PS AUDIO: Tuning out problems

Paul McGowan ......

If you had a chance to read yesterday’s post you’ll remember we’re in the process of setting up Music Room number Two, where we have a pair of floor standing 2-way Thiel loudspeakers.  That room is considerably smaller than Music Room One, measuring 12 x 15 feet, compared to Music Room One’s 15 x 23 feet dimensions.

Because of the room’s layout, relative to its entrance door, we are forced to place the loudspeakers on the short wall, giving us only 12 feet to work with for both loudspeakers and listeners.  I like this setup because it is perhaps more typical of rooms that many of you might have and suggests problems that are similar as well.  I typically like pointing the speakers into the long dimension of the room to give more space for both the listener and the system but, as many of you no doubt experience as well, circumstances just prevent that option.

In this setup it is not going to be an option to use our classic rule of thirds, which would place the loudspeakers 4 feet away from the wall behind them and the listener with 4 feet behind as well.  This wouldn’t work because you’d then sit a mere 4 feet away from the loudspeakers and that’s far too close – it’d be like wearing the Thiels as headphones.  I like to have at least 7 to 8 feet between the listener and the speakers.

So the first choice comes down to placement of both the listener as well as the loudspeaker and which is more important.  In almost every case the loudspeakers must be removed from the rear wall if you’re going to have any chance of making this work.  By default, this means the listener must sacrifice their space behind them.  The reasons for this are fairly straightforward: with but few exceptions, loudspeaker designers voice their speakers away from any wall boundaries and getting them too close to a wall changes the tonal balance of the speakers.  Several exceptions to this have been presented over the years, I believe Naim has a loudspeaker pair designed to go up against the rear wall, but generally this just isn’t true.

As you move a pair of loudspeakers closer to the rear wall lower frequencies tend to become louder, relative to higher frequencies, because the wavelength of the lower frequencies is longer – thus the wall reinforces the waves that bounce off of it – in a manner similar to an acoustic horn (the higher frequencies tend to go straight ahead and don’t get reinforced).  You can hear this effect easily if you listen to the tonal qualities of your voice changing as you walk into a wall (careful now).  Getting the speakers too close to the rear wall also changes, rather dramatically, the imaging of those speakers – with depth of soundstage increasing as you move them away from the wall – but getting them too far into the room has downsides as well.  Point is, you have to get them in an optimal place, relative to that rear wall.  In our case, we’re out from the wall about 4 feet and as we place our listening position up against the wall behind the listener, we’re at approximately 8 feet from the front of the speakers.

In such a small space we’re going to have problems with both imaging and tonal balance.  I mentioned yesterday that I am having trouble getting the same measure of soundstage depth as I have with the IRS in Music Room One.  I have followed the process I wrote about yesterday, and gotten good results but nothing to write home about – and my ultimate goal is to have a miniature version of Music Room One in Music Room Two.  So what to do?

If you’re battling a room, which is exactly what we’re doing given the compromises I’ve described above, then your next steps are to help the room and that’s exactly what I did to fix the depth problem.

I’ll go over those steps in some detail tomorrow.  For today, let’s absorb a simple rule of thumb: if your room dimensions allow you to use the rule of thirds with the speakers at least 7 feet away from your chair, you’ll get 80% of what you want without room tuning.  If you’re room is small enough to negate the opportunity for the rule of thirds, as just described, then you’re only likely to get 60% of what you want without room tuning.

In my case, we’re going to have start tuning.