Technical Comments by Other Parties

Last edited by Lynn Olson on 11-07-2007 at 04:05 PM (Un-Edited)

Joe Rasmussen has a crossover design philosophy that overlaps with mine to a large degree. Not identical, mind you, but a lot of areas of agreement. I mainly use low-Q 2nd-order networks, but am quite partial to 1st-order combined with a notch filter as well, depending on what the driver wants to do.

Linear phase I can take or leave, but the phase angles between the drivers are very very important and are quite audible as "phasiness" with pink-noise stimulus. A correctly designed crossover does not sound "phasey" and more importantly, sounds like a single driver, even when quite close-up to the loudspeaker.

It is certainly true that high-quality cone drivers typically have a single well-defined peak at the top of the range, and this single peak is amenable to notch-filter equalization. I agree with Joe's comment these clean, well-defined peaks are not breakup, but are artefacts of the cone shape itself. They are especially evident in top-of-the-line cones with low inductance figures - in a more typical high-inductance driver, the peak is intentionally masked by voice-coil inductance. Since VC inductance is quite nonlinear, low inductance is a good thing - but it does make the FR look different than you might expect.

It's the drivers with ragged responses above the top of the range that are more problematic to cross over and equalize - any driver with a whizzer or poorly designed dustcap or phase plug qualifies here. These are the notorious directional peaks you've seen me complaining about - the famous KEF B110, as used in the BBC LS3/5a, had three directional peaks 100 Hz apart in the 3.5 kHz region, as well as a single broad peak at 1.5 kHz (which was equalized in the LS 3/5a crossover).