thomas wrote:For the full xover (4 ways) I need in total 8 coils.
Most important is the xover between upper bass and mids which will be
around 500 - 1k Since I'm still playing with the xover frequency the adjustability comes
in handy. For this I need a value around 100-200mHy. I need 4 of them and they
should all be the same and will be set for the same airgap. I need 4 (2
per chanel) since I'm doing LCR type filters
I think the first one will do nicely for that, it will let you play with the series connection (higher DCR, larger gap, and more linearity) and the parallel connection (lower DCR, smaller gap, less linear) to see if there is a problem.
I'll do 4 of those.
For the 1.8Hy a DCR of 16Ohm ist still fine.
I think you might need to go to a bigger core or a higher dcr to keep it reasonably linear. If the 25 ohm dcr is too high, going to a bigger core will get some more linearity. These are all (core type construction) so there are two bobbins and a single core, so maybe the best approach is to arrange it so the bobbins in parallel and a small gap give 1.8hy at 15 ohms, then in series, you will be able to increase the gap to get a nicely linear device at 60 ohms... If 60 ohms is too high, give me an absolute maximum DCR and I'll do that for the series connection and see where the parallel one puts us.
And for the tweeter I need something in the
range few mHy up to 10mHy.
here is where i would expect the amorphous cores (or high nickel) to help out, while the resonant frequency of the others is still well below 10K, when you get to the tweeter, you need to be sure your choke is behaving as one. an air core seems wrong to me since they will have more capacitance.
What I use now (the Lundahl coil) has 25 Ohms so this would be noimprovement with respect to DCR.
The issue with DCR is less critical in the subbass xover. All it does is some gain loss due to the resistance which forms a voltage divider with the terminating resistor. But still it's preferable to loose as little gain as possible.
I'm currently playing with the impedance of the LCR networks, and am going lower with it. In the moment I have networks with impedances around 300 Ohms and below. In this case the impact of the DCR becomes more critical.
The woofers which I use in the subbass are the least efficient compared to upper bass,mids and treble. So I already need more gain in the respective amps aqnd want to loose as little as possible.
The subbass just kicks in with a slope of 6dB below 50 Hz. The drivers covering upper bass/mids are not rolled off in that region. So the DCR really only looses gain and does not alter the frequency response.
In the mids region I'm doing a 'real' crossover and the DCR has more side effects.
so for the pair of 1.8hy i'll stick with the 12-15 ohm range.
then i'll look at a bigger core, i really think you want a gap of .01 or more. I'll still keep the DCR at 12-16 ohms and see what the math suggests. and then give them a go on the winder. I'll attach the graph of what we should get from 2 core sizes bigger.
it would be nice to get a butt gap to give you the needed 1.8hy since maybe DCR is really more important than linearity.
