Where to Buy a 0.21mH Air Coil?

[mrtn400]

I recently got a pair of JBL HLS 820 for pretty cheap because the last owner blew the tweeters.

I ordered a new pair from JBL and when I pulled out the crossover network when I went to swap the tweeters, I noticed that a coil is melted in both networks (L3 in the linked schematic).

I've googled quite a bit and I can't seem to find 0.21mH air coils to replace them with. I'm 99% sure that I can order two whole crossover networks from JBL, but I'm really hoping to not go that route.

[Pano]

Parts Express? Madisound?

[wakibaki]

Just wind them.

Count or estimate the number of turns in one of the existing ones.

Make them too big, measure them, remove some turns.

w

[PH104]

Check out

Solen Electronique Inc.

At a quick glance I saw that they have 0.2 mH and 0.22 mH coils.

[mrtn400]

Thanks. I don't know why I didn't think to check parts express.

Both Madisound and Parts Express have 0.20mH and 0.22mH coils. What effect would the 0.01mH difference have on the HF signal and would it even be perceivable (here's the schematic I forgot to link previously)? Should I go with the 0.20mH coil or the 0.22mH coil?

Also, the coils that I'll be replacing are wound with very thin wire. Should I try to get a coil wound with the thinnest (largest gauge?) wire to try to match the resistance (which is an unknown value)?

[PH104]

Solen has what they call Litz coils. I'm not sure I'd call them that but they are wound with multiple strands of high gauge wire so you could go with lower overall gauge that way. If you can measure inductance, buy 0.22 mH from whomever and peel off turns until you hit the right value. If you can't measure, don't sweat it -- with either 0.2 or 0.22 you're only 1 part in 20 (5%) away from target value.

[mrtn400]

Thanks PH104.

No, I don't currently have a way to measure inductance, but I think I'll go with a 0.22mH in case I ever get an oscillator and have the time to go back through them.

Thanks for the help, and I can't wait to hear how these sound compared to the pair of HLS 610 I grabbed in the same deal (they also had shot tweeters but didn't have any crossover damage).

[Pano]

Yep, just get the 0.22 and unwrap a few coils. If you tell us which coil you get, we can probably figure out how much to unwind. Tho I really doubt the extra 0.01mH will make much difference. You'll pull the lows out of the tweeter a tiny, tiny bit faster, but I doubt you'd ever know. It might even be better.

[PH104]

I've got a couple of the Solen 0.2 mH coils. I'll post some info on it tomorrow -- maybe it'll give you guys some place to start on the calculations to mod the 0.22 mH coils.

Cheers

Phil

[mrtn400]

Well, I've heard that tweeter failure in the HLS line is pretty common, especially in the 820s because they're crossed a little lower than the rest, so the 0.20 coils may have been a smarter choice.

I ended up grabbing two regular wound 0.22mH 20AWG coils figuring that I could unwrap them like you said, but I'll probably need a little help with that when they get here.

Thanks for all the help everyone, and this seems like a pretty neat website and I think I might find myself snooping around here fairly often.