Subwoofer X/O frequency experiments

I have really been going crazy trying to find the best X/O frequency for my elaborate 6-driver subwoofer set and my three Maggie MG1.6. I finally had the thought that the optimum frequency depends on the kind of music being played. So I bought an electronic crossover that I can locate in the listening room and make various adjustments (including X/O frequency) while music is playing. (My old X/O was located in the cellar with my power amps, and the frequency can only be changed by plugging in a different module…not very convenient for experimentation). Initial tests confirm what I thought.

First I played a CD of Wurlitzer theatre organ music. Heavy duty bass! No doubt that the best results were with the X/O set to 300-400Hz. Not all subwoofers can do 400 Hz, but mine can. Interestingly when I cranked it up to about 800Hz harmonic distortion became evident, but not unpleasant…it sounded exactly as if the organist had pulled out another stop. Organ pipes produce very pure tones, and little pipes are played simultaneously (via stops) so as to produce harmonics and make it sound nice. I did the same thing electronically. Sort of “tube amp sound”.

Next I played a Mozart Symphony DVDA (MDG 940 0967-5). Again this is a massive complex sound source, mostly loud, and 130 Hz or thereabouts seemed best.

Last I played a DVDA Emmylou Harris, Producer’s cut (Warner R9 78174). On this one anything over 50 Hz was bad. It has the usual pop music bass line, probably exaggerated to sound better on inferior systems.

I know that the audiophile party line is that the subwoofer should be crossed over where the main speakers roll off, generally below 50 Hz. This is a “safe” bet if you have to pick one frequency and stick to it. Been there, done that. However, I suggest that there is (or ought to be) a significant overlap of frequencies that both the main and the subwoofer can reproduce well, and that the optimum X/O varies depending on the music.