Steve Cook

7.1 Speaker Placement on Back Wall

I'm converting my cellar into a home cinema. The room is 6m20cm (20') long by 2m70cm (9') wide, by c. 2m10cm (7') high. Plan is to have the screen filling the shorter wall.

There is a window behind the back wall limiting speaker placement.

I have a Sony STR-DB795 Reciever delivering 7 x 100W together with an older Sony DVD player. I plan to buy an Optoma HD70 projector and KEF KHT 1005 / HTS1001 speakers. (Later on upgrading the other components)

I want some advice regarding best placement for the rear speakers as I need to put the cable runs in before the suspended ceiling is added (to cover loads of pipes).

We plan to watch mainly from a sofa, placed against the back wall. On the left hand-side is an alcove, preventing the placement of a speaker on the "wall".

Is it OK to put all four speakers in a line along the back wall? If so where do I put them?

Due to the window I'll probably need to put the speakers at ceiling level.

Any advice is appreciated.

Thanks

Steve

SethH

Re: 7.1 Speaker Placement on Back Wall

If possible I would suggest moving the seating out from the back wall by a few feet. I would then try to place the side speakers directly to the sides of the primary seating area on the walls about 2 feet above head-level (when seated). Ideally you would then place the back speakers on the back wall -- if that's not possible then you might consider using in-ceiling speakers or speakers on the floor pointed up behind the couch.

LanceJ

Re: 7.1 Speaker Placement on Back Wall

The 7.1 channel system was designed for rooms where the rear surround channels (in a 5.1 system) would have to be placed so far apart that a sonic "hole" would be created behind the listener's head. So to remedy that, an electronic system was designed to artificially generate two extra "back" surround channel signals, and via two loudspeakers placed behind the listening position, those signals would then fill up that hole.

So in this situation - a 20ft X 9ft room with the screen on the 9ft wall - personally I think a 5.1 system is plenty.

And I totally agree with Seth: DON'T place your couch directly against the back wall.

The whole point of a surround sound system is just that, to surround you with sound and IMO placing your ears even with the rear channels will prevent that. I've played around with this configuration myself & know that it is definitely lacking compared to having the rear channels behind (and to the side of course) of my couch. Actually, I'm stuck with this side-of-my-head configuration right now because due to WAF issues, I had to move my HT system to my "mancave" after using it in the living room the proper way for three years.

LanceJ

Re: 7.1 Speaker Placement on Back Wall

BTW: if this is the system you're looking at Steve, for a room of that size IMO that KEF system is too small. Satellites using drivers only 3" in diameter like those KEFs may still generate decently loud listening levels, but will sound strained doing so & will also probably sound on the thin side. Same with the sub (an 8" driver just cannot produce much impact in a room that size, and I'm not even into the fridge-size subs some members own).

Steve Cook

Re: 7.1 Speaker Placement on Back Wall

OK - I'm convinced, the sofa may "live" against the back wall - but when watching movies I'll pull it forward. This will allow me to mount the surround speakers on the wall. Is it possible that they are a little forward of the listening position?

If the KEF KHT 1005 is too small what would you recommend to fill the room. I live in Germany so don't worry about exact prices - I can easily research that, but I have allocated most of my budget to the project so am looking to spend that sort of money.

For speaker cable what is better a cheaper 4mm² or relatively more expensive 2.5mm² giving the same total cost?

Thanks for all your help.

LanceJ

Re: 7.1 Speaker Placement on Back Wall

Surround speakers ahead of the listening position?

For a room that size, I think KEF makes a similar system with their traditional 5" coaxial driver and I would feel better with that.

Based on my own experiments & reading professionals' opinions on this issue, personally I think a satellite with at least a single 6.5" woofer is needed to properly & smoothly blend with a subwoofer at the typical 80Hz crossover frequency. And worse, with most smaller speakers you'll start hearing that "thin" or wimpy sound - male voices, many stringed intruments, certain movie effects etc etc - many complain about as far as HT systems are concerned, because IMO woofers 5" and smaller just cannot reproduce the frequency spectrum around the 80Hz point very well if at all. And moving the crossover point upwards to help compensate for these smaller speakers then starts affecting how the sub performs, plus it's output is more localizable (a sure way to negatively affect that "suspension of disbelief" concept, especially while watching movies) and so on.

Wire? The speaker manual is the best source for this information, but for me 16 or 14 gauge wire is what I use myself, specifically the lamp cord sold at Lowes for example. Along with what the manual for my Boston Acoustics speakers advised, this site helped me make that decision, put together by a former employee of McIntosh: Speaker Wire