The most dynamic speaker you've heard...

I've always wanted to know what a "field coil driver" is, anyway. Can anybody enlighten me?

Instead of being generated by a permanent magnet, the magnetic field within which the voice coil moves (the voice coil being what conducts the audio signal) is generated by a DC current flowing in a different coil, referred to as the "field coil."

Field coil speakers were used in many radios of the late 1920's and the 1930's, before permanent magnet technology came of age. Those included high end radios manufactured by companies such as E. H. Scott (no relation to the hifi manufacturer H. H. Scott, who came later) and McMurdo Silver, which can be considered to be precursors of modern hifi systems.

I believe that the main theoretical advantage of a field coil driver is that there is less variation of the strength of its magnetic field as a result of vibration and perhaps other effects related to the audio signal.

Regards,
-- Al

"Has anyone heard Casta Acoustics? Would the model "A" specs fall into the realm of great dynamics compared to my Paradigm Signature S2's(V3)?"

The 93 dB efficiency of the Casta Model A bodes well for good dynamics, though I'm a bit nervous about what seems to be an 18 watt power handling rating. But maybe they follow a different convention than we do over here.

What you don't want is, a significant mis-match in the thermal compression characteristics of the woofer and tweeter. When you have that, the tonal balance can change with the volume level. So if the woofer on the Casta Model A goes into thermal compression long before the horn-loaded tweeter, at high SPLs the speaker will tend to sound bright. I'm not saying this is the case, as I don't think there's enough information on their website to reliably judge.

Another possible issue is their use of a diffraction horn on the compression driver. Diffraction horns can have a tendency to sound a bit harsh at high SPLs, in my opinion, but usually not at low and medium SPLs, assuming good system design.

Duke
dealer/manufacturer

Mapman, I haven't heard a field-coil version of the CAR Hartsfield, but it would probably surpass the "regular" version that I've heard several times over the years.

Duke
dealer/manufacturer

MBL 101E Ridiculous!! These blew my mind!

Going off tangent a bit, but field coils do open up a lot of possibilities that fixed magnets can't match. You could have active flux modulation compensation for example.

Power supplies have to be incredibly well regulated so that back EMF generated by the amp and voice coil don't cause the magnetic flux to wander.