In message , Dave Plowman
writes
In article ,
Wally wrote:
Given that my speaker rebuild fantasy is gradually taking shape, I'm
starting to think about what to do about crossovers. The plan is to
bi-amp, one amp to the B139 drivers, the other to the B110/T27. I'd
rather ditch the orginal KEF DN12 units and make new ones for the
mid/top, probably keeping to the spec crossover frequency. So, I have
some questions about components...

Am I right in thinking that air-cored inductors are better than those
with some sort of ferrite(?) core? For the same value, would an
air-cored version be physically larger? If so, is that because it
requires more turns?

What is the best type of capacitor to use wthin sensible cost limits?

If you are going to bi-amp, it makes much more sense to design the
crossover to go before the amplifiers - it's much easier to produce
filters using ICs than large inductors and capacitors.


Oh Oh! I've just seen that he intends to bi-amp. In which case, ignore
my advice about coils and capacitors in my other post, and follow Dave's
advice. Active filter crossovers before the amps are MUCH more
sensible.

You could even design some 'constant voltage' subtraction type active
crossovers to keep a flat summed amplitude and phase response. (in
theory at least. I fear your venerable drive units will impose a sonic
signature whatever the crossover. Both the B139 and the B110 had some
nasty resonances.)
--
Chris Morriss