Basement Theater

Hi my name is Dan and I am new to the forum. I am currently is the design faze of my basement home theater. I have read a few threads on how the size of the room affects the sound. The space I have available is 13'-9" x 26' (Max), with poured concrete walls. From the floor it the joists is 93 1/2", there is HVAC running also so the ceiling will be lower at some points.
What would be the best dimensions for my room?

My equipment is as follows:
Sony SXRD LCD Projection (Will be replaced by a projector)
Onkyo TX-NR801
Sony 400 DVD Disc Upconvert
4 Paradigm Studio 60 V.3
Paradigm Studio CC-570 V.3
2 Paradigm Studio 40 V.3
2 Paradigm Subs PW-220 V.3

I just want one seating area not any thing special.

Thank you for you advice!

[bpape]

How many seats are you trying to accomodate? Is this going to be a dedicated space or will it also potentially have other things in it like a bar, etc? Are you going to be able to close off the space completely?

Bryan

I will put one couch there. This will be a dedicated room, closed off completely. The basement is in an "L" shape and I will frame this room separate from the other rooms.

[Sonnie]

This was posted in another thread here...

Height Width Length
1 1.28 1.54
1 1.26 1.59
1 1.4 1.9
1 1.6 2.33


Of the above ratios, it appears to me that 1 X 1.28 X 1.54 has the best LF room response, but the others should fair well too.

You are 7'-9" x 13'-9" x 26'

With your height it would be hard to get to any of those ratios, but I don't think I'd give up any width... maybe some depth with an equipment wall with rear access. Then treat it with traps and panels.

I know I will loose a some width with framing and drywall. The height will shrink with the carpet and pad.

[Sonnie]

I probably wouldn't frame a full 2 x 4 depth on the walls unless you just have to. I'd probably rip them in half and frame thin. I assume you are framing the walls for wiring.

[basementjack]

Hey Dan, you might want to check out the software CARA. (www.cara.de)

It lets you plot out rooms, add furniture sofits etc.. and it will map out what the frequncy response will be, early reflections, RT-60 etc...

Also be sure to take advantage of common theater features by stuffing them with insulation - rasied platforms, stages, sofits, and columns are all great places you can put insulation - which will help with the low frequencies.

depending on your budget you might want to plan the decor around the acoustic panels you'll use inside the room - ie I've seen nice wood trimmed panels with columns etc.. nice looking, and functional.

[bpape]

Sorry - but I'd build full 2x4 walls. Having that depth allows easier running of wiring without weakening the structure and also allows the use of full R-13 insulation for both sound and warmth issues. If you go thinner, you'll compromise both by having to compress the insulation.

Don't get too hung up about perfect dimensions. The idea is to stay away from particularly bad ones. Even rooms with 'perfect' ratios still have the same modal problems - they're just not on top of each other. Personally, I'll take as much space as I can get.

Bryan

[basementjack]

As for the studs - I live in Chicago, I did 2x4's and left a 1 inch gap between the wall and foundation.

Interesting to note that depending on where you live, different approaches have different values - I'm sure Alabama is a bit warmer than Ohio so ripped 2x4's might make sense there.

DanM, are you going to do this work yourself?

I did my basement and have more than a few thoughts to share...

First of all, home depot sells little riser boards - they are like 3/4 inch chipboard with a plastic button matrix underneeth. I wish I would have put these down - They'd not only make the floor warmer, but they are a life saver if you ever get any seepage, or your sump pump stops. (Mine did, and $2500 worth of new carpet had to be replaced)

Also on your walls, when it's time to do drywall, if water is a concern, you don't want it going all the way down to the floor - it will suck water 4 feet up into your walls if it ever touches - instead leave as much of a gap as possible.

Where sound control is a concern, staggered studs are the way to go - this involves using a 2x6 on top and bottom, and 2x4's for uprights - every other upright is aligned with the front, then back of the 2x6.
This prevents vibration from traveling through, is easy to do, doesn't require anything special etc..

[Sonnie]

Well my thoughts were that in a basement you usually don't have wall insulation issues, at least I wouldn't think you would. Maybe Ohio is a lot different Our basement walls are concrete block and its stays comfy all year long. If I were building in ours (which is too small, so I never would) I'd only be worried about the sound insulation for the ceiling... nothing but dirt on the other side of the walls... Then for sound treatment I'd look at treating the walls with panels or maybe even some partial carpet. However, I'm not pro at it... that is for sure.

[bpape]

Yeah - understand the thinking. The thing is that any sound that gets through the wall is going to go right up through the floor in the space between your wall and the concrete wall. This is what's known as flanking. Sound will find any path to move. The deeper the cavity (and more insulated) between the drywall and the concrete, the lower the resonant frequency of that cavity (and usually less often excited) - so there is less 'boom boom boom' heard upstairs. If there is space, the normal optimal recommendation is at least 12" from the back side of the studs to the concrete wall. In my room, I have 16" on the thinnest one.

All depends on the space you have to work with.

Bryan

Thank you to everyone for the input.
I'm going to have the basement professionally finished in fazes. I will have the studs put in first and I will insulate and wire it myself. I had planed on insulating the walls for acoustical and temperature comfort reasons.
Is there a better insulation to use for acoustics that is easy to find? Should I use a different insulation in the ceiling than in the walls to prevent the sound from shaking the house?

Thanks again!

[basementjack]

Are you planning a drop ceiling or drywall?

is the theater going to be an isolated room or is it going to be one big open basement?

[bpape]

Well, for a combination of heat insulation and acoustics, using an R-19 in a 3.5" cavity is going to reduce the thermal efficiency. So, that leaves an R-13. The other option, though more expensive, is to use mineral wool (2.5lb or denser) in the cavities. This is labor intensive and more expensive but just as good if not better thermally and better for lower frequency isolation in this application.

Using a 4" mineral wool in a 3.5" deep cavity is OK if you just strap on the backside of the wall with something that will give to allow the wool to stay at 4".

Good luck.

Bryan