My HT is on the way (ceiling is dong, 1st layer of walls is up) .. meanwhile i'm thinking what I"m gonna do for acoustic treatments. My room is 21'8' x 10'5" x 6'8"

Towards the rear wall, i'm going to have a couch (with maybe a few inches of space to the rear wall). This couch is about 9' wide. There is also an hvac vent about 6" from the side wall in one of the corners (about 12" up from the floor). I want to put some corner bass traps but am wondering what exactly I can fit with the couch and the vent being there. I also need to place rear speakers somewhere around there (probably back wall). (I attached a pic of the approximate layout.)

So with that in mind, I can't exactly do a corner triangular trap (at least not full height). Also, the standard 24x24x34 that most people use may be too big here. Would I be better off putting in a smaller (thinner) trap or putting a panel like the MiniTrap between the hvac vent and the rear speaker?

There is also the option of putting something behind the couch. How effective would that be?

My room is 21'8' x 10'5" x 6'8"

Any chance you can rotate the setup so the speakers fire the longer way down the room? That will be much better acoustically, as explained here:

How to set up a room (http://www.realtraps.com/art_room-setup.htm)

I want to put some corner bass traps but am wondering what exactly I can fit with the couch and the vent being there. I also need to place rear speakers somewhere around there (probably back wall).

Both of those problems go away with the long orientation.

There is also the option of putting something behind the couch. How effective would that be?

The closer the wall is behind your head, the more important it is to treat that wall.

--Ethan

Thanks Ethan - I think my picture is misleading though. In the pic you're looking head-on at the couch by the rear wall. I'm attaching a better view of general layout. I'll try to take some pictures later so I can more effectively demonstrate what I mean. Basically the vent is almost directly beneath the rear right channel.

I also am having an issue as to where to put rear channel spakers but I don't have much choice due to size constraints. It'll probably end up being on the rear wall or in the corner at 45 degrees.

So assuming I have the back row almost directly at the wall, would you recommend I treat most of the wall? and in that case, what kind of treatment?

Thanks

The obvious solution is to pull the rear couch forward a bit if possible. This gives better sound and also lets you put the rear speakers behind the couch. But even then the wall behind is very close and needs to be treated. At that distance I suggest absorption over diffusion. The panels need to be at least three inches thick. If you can space them off the wall a few inches, all the better.

--Ethan

+1 to Ethan's advice. Also, don't forget the rest of the room...you've got reflection points on the side walls that you can treat with 4" broad band panels. That'll help a lot with low end control and with evening out decay times.

Definitely move that couch up from the back wall too...

Frank

Thanks for the replies - I'm sure I can get the couche forward a few inches. I am most likely going the OC 703 route for panels - would you recommend i treat the entire rear wall in 3-4" of the stuff? Also, would 3" spaced 1" away from wall be more effective than 4" attached directly or is it all about the same?
as far as side walls, I do intend to have panels at reflection points but didn't realize I need them that big - i was gonna make 2" panels or so. would a thicker panel have that much of an impact?
I have a fairly narrow room (11') so I'm trying to squeeze every inch in.. on the other hand i also have a VERY low ceiling (6'8") so that won't help the acoustics any

Do you recommend treating the front wall as heavily as rear ?

Thanks for the replies - I'm sure I can get the couche forward a few inches. I am most likely going the OC 703 route for panels - would you recommend i treat the entire rear wall in 3-4" of the stuff? Also, would 3" spaced 1" away from wall be more effective than 4" attached directly or is it all about the same?
as far as side walls, I do intend to have panels at reflection points but didn't realize I need them that big - i was gonna make 2" panels or so. would a thicker panel have that much of an impact?
I have a fairly narrow room (11') so I'm trying to squeeze every inch in.. on the other hand i also have a VERY low ceiling (6'8") so that won't help the acoustics any

Do you recommend treating the front wall as heavily as rear ?

You don't have to do the whole wall. A few panels side by side should be fine.

3" with 1" of airspace will perform better.

You have a long, narrow room...it's almost exactly twice as long as it is wide, and with the short ceiling you'll need as much broad band control as you can get. That said, if you absolutely can't spare the room 2" panels are better than nothing.

The front wall doesn't necessarily have to be treated as heavily as the rear, but it does have to be treated.

Frank

Thanks Frank, when you say "a few panels side by side," how big should the panels be? how much space by them, where to best locate them? I have to strike a nice balance between performance and aesthetics so it's important for me to know these things.

Also - is there any way to deaden the ceiling w/o panels? (some sort of paint or something?)

Thanks Frank, when you say "a few panels side by side," how big should the panels be? how much space by them, where to best locate them? I have to strike a nice balance between performance and aesthetics so it's important for me to know these things.

The panels are typically 2'x4'...they can be centered on the back wall with a few inches of space between them.

Also - is there any way to deaden the ceiling w/o panels? (some sort of paint or something?)

Acoustic tile to some degree. There's nothing like paint that will do it though.

Frank