In-Wall/Ceiling 7.1 Construction

[Sledge]

Hey guys, I'm new to the forums but have been following the website and the YouTube channel for quite a while.
I recently purchased a home, and decided to do a 7.1 system setup for the main living room and I have a few questions I need to sort out. Since I will be adding a dedicated media room later on, the living room setup will be a in-wall/ceiling design. After listening to a number of systems, I found I preferred the sound of the Martin Logan Edge and Electromotion R speakers paired with a Marantz Receiver (I will likely go with the SR7009's replacement when HDCP 2.2 and DTS:X come out).

First, since I don't have the luxury of moving these speakers around after they get hooked up, I want to get the math right before hand to give me the best shot at having the proper setup. I decided to base my placements on having a minimum of 2' between the center-line of any speaker and the wall (the Left, Surround Left, and both Surround Rears adhere to this constraint). I was going to insert some CAD drawings of the room, but was unable to post any pictures or links until I reach my 10th post. If anyone wants them I assume I can PM them the links.


For Reference:
The size of the room is 524.6 Sq-Ft
The volume is 4721.1 Cu-Ft


Since this is a remodel, and the wall the TV and Edge speakers are mounted to a wall shared by the Master bedroom, I have decided to insulate and sound-deaden that wall (on the far right of the photo above). Since the existing wall is already insulated (and likely load-bearing), I am just going to add another 2x4 wall in front of it. I plan on putting foam board all over the existing wall, and then building the new wall as stiff as possible right in front of the other, but not touching it at any point in hopes of minimizing any sound transfer into the bedroom wall.

Here are my questions so far:

Considering that I am building the wall from scratch, are there any other things I should do prior to mounting the speakers? Should I build a box around the speakers in the wall?

Is the 2' distance between the speakers and the wall sufficient, or should I increase the distance and recompute?

With the cable runs for the rear speakers being close to 35', what gauge speaker wire should I run? Any recommended brands? I fell for all that Monster Cable crap when I was younger, so I just want something cheap and good.

Anything else I should be considering?

 

[rojo]

Firstly, let me point out that in-wall speaker responses are going to be largely unpredictable. Drywall is not as inert as MDF, and will resonate and color the sound. The way you heard the speakers in a showroom will probably be different from how they sound in your room. Additionally, the inability to toe in your speakers could leave you without a sweet spot. Your speakers will make lovely noises, but there might not be a sound stage or any accurate imaging to speak of. You should consider bracket or threaded wall mounts and bookshelfs for your front stage LCR -- the Ascend Sierra 2 for example. In-wall / in-ceiling would still be great for surrounds, though.

If you're still set on the ML in-walls for your front stage, then yes, I think building sealed back-box enclosures for them with some foam absorption will help both with bass extension and with isolating the sound from adjacent rooms. Further reading on the matter.

For wire, go with Monoprice 12AWG OFC speaker wire. More on speaker wire gauges.

 

[Sledge]

Firstly, let me point out that in-wall speaker responses are going to be largely unpredictable. Drywall is not as inert as MDF, and will resonate and color the sound. The way you heard the speakers in a showroom will probably be different from how they sound in your room. Additionally, the inability to toe in your speakers could leave you without a sweet spot. Your speakers will make lovely noises, but there might not be a sound stage or any accurate imaging to speak of.

Unfortunately, my wife prefers credenzas over crescendos, so the Living room system needs to be concealed (even the TV is going to be flush mount). I almost sold her on the ESL's, but she backed out when I told here they needed to be a few feet from the wall. Either way, the speakers have already been ordered, so this is what I got.

As far as the construction, I can build the wall however I want. I could likely make a box out of fiberboard in the wall, leaving only enough drywall on the sides for the wall-mount legs to attach the speaker firmly, then line the inside of the box with foam board. I've also noticed that the Edge speakers have a tweeter that can be removed and rotated without tools, for mounting either horizontally or vertically. I might experiment with shimming the tweeter mounts to point more centrally towards the room, it might help with the more directional higher frequencies. The speakers are going to be over 17' from the ideal listening position, so I will not need much of an angle.