Try this link i hope you find the answer it is for subwoofer. Take note you have a Power amplifier to run a subwoofer speaker, this cicuit is driver only.
That Greek sub-woofer filter circuit is a nightmare. It is a project at Electronics-lab.
Its schematic does not agree with its parts list which does not agree with its parts layout because some capacitors are actually two capacitors in parallel.
A speaker makes a poor microphone because it has a low frequency resonance that makes it sound "boomy".
An electret microphone has excellent sound and is inexpensive and small.