# 7.1 Speaker Placement THX vs. Dolby



## devildog1679 (Aug 3, 2012)

I have a build thread on here, thought this place would be better for speaker placement specifics. First the room and system. The room is 30’x11’x8’6”(LxWxH) with only one door and no windows. Audio is Onkyo 9400 THX (7.1 THX cert), Video Epson 8500UB. Will be projecting a 98” screen which makes it 4’ high and 7’ long. Seating position will be 12’ from screen. Center as well as L&R speakers will be mounted on the front wall 40” from floor. This means the screen will be 2’ from top and start right above the center channel. The L&R will be 1’ from edge of side wall. L&R side surrounds will be 6’ high and at about 1’ behind the main listening position. The rear surrounds are the ones I’m having trouble with.

1. Can the front L&R be closer than 1’ from the side wall? I ask because if I can move them closer to the walls I can go from a 98” screen to up to a 112” if desired  . 
2.	Rear Surround set-up- THX recommended of the rear surrounds together or traditional set-up Dolby recommended of the rears at 135-150 degrees?
3.	Assuming I go with THX set-up, the rears will be 18’ from listening position. Is that too far back? Speaker specs below. Speaker stands are not an option with a 1 year old running around. 
4.	Assuming I go traditional, due to speaker to listening position distance the best I can get is 165 degree which is out of range. Is this too far out of spec? If not, is the 18’ distance to speaker to much? A solution to both is to place the rear surrounds on the side walls vs. the rear wall at 8’ back from listening position. This yields a 145 degree angle. 

Thoughts on this?

View attachment Onkyo 9400 Speakers.pdf


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## ALMFamily (Oct 19, 2011)

devildog1679 said:


> I have a build thread on here, thought this place would be better for speaker placement specifics. First the room and system. The room is 30’x11’x8’6”(LxWxH) with only one door and no windows. Audio is Onkyo 9400 THX (7.1 THX cert), Video Epson 8500UB. Will be projecting a 98” screen which makes it 4’ high and 7’ long. Seating position will be 12’ from screen. Center as well as L&R speakers will be mounted on the front wall 40” from floor. This means the screen will be 2’ from top and start right above the center channel. The L&R will be 1’ from edge of side wall. L&R side surrounds will be 6’ high and at about 1’ behind the main listening position. The rear surrounds are the ones I’m having trouble with.
> 
> 1. Can the front L&R be closer than 1’ from the side wall? I ask because if I can move them closer to the walls I can go from a 98” screen to up to a 112” if desired  .
> 2.	Rear Surround set-up- THX recommended of the rear surrounds together or traditional set-up Dolby recommended of the rears at 135-150 degrees?
> ...


1. They can, but you will have to be more concerned about boundary reflections.
2. IMO - traditional set-up. It seems if you are going to place them side by side, you could do just one instead of two.
3 and 4 - I would wire both positions to give me the flexibility to move them to determine which sounds better.


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## devildog1679 (Aug 3, 2012)

ALMFamily said:


> 1. They can, but you will have to be more concerned about boundary reflections.
> 2. IMO - traditional set-up. It seems if you are going to place them side by side, you could do just one instead of two.
> 3 and 4 - I would wire both positions to give me the flexibility to move them to determine which sounds better.


I guess 98" is plenty :bigsmile: I think wireing both locations will be good, might as well with all the wires I'm running. Easy to switch speakers to see if THX set-up or Dolby sounds best. 18' just seems like a long distance, especially for HTIB speakers.


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## phreak (Aug 16, 2010)

devildog1679 said:


> If not, is the 18&#146; distance to speaker to much? A solution to both is to place the rear surrounds on the side walls vs. the rear wall at 8&#146; back from listening position. This yields a 145 degree angle.
> 
> Thoughts on this?


18' is a long distance. In order for it to sound right at the listening position it will be very loud to anyone in the rear of room. I would go sidewall at the 8' mark you mentioned. Unless.... Could you mount speakers from the ceiling, say 4-6' behind?


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## devildog1679 (Aug 3, 2012)

phreak said:


> 18' is a long distance. In order for it to sound right at the listening position it will be very loud to anyone in the rear of room. I would go sidewall at the 8' mark you mentioned. Unless.... Could you mount speakers from the ceiling, say 4-6' behind?


I could do ceiling but then the hight will be more than the side surrounds.


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