Actually, I have been meaning to ask for a while:
How do manufactures tuned same specs driver to have somewhat different sounding? (ceteris paribus with housings, cable and jacks)
Do they flock the housing differently?
Do they perhaps solder on some resistor to the driver change the sound?
It has been a great mystery to me.....
Diaphragm material, composition, and thickness. voice coil material and wire thickness, housing design, internal dampening, open vs. close vs. semi-open, front grill / vent, etc. Everything that can be changed, can be used for tuning. Impedance is only a very small part of whole design, and certainly not a determine factor of how a driver should sound like. Sometime two driver might look similar in spec, but can be very different sounding because they really just 'look' similar by eyes, but not by measurement. Even a simple open vs. close design can change how the same driver behaves.