Axiom Home Page Forums General Discussion Home Theater Finally - I have a listening room

well well well,

I'm moving next week and I have two rooms in my new apartment, one of them being a nice rectangular 18 by 12.

I'm going to put the TV and main speakers along a 12 wall.

What distance from the back and side walls should I put my M80's?

Have any of you experimented with QS8 placement? I was going to put them on the side walls, 7 feet up at the listening position. The listening position will be about 8-9 feet back. Any other suggestions?

Your planned placement of the QS8s sounds great. As to the M80s, experiment, experiment, experiment. You could start with them about 9 feet apart, which would put them 1.5 feet from the side walls. Toe them in a bit, too.

Also, try to keep the distance to the rear wall different from the distance to the side walls.

Sounds good. One thought -- looks like your room might have a bit of a peak at 94 Hz which you could reduce by having the fronts of the speakers about 3 feet from the back wall, ie speaker ~1.5 feet out from the wall. In that case you would probably want to put the speakers a bit closer together, say 7-8 feet apart ie 2-ish feet from the side walls. That separation should be fine if your listening position is 8-9 feet back.

Dumb question, do you see the listening position as 8-9 feet back from the wall, or 8-9 feet back from the fronts of the M80s (ie 11-12 feet back from the wall) ?

They're big speakers, you gotta think about these things

thanks for the suggestions.

I actually made a calculation mistake (I failed math miserably).

I will have the M80's in the 12 foot wall and the listening position will be about 12-13 feet behind the front wall.
THUS, if the M80's are 3 feet out, the listening position will be about 9-10 feet behind the speakers.

bridgeman, how did you come up with the 94hz?

pmbuko - toe in? really? i'll experiment. I guess as it's a bit wide a slight toe in would help.

Ravi, one suggestion would be if this is going to be a 5.1 setup without back speakers, the QS8s could be placed maybe 2' farther back than the seating position, to give a little more back effect.

>>bridgeman, how did you come up with the 94hz?

I plugged 18x12 (and guessed at 8 foot height) into MODECALC, a little DOS room mode calculator you can download from the realtraps site. 18 x 12 is a pretty decent size so the room modes are spread out nicely (a 7 foot ceiling would be perfect, I think) and 94 Hz was the first point where the modes started to pile up on each other... 18 feet gives you peaks at 31, 62, 94, 124, 155... Hz, while 12 feet gives you peaks at 47, 94, 141 Hz etc...

Modecalc only shows you the peaks not the dips but it's a good start and easy to use. Free is nice too

JohnK,

thanks for the tip. It is a 5.1 setup. I had thought of putting them behind the listening position but wasn't sure if that's a great idea or not. i'll have to tinker.
bridgeman, the ceiling is about 8-9 feet, no higher than 9. I'll have to look up that program. It seems useful

>>I'll have to look up that program. It seems useful

Treat it like Tarot cards. Gives you useful things to think about, but it's not the complete answer...

The other useful thing to keep in mind (thanks JohnK) is the cancellation / reinforcement effect you get from being close to a wall. Whatever distance your speakers are from the wall (measure from the fronts) you get a dip at (282/distance in feet) Hz and a peak at (565/distance in feet). You can use that to help reduce the effects of the room modes (based on length, width, height) but it's all a horribly black art...

Quick hijack here. Sorry Ravi.

John(bridgman), you do realize that a torrid posting style like yours will eventually lead to a massive coronary? J/k.
Later,
Michael

Quick hijack here. Sorry Ravi.

John(bridgman), you do realize that a nonstop, torrid posting style like yours will eventually lead to a massive coronary? J/k. Keep up the good work.


Later,
Michael