Wire gauge for crossover coils OA-12/OA-14

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arb
 
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Wire gauge for crossover coils OA-12/OA-14

Inläggav arb » 2011-11-24 15:08

Hello,
What wire diameters are recommended for the coils in the revised crossovers used with the new driver elements (B65oa II and T22-oa).
I found references to 1.2mm dia for the 0.4mH coil and 1.0mm dia for the 0.6mH coil, but apparently no recommendation for the 1.8mH coil.
So any input about the best wire dia for the 1.8mH coil?
(I am aware that most folks keep the original coil, but is 0.7/0.8mm
wire diameter optimal?)
Thanks!
ARB

P.S. I apologize for writting in English but my Swedish skills are nil, I can read some though, so, for all the expert people out there (and I know you are quite a few!), please, feel free to write in Swedish: I think I'll get it...

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grafpro
 
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Re: Wire gauge for crossover coils OA-12/OA-14

Inläggav grafpro » 2011-11-27 16:01

arb skrev:Hello,
What wire diameters are recommended for the coils in the revised crossovers used with the new driver elements (B65oa II and T22-oa).
I found references to 1.2mm dia for the 0.4mH coil and 1.0mm dia for the 0.6mH coil, but apparently no recommendation for the 1.8mH coil.
So any input about the best wire dia for the 1.8mH coil?
(I am aware that most folks keep the original coil, but is 0.7/0.8mm
wire diameter optimal?)
Thanks!
ARB

P.S. I apologize for writting in English but my Swedish skills are nil, I can read some though, so, for all the expert people out there (and I know you are quite a few!), please, feel free to write in Swedish: I think I'll get it...


For the 0,4 and 0,6mH coils in the T22-filters the coil resistance plus the resistor should be around 2,5ohm, so one could use a much cheaper coil with thin wire and a smaller resistor (or none at all).

For the 1,8mH in OD11/OA12/OA14 the original is as you say 0,8mm resulting in about 1ohm resistance, giving an attenuation of less than 1dB at any frequency. A larger coil will reduce the attenuation at most a few tenths of a dB. That is quite insignificant, so almost anything around or more than 0,8mm goes.
Drev HiFi-butik med Sonabprodukter, byggde studio- och orkesterelektronik och gav ut vinylinspelningar i ett tidigare liv. Gillar modern konstmusik. Är sannolikt tondöv.

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arb
 
Inlägg: 19
Blev medlem: 2011-11-23

Re: Wire gauge for crossover coils OA-12/OA-14

Inläggav arb » 2011-11-27 18:48

Thank you!

"For the 0,4 and 0,6mH coils in the T22-filters the coil resistance plus the resistor should be around 2,5ohm"

- keeping the 2R2 specified resistor then, the matching 0.4mH coil wire should be 1.0mm (DCR= 0.29ohm) and the 0.6mH coil wire 1.2mm (DCR= 0.29ohm), although 1.0mm wire would probably work as well in that case (DCR= 0.37ohm)...
- by diminishing the resistor to 1R8, a 0.7mm coil wire could be selected (DCR= 0.6-0.7ohm), reducing somewhat coil costs,
- eliminating the resistor entirely would require going down to 0.3mm wire, which, I feel, may be somewhat too extreme (with regards to current capacity).

"For the 1,8mH in OD11/OA12/OA14 the original is as you say 0,8mm resulting in about 1ohm resistance, giving an attenuation of less than 1dB at any frequency. A larger coil will reduce the attenuation at most a few tenths of a dB. That is quite insignificant, so almost anything around or more than 0,8mm goes."

- the only other valid reason to increase wire size is lowering heat dissipation somewhat, within reason though, since size (and cost) are going up almost exponentially.
- 0.8mm for all coils (the original design) looks like a very good compromise (but, that was expected...),
- 1.0mm or 1.2mm for all coils could be another one, accounting for the higher power dissipation normally requested today (the target design was for 40W back in the 1970's)...
- beyond that, money is probably better spent, on software (music) rather than hardware, at least that's how I view it...
Best regards,
ARB


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