OC 703 faced?

what are you using it for?

find non-faced batts.
you could use faced and face it towards the wall, but then you're restricting yourself to a single, thin absorber of which you cannot utilize an air-gap. you'll want 4" OC703 (2x 2" unfaced batts stacked together) + 2-4" air-gap.

Assuming you don't have 6-8 inches to spare per side in your theater, and this is the only material you can afford, use it face toward the wall on the front screen wall and the front side walls (front is in front of your prime seating location). On the rear side walls use it face side out above ear level, face side toward wall below. On the rear wall use it in two layers face side out on the outer, face side to the wall on the other.

just understand that with thin absorption you're essentially EQ'ing or coloring the reflection since you are attenuating the HF content but the lower-mid specular energy will persist (filtering the reflection).

Having just done an audio plan from BPape, he recommended faced OC-703 for the rear wall only, with the facing being against the fabric and not the wall.

On the side and front walls he had me use 1" and 2" thick cotton, but you could use UN-faced OC-703 there if you wanted to do it in a less expensive way.

Understood, but from experience attenuating those frequencies improves the clarity of the dialog in movies. Maybe not perfectly, but better.

if one is looking to reflect HF content from the rear wall, then used faced. but i am not sure why one would do that. you're still filtering the reflection from the rear wall.

there is more energy in the lower-mid specular range (longer wavelengths), - thus they are more detrimental and require more effort to attenuate.

many are religious about maintaining the spectral balance in the room, then deliberately filter (EQ) he reflections via thin absorption. if you're absorbing a reflection, then it needs to be properly attenuated.

you would only be placing the panels at early reflection points - not the entire boundaries (unless you are looking to create a dead room)

Localhost127: having read a number of your posts your advice is running contrary to a couple of Theater designers/audio advisers who have hung out here over the years, specifically Dennie Erskine and Brian Pape I would to see you guys have a discussion on treating a dedicated theater space

I was thinking that all you has access to was the faced one inch, rather than getting some unfaced 2 inch to make bass traps in the front corners and use on the front/back walls. There have been claims made that 1 inch of bonded acoustical cotton is better than 1 inch 703/Linacoustic/TheaterShield but I'm not convinced yet. The raw data I looked at didn't show much difference but I am sure there are other measurements.

regarding what aspect?

if you're using rigid fiberglass / porous insulation to absorb early reflections - then you need to use a proper solution that sufficiently attenuates the reflection! who is disagreeing with this statement?

attenuating the early reflection is to get it down below the human detection threshold so it is not competing in the brain with the direct signal (re: localization) - as well as intelligibility if the reflection is arriving within the haas interval. attenuating it below the human detection threshold doesn't mean you don't hear it - but the brain is not processing it as a discrete, separate signal that is competing with the direct signal.

if one is using thin absorption, you're effectively EQ'ing the reflection and altering the spectral balance / coloration.

of course, we can eliminate all of the guesswork by measuring with the envelope time curve to actually measure what the dB attenuation is of the reflection vs the original signal after the absorber has been placed.


better at what? it is dynamic. if you're changing thickness, then different density/flow-resistivity materials may provide better results vs a thinner panel. it's a system w/ variables. one also needs to be mindful of how such measurements are being made (see 2nd paragraph on bob gold's page).

I think the biggest difference in approach is your advice for much thicker and undoubtedly more absorbent treatment of first reflection surfaces versus their more decorator friendly/ space conserving approach of treating more surface area and their use of scrim on potions of the rear side walls and rear walls.

Having seen Dennis and Brian's full room prescriptions (and listened to the results) for a dedicated theater space I would be curious how you would treat a 15x24x8(or 9) ft room With two rows of seating. Two feet of space are available behind a false fabric wall with an Acoustically transparent screen.

Soffits and riser are available for bass traps.

just about every post i give instructs the user to use the Envelope Time Curve response (part of the free measuring suite: Room EQ Wizard) such that one can see just how strong the early incident energy is (which dictates whether the user even needs to apply absorption at the early reflection point in the first place) - and also verifies how effective the absorber is at attenuation of the early reflection once the treatment has been procured and installed.

there is no getting around the fact that the lower specular region has longer wavelengths, with inherently more energy content - and as such, needs more attnetion to be addressed that thin absorption cannot provide. if you are applying thin absorption and not properly attenuating the entire specular reflection to below the human detection threshold, then you are effectively EQ'ing the reflection which will combine with the direct signal and continue produce filtered comb-filtering effects for whichever band was not attenuated by the thin absorber.

again, without actually measuring with the ETC - one does not even know how specular energy is impeding the listening position. hence, the advice to measure with the ETC before procuring 'treatments' is generally offered.

but the fact remains that in small acoustic spaces, we generally have to deal with specular energy down to 300hz.

applying thin absorption in a room will effectively attenuate the HF content and allow the lower-mid specular content to persist which can easily make for a worse, filtered response.

if you're going to 'absorb' your early reflections, then by all means do it properly and fully attenuate it (and measure for verification).




treat a room? how can you treat a room with solutions without knowing what the inherent problems are to begin with?

also,


unless the goal it to soak the energy out of the room and create a dead space, then you should only be surgically applying absorption at boundaries that are incident for early energy (in the specular region - in the LF modal region then you need as much LF absorption as possible).

i dont design dedicated theater spaces like those experts do. that's a packaged services solution.

im just a hobbyist who offers input on how to address specific problems that are inherent in small acoustical spaces.

i cant recall ever offering a "solution" to a home theater design on these forums. most of my commentary is directed at the acoustics aspect or pointing out possible misconceptions regarding small room 'treatments'.

Why not OC 705 2 or 4 inch? I'm using it in my dedicated my room and reflections are pretty well controlled. Some eq'ing was needed but nothing dramatic.

Something a lot of people would like to see. That is the essence of what this forum is about.

Maybe, but only to the degree that others are mistaken or that one may have misinterpreted them.

Faced porous material is used ONLY to minimize the mid and HF absorption of LF bass trapping!

It is absurd to use faced material as absorption for early arriving high gain reflections as it is reflective to frequencies above ~600 Hz!

This material is well known in studio design and has been for years!

The biggest problem being that too many people are using too thin material that fails to be effective over the entire broadband specular bandpass, effectively EQ in the reflected energy causing coloration when it superposes (sums) with the direct signal!

This behavior of the material faced with at a minimum of at least 6mil plastic is precisely what is leveraged in the large LF corner 'superchunk' style bass traps in order to create frequency selective bass traps in order to retain the finite amount of mid-high energy in the room. (Also, for such large volume traps, the 'pink fluffy stuff' offers superior performance compared to the more traditional OC703 or 705 (3pcf or 6pcf respectively) material.

And using what is expedient rather than what is correct is NOT the proper/effective way to treat a room!


No. The problem with this is that while it does fine on the upper mids and highs, it is not sufficiently effective on the higher energy content lower-midrange specular energy. Absorption for specular reflections to be effective must be broadband. That means that it must absorb effectively over the full bandpass from ~300 Hz up. The highs are easy, the mid range is not.

The problem is that such treatment only modifies the spectral content of the reflected specular energy. It does not effectively absorb the energy and unfortunately the problems caused by the superposition of such energy not only is not remediated, but the resulting spectral imbalance that causes the indirect energy to now be significantly different from the direct energy causes additional coloration. In other words, you either do it properly and completely, or you cause more problems.

And you do NOT use EQ to remediate non-minimum phase spectral issues!!!!!!!!!!!!

Who is saying to use faced for absorption? , the OP wants to use material backwards with the face on the wall.

He also pointed out correctly that not only is faced material not suitable for use with the facing being placed facing outward, as the insufficiently thick panels placed against the wall are not sufficient to remediate the broadband energy.

Spin it however you choose, It is not suitable for the effective control of early arriving high gain reflections.

paragraph after paragraph - all of this would be summed up with a simple ETC (one speaker at a time) which would clearly identify the room's total specular response and as such, would completely obliterate any guess work as the what the inherent problems are and what the 'treatment' must be in order to address.

has the actual problem with regards to the OP's rear wall been identified before we as a community can offer a possible solution?

Most of the DIY theater builders coming to this forum are dealing with basic rectangular drywalled rooms with carpeted floors. There are plenty of theater builders in this community with experience with similar rooms that can offer suggestions to get the new builder close to an acoustic solution suitable for their needs. Some of those solutions like building broad band bass traps into risers and soffits can only be accomplished during the early construction phases not after measurements can be taken in a finished room.

Applying wall treatments behind fabric covered walls with trim molding and columns hiding the staples can also only be done during the construction phase.

For these reasons builders look for solutions early in the construction process not after room measurements can be made. What has proven to work in one similar sized room is leveraged in hopes that it will work.

Localhost and Dragonflr, it might help if you tell us (pictures would be nice) about your home theaters and what treatments you found necessary.

i would advise caution if you are implying that there is some sort of 'catch-all' criteria for any and all members who may wander into this sub-forum.


quoted for effect !!!

this is the exact psychological position that disrupts this forum! as if some million dollar theater room will suddenly validate any of the concepts that are being discussed.

First time I've been called a disrupter