Experimenting with placement, want some thoughts, advice.

[mbaylor]

Please see attachment to see shape of room. Current placement is what I threw together, but I am looking for advice on room layout.

The rear wall has a rear center channel and 2 side channels. As you can see the front of the room is more narrow. How will this affect sound? Also, where should I place speakers and TV. Should I try to center them off the rear of the room so the tv is centered with the back of the room and not the front, or should I center the TV with the front of the room?

Please bear with me as this is my first home theater.

 

[bpape]

If it was my room, I'd turn in 180 degrees. That gets your main soundstage in a symmetric position and without the doors to contend with. The lack of symmetry is much less of an issue in the rear of the room than in the front.

Bryan

 

[mbaylor]

Thanks bpape, I will definitely consider doing this.

So what you are saying is that the having different distances in the rear (as far as rear speakers are concerned) is not as big of a deal as having a perfectly symetrical front soundstage. That seems to make good sense.

Any rules on distances to put speakers from side and front walls?

 

[Ethan Winer]

MB,

> Any rules on distances to put speakers from side and front walls? <

I agree with Bryan about flipping the layout around. As for speaker placement, start by establishing the listening position 38 percent of the way back from either the wall in front of you or in front of the wall behind, centered left and right. In your case I'll guess you want to be farther back in the room. Then set the speakers to form an equilateral triangle with the listening position, so each speaker is the same distance from you, and that same distance is between them. To fine tune the placement further requires measuring the low frequency response and adjusting for the flattest response. I don't know of any way to accurately predict the best location.

--Ethan

 

[Savant]

mbaylor,

There are computer programs that can assist you with layout and placement. I don't know if it's popular on this forum, but CARA is quite useful, even if the learning curve isn't that great. RPG's "Room Optimizer" will also do a good job, though, again, the learning curve is a bit steep. Both programs are priced below US$100.

There are also various thoughts ("rules of thumb") on placement of loudspeakers and listeners with respect to room mode distribution. One of those is given in a post above. Another is placing speakers to correspond to strong modal nulls - e.g., nx/4, where n is an odd integer and x is a room dimension. This tends to work best for full-range loudspeakers and subs. This suggestion is usually accompanied with placing listening seats at mx/3 and/or mx/5 (and/or, if the room is big enough, mx/7) locations, where m is an integer, to avoid any strong modal peaks or nulls. (If you do the math, this jives somewhat with the method above since 2/5 = 0.40, which is close to the 38% figure.)

Yet another suggestion would be to use the mx/3,5,7 method for loudspeakers and listeners.

There are more suggestions that involve, for example, front channels being at least x/10 from the front wall (where x is the front-back distance); placing the listening position 0.7*width back from the front wall (e.g., if the room is 20 feet long and 15 feet wide, place the listening position at 0.7*15 = 10.5 feet back from the front wall); and so on.

It might be more important to remember that there are definitely some placements to avoid completely. The center of the room (something the 0.7*w formula often comes close to, unfortunately) is to be avoided. Having a couch up against the back wall when the purpose is surround sound is also a big no-no.

Having adequate acoustical control in the room can also make exact placement much more of a non-issue.

 

[bpape]

Agreed. There are many ways to skin this cat. Most of them will get you 'in the ballpark' and then you play from there. Personally, I try to put the seat in a good position and then arrange the speakers and sub accordingly for imaging and bass response.

In addition to the above, another 'rule' for a starting point for the sub is to use x/7ths of the room's dimensions. For instance, if a room was 14' wide and 21' long, you'd maybe start out with the driver center 2' from the side wall (1/7) and 3 or 6' from the front wall (1/7 or 2/7). Some rooms this works, some it doesn't. Every room is different.

Just remember that the only place it matters what the FR is, is at the seating position. Get that right first and then work the other things into position. I also agree that properly treating a room will go a long way to help to tame some of the FR abberations and also control the decay times.