>      have read many books on sound reproduction, but I still can't 
 > quite grasp how one driver can reproduce more than one frequency at 
 > the same time. I have trouble expecting a driver to reproduce a 
 > bass guitar and low synth, *and* the quick pop of a kick drum. Care 
 > to try and explain it?
     
        Turning it around and asking the opposite end might help.  How can 
your ear drum (not terribly unlike a speaker cone) receive more than one 
frequency at a time?  In order to hear a low synth, bass guitar, and a kick 
drum (and even an entire orchestra) all at the same time, it must respond to 
all of these.
        The answer is that all sounds other than pure sine waves are a 
combination of overlapping sine waves that essentially combine to form one 
complex waveform, (you can observe it visually on an oscilloscope).  As long 
as your ear and/or the speaker can reproduce this complex wave, your brain 
can then separate all the individual instruments it recognizes within the 
complex wave.  Both speaker cones and the human eardrum have their limits, at 
which point their response either rolls off or distorts.  Actually, the ear 
is a bit more complex, as the signal is actually recieved in the cochlea 
(which we don't understand very well at all), converted to something similar 
to a digital signal and then decoded in the brain.
        I realize this isn't a great description of what is going on, but it 
might give you a basic idea.
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