I'm thinking these THD are "similar" or "relative" to the THD we see in amps. Sure, the THD are there and some are higher than others, but as you have experienced, are they truly audible?
Of course THD in speakers is audible. In amps we're talking about 0.05% type THD at ultra high levels.
Distortion is most certainly audible.. in many speakers it's generally at least 1% and probably closer to 5 to 10% on dynamic transients. It's useless to measure THD+Noise though. Because of masking effects in music, we don't
notice 2nd order THD or even 3rd order even though we hear it. But if it's there in the form of 4th/5th or higher order THD we not only hear it but it's noticible in one way or another.
It's all part of power compression. Look at the change in FREQUENCY RESPONSE FLATNESS at 95db of some of these speakers.
A good motor design with smart use of demodulation flat out sounds better, and of course a smart crossover design.
Looking at that zu audio graph, I saw a huge sharp THD peak near 5khz. I'm willing to bet it's much more offensive than it looks. And I'd bet that it's ringing in the time domain at that frequency.
The other thing you need to realize is the driver producing the THD.
Let's say it's 100% clean from 100hz to 3khz but at 6khz it has a resonance. Not a big deal with a 2.5khz crossover right? Well.. if the motor is distorting, that means that if the 3rd harmonic at 2khz is played through the driver, the 3rd harmonic will be played through the same driver, even if the crossover is filtering that out. So you could actually hear some metal ringing or what have you. So you need a motor that won't accidentally trigger that harmonic. These get filtered out from amps by crossovers, but not by motors themselves.
