Speaker Placement

Jimbo: Planers are very finicky--they require far more attention to placement and environment than dynamic speakers do. The other aspect that is very important to planer is that symetric placement is critical to good imaging. I believe this is important for most speakers, but have found it to be particularly true for planers. This is contrary to what you may have read previously. We had a lot of people asking about speaker placement and have put a short tutorial on our website. If you go to www.rivesaudio.com and enter the site then click on acoustical issues. This will take you to the listening room, once there select speakers and you will get a link to that tutorial (the whole listening room is a tutorial--but the speaker section is probably of most interest to you). One thing that is not covered in the tutorial (as we wanted to keep it brief), is some of the things to keep in mind with planers. I already mentioned the symetry, but the other aspect is the rear wall. Most planers require something reflective but diffusive as well. Absorbing will dull the sound too much. The reason we didn't include this in the tutorial is that speaker placement of planers is very dependent on this rear wall. Changing the material on this wall will change the optimum placement and thus change the entire sound. If you read the tutorial, it discuss the iterative process in the width between the speakers and canting the speakers. For planers there becomes another variable, the rear wall material, which effects canting, width spacing, AND rear wall to speaker spacing. If you can modify the material behind the speaker I would recommend first overdamping that space dramatically (hang wool blankets or something) and listen and then place the speakers. They won't sound very good, but the point is to educate your ear on what overdamping does. Then do just the opposite, get something completely reflective behind them (wood doors work pretty well, even smooth plywood can be okay for experimentation). Again, this won't sound so good either. Lastly get something to diffuse, but not absorb the sound (If you can get full length shutter or wooden blind type material this works very well). The diffusor is most likely what you will want to use, but the process of listening to these should help you in your overall quest to find the best speaker placement and overall sound.

Try cardas.com for their golden room ratio's, speaker placement, etc.

Overall, it's an excellent start and pretty basic.

try HP's rule of thirds, 1/3 of 22 1/2 is 7 1/2 and 1/3 of 16 1/2 is 5 1/2 so, place the speakers 7 1/2 out into the room and 5 1/2 feet apart (At least 5 feet out into the room is necessary IMO). I know this is radical but the results in my system resulted in the best bass and continuity. At least use this for a starting point. BTW toe them in slightly and experiment with toe in, usually aim them just outside of your ears works with Maggies. I have 1.6's myself.

Thanks, guys. I am just looking for a starting point so I don't have to chase my tail for a few hours.

Cardas'formula doesn't take into account a sloped ceiling, so, it's not clear what ceiling height to plug into the equation. But, melding everyone's input together suggests a distance of about 5 1/2 feet from the back wall and about 5 feet from the side should work as a starting point. (Although, perhaps the speaker's distance from the back wall should not approximate the distance from the side walls????)

Rivas, your formula wasn't on your web page so I don't know how it would campare to the other suggestions, but I will be incorporating your idea of diffusion. The only questions I have for you on that is: 1) Is it preferable to have the diffusion material directly behind the speaker and 2) what size range should the material be? (is 6'H x 3'W adequate?)

Again, thanks to all.

Jim

Jim: You are right about the forumla. I've been considering putting up some type of formulation, but the problem I have is that it can be very dependent on other variables in a room and speaker dependent, and it's impossible to incorporate all of that. The CARA 2.1 software comes the closest, but it still doesn't take into account many speaker variations very well. As to your question about the diffusion material, in general I like diffusion behind the speaker (or front wall) and more absorbing on the rear (behind the listener). How high and wide should the material be depends on many things. The most important is the speaker size, placement, and rear dispersion pattern. Then you have to consider the rest of the room and how those diffracted and non-diffracted rays will interact with the rest of the room. Diffraction also behind the speakers in general should not be randomized. There are diffraction patterns that attempt to diffract all frequencies (not the lowest of course) in a randomized way. This to me doesn't really work with planers as they lose the rear reflection coherency. Someone once suggestion slats like blinds slightly tilted upward. I haven't tried this yet, but based on other diffraction (diffusor) methods I have used I suspect this will work quite well. I can't say for sure about the size you proposed (having little information about the rest of the room, etc), but it seems reasonable, and certainly a good starting point if you are doing this by ear. You might consider buying the CARA software (we sell it--so I am partial to it). I've found it to be very useful in situations such as yours, when you would like to know the answers for a select few variables (such as the size of a diffractor), it can get you very close, and show you what happens with speaker placement pretty reasonably without too much time involved.