When a coil is connected in parallel to a loudspeaker something else happens.
At quick current / voltage changes the coil changes its magnetic field and
lets the AC voltage pass through. The coil works like a filter, letting high
frequency oscillation pass through to the loudspeaker connected in parallel.
far superior to all other coils regarding impedance
response, vibration and microphonics effect: the foil coil by Mundorf
Additional important notes: If a crossover is optimised for a high-impedance
coil, the use of a low-impedance coil often doesn't show any advantage. The
crossover needs to be tuned again incorporating the high quality component.
A re-tuning is also advisable when exchanging a coil with core for a coil
without core; since distortion is reduced the result would be rather positive.