changing .68mH to .65mH by removing coils ???

[bbaker6212]

Re: changing .68mH to .65mH by removing coils ???

I ordered a pair of Solen Hepta-litz .68mH inductors but I really need .65mH. Anyone know how to make/calculate how to remove the appropriate amount of turns to effect this change?

 

[Eric]

I think the best way is simply to start unwinding at the end of the coil. Do not cut off what you unwind, just unwind it a little bit at a time and measure the resulting coil with an LCR meter.

You shouldn't have to unwind much at all (1-2 turns, maybe) to make the change you want.

 

[bbaker6212]

I don't have an LCR meter

btw, they are 12 guage coils

 

[joeblutz]

If these are single-layer, air core inductors inductance should scale essentially with number of turns. You want to reduce inductance from 68uH to 65 uH, a change of about -4%. Remove 4% of the turns.

Even if they are not single layer, I would expect the scaling to be close enough.

Joe

 

[bbaker6212]

4% of the turns? How do I do that? I don't know how many turns there are!

The guy at PartsConnexion said just do it by weight. Remove enough turns to equal about 5% of the weight. You buy that?

 

[planet10]

4% of the turns? How do I do that? I don't know how many turns there are!

The guy at PartsConnexion said just do it by weight. Remove enough turns to equal about 5% of the weight. You buy that?

That should work. The outer turns won't be quite as tight as the inner so that is why 5 instead of 4%.

dave

 

[bbaker6212]

Now the problem is having a scale accurate enough to do the weight measurements

I think I'll just remove one turn and have done with it!

 

[bbaker6212]

Just found this on the Hammer Dynamics Super 12 tweaks page (on the full range driver site) so I suppose 12 ga shouldn't be much different - and it seems to have worked well for him...

"I just installed a 10 ga Solen Hyperliz inductor in the 0.65 H notch filter (remove 1 turn from a stock .68)"

 

[Peter Daniel]

Instead of doing by weight, you could check the resistance and decrease by 5%. If your meter can't read it you won't hear it either.

 

[Duo]

Might I ask what the inductor is for?

 

[bbaker6212]

It's for a speaker crossover. I know, others have already told me that such a small difference won't matter.

 

[Duo]

Well, to tell you the truth, you most likely won't notice the difference, but then you'll always have a negative impression on the xovers because of the placebo effect.

In my cases, I'm extremely picky about part values for hifi equipment. If I could have my way, that inductor would be on the dot! But that's just cause I'm picky about what goes into my system. Anyway, try the inductor in there as it is and see if you're satisfied with the sound. If not, try undoing the wire until it sounds right. With most inductors, you can remove windings while the audio is passing through and you can hear your adjustments in real time. Just make sure not to go past undoing two windings or you'll get mess going in no time.

 

[roddyama]

Hi Brad,

I had to do the same to my Solens. I counted the turns across the outer width and the layers from the inner to outer diameter. Multiply the two and you have a fair approximation of the total number of turns. Then roll off 4% of the total. If your nervous, just take 3% off.

Worked fine for me.
Rodd Yamas***a