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> what's the time constant for an LC filter having no R?
The "R" in a passive analog crossover is the load of the speaker driver.
That "R" is actually an impedance that varies with frequency so the
textbook passive crossover formulas don't work with real speakers and
the component values need to be adjusted.
> There is a modification of the T3 filter that is critically damped.
In crossovers, the Q = 0.5 Linkwitz-Riley alignment is critically damped
and down 6dB at Fc. The Q = 0.7 Butterworth alignment is down 3dB and
rings slightly (but not that badly.) Most of the formulas I've seen for
simple IIR digital filters are for the Butterworth alignment. You can
stack two Butterworth filters to build a critically damped LR of twice
the order. Q = .7*.7 = .5 . Of course that simple filter probably won't
perform as well as Bob's thingy but it will be critically damped.
> I have reproduced one of his older ones as well. And I have a pretty good
> approximation to his latest version but haven't published it since he is a good
> guy and makes a living selling this stuff... (See attached)
Nice!
--
Dennis
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