DIY Servo Sub- need help with control circuit
I am designing a 15" driver with high power handling and high excursion, and would like to incorporate a servo feedback system into it.
I plan to use a second small voice coil attached to the inside of the dustcap with its own magnet assemby, doesnt need to be big as it will only be acting as a transducer to give an output waveform that represents the cones movement.
What is the best way to take this signal, to compare it against the original and make any adjustments needed to reduce distortion etc?
I thought of using opamps to split the incoming signal, feeding it to the amp and also combining it with the output from the transducer coil, phase inverting it so that the two signals largely cancel each other out, in theory leaving the distortion component of the signal, that can then be inverted and sent to the amplifier.
Is this along the right lines or am I way off? What is the best way to achieve this? Any thoughts or suggestions would be welcome. I have had a look at other threads and there is some discussion on available kits or different ways of getting the feedback signal, but I couldn't find any info of relevance to my question. All help is greatly appreciated, thanks in advance