[quote name='thebuckets' timestamp='1336214109' post='1642543']
when you say different motors do you mean different sizes? Or does it go deeper?
[/quote]
I mean motor, as in the magnet and coil part on the back, they determine how the speaker reacts to applied voltage, same motor will do basically the same thing even if has a different cone on it, keeps the phase relationship close, so you can mix a Kappalite 3012 and 3015 and the result will be reasonably predictable, because they have the same motor. Different motors mean that one speaker might be moving forward, whilst the other is moving backward at some frequencies and make a mess.