That is a great explanation Alan which only brings more thoughts to the forefront:
1) If distortion occurs at levels >95dB (or another relatively high value) that effects the overall THD for towers, then the point of using a subwoofer as the substitution for the low end tower bass is really only applicable at higher volumes
2) If you take the idea that a subwoofer will lessen the audible distortion b/c is it better suited to reproducing this low frequency range (unless one prefers to hear bloated bass), then why bother making towers at all? Why not simply make only satellites with subwoofer additions?
I think part of this is probably answered in the first point regarding the volume at which the distortion becomes audible and to what extent.
In reply to:
It would be interesting to measure the differences and perhaps Axiom will have time to do so in the future. But loudspeaker distortion is well documented, and audible, especially with smaller bookshelf designs
3) Just how low a frequency would the cutoff for audible distortion be (if an exact point exists) and at what volumes then (e.g. 0% THD at 80dB? 1% at 90dB? etc)? (obviously a question answered only by alot of measuring of every individual speaker out there)
This may help to answer the exact point at which a user may want to switch their sub over to handle the entire low end and where to set a crossover in their receiver settings for their towers, if they are still being used in the 'large' mode and if an adjustable receiver crossover is possible.
One more thing to note, it appears that the THD for the M80s between the 100Hz -200Hz mark is virutally the same for both SPLs and just as significant as the THD hit by the lower bass around 50Hz. Just offhand most receivers would be set for a crossover of 80Hz with the towers set to small and yet the tower would still play this 100-200Hz sound range.
I find it interesting how there is significant THD in the range that the subwoofer would not be playing anyway. Forget the low bass, how about the audible distortion in the low midrange?
