Archive of the former Yahoo!Groups mailing list: MOTM

I used a similar method for determining the proper frequency for
bass traps in my control room. I recorded a series of sine waves
into ProTools at different frequencies then truncated them at the
zero crossing points. I played them through a set of monitors (a
pair of JBLs that I had the manufacturers frequency response plot
for.) I recorded the tone bursts back into ProTools using a flat
mic and preamp. The microphone was placed at the console center
listening position. I tried several different locations for the
monitors to eliminate standing waves but mostly used the near field
position. I then determined the room response by adjusting the
amplitude of the re-recorded tone bursts for the frequency response
of the monitors. I also looked at the amount of time the
room "rang" at the different frequencies although some of this was
probably due to the speaker cones ringing.
I did determine an optimum frequency for bass traps and constructed
them to attenuate that frequency. That and the overall shape of the
room as well as the combination of absorbant and reflective
materials yielded a room within 3 db of flat and with great imaging.
The downside was that in an attempt to "excite" the room into
resonance I blew the woofers in both monitors. So be careful!!!
I was not in the room when I tested it. I value my hearing!
Another interesting technique is to place a white syrofoam ball
where your head will be (in the center monitoring position) cover
all reflective surfaces with aluminum (aluminium for you Brits) foil
shiny side up. Take a laser pointer and hold it where your monitors
will be and see whether you can prevent any reflections from hitting
the styrofoam by adjusting the angle of your console and other
equipment. You'd be amazed at how much the elimination of first
order reflections will improve the sound of a room.