Iron core vs. normal filter coils?

[sebackman]

Dear all,

Several of the JBL original filters use iron core inductors. Is there any advantage at all using iron core coils or is it just to save money and weight?

I guess using iron core inductors will use shorter wie and less windings and hence lower internal resistance but this should be possible to mitigate by using thicker wire?

I'm about to build some clones of original JBL filters but would like to use normal inductors.

All the best
//RoB

[4313B]

They used iron cores because they packed them into groovy little aluminum cans. Iron cores are generally smaller in size and can be placed close together without interference.

[sebackman]

Thank you for the quick answer. I also found some info in older threads so I probably should have done some more homework before posting...

I will try to figure out the DCR of the iron core JBL coils and use non core coils as I do have a few massive coils just taking up space.



All the best
//RoB

[DavidF]

Thank you for the quick answer. I also found some info in older threads so I probably should have done some more homework before posting...

I will try to figure out the DCR of the iron core JBL coils and use non core coils as I do have a few massive coils just taking up space.



All the best
//RoB

Cored coils allow for less wire (big savings with copper prices) and less resistance using smaller gauged wire. There are differences in performance with different materials used for cores (steel laminate are my preferred type). Try to keep the resistance under 0.5ohm in general for coils in series.

NOTE: some coils in the shunt position have higher impedance by design.

[4313B]

Cored coils allow for less wire (big savings with copper prices) and less resistance using smaller gauged wire. There are differences in performance with different materials used for cores (steel laminate are my preferred type). Try to keep the resistance under 0.5ohm in general for coils in series.

I found that one way to kill a bit off the Everest II bottom end was to replace those dual 10 mH coils with a single 20 mH Erse coil. It definitely cuts down on the bloom. Of course, going active "fixes it" altogether.

NOTE: some coils in the shunt position have higher impedance by design.

Excellent point, it turns out that can be quite critical.