Crossovers - an old paper, a new article

Hello Filter fans - a couple of things to ponder over the weekend.

First of all, if you don’t subscribe to AudioXpress magazine, go take a look. Audio is almost as close to my heart as filtering. AudioXpress magazine covers a multitude of strands of audio design and industry news. The September 2024 issue has some interesting preamp and crossover design stuff.

The technical editor is the great Jan Didden who produced the Linear Audio bookzine series some 10 years back (I have a couple of articles in those). www.audioxpress.com gets you there!

I need to find the time to write a detailed response to Charlie Laub’s article involving sticking transmission zeroes into crossover filters. We wait to see what the actual simulated response of complete speakers might be with such filters. But as you might guess, the piece got me thinking, and it reminded me of the work I did around 40 years back following a great paper by John Vanderkooy and Stanley Lipschitz. The paper is “A Family of Linear-Phase Crossover Networks of High Slope Derived by Time Delay”, reference: J. Audio Eng. Soc. Vol. 31 No. 1/2, 1983 January/February. You can buy this from the AES if you’re not a member, and you might be able to locate a copy on the web (but do be careful when you go clicking…).

I collected and posted some of my old work on this a few years back, I’m heading off into my archives to seek it out. The Holy Grail in those days was to create filters (in the analog domain, no digital allowed!) with good slope that summed to produce a linear phase in-band response and give good control of total radiated power (almost more important than on-axis response).

Anyway, enough to keep you going over the weekend! — K