View Single Post
Old 16th July 2011 | Show parent
Lives for gear
JohnRoberts's Avatar

For the record that polarity inversion circuit is not a simple all pass filter. It's more like a polarity inversion circuit.

All pass filters are archaic technology used in the pre-digital days to make a short time delay. It only looked like a constant delay within a limited bandpass. So they were difficult to apply effectively. As I recall one application was to correct fractions of a mSec delay issues between loudspeakers drivers, to time align them, for the driver's different depth behind the loudspeaker baffle plane.

To make several mSec of delay (a lot more than needed in a crossover) you could stack up multiple all_pass sections, but this seems awkward.

Maybe look for old analog loudspeaker crossover schematic, I think Rane may have used adjustable APF in a few models back in the '80s for time alignment.. One more thing that modern digital technology is superior at.

I do not think this is a profitable use of time, but it's your time not mine... so enjoy.

Show replies