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Discussion Starter #1
OK, this seems straightforward from searching AVS and studying theater wall treatment...


FRONT WALL: Acoustical treatment (1" Insul-Shield) floor-to-ceiling.

CEILING: No acoustical treatment - none, nada.

FLOOR: Thick, plush carpet is fine.


But here's where it gets confusing, and I need help...


SIDEWALLS

A) Acoustical treatment (1" Insul-Shield) from floor to ear-height (44"), with 16oz polyester batting above.

--or--

B) Acoustical treatment (1" Insul-Shield) from floor-to-ceiling on all 1st reflective surfaces.


These 2 theories seem to contradict each other. So which is it?



BTW, for those searching for Insul-Shield type product, here are the substitutes which seem to have identical acoustical absorption ratings:


Owens Corning Select Sound Black Acoustic Board

Owens Corning Fiberglas 703 Series duct insulation.

Johns Manville Insul-Shield

Johns Manville Linacoustic Permacoate rolls.

Certainteed Certpro Acoustaboard Black

Knauf Duct board EI-475

Knauf Duct liner EM


...personally, I found the Knauf EI-475 easiest to find (4' x 10' sheets @ $40) from a general heating and air conditioning company.
 

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First, (B) is wrong. Virtually every surface is a first reflective surface (speaking of walls). "B" is actually treating those early reflections which meet the listener's ears within a time frame described by Helmut Haas (further researched by Toole and Olive). Depending upon the delay due to the longer path to the ear will result in the sound being perceived as a distortion, or echo. As well, sounds reflecting off a surface suffer timbre shift. Next, you don't care a twit about "early reflections" that don't intersect the listening position.


The 'early reflections' technique is more typically found in two channel playback environments where higher reverberation times in the room are required to make up for the absence of surround channels (or intelligent surround processing techniques).
 

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JB,


I agree with Dennis that B is wrong. I'll go even further and say you should never cover any large surface area with material that absorbs the mids and highs. It makes the room too dead sounding, and does nothing to solve the inevitable low frequency problems. Much better is a mix of bass trapping and mid/high absorption, with no one area all live or all dead.


--Ethan
 

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Now "A".


Requirements for multi-channel (more than 2) are different than that required for 2 channel.


In multi-channel, the entire wall behind the front speakers is treated. You want none of the back reflections to overlay the surround field or the bring the reverberent field forward (your reverberent field and surround field is created by the multi-channel processor or mix, not so much the room as is mandatory for 2-channel). Depending on speaker placement, this treatment is brought forward along the side walls. Wall treatments are floor to slightly above ear level (where exactly is also a function of front speaker heights). While one could argue the sound at their feet is of no concern, often that square footage of treatment is required to bring the room's RT60 down to the lower levels required for multi-channel playback.


If you have soffits, the bottom of the soffits is also treated...several reasons, right tricorners among them.
 

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Discussion Starter #5
Sorry, two additional questions...


1) Is 1" Insul-Shield (or equivalent) adequate for the front wall, or should it be increased to 2" if possible?


2) If side wall treatment is only be up to early level, then what should be done to fill out the 1" fabric above ear level: polyester batting or 1" styrofoam insulation to maintain the full reflective surface? I've heard both argued, but don't know if there's much difference.
 

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The diferent reqiurements for 2 channel and multi channel is interesting. So obviously there is no way to make a room work as well for both uses as it would for each task specifically. However what should be the general guidelines for a room that would be used for both 2 and multi channel - so as to do the least damage to either format?
 

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Compromise between the two playback scenarios is not a good option. Effectively you're saying you're (a) willing to spend a bunch of money and (b) happy to make the room sound poorly in either case.


If you have a good surround processor and a well set up multi-channel room, play your 2 channel recordings in multi-channel mode...a better result. I can assure you a good surround processor will do a whole bunch better job of creating the spaciousness than your room can accomplish.
 

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Quote:
Originally posted by Dennis Erskine
If you have soffits, the bottom of the soffits is also treated...several reasons, right tricorners among them.

Very informative thread as usual from Dennis. So are the undersides of the Soffits treated for absorption (Insulshield) or diffusion (batting)?


Tom
 

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Since this thread is going, I also have a question -


You have mentioned the front wall and the side walls for acoustical treatment, but what about the rear wall? Is it different with a 5.1 setup vs a 6.1 or 7.1?


Pam
 

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Quote:
Originally posted by obie_fl
Very informative thread as usual from Dennis. So are the undersides of the Soffits treated for absorption (Insulshield) or diffusion (batting)?


Tom

Tom,


I don't want to speak for Dennis but the underside of your soffits should be treated for absorption. (Insul-Shield)
 

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Discussion Starter #12
Treating the underside of cove lighting soffits will have to be explained to me... especially if they are at 8' height (with the majority of ceiling at 9'). If one is using dipole surround speakers, it would seem that treating the soffits could make the surrounds less diffusive and more identifiable to the ear.
 

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I am also interested in the question Pam asked about the rear wall in a 7.1 setup. I will likely use duct wrap on the front wall and below ear level on the side walls. The consensus seems to be nothing on the rear walls or ceiling - correct?


Another question - A non-perf screen reflects quite a bit of sound, but does it pass enough to acoustically treat the wall behind it?


Dennis
 

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I am curious about the room treatment used specifically on the front wall behind Omnipolar speakers(Mirage OM 10). Does too much apsorption defeat the Omnipolar characteristics of a speaker?
 

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Quote:
Originally posted by JBS
These 2 theories seem to contradict each other. So which is it?

Hello JBS.


You may want to check my free Mediaroom spreadsheet. Send me email at [email protected] .


As Dennis points out, music listening has different requirements than HT, especially with stereo/mono sources.


At this point I believe the best arrangement for a multi-purpose room is to make it deadish for HT and perhaps m-ch mixes, and use the same setup for recreating or extracting ambiance for 2-ch music sources.


Best regards.
 

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I would offer that treating the undersides of large soffits could overdamp a room. Ideally you'd leave it alone until tested.


Ted
 
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But what about that rear wall guys???


Do you treat it or not? Do you treat it differently if it were 5.1, 6.1, or 7.1 surround?


(Can you tell I'm getting close to that part of my construction?)


Please help this pitiful female...

Pam
 

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Thank you, Randy! I feel better now....


Crisis averted for now. Hysteria is gone.


Pam
 
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