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I'm trying to optimize acoustics of my future home theater by maximizing dimensions to minimize standing wave problems. I would like to minimize the thickness of a finished wall consisting of drywall mounted on a basement concrete wall.

I know there are differing thicknesses of drywall, but I'd like to know a range. My understanding is that typically two by fours are used for the framing.

From what I saw in my cursory web searching was that they are mounted on concrete walls sometimes with the shorter two-inch section protruding perpendicular from the concrete rather than the typical free-standing orientation where the longer dimension (3.5") is perpendicular to the wall surface.

In the image below, the top section along the HVAC wall shows the shallower orientation, and the section below that shows the deeper orientation.

enter image description here

Is my understanding correct that the shallower orientation would measure 1 1/2" plus the thickness of the drywall (3/8" or 1/2")?

Is there any drawback to maximizing interior dimensions by mounting the two by fours this way other than it likely disallowing room for running electrical and other wiring?

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  • The thickness is entirely an artifact of how the wall is built, which is largely based on the insulation amount and type used, which is based on the climate conditions. If you have an existing wall, and want to know how it was built, you'll have to look somehow (eg, cut a hole). If you are building new, you must start with the insulation required and type of insulation you'll be using and work backwards from there.
    – gregmac
    Aug 11, 2014 at 18:32
  • @gregmac This is for new basement construction planning; I'm not looking to measure existing dimensions. Sorry for the ambiguity! See my edits.
    – glenviewjeff
    Aug 11, 2014 at 18:32
  • The best thing you can do to minimize standing waves is to build the walls NOT square and/or parallel to each other. Even a little will help, a significant amount will help more. Consider the shape of a good old-fashioned theater - much wider at the back than the front. Make the walls not flat and it helps even more....(comment rather than answer since it addresses your problem, not your question.)
    – Ecnerwal
    Aug 11, 2014 at 20:17
  • @ecnerwal see my related physics question: physics.stackexchange.com/q/129942/12886. I'd read about angled walls, which I also plan to do via the ceiling and floor. I've also read room volume is important, hence maximizing interior dimensions. Especially that 2,500 cu ft should be minimum volume. I'm at around 2,200 if using standard 5" thick walls.
    – glenviewjeff
    Aug 11, 2014 at 21:02

2 Answers 2

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When the construction is non-structural, then 1x furring strips can be used to attach the gypsum board. However, for a home theater, prioritizing acoustical performance may make more sense than prioritizing an inch or two of additional floor area - particularly given that furniture/equipment selection and arrangement is more directly related functional floor area.

This is to say that selection of construction systems that minimize the transmission of airborne and structural sound may be worth more than going from 14'-8" to 14'-10" in room width. What matters is how the space is allocated to provide better function.

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  • Well, the purpose of optimizing room size is actually to do what I can to improve acoustics by minimize standing waves. If you know better, please let me know. I'm not at all concerned about sound transmission through the concrete foundation. It would buy four inches in one dimension plus two inches in the other dimension since three sides are concrete. Additionally, I could probably even get the fourth wall slimmed down as well. There will also be internal acoustical treatments as needed.
    – glenviewjeff
    Aug 11, 2014 at 19:40
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    The more sound energy the walls absorb, the less they reflect. The less they reflect the less issues with standing waves. The less of a flat plane the walls are the less issue as well.
    – user23752
    Aug 11, 2014 at 22:14
  • Per @ben rudgers: use furring strips and 1/4" drywall.
    – Jimmy Fix-it
    Aug 12, 2014 at 3:47
  • @JimmyFix-it, Those are not my recommendations for acoustic performance. In addition, 1/4" gypsum board is highly unlikely to provide the basis for a quality finish in terms of aesthetics.
    – user23752
    Aug 12, 2014 at 13:58
  • @glenviewjeff As a rule of thumb, light gauge metal framing will provide better acoustical performance than wood, and multiple/thicker layers of gypsum board will provide better acoustical performance than single/thinner layers because of increased mass. concrete wall -> airspace -> free-stading metal stud partition with acoustical batts-> resilient channels -> multiple layers gypsum -> acoustical treatment might be preferred. See page 12: usg.com/content/dam/USG_Marketing_Communications/united_states/…
    – user23752
    Aug 12, 2014 at 14:04
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The short answer is maybe.

When it comes to home improvement some people do very strange things.

If you must be sure (you don't mention what you intend to do with this information which would be helpful) your best bet is to find a corner, maybe in a closet if there is one, and cut a small section of the sheet rock out, check it and patch.

---- Edit Below ----

No there is nothing to stop you from mounting items this way apart from, as you mentioned, being able to run electrical and plumbing behind the wall. That said, these studs will not be load bearing (other than the weight of the drywall) so you could leave a 4" (arbitrarily chosen length) gap in the studs and run wire through it. So basically cut all the studs in two and leave a gap between the pieces for running wiring.

If you do plan to run electrical make sure your junction boxes will fit between the wall and the sheet rock.

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  • This is for new basement construction planning; I'm not looking to measure existing dimensions. Sorry for the ambiguity! See my edits.
    – glenviewjeff
    Aug 11, 2014 at 18:32
  • Ah ok that makes things a little easier.
    – James
    Aug 11, 2014 at 18:36

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