Toroidal Inductors for crossovers

[omni]

I am in the process of modelling my 3 way crossover, and will be needing a few large inductors for woofer section. I recently recieved Parts Express new catalog, and they are offering Toroidal C Coils. Does anyone here have any experience with these, or information about them ? What are the upsides, or downsides to them. How do they compare to iron cores, performance wise, distortion wise, etc. Any information you all may have to share is greatly appreciated................Thank You.........Omni

[RJ]

I bought a pair of 4.7's to try out on my 2.5 MTMWW's.
They're nice and heavy for one thing, another might be less heat and less hysterisis loss than iron cores.
I went for less heat production.
I would notice air cores and some iron cores getting warm and even hot during loud sessions on my speakers. These C-cores never even warmed up.

A site on core types;
http://www.butlerwinding.com/core-ty...dex.html#ccore

[omni]

RJ Thanks for your input and the link. I read a lot of it and must admit much of it was "Greek to me", however it does suggest an improved performance with these type inductors. What are the dimensions of the coil you bought? How did you mount them? Also, I have read debates on wiring the leads to + or - on the driver to the inside wire or outside wire of the inductor.{I think it was a thread on this forum}...........Is there a specific wiring direction you took with these inductors?....................Respectfully........ ....Omni

[RJ]

Originally posted by omni
RJ Thanks for your input and the link. I read a lot of it and must admit much of it was "Greek to me", however it does suggest an improved performance with these type inductors. What are the dimensions of the coil you bought? How did you mount them? Also, I have read debates on wiring the leads to + or - on the driver to the inside wire or outside wire of the inductor.{I think it was a thread on this forum}...........Is there a specific wiring direction you took with these inductors?....................Respectfully........ ....Omni

They're about the same size as an edible donut.
I mounted them on perf board with plastic wire ties.
I never worried about polarity on inductors. I think orientation is more important so there is no cross magnetization.

[Shaun]

Orientation is less of an issue with doughnut-shaped inductors, as there is little flux leakage. The series resistance should be quite low, resulting in less power loss (the heating referred to above). Inductor polarity does not matter, unless you're trying to use the electromagnetic coupling effect with another inductor (effectively making a transformer). But this application has no use in passive loudspeaker filters.

[noodle_snacks]

Originally posted by RJ



They're about the same size as an edible donut.
I mounted them on perf board with plastic wire ties.
I never worried about polarity on inductors. I think orientation is more important so there is no cross magnetization.

polarity???? why even consider worrying about this? speakers are AC devices...

[omni]

Shaun, you mention that this application has no use in passive loudspeaker filters.........Can you explain ?

[soongsc]

Parts express also has some O cores from Jantzen, they have less effect on components beside them. I've used Duelund O cores, and they were okay for BSC in a full range, these should be quite good for low frequencies.

[Jim85IROC]

Originally posted by omni
Shaun, you mention that this application has no use in passive loudspeaker filters.........Can you explain ?

He's referring to the "electromagnetic coupling effect" which is what is used in transformers to change AC voltages. This is is a completely different application than an audio filter network in which there is no desired coupling effect between inductors, and they are specifically oriented to minimize this effect. Because of that, the polarity of the inductor is of no concern in these filters.

[Shaun]

Originally posted by omni
Shaun, you mention that this application has no use in passive loudspeaker filters.........Can you explain ?

Well, transformers have been used in loudspeakers before (usually autotransformers) for impedance matching, and sometimes for attentuation. But it is poor practise (rather arbitrary) to use two separate inductors to achieve coupling, as the coupling will be very weak, with minimal power transfer. It is this arrangement that is of little use in passive crossovers: usually one tries to overcome any power losses, rather than introduce them (except, of course when attenuating a tweeter or mid).