building my first crossover

[jaygeorge1979]

i am building the crossover for the zaphaudio.com hivi b3s projects, i am building it exactly to his specifications

the inductors i am using are madisound air core inductors...and the coils have tape wrapped around them

I know i need to adjust the .1 mH inductor to be .08mH, so i will have to remove some coils....my question is, do i replace tape around the coils when i am done? does the tape serve any purpose? do i need to remove the tape off of the .8mH inductors, even though i dont need to adjust those? i wont touch em till somebody gives me an answer...

[jaygeorge1979]

while we are at it, i am having trouble calculating how many turns to unwind...he said to use that online calculator, found at this link:

http://www.lalena.com/audio/calculator/inductor/

but i dont know what values to enter for the coil diameter and coil lengh....this is the inductor i bought:

http://www.madisound.com/cgi-bin/ind....19618&pid=567

and it says this under item description:

0.1mH Inductor 19 awg Air Core Medium Bobbin 48mm Ø x 23mm T

somebody please help!

[simon5]

48mm is the diameter and 23 mm is the height.

Coil length, I have no idea.

[jaygeorge1979]

ok...so is the only way to find coil length to unravel the whole thing? there has to be a better way...

also, what about that tape?

[simon5]

Dunno about the tape, that's why I didn't answer the first time. I think you can safely remove it but I would prefer if someone else confirms.

To get coil length, you could do this...

pi x diameter = length of a single turn

length of a single turn x number of turns = total length

[jaygeorge1979]

now THAT is a darn good idea...thanks simon5...or should i say sir...

anyone else about that ol' tape...

[owdi]

You can estimate the wire length by measuring the resistance. That inductor probably has a resistance of around .15 ohms. 19awg copper wire has a resistance of .008051 ohms per foot.

.15 / .008051 = 18.6 feet

I measure my inductors using speaker workshop, but this method should work too.

Dan

[jaygeorge1979]

so doi just assume that it is .15 ohm or do i look it up? how would i actually measure an inductor using a computer program?

now what about that pesky tape?!/!

[hongrn]

so doi just assume that it is .15 ohm or do i look it up? how would i actually measure an inductor using a computer program?

You can't. Use a digital multimeter like this one. Invaluable tool.

http://www.apexjr.com/new.htm

Hong

[simon5]

Can't measure a really low resistance like that directly with a multimeter, sorry, unless you pay several hundreds $$$.