Acoustics Inquiry

THREAD : Acoustics Install question
Started at 01-07-07 09:21 PM by karrman
Visit at http://www.avsforum.com/avs-vb/showthread.php?t=782927
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[Post 1]
Author : karrman
Date : 01-07-07 09:21 PM
Title : Acoustics Install question

I'm a new guy and am building an HT in my basement.

I know to install one of the following in my HT for better acoustics:
Owens Corning Select Sound Black Acoustic Board
Owens Corning Fiberglas 703 Series duct insulation.
Johns Manville Insul-Shield
Johns Manville Linacoustic Permacoate rolls.
Certainteed Certpro Acoustaboard Black
Knauf Duct board EI-475
Knauf Duct liner EM

My Question: Do I install these first and then put drywall over them?

My other question: If the above answer is yes, do I just move the electrical boxes out a little farther so that outlets/swtiches/etc. will install correctly?

Thanks.

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[Post 2]
Author : ecrabb
Date : 01-07-07 10:41 PM

I think this forum really needs a DIY theater-building FAQ for beginners... something to outline all the options, rough guidelines for performance goals and what it will cost to achieve (rough figures, or scale factors, i.e. 2x, 3x, etc.)

That said, you really need to skim over the Acoustical Treatments Master Thread sticky at the top of the forum to familiarize yourself with those products and the general concepts of sound treatment and isolation. The materials are too expensive and your time is too valuable to tear stuff out because you didn't understand the application.

To answer your question, though - no, you put the drywall on, and put a material like OC703 over the drywall and cover it with fabric to reduce reflections in the room. It deadens the room, or makes it less "lively". That's the "room treatment" part of the equation. Then, there's the isolation or transmission part of the equation that deals with sounding entering and leaving the room. To answer the other part of your equation, depending on the depth of your drywall and wall treatments, you need to either leave more box hanging out, or more likely add extensions to the boxes.

Start doing some reading... lots of reading.

SC

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[Post 3]
Author : Tboy555
Date : 01-07-07 11:06 PM

Well is there another option thatn reading that hUGE thread? Kind of a down a dirty so people can get the high/lows and then decide what they need to do, the research that option.

I know I've been looking at the thread and meaning to get started.
Tboy

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[Post 4]
Author : ecrabb
Date : 01-08-07 01:42 AM

I understand your desire, but it's a little like asking if there's a down and dirty on nuclear physics. I'm exaggerating, but there are so many options and levels of performance (and cost), it's hard to put it in a nutshell.

For isolation, there's everything from nothing, to double-drywall, double-drywall with green glue, triple-drywall with green glue and RSIC clips on staggered studs - full-on "room within a room" construction. If you go that far, then you can start talking about special doors with seals, you can go to great lengths to specially design or treat HVAC supplies and returns, etc.

For room treatment, you can hang wood-framed fabric-covered OC703 panels at the first reflection points, to full Linacoustic/batt treatment, to soffits that fuction as bass-traps.

Perhaps you should each start your own threads with some specific questions and some basic info such as room size, rough budget for room and equipment and the goals you hope to achieve; i.e. "I'd like to watch a movie at reasonable volumes in the basement while my kids are asleep on the second story and my budget is $10,000 for the room" or "I'd like to listen at reference levels and my budget is $50,000 for the room".

Anybody know if the home theater ebook delves into much detail on room construction as it relates to isolation and treatment?

SC

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[Post 5]
Author : karrman
Date : 01-08-07 08:02 AM
Title : Agreed

It would be nice to have a thread devoted to beginners . . . as I spent quite a bit of time reading and just didn't find the answer to the above without asking--so thank you.

It would be nice to know if the book you mention covers more about room construction and design.

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[Post 6]
Author : bpape
Date : 01-08-07 08:35 AM

Want the basics?

Sound travels through air and structure - deal with both. Seal the room and don't let the inner room contact solidly with the outer one - many methods to do this - see master thread. Isolation like this is as or more important to keep sound from getting in as it is to keep sound from getting out. Physical separation and mass are your friends.

Inside the room, know your enviornment. Know what will be in there and how it affects the decay time at different frequencies. Shoot for a balanced ending decay time across the spectrum by adding appropriate materials in appropriate amounts in the room. Deal with bass control issues and reflection points specifically as well as the front wall. After that, it's a matter of getting the right amount of the right material spread throughout the space to get the decay times within the target ranges.

People and furniture are great absorbers - don't forget to account for them in your calcs.

Plan, plan, plan. Don't waste all your work with isolation by cutting tons of holes in the room for lights and outlets. Plan for them to be boxed in and entries into the room to a minimum.

Know what you want to use the room for! If it's all 5 channel listening vs 50/50 2 channel music and HT, the design goals are a bit different.

Wish I could be more specific but everything really depends on your situation, your room, your goals, etc.

Bryan

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[Post 7]
Author : Logic_BomB
Date : 01-08-07 10:56 AM

Although a beginners thread for home theater construction would be awesome, there is definitely value to reading as much as possible. Seems like every thread (even the redundant ones that you think you have a handle on) gives you at least another small tidbit you can add to your vocabulary.

I don't even have the house I plan to build a HT in and I'm starting to make notes on riser construction, room isolation, materials, etc. Reading SandmanX's bohemoth of a thread took time but was probably the most information in 1 place that I've found thus far which is awesome. Haven't got the chance to look at many other construction threads but you can be guaranteed that everyone's theater from large to small will have something new to learn from.

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[Post 8]
Author : Ethan Winer
Date : 01-08-07 02:22 PM

[QUOTE=Tboy555]is there another option thatn reading that hUGE thread?[/QUOTE]

Yes, look here:

www.ethanwiner.com/acoustics.html

--Ethan