Here is the list of Qtc and their characteristics from the textbook.
Qtc = 1 is Chevbychev
Qtc = 0.707 is Butterworth
Qtc = 0.58 is Bessel
Qtc = 0.5 is Linkwitz-Riley
Most of the textbooks explain all of above alignments clearly including the case that Qtc is greater than 1. Unfortunately, I couldn’t find the explanation of Qtc of lower than 0.5.
I’m curious what will happen if I design the passive crossover with extremely low Q—lower than 0.5. For example, Q = 0.25.
In fact, I have tried experimenting already; with the traditional second-order crossover. But, I couldn’t hear anything abnormally. So, I’d like to ask for clearer explanation of the results/effects when utilizing the extremely low Q crossovers (lower than that of L-R alignment).
Qtc = 1 is Chevbychev
Qtc = 0.707 is Butterworth
Qtc = 0.58 is Bessel
Qtc = 0.5 is Linkwitz-Riley
Most of the textbooks explain all of above alignments clearly including the case that Qtc is greater than 1. Unfortunately, I couldn’t find the explanation of Qtc of lower than 0.5.
I’m curious what will happen if I design the passive crossover with extremely low Q—lower than 0.5. For example, Q = 0.25.
In fact, I have tried experimenting already; with the traditional second-order crossover. But, I couldn’t hear anything abnormally. So, I’d like to ask for clearer explanation of the results/effects when utilizing the extremely low Q crossovers (lower than that of L-R alignment).
When you lower the Q below 0.5 (for a second-order HP or LP function) the curve sort of degenerates into two cascaded first order filters with their corner frequencies split apart symmetrically left and right of the original filter frequencies, the lower the Q the wider apart. Technically it's actually called "pole splitting".
1000Hz, Q=0.2:
1000Hz, Q=0.2:
So the pros are the amplitude response becomes closer to first order slope; and for the cons, the FR curve will become un-smooth due to the presence of two splitted poles, am I correct?
One of the things you get with a crossover is the ability to control the amount that each range contributes. It's possible to have needs in that area that set your rolloff, but have nothing to do with what the slope appears to be namewise. These factors, plus the combined responses (being flat overall, for example) have an effect.. the slope may not always have a chance to be a dominant issue.