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Posted by on October 12, 2007, 12:55 pm
> On Oct 11, 8:10 pm, sargon19552...@yahoo.com wrote:
>
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>
> > > On Oct 11, 4:00 pm, sargon19552...@yahoo.com wrote:
>
> > > > I want to stiffen an interior wall in which I plan to install
> > > > subwoofers for a home theater. I would like advice on the best way to
> > > > do it.
>
> > > As Rico mention, adding significant out of plane stiffness to a
> > > timber framed wall means adding depth (thickness) to the wall.
>
> > > Without increasing wall depth (thickenss) you could opne up one side
> > > & sister heavy steel channels to the 3.5" dimension of the studs. An
> > > expensive & labor intensive effort
>
> > > Alternatively you could open up the wall on both sides and sheath
> > > both sides with plywood; glue & staple, creating a very stiff plate
> > > structure.
>
> > > when you say stiffen...how much do you desire to increase the
> > > stifness? +50%? 2x? 5x?
>
> > > cheers
> > > Bob
>
> > Hi Bob,
>
> > I should have stated that the wall in question is still under
> > construction (no drywall up yet), so I can modify as I wish. It's 3
> > feet in front of an exterior wall. The idea is to effectively make an
> > enormous speaker enclosure (infinite baffle). I want to stiffen the
> > wall so that the force of the subwoofers (a pair of panels with 4 15"
> > woofers each) doesn't make the wall move. I'm not sure how much
> > stiffer it needs to be. Could I add, say, unistrut to the studs
> > ( think that's what jloomis was talking about)? Or how about putting
> > pairs of scissors trusses between the wall and the exterior wall where
> > the subwoofer panels are? The exterior wall is stucco on the outside,
> > and half of it has shear wall panels.
>
> This is the operative phrase.
>
> >>>I'm not sure how much stiffer it needs to be. <<<<<
>
> If you don't know how much stiffer it needs to be, how can you
> determine how to make it stiffer?
>
> Your exterior walls & shear walls are primarily for gravity load &
> lateral (in plane) loads. They really are not for out of plane
> loading (except wind).
>
> A 2x8 wall (out of plane) is about 10x stiffer than a 2x4 wall. Will
> the new wall have any cutouts or penetrations?
>
> With out knowing how you want this thing to perform, we're all just
> guessing.
>
> The ceiling diaphragm needs to be plywood against the ceiling joists &
> then drywall covering it. Just stiffening the wall without
> considering the overall load path is going to get you into trouble.
>
> What does the speaker mfr suggest?
>
> I'd mount the speakers ASAP & give them a test drive before the wall
> is finished / finalized......a lot easier to make changes before
> everything is finsihed.
>
> cheers
> Bob- Hide quoted text -
>
> - Show quoted text -
There are no specific listed requirements for the speaker drivers.
They're actually designed for car audio, so the assumption is they
would go into something like a trunk panel. What I plan to do is
mount the drivers on a panel (4 to a panel) made of a triple layer of
3/4" plywood and MDF, then screw the panel into the studs over a
cutout of the drywall. Based on what you said about a 2 x 8 wall
being 10x stiffer than a 2 x 4 wall (10x stiffer sounds adequate), it
sounds like the best approach will be to add extra wood so that it
effectively doubles or triples the thickness of the studs.
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