Soft clipper improves bass response
Nothing really new. The radiation resistance of a piston type speaker drops with falling frequency , therefore for constant acoustic outpunt cne excursion rises.
This can cuase distortion, compression, and in worst case mechanical defects.
A simple soft clipper prevents this. A SallenKey Lowpass with amplification provides input for a chain of comparators, these drive CD4066 analog switches.
The image shows just the idea , actually one needs 16 analog switches , that is 4 CD4066. This attenuator drives then the low pass filter for the woofer amp thus that the soft clipper does not add much distortion. The simple circuit yield an audibly clearer rather precise bass reproduction at high sound levels. It has no effect at levels below the threshold given by woofer xmax and enclosure.
The same circuit can be used as a soft clipper for the active speaker box amps. A fairly crucial point is how fast the opamps as comparators are. Too fast can cause distortion , too slow can as well. The type used in simulation is a bit too fast, while a cheap quad LM324 is too slow.
The soft-clip in most NAD amplifiers is actually a hard diode-clip on the input of the amplifier.
The clamp threshold voltage follows the supply voltage for maximum dynamic range.
By pre-clipping the input signal the feedback loop in the amplifier is stable, and it sounds much, much better. It also does not blow up woofers either.
You seem to have re-invented the wheel in a more complex fashion.
Nothing wrong with that.
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