In response to last week’s EQ tips (inSync 2/18/00), a few readers responded with their methods. One such message draws what I think are some erroneous conclusions.
“I have a problematic control room. I resorted to a graphic EQ (Klark Teknic) which I had from my live sound days. I considered myself a bit of a whiz at EQ from the live work. I achieved some improvement in the monitor sound (Genelec 1030), but have been promising myself to tackle the acoustic treatment soon. Recently I used the SoundCheck CD which has 1/3 octave bands of pink noise. I simply metered the output of a flat mic (Countryman Iso Omni) on a PPM (Ed – Peak Program Meter). I must say that the results were spectacular. The process doesn’t seem to be too fussy about where the measurement mic is, unlike the Pink Noise/RTA approach. The listening experience is vastly improved.”
While I am thrilled that your methods appear to have worked for you I do see some problems. The most notable of those is the assumption that your mic and methods aren’t sensitive to the location in the room. Unless your room has spectacular acoustic properties the results will be affected by where you position the mic, regardless of what the measurement device and noise source is. There is some merit to energizing the acoustic space with smaller, band (bandwidth) limited frequencies of noise one at a time (as you did), but there is also merit to looking at the response of the room as an aggregate (the RTA approach). Acousticians also look at (among other things) the RT60 properties. For example, an RTA measurement may show excess energy at 200 Hz, but a device such as a TEF machine may reveal that this excess energy is due in part to reverberation or a standing wave at that frequency. In those cases reducing the amplitude of that frequency coming out of the loudspeakers (equalizing) is a very poor band-aid. The real solution is to change the mechanical/acoustical properties of the space to solve the actual problem.
This is the type of thing I alluded to last week when I wrote that there is much more science and art to this than meets the eye. The important point to take away from here is that generally speaking an equalizer is the last line of defense for tuning speakers to a room. Selection, placement and acoustic treatment are where most problems can be best solved.