So, if I can also hear the harmonic resonances, would it help to turn the crossover on the sub down?

Right now, the cross over on my Hsu stf-2 (downfiring woofer, btw) is taken out of the loop, and the bass management/crossover work is being done by the Yamaha.

Question - if I turn the cross over on the sub down to, say 100, will the sub still produce the 160 and 240 harmonics? I.e. is that a sound that the sub is producing, or is it a natural by-product of the 80hz soundwave?

Thanks.