I didn't know exactly where to put this post, but thought I'd start here. I am currently attempting to install RBH MC-616's in-walls across the front of my room. I will be installing a Mitsubishi HD1000U projector very soon, and going with a DIY laminate screen somewhere between 92 and 106", with a viewing distance of about 12 feet. I planned for in-walls from the start, and so pre-wired for them. I've run into a problem after cutting into my drywall ; seems my helpers I had assisting with my boarding got a bit overzealous and put a 2X4 backing piece for drywall (obviously when I wasn't looking!) in the exact spot my left channel is/was to be going. Faced with this, I had even briefly considered sending back the 616's in favour of the smaller 414's to fit this opening, but have decided against doing so.
Now I see that I have 2 options with the 616's. Regardless of which route I go, I will mount my centre channel horizontally below the screen. First, I can attempt to cut through the offending stud and remove it, and hope to not damage the drywall and corner joint (on the wall adjoining the fireplace) too badly. This would allow me to keep my L/R channels at the same placement I originally intended, oriented vertically. The L/R speakers would be about 8-1/2 feet, tweeter to tweeter, and the tweeter height would be about 38" (I'm short, so pretty close to ear level when sunk into my couch).
Alternatively I could patch up the hole I've cut, and mount the speakers all horizontally underneath the screen position. I have 96" (with 24" centres between my front studs to do so) which would put the L/C/R tweeters a little over 3 feet apart. The distance between the tweeters from the left channel to the right would then be about 6-1/2 feet. The height of the tweeters would then be only about 22", and would all have to be swiveled up.
BTW, I see this latter option as being the least amount of work, and a bit less risky as my demo skills aren't stellar. Would mounting the speakers closer together (and lower) like this result in a dramatic difference in my sound field?
Here's a picture
of the front of the room. Where the speakers sit on the floor in the photo is very close to where they would be, horizontally, if I went with option 2. Might there even be some merit in orienting all three speakers the same way, and having them at the same height?
The wall is currently insulated with flexibat, and I was planning on just putting 1/2" rigid foam between the speaker and back of the wall after I cut the insulation out. Would there be benefit in doing this to prevent bleed through into the adjoining room? And what about building enclosures, say out of MDF... more trouble than it would be worth?