Technical Comments by
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
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).