# Treatment behind non-perf screen?



## NoDestiny (Oct 28, 2009)

Hey gang,

Trying to decide if this is worth it. I have a 7.1 setup in my home theater room. The screen, 100" from 2x4" framing and blackout cloth, is one of the primary first reflection points of nearly all the speakers. I was debating on putting some 2" rockwool I have behind the screen to help with that, but being non-perforated, may be a bit of a waste. Was curious if anybody wanted to throw in some input on the matter. I can always find another place to put it, but all side walls are treated, bass traps in place, and ceiling is on the list.

Thanx!


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## Prof. (Oct 20, 2006)

NoDestiny said:


> The screen, 100" from 2x4" framing and blackout cloth, is one of the primary first reflection points of nearly all the speakers.


I'm not sure what you're saying here..
The first reflection points are forward of the screen..These points can be determined by sliding a mirror along the sidewalls (in line with the speakers) until you can see a reflection of the speaker, when sitting in the centre seat..

Covering the front wall with 2" insulation is recommended in all dedicated theatre installations..


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## NoDestiny (Oct 28, 2009)

First reflection points for the surrounds off the front wall (the screen). Not sure if you would count the front speakers or not, really. I have already taken care of all the side walls and am working on the ceiling right now. Have a DVD shelf in the rear for diffusion back there, plus some plans to diffuse further. Just trying to find out if it would be worth putting some absorption behind the screen, despite it being non-perforated.


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## bpape (Sep 14, 2006)

The entire front wall should be dead. Behind the screen, if you can do 2", it will still help from say 125Hz up to about 1kHz before it starts to reflect the highs pretty quickly. At least you're covering 90% of the vocal range that way.

Bryan


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## NoDestiny (Oct 28, 2009)

Cool, thats what I was after! Looks like i'll have to order another 6'er of roxul. Thanx!


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## Dennis Erskine (May 29, 2010)

oops ... Houston, we have a problem.

You do not want to put an exposed fiberglass or mineral wool product up behind the screen (or in an open air space like that). You need a product which is approved for exposure to living spaces (Johns-Manville InsulShield is one such product). 

2" will be very helpful but as pointed out above, of limited value in the mid to low frequency ranges. You can dramatically increase the LF performance of your 2" material by using two 1" layers and installing a 3 mil plastic or vinyl sheeting between the two layers (it can be less than 3 mil by the way).


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## Dennis Erskine (May 29, 2010)

Just a comment on the early reflections thing ... YES, you can and do have early reflections from a front wall for the front speakers.

For the record, I've actually been to Payette, Idaho.


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