Audio Systems: subs, dual voice coil, two subs

Question
is a dual voice sub better and does a dual voice use the same power as 2 mono voice subs

Answer
If your question is; is a dual voice coil better than a single voice coil my answer would have to be no. The answer is only from a purest point of view. Two voice coils on a single driver will create some adding and opposing electromechanical energy depending on the phase of the signal from an amplifier. Unless the cables from the amplifier are of the exact length, with resistive & capacitive properties there will be minute differences at certain frequencies.

Having said that I would still recommend the use of dual voice coil drivers in certain applications. Even from a purest point of view there are also variables when using two drivers either in the same box or different cabinets. The resultant movement of the driver is governed by the combination of a left and right signal being applied to the dual voice coil driver and the effective SPL is delivered in mono since it is only one cone.

Given the same power, two subs would probably deliver higher SPL since you are doubling the cone area.