Oh well...in my opinion



Somebody may say that it's some kind of Doppler distortion...
Caused by the impossibilty to move at the same time at 100 Hz and at 10 KHz
Others would say that the pistonic region would allow only a certain range to be played correctly. As a loudspeaker is still a passband device, it would allow
to focus its activity in its mid-band, being the extremes not necessarily useful
to detect the 'message'. But then it comes the term 'Hi-fi' which means that the original recorded event to be reproduced, it could be played at a level that it would make it seem to be played like it was in front of you. Electronic music
is another department because there is no precise relationship between an oscillator-generated sound and what you can find in the real world.
So generally for a relaxed low level listening or background music or just for the
news, it is not strictly necessary to display a system that has high dynamics. those high dynamics require the specialized drivers which are woofers-midrange and tweeters. But I see nowadays that some FR are aknowledged to play at satisfactory levels, only needing a subwoofer to meet
the high excursions to move big masses of air at low frequency.
I'm using some 2" FR such as Monacor SPX 20 and SPX 21 as mid-tweeter
and they perform quite good, being quite easy to 'cross' with a woofer with 1st or 2nd order slope filters.