Anyone With A Class 'D' Amp Play A 4 or 2 Ohm Speaker?

I play them in extended mode. I have a very big room.

I would advise caution in extrapolating from the results others report with different speakers!

Even with the Scintilla. Not only does the impedance of your speakers go a bit lower than the impedance of that speaker at some frequencies, but I wouldn’t be surprised if the phase angles of the Scintilla’s impedance may be less demanding.

Regards,
-- Al

Mitch, are you using the speakers with their "extended/normal" switch in the "extended" position (which iirc seemed to be the most commonly preferred setting), or in the "normal" position?

In the "extended" mode the Kappa 9 goes down below 0.8 ohms at multiple bass frequencies, where lots of energy is typically required. The "normal" mode is not quite as severe, but is still very challenging.

Also, regarding the mention that was made of operating Adcom 555s in bridged mode, keep in mind that a bridged amplifier will "see" a load impedance equal to the speaker impedance divided by 2. In other words, less than 0.4 ohms at multiple bass frequencies if the speaker is in "extended" mode.

Regards,
-- Al