Generic Advice on Accoustics - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 24 Old 09-24-06, 07:29 AM
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Re: Generic Advice on Accoustics

Hi Alan.

Your description of design GOALS of speakers are very correct. However, in order to get that to translate into a pleasant sounding speaker a designer must consider room gain (specifically in the bottom end).

As for anechoic and 'outside' being the same - sorry to say they're not. Anechoic is just that - no echoes through the use of heavy, heavy absorbtion and tons of large diffusion. It also has an extremely low noise floor. Outside has one absorber - air. Also, outside has a relatively high noise floor which severly restricts dynamic range. Ever heard an outside concert capable of an 80db dynamic range? Nope.

However, don't confuse damped with quiet - two very different things. One can have a room that is not overdamped and is still very quiet. On the contrary, I can have a room that is way overdamped but not at all quiet in terms of noise floor.

Hey, being a seller of acoustic materials, you'd think I'd WANT what you said to be true - cover every surface and make the room completely dead. We'd sell a lot more don't ya think? It'd be easy enough to prove that thin absorbers won't handle the full range and the effects of same.

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post #12 of 24 Old 09-26-06, 03:39 PM
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Lightbulb Re: Generic Advice on Accoustics

Guys,

Interesting thread. And of course I have some opinions to share.

> By room gain you mean multiple echos <

"Room gain" is a colloquial expression that means the room resonates at certain frequencies related to its dimensions. By extension, the resonances yield higher SPL levels at those frequencies for the same amount of input power. So while technically the resonances are related to "echoes" (reflections really), I don't think it's accurate to refer to room gain as being the same as echoes.

It's also important to distinguish between over-damping a room at mid and high frequencies, which is what creates an unnatural effect, and having plenty of bass trapping to offset all the problems that come with room resonances. So I'd say that outdoors is indeed the perfect environment for bass, but probably not for frequencies above around 300 Hz. Then again, I've heard outdoor concerts that sounded great. So go figure. That's the wonderful thing about room acoustics - it's 100 percent science, but there's an additional 20 percent for taste and personal preference.

BTW, I found it really difficult to avoid using 100 smileys. This forum has hands-down the largest and best collection I've seen anywhere!

--Ethan

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post #13 of 24 Old 09-26-06, 03:43 PM
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Lightbulb Re: Generic Advice on Accoustics

Bryan,

> almost all speakers are designed with room gain in mind and accounted for. <

How could that be? Every room has multiple resonances at different frequencies, so how could a speaker be "designed" to take advantage of resonances whose frequencies are unknown? It seems to me that all speakers aim to be as flat as possible - once they're in a room the chips will fall where they may, so to speak.

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post #14 of 24 Old 09-26-06, 05:21 PM
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Re: Generic Advice on Accoustics

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As for anechoic and 'outside' being the same - sorry to say they're not.
Anyone who's had the privilege of standing in an anechoic chamber will never say that outside is the same as anechoic.

It's probably one of the strangest experiences you could ever have. Stand face to face with someone and speak - no problem. Turn your heads 45 degrees and speak again. You can hardly hear each other. Very strange........ The worst thing is listening to the unbelievable silence and the deafening ringing in your own ears.

A true anechoic chamber is a wonder to behold for sure. It's interior is covered in immense wedges of foam, deep enough to absorb the entire hearing spectrum. The walls are very thick and the entire structure is floated on a set of springs to complete the isolation. If you ever have the opportunity to "get a ride" in one, take it. You'll never confuse it with being outside again.

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post #15 of 24 Old 09-26-06, 05:29 PM
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Re: Generic Advice on Accoustics

What, Ethan, you’re only going to visit us once every two months?
Quote:
How could that be? Every room has multiple resonances at different frequencies, so how could a speaker be "designed" to take advantage of resonances whose frequencies are unknown?
Apparently reality is stranger than speculation! This is from Axiom Audio’s website:

Look at a Bookshelf System if you are considering a home theater for apartment-sized living rooms and bedrooms as well as dens.”

Look at a Tower System if you are considering using a home theater in larger rooms or 'great rooms' with vaulted ceilings, which require the higher volume output capability and bass extension of floorstanding main speakers...”

Regards,
Wayne
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post #16 of 24 Old 09-27-06, 02:46 PM
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Re: Generic Advice on Accoustics

Hi Wayne,

> What, Ethan, you’re only going to visit us once every two months? <

Actually, I sort of forgot about this forum after I first visited some time ago, though I do know about JohnPM's REW section. Then the other day I got an email from (I presume) the forum owners asking me to come visit again, so here I am!

> Apparently reality is stranger than speculation! This is from Axiom Audio’s website <

I read that very differently. Not that any company's marketing and ad copy would ever sway my opinion!

I agree that larger rooms require speakers capable of higher output capability. I disagree that smaller rooms won't benefit from "bass extension." I mean, why wouldn't you want to hear the full frequency range regardless of the room you're in?

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post #17 of 24 Old 09-28-06, 11:40 PM
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Re: Generic Advice on Accoustics

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Ethan Winer wrote: View Post
Actually, I sort of forgot about this forum after I first visited some time ago, though I do know about JohnPM's REW section. Then the other day I got an email from (I presume) the forum owners asking me to come visit again, so here I am!
Forgot about us... that's why we sent you a wake-up call...



Quote:
brucek wrote: View Post
The worst thing is listening to the unbelievable silence and the deafening ringing in your own ears.
Tinnitis maybe?

Btw... very interesting description of an anechoic chamber... I'd like to visit one some day... other than the ringing in my ears part (yes, I have it!)
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post #18 of 24 Old 09-30-06, 01:11 AM
 
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Re: Generic Advice on Accoustics

Brucek,Gooday, I thought top manufactures of speakers tested their spkrs in the anechoic chambers as "they" consider the chambers a typical room with no walls,no echos, and when it is raining they they wont get their "smokes "wet. Kind regards alan
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post #19 of 24 Old 10-01-06, 12:54 PM
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Re: Generic Advice on Accoustics

Sonnie,

> that's why we sent you a wake-up call... <

And thanks for that. Here come some more of those fabulous smileys:



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post #20 of 24 Old 10-03-06, 07:21 AM
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Re: Generic Advice on Accoustics

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I thought top manufactures of speakers tested their spkrs in the anechoic chambers as "they" consider the chambers a typical room
No, they test speakers in anechoic chambers to remove any room effects, such that they can reveal the speakers true response. This keeps an apples to apples comparison between manufacturers.

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