This was hotly debated in the speaker world when driver testing first rose to prominence. I sit a bit in the middle. Mathmatically, xnor is correct - that for any given impulse response measurement, it's possible to correct it to a near-ideal impulse. However, I do think it's critical to remember that nothing has been done to actually alter the mechanics of the system - we haven't added damping to change the mechanical resonance. All we can do is reduce the energy exciting that resonance, so that *over the measurement interval* we net out to the same overall energy as for other parts of the spectrum.
What this means in my mind is that
- how the resonance shows up in the impulse response/ freq response is going to depend on how long your measurement interval is.
- ultimately as the damping of the resonance goes to zero, the correction filter will tend towards an infinite notch.
What this means is that the degree of peak associated with a resonance is going to depend on how long you measure. For a very undamped resonance you'll see a bigger peak in a 20ms window than a 10ms window for example. This is going to alter the correction filter you apply - a deeper notch will show up in the longer filter than the shorter. For the limit condition consider something like a tuning fork that rings for like a minute after being struck - if we could somehow alter the spectrum of the impulse that excites it, we'd have to completely notch out it's fundamental to the point of injecting zero energy in order to have it not ring.
So, for 'relatively benign' resonances that decay 'a bit slower' than the rest of the spectrum, I think xnor's approach should work well. The worse the resonance gets though, the more problematic it will become.