Dual voice coil sub, with active passive radiator?

[Ron E]

question.

if you use a speaker in place of a pr and place a potentiometer across the terminals and tune/adjust it properly, won't this achieve the same as a pr with more xmax?

Only by the extent that it will reduce output at resonance, and ultimately bass extension. A passive radiator with high losses is effectively a sealed box.

 

[boris81]

There is another application for dual coil subs.
Rythmik Audio uses the second voice coil as a detector for the cone movement and then a circuit adjusts the power to the primary coil to compensate for errors.

Rythmik Audio • Direct Servo - how it works