RE: DIY HT build & acoustic treatment questions - AVS Forum
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Old 05-26-2013, 11:04 PM - Thread Starter
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Hi,

I am new to this forum. I am working on my first dedicated home theater in my basement. Here's some information on the room.

Room dimensions: L= 22.29' , W=14.56', H (to soffits) =8.73', H (to ceiling): 9.73'

Left & right soffits: 16.88' (L), 3.45' (W), 1' (H); right soffit houses HVAC ducts and plumbing.

Rear soffit: 15.23' (L), 5.42' (W), 2' (H); houses HVAC ducts.

Seating plan: 3 home theater reclining seats (I haven't decided on brand yet) in front row-directly on floor
3-seat sofa on a 108" x 72"x 7" riser

Floor: carpet except a small rectangular area (not sure of dimensions yet) at the double French door will have hardwood.

Screen: ~110 -115"; 6:9; painted

There will be a closet behind the screen wall.

Equipment:
TX-NR509 receiver
Projector: Epson 8350
DVD Player: Panasonic BDT-220
Energy RVSS bipolar surrounds
Energy A3+2 bipoles fronts
Energy center channel
1 subwoofer: Paradigm PDR12
AV cabinet will be behind the rear side door

I am planning to install RC-8 resilient channel, 5/8" and 1/2" drywall on the ceiling, front, left and rear walls. Exterior wall with windows will have double drywall but no RC-8.

I plan to put 2 Billy book cases (IKEA) on the rear wall either side of the door and fill with books to serve as diffusors.

Questions:
1. I plan to build bass traps in the left soffit and possibly the rear soffit (close to double French door). I have read several threads on bass traps but am still unclear on the actual
construction within the soffit. Please provide a detailed description (include pictures/sketch) on how you built your bass traps. Will 2 ports on the bottom and side of the bass trap close to the tri corner be effective as apposed to doing a fabric covering (e.g., GOM) on the entire bottom?

2. Do I need to install RC-8 on a soffit that will be used as a bass trap?

3. The 3 windows will be covered with wood blinds and velour curtains. I would like to build 2 columns between the windows and have sconces mounted on them. There will be matching
columns on the opposite wall. Any suggestions on column depth considering the curtains will be touching or close to them?

4. Riser (7" high) will double as a bass absorber with ports in each joist bay. Will R13 insulation be okay for this purpose?

5. Acoustic treatments for primary reflections points:
1" OC 703 on fabric wrapped frames. Will this suffice or do I need to do some intricate calculations before deciding on these treatments?

I want to complete the project this summer and would appreciate any advice you can provide.






Thanks,
Allan
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Old 05-27-2013, 03:24 AM
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You might want to consider this

Peter the Greek

Downunder Theatre MkII
Redefining snail pace construction
"what is worth knowing is difficult to learn"

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Old 05-27-2013, 10:07 AM
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The layout service isn't a bad idea, but we can give you some direction on most of these details.

1. I can't give you a schematic for soffit traps, but I can tell you this: enclosed air spaces tend to resonate. The more open the structure the more broadband its effect.

2. If the soffit is suspended from decoupled structures, no further decoupling is needed. Be careful about the weight ratings and clip spacing, if that's what you do.

3. I think you'll find this is an entirely personal aesthetic choice, as long as they match visually. Have you looked at the show-me thread?

4. ? wink.gif

5. R13 should be fine, R19 might be better.

6. Generally if reflection absorption is warranted, more depth is appropriate. Two inches spaced two inches off the wall is probably the most effective, IMO.
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Old 05-27-2013, 10:50 AM
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The 7" riser sounds too low to me - but maybe the seating height on the couch in the second row makes it enough - might want to validate using the riser height calculator sticky, if you haven't already.
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Old 05-27-2013, 11:43 AM - Thread Starter
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Thanks. I will seriously consider it if I have to.

Allan
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Old 05-27-2013, 12:03 PM - Thread Starter
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Quote:
Originally Posted by HopefulFred View Post

The layout service isn't a bad idea, but we can give you some direction on most of these details.

1. I can't give you a schematic for soffit traps, but I can tell you this: enclosed air spaces tend to resonate. The more open the structure the more broadband its effect.

Will it still resonate if stuffed with R30?

2. If the soffit is suspended from decoupled structures, no further decoupling is needed. Be careful about the weight ratings and clip spacing, if that's what you do.

The soffit is not decoupled. I know this is not ideal but was considering nailing OSB on joist and wall within soffit and then building the bass trap within using 3/4" MDF.

3. I think you'll find this is an entirely personal aesthetic choice, as long as they match visually. Have you looked at the show-me thread?
I will take a look at the thread.

4. ? wink.gif I edited the thread after positing but forgot how to count!

5. R13 should be fine, R19 might be better. Will consider

6. Generally if reflection absorption is warranted, more depth is appropriate. Two inches spaced two inches off the wall is probably the most effective, IMO.


Allan
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Old 05-27-2013, 12:12 PM - Thread Starter
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Will do. thanks
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Old 05-27-2013, 02:54 PM - Thread Starter
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Quote:
Originally Posted by Brad Horstkotte View Post

The 7" riser sounds too low to me - but maybe the seating height on the couch in the second row makes it enough - might want to validate using the riser height calculator sticky, if you haven't already.

Will do. thanks
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Old 05-27-2013, 05:28 PM
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You don't want resilient channel. You want to use sound isolation clips and 25 gauge hat channel.

If clips aren't in your budget, save yourself the hassle and just attach the drywall to the joists.

Yes, there is some scientific reasoning professed by some people smarter than me as to why RC is bad. I can't give you the scientific explanation; I've just been around long enough to hear them say it over and over..

Tim
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Old 05-27-2013, 07:06 PM
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If you are decoupling the drywall - through whatever means - don't skip the soffits and couple them back to the rest of the building. If the soffit structure needs to be coupled to support the weight, then you need to think it through. I'm not sure there will be a worthwhile way to decouple the soffit sheathing (drywall) and still use it as a bass trap.
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Old 05-27-2013, 07:37 PM - Thread Starter
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Quote:
Originally Posted by Mr.Tim View Post

You don't want resilient channel. You want to use sound isolation clips and 25 gauge hat channel.

If clips aren't in your budget, save yourself the hassle and just attach the drywall to the joists.

Yes, there is some scientific reasoning professed by some people smarter than me as to why RC is bad. I can't give you the scientific explanation; I've just been around long enough to hear them say it over and over..

Tim

Tim,

I did some research on decoupling before deciding on RC-8 but didn't come across any negative reviews on AVS and elsewhere. Too late to return it anyway.

Allan
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Old 05-27-2013, 07:49 PM - Thread Starter
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Quote:
Originally Posted by HopefulFred View Post

If you are decoupling the drywall - through whatever means - don't skip the soffits and couple them back to the rest of the building. If the soffit structure needs to be coupled to support the weight, then you need to think it through. I'm not sure there will be a worthwhile way to decouple the soffit sheathing (drywall) and still use it as a bass trap.

I was concerned about the weight and so I decided not to decouple with clips.
Thanks. Allan
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Old 05-28-2013, 03:34 AM
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Quote:
Originally Posted by AP675 View Post

Tim,

I did some research on decoupling before deciding on RC-8 but didn't come across any negative reviews on AVS and elsewhere. Too late to return it anyway.

Allan

Something here, and here, another here. There's a lot more, I just picked out the first few.

I'm not trying to make you feel bad, just trying to avoid a big mistake before you even get going. If you are going to couple the soffits it is doubly ineffective. Too bad you can't return it.

Tim
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