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Even at high SPL the sound is precise and distortion
very low.
Thanks to MFB the driver "overshoot" is dramatically
reduced adding to the perfect timing. The figure shows
the overshoot of a woofer with and without MFB.
MFB controls the woofer and eliminates the overshoot
very quickly. The woofer is simply able to start and stop
correctly.
The
MFB
comparing
diaphragms movements
with the input signal.
The transducer at the
back of the diaphragm
monitors the movement
of the diaphragm by
measuring
acceleration of it. In the
feedback circuitry the signal is converted to a signal
proportional to the speed. The speed is highest at the
resonance frequency and so is the negative feedback.
Consequently, the woofer receives less power in this
area, and combined with equalization the frequency
response reaches 20 Hz (-6dB).
It would be possible to make a subwoofer this size
reach 20 Hz just with pre-filtering/equalizing, but that
would create severe timing problems. This would be
heard as the subwoofer "rumbling" all the time – i.e.
not able to start and stop correctly. This might sound
circuit
is
the
the
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