Here are a couple of other interesting ideas of using the built-in AUHighpass and AULowpass AU plugins that are part of the default MacOSX installation.
I was using them one night to test out the frequency ranges of my near-field monitors, it was interesting to hear how low and high the monitors could reproduce frequencies — this by filtering upwards or downwards audio material.
Then I wanted to also find out if my hearing has decreased, a constant worry when dealing with music business. Fortunately, I could still hear up to 18.5KHz, after all these years, so I’m happy.
You could also sweep down to various frequency ranges and see how much energy is present, or isolate problematic frequency areas. There’s also a band pass filter — AUBandPass — that you could use for this purpose.
These filters don’t take much CPU cycles. The only issue I’ve had with them so far is latency delays, but by placing the same filter on all the tracks it seems to handle the compensation automatically.