I’m so diffused

The first time I can remember anyone paying attention to room treatment was back in the mid 1970′s when the local manager of our Pacific Stereo store added a brick surface to the wall behind his loudspeakers, a pair of Bose 901 Direct Reflectors, in an effort to provide a “perfect” reflective surface for the Bose. The system screeched like a wounded owl and required either a lot of alcohol or a quick exit from the room to enjoy the results.

The industry and knowledge base has come a long way in the many years after this first encounter: due mostly I would imagine to the high-end borrowing from the recording and pro folks who have used some form of room treatment for decades before anyone in the high-end figured it out.

There are two main schools of thought when it comes to treating a room: absorbing or diffusing or a bit of both. Many devices created for this task have both a reflective and an absorptive surface that can be employed in the service of making the room a friendlier environment for our stereo systems.

Absorbing the sound is a near impossible task because you pretty much can’t absorb all frequencies. Absorbing the higher frequencies is rather easy but as the frequency of the music gets lower and lower it becomes increasingly difficult to absorb and eliminate the sound. Furthermore, it seems to me to be the wrong idea if we’re considering the room as our friend we want to include it in the system instead of fighting it at every turn. I think diffusing the sound is by far the best way to go.

Diffusing the sound scatters the sound in such a way as to allow your ear/brain mechanism to pay less attention to it than the directly received sound. This allows us to ignore (or reduce our awareness) of the scattered sound in favor of paying attention to the more direct sound – kind of like what we want to achieve with absorbing without having to use such brute force measures as are required with any absorber type of system.

One of the first tasks we’re going to start with is to try and eliminate the point of first reflection from the sidewall. This is the classic area to start with assuming you’ve placed a throw rug or some type of absorbing material on the floor in front of the speakers (diffusing on the floor is nearly impossible from a practical standpoint) and the ceiling is pretty far away. If the ceiling is as close to the speaker as is the sidewall you may wish to explore the idea of repeating the process we’re going to next suggest – on the ceiling.

For this exercise you’ll need the help of an accomplice holding a small mirror that isn’t overly concerned with looking a little goofy. First, remove the grilles on your loudspeakers. While you’re seated in your listening position, which was set in the procedure we detailed in yesterday’s post, have your cohort stand with his/her back touching the sidewall in front of the speaker, perhaps halfway between the speaker and your seating position, holding the mirror directly in front of them and parallel to the sidewall behind them.

You want to look at the image in the mirror and have them move toward or away from the speaker until you see the speaker’s tweeter in the center of the mirror. This is the point of first reflection where the sound from the tweeter and midrange first strike the wall and then point towards your ears. Because the distance traveled from the loudspeaker to your wall and then to you is greater than the direct sound, you hear a slightly delayed version which confuses the image. So it is at this very spot you need to diffuse the sound so no longer is your ear/brain confused. The improvements in imaging can be significant.

A good diffusor is important but almost anything will be better than a bare wall.

Tomorrow I’ll discuss what I use and recommend for diffusors.

Paul McGowan – PS Audio, Intl.

Room Treatment

This will be the first of a few posts on room treatment, so big is this subject I will be writing about.

When we first started this series of posts on the setup of your system I made the point that the room is a critical component in the chain we call the stereo system. Without it you haven’t anything useful and with it you have a bunch of headaches. It’s a double edged sword the likes of which can be very frustrating. But treating the room as a friend and working with its issues, in the same way you might treat an older piece of kit you value, is the right approach and we’ll be best served working with the room and not against it.

Working against the room might have us using absorptive panels throughout to try and deaden the reflections giving the loudspeaker pair clear dominance over the audio in the room. That would be a bad idea because we want the reflections and we need them – we just need them where and when they make the best sound quality in any given room.

One of the most basic of concepts for room treatment is something I shamefully left out of the first part of this series, so sure I was that everyone knew this little tidbit. Whenever possible we want to point the speaker pair into the long part of the room (if it’s a rectangle) rather and the short part. I shouldn’t make such assumptions so to those of you that followed the setup guide to a tee and now realize you have to redo do it going into the long end the room please accept my apologies. Others know this rule and yet haven’t any choice given the WAF or just plain practical limitations and to those folk I know you did your best to get the best under trying circumstances.

Everything we’ve done so far has been in an effort to use the room to our advantage and place the loudspeaker pair where it interacts in the most favorable way with the area we have to work with. Now it’s time to perform a little magic to take advantage of everything we’ve managed to dial in so far.

The first subject I’d like to approach is your seating position – it is now dependent more on the room than anything else – and also offer a gentle reminder that the seat itself is really important. I hope during this setup procedure you’re using a single seat so it’s easy to move around. If you’re using a couch or small love seat, it’ll work but it’s harder to move around.

The process I use is simple to start with – as my reference tracks are playing I move myself back and forth, up and down ever so slightly to see where the best seating position is to maximize everything I’ve been doing. You may find that even a few inches makes all the difference in the world – this is proper and good. Should you find that getting your seating a little higher or lower is beneficial you can tilt the speakers back or down if you can’t adjust the seat height (we discussed part of the yesterday).

So get your seating position right where you want it and then mark the position with the same blue painter’s tape as we did the loudspeaker pair.

Tomorrow we’ll find the point of first reflection.

Paul McGowan – PS Audio Intl.