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...
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...
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/index.cgi?cart_id=4095171.19618&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!
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/index.cgi?cart_id=4095171.19618&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!
You can't. Use a digital multimeter like this one. Invaluable tool.
http://www.apexjr.com/new.htm
Hong
simon, your formula assumed i know the resistance of the inductor, which i do not...unless you are saying that the estimated value of .15ohm is accurate for my inductor? i cannot unwrap 1/5 for two reasons...
number one, i would have to unravel the whole thing to find total length and then caclulate what 20% of that is before cutting it and then putting it all back together
number two: the relation of the two inductors is not linear...just because .08 is 1/5 of .1 doesnt mean their turns have the same relationship
number one, i would have to unravel the whole thing to find total length and then caclulate what 20% of that is before cutting it and then putting it all back together
number two: the relation of the two inductors is not linear...just because .08 is 1/5 of .1 doesnt mean their turns have the same relationship
If you're using that lalena.com site, put inductance of .1mH, wire guage of 19awg, diameter of 1.89 inches (48mm) and length of .905 inches (23mm) gives you these figures:
Inductance 0.1 mH
DC Resistance 0.19 Ohms
Wire Gauge 19 AWG
Wire Diameter 35.9 mils (1 mil = .001 in)
Coil Length 0.91 in
Coil Inner Diameter 1.89 in
Coil Outer Diameter 2.03 in
Average Turn Diameter 1.92 in
Wire Length 22.63 feet
Copper Weight 0.09 pounds
Turns 45
Levels 1.79
Turns/Level 25.21
The copper weight seems to match with the figures on the Madisound website.
It looks like you've got 45 turns for your inductor (but you can always check by unwinding the whole thing - it's only $1.90 and you can by another if you can't get it together). So just unwind 9 complete turns and you should have your .08 mH inductor.
I hope you've included the .19 ohms series resistance of the inductor in your cross-over calculations
Inductance 0.1 mH
DC Resistance 0.19 Ohms
Wire Gauge 19 AWG
Wire Diameter 35.9 mils (1 mil = .001 in)
Coil Length 0.91 in
Coil Inner Diameter 1.89 in
Coil Outer Diameter 2.03 in
Average Turn Diameter 1.92 in
Wire Length 22.63 feet
Copper Weight 0.09 pounds
Turns 45
Levels 1.79
Turns/Level 25.21
The copper weight seems to match with the figures on the Madisound website.
It looks like you've got 45 turns for your inductor (but you can always check by unwinding the whole thing - it's only $1.90 and you can by another if you can't get it together). So just unwind 9 complete turns and you should have your .08 mH inductor.
I hope you've included the .19 ohms series resistance of the inductor in your cross-over calculations
Cloth Ears - .19 seems high. I got my estimate of .15 from looking at the air core inductors at partsexpress, where the 18 awg was .13 and the 20awg was .19. I know the shape of the coil matters, but I doubt madisound would waste copper.
jaygeorge1979 - There is no guarantee the response peak of your speakers is in exactly the same place as the one's John Kurke used. Without knowing the impedance and response of the B3S in the baffle you will use, and without knowing the exact impedance of your coil, there is no point in being precise. Since you can't measure everything, just guess.
I'm pretty sure the madisound inductors are only built to 5% tolerance, so right now you have a coil with an inductance of .95 to 1.05. Take off about 8 turns, you'll be close enough. You will not hear an audible difference between a .075 and .085 coil.
btw, you're building a filter, not a crossover.
Dan
jaygeorge1979 - There is no guarantee the response peak of your speakers is in exactly the same place as the one's John Kurke used. Without knowing the impedance and response of the B3S in the baffle you will use, and without knowing the exact impedance of your coil, there is no point in being precise. Since you can't measure everything, just guess.
I'm pretty sure the madisound inductors are only built to 5% tolerance, so right now you have a coil with an inductance of .95 to 1.05. Take off about 8 turns, you'll be close enough. You will not hear an audible difference between a .075 and .085 coil.
btw, you're building a filter, not a crossover.
Dan
also, if i cant use the DMM in the lab, i have another idea, that works well along with guessing...how about i hook up everything to my breadboard to build the filter,and hook this up to the speaker...hook it up to an amp, and play some songs...i can unwind the coil one turn at a time until desired sound is reached, right? according to john, the coil MUST be .08mH, so i am guessing that when the right inductance is reached, i will be able to tell because it sounds best...if i go to far, i can simply rewrap the coil until i am agian satisfied with the sound, cut it, and tape it....any flaws with this plan?
It will be very hard for you to tell the difference, since you have to listen for something very specific. Using test tones you may be able to get close, but there's no substitute for electrical and acoustic measurements.
I'm in the middle of a B3S project myself, and I haven't unwound my .1 mh coils yet. I'm waiting to break in the speakers and complete the enclosures before I tweak the filter. If you like, I can post/email how many turns I unwind, although I'm using slightly different coils from Parts Express.
Dan
I'm in the middle of a B3S project myself, and I haven't unwound my .1 mh coils yet. I'm waiting to break in the speakers and complete the enclosures before I tweak the filter. If you like, I can post/email how many turns I unwind, although I'm using slightly different coils from Parts Express.
Dan
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