chokes Vs. air coils

[robertbartsch]

I'm re-caping a couple of old crossovers and did some searching about the process.

One thread I found showed a network that used new copper air coils in place of the old chokes.

Should old chokes be replaced and if yes, why? I thought only old caps drift out of spec.

Thx...

[jcrobso]

I'm re-caping a couple of old crossovers and did some searching about the process.

One thread I found showed a network that used new copper air coils in place of the old chokes.

Should old chokes be replaced and if yes, why? I thought only old caps drift out of spec.

Thx...

An Iron core choke has a higher "Q" this is the ratio DC resistance to the inductance of the coil. The Iron core gives a higher value of inductance with less wire, this is good, less wire means lower DC resistance, lower the better.
The downside is that the Iron core can saturate and do nasty things to the audio signal.
Air core inductors do NOT saturate, this is good! The downside is that you have to use more wire to get the same inductance value, thus DC resistance will be higher and the "Q" lower.
Many of the vintage crossovers used Iron core inductors, since amps of that day had lower power output and would never saturate the core of the inductor.
But times have changed and high power amps are here, most good crossovers now use air coils of large gauge wire, 16 & 14 are very common to keep down the DC resistance. With Iron core inductors 18 and 20 gauge were used and still have a very low DC restiance.

The end result is that the value of the inductors has not change, but using air coils eliminates the chance of core saturation.