Originally Posted by
Ruediger
A low frequency speaker "sees" a generator impedance of hopefully much less than an Ohm. It consists of:
a) the amplifier's output impedance, e.g. 0.04 Ohm
b) cable resistance, e.g. 0.1 Ohm
c) resistance of series coil in the crossover, e.g. 0.5 Ohm
When using an active crossover You can get rid of "c", and it pays to invest in "b" (thicker cables).
This combined generator resistance determines (together with other things) the Thiele parameter Qt.
When placing another driver in series You add that driver's DC-resistance (e.g. 5 Ohm) to the combined generator resistance. That will spoil any cabinet design which depends on a certain value of Qt. In most cases You will end up with a "boom box".
So don't wire loudspeakers in series if possible.
Ruediger