd

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Jun 23, 2015
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Ah, OK. I have them angled so the reflected sound from both speakers is directed away from the listening position, as well as away from the side walls.
Excellent.. I like this program to make sure
Clunky but simple
Can surprise what happens with second speaker and reflector for first speaker
Phil
 

VLS

Active Member
Mar 7, 2019
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Excellent.. I like this program to make sure
Clunky but simple
Can surprise what happens with second speaker and reflector for first speaker
Phil

Great minds, etc.

C24C19D0-9D94-43E4-A577-9E3573613D88.png
 

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