Just wondering if my movie room is 13.5 x 18.5 x 7.5
is there really a big difference with the rear channel given I will be using the QS8's for side rears ?

Troy, it depends not on room size alone, but on the amount of room behind the listening position for a rear sound field to develop. I suggest that at least 4' be available to make 7.1 back surrounds useful.

My room is a little bigger, with cathedral ceiling. I was relatively unimpressed by adding the rear speakers. In retrospect, I'd probably have been happier with 5.2 than with 7.1.

For me I went 7.1 (will be 7.2 if I ever build my second sub - have all of the electronics for it), but that was really mainly because I had 2 rows of seats and I wanted the larger surround sound-field to envelop both rows of seats. If I didn't have a 2nd row I would probably have just stuck with 5.1 (or 5.2).

For reference, my room is 14' wide, 24' deep (but with a 2 foot deep false wall up front) and 7'9" tall.

I WAS at 5.1 until I sold my house. When the reno's are complete I'd like to build a couple of subs and add a couple of extra surrounds.

Adrian!!

Yeah, nice to see you, Adrian. Now when is Dean coming back?

Neat timing for this conversation.
My room is 16'2 by 22' with ceilings starting at 8 going to 12.

The 22' wall is the viewing wall. Viewing is at 11' from it with 5'2" to the rear wall.

I am finalizing location for the rear surrounds and unless I come across some really bad angles and where I can place them, going 7.1.

Later on I will probably go to .2 . Going 7.1 already is over budget as I had budgeted for 5.1 initially.

Mark, you appear to have enough room behind the listening position to make back surrounds in a 7.1 channel system worthwhile. They should be mounted about 3' above ear level and separated about as much as the distance from the listening position, say about 6'.

Incidentally, on a point of terminology, if by ".2" you mean two subs, that remains .1 with two subs in the .1 LFE channel. The numbering(e.g., 5.1, 7.1)refers to the number of channels, not the number of speakers. There are no .2 channels formats, and a 5.1 system with two or four subs is still 5.1, not 5.2 or 5.4.

yes by .2 I was referring to a 2nd sub.

Here's a Q. For rear surrounds, what I have planned is left surround at 132* (recommendation is 135-150*). I can not increase this angle.
The right, to keep some symmetry on the back wall, is planned at 146*

Thoughts on that?

Also as far as height, I am planning on the sides to be the same elevation as the rears. Planning on QS8s for those positions, and not sure how much clearance is desired to the ceiling.

Currently I have the bottoms of the sides and rears at 95 1/2 " (just shy of 8 ft). that places them roughly 49 1/2" above listening level.

On the sides that allows the tops of the speakers to clear the
the ceiling by 27 1/2 ".

I can not lower the sides, I can raise them though if desireable.

Keeping the sides and rears bottoms level, the rear tops of the speakers have clearance to the ceiling of roughly 41 1/2".

Thoughts?

Other Facts: The sides are at 90*. I could if needed increase this slightly.

The front mains are at 14* each. I can not change that. I know 22-30* is desired.