For instance, when does the difference in DCR between two coils become significant?
Would there be an audible difference between a 2mH inductor with 1.6 dcr vs. one with 3.2? I ask because it seems that people tend to avoid using iron-core coils in the mid-range due to, among other things, hysteresis, but I'm wondering if the higher dcr in an air core is worth it.
Hi Ethan,
Yes, I believe there
would be a difference in sound between a 2mH inductor with 1.6ohm DCR vs. one with a 3.2ohm DCR. The inductor with the 1.6ohm DCR will deliver better bass dynamics ... that's because the less DCR you load in front of a driver, the more dynamic it sounds - hence, typically, active equivalents of passive speakers sound more dynamic ... because they have
no DCR "in the way" between the amp and the driver!

How do I know this ... because I have replaced the coils in the passive XO in my Maggies with lower DCR coils. Please note - just because the stock coils might be iron-cored doesn't mean you can't replace them with
air-core inductors with lower DCR. Just go and visit Michael Percy (for their 12g copper ribbon inductors) or North Creek (for their 8g & 10g round-wire inductors) to see what DCR these have.
Just for comparison, the North Creek 8g air-core 2mH inductor has a DCR of 0.08 ohms. However, it is physically very large!

Regards,
Andy