# sitting close to back wall, how do I handle the known problems?



## penngray (Feb 21, 2007)

Well my room design is one that breaks most of the logical rules of building a HT room. 


Here is the problem room.....

- The room is 25x13 
- Im designing it going 25 wide and 13 long
- screen on the side wall, subs, speakers, AV equipment built into the side wall.
- Im sitting 11 feet from the wall, 2 feet off the back wall

This weekend Im starting my raw room measurements, I have carpet and the berklines in the room, I have the audio equipment hooked up and I have zero treatments and zero fabric on the walls. 

General treatment plans from lots of advice and reading on the AVSForum

- 12x12x17 bass traps in 3 corners, 6 feet high...Ultra touch cotton.
- 1" OC703 at the reflection points on the side walls. Only up to 42" and only about 5' long based on modeling software I downloaded and equations off several sites.
- 1" OC703 across the screen/speaker wall (top and bottom).
- 2" rockwool 60 across the back wall.
- another 4" panel behind the seating, 48" high x 96" wide

As I add these treatments I will continue to measure and document the changes.

Is there anything Im doing wrong other then the obvious that doing my room "sideways" is just goofy?


----------



## salvasol (Oct 31, 2006)

penngray said:


> - 12x12x17 bass traps in 3 corners, 6 feet high...Ultra touch cotton.
> - 1" OC703 at the reflection points on the side walls. Only up to 42" and only about 5' long based on modeling software I downloaded and equations off several sites.
> - 1" OC703 across the screen/speaker wall (top and bottom).
> - 2" rockwool 60 across the back wall.
> ...


I'm sure Bryan (bpape) will give you the best advise ... :yes:

My only opinion is to use 2" OC703 to cover 100% of the screen/speaker wall and first reflection points instead of 1" (I'm using 2' x 2' x 2" panels to cover the reflection points, but I have accoustical carpet from floor to railchair (around 36" high) :bigsmile: )

Is there any reason Why you're not using the short wall (15') for your screen LCR speakers??? :dontknow:


----------



## bpape (Sep 14, 2006)

Sorry, but with a nice long room like that, I'd do everything possible to turn it.

The treatment scheme sounds pretty good. Just a couple thoughts.

42" is borderline high enough. Seated ear position is usually around that. If tweeter level is that or higher, you're getting decay time help but completely missing reflections.

Bond an FSK face to the rear wall treatment. We want that to do primarily vocal through bass control but leave the surround field lively. You have plenty of other HF absorbtion in the room. Keep things balanced across the spectrum.

Bryan


----------



## solid7 (Jan 31, 2008)

I have a similar scenario to penngray, and unfortunately, I don't have a clue what you just said. :dumbcrazy:


----------



## bpape (Sep 14, 2006)

LOL - sorry.

What I meant is that usually when you sit, your ears are about 40-42" off the floor. If your tweeters of your mains are higher than ear position, the reflection will hit the wall above the absorbtion and be missed if the absorbtion only goes to 42" high.

FRK/FSK is Foil Reinforced Kraft Paper. It is a rolled material that is glued to the absorbtion to allow it to reflect high frequencies while enhancing low frequency absorbtion. That allows the surround field to stay nice and lively yet still get good bass absorbtion in the longest dimension of the room which is usually the length.

Bryan


----------



## penngray (Feb 21, 2007)

> Sorry, but with a nice long room like that, I'd do everything possible to turn it.


Yeah, it bugs me daily but it is what is now and I will make do.



> 42" is borderline high enough. Seated ear position is usually around that. If tweeter level is that or higher, you're getting decay time help but completely missing reflections.



If my tweaters are close to that or higher I will add material to higher up also....Im doing a chair rail at 42" and fabric on top and bottom so adding acoustical material even higher can be done. Is there actually a range of dispersment? Say my tweeters are at 36"? does that mean I should cover 12" above and 12" below?



> Bond an FSK face to the rear wall treatment. We want that to do primarily vocal through bass control but leave the surround field lively. You have plenty of other HF absorbtion in the room. Keep things balanced across the spectrum.


I can order the FRK from your company right? Are you saying put it over the 4" material or over the whole back wall?


----------



## bpape (Sep 14, 2006)

Good deal. The all cloth walls make life easier. Reflections are somewhat more of an area thing rather than a point but the point is easy to ID as the center of the area. If you actually map where the points are and get 3-4" higher, you should be fine. 48" and you should be good to go no matter what. This is all based on only 1 row of seating as the reflections for a raised 2nd row would be higher on the walls.

I can get you just the FSK if you need it.

Bryan


----------



## penngray (Feb 21, 2007)

> I can get you just the FSK if you need it.


Great, I did just go on your website (sensible sound solutions) and order 2 42" foil scrim rolls but I didnt ask for Paypal or a credit card?? Weird...I placed the order and it said, order has been processed...I guess you send me an email so I can pay??


----------



## penngray (Feb 21, 2007)

Another thought on the back wall....

What if I just run 4" on all of it? instead of my 96" area just behind the seating. It would make it easier on me instead of having to build something 4" thick and plac it on the wall after the fabric is up.

I was also thinking about creating that "air gap" I read about in the GIK traps...so it would be 4" of acoustical material and a 1" air gap between the material and the drwall, I can place 1" furring strips on the wall to keep the material off the wall.


----------

