Jacques, the "roll" that using different frequencies plays when calibrating for equal speaker volume is also interesting. Primarily electronic components such as receivers and players have so little variation in frequency response across the 20Hz-20KHz range that using one frequency(e.g. 1000Hz)to set levels equal will result in audibly equal levels for the entire range. Speakers, on the other hand, have much larger variations which often occur at different frequencies for different speakers. For example, if speaker A was 2dB louder at 1000Hz than was speaker B, lowering A by 2dB would result in equal volumes at that frequency, but if B was 2dB louder than A at say 2000Hz(certainly a common possibility)then the 2dB adjustment previously made because of the 1000Hz measurement would result in 2000Hz now being 4dB louder in favor of B.
Using pink noise, which contains the entire frequency range in a way roughly similar to music, rather than a specific frequency when setting levels can result in a better average leveling result when comparing speakers with music selections. It would be interesting to hear Ian's comment on what Axiom uses in equalizing levels.
my guess is they usually use band limited pink noise, maybe something like 300-3000 Hz. this should give a good match for the average SLP put out by the speakers.
