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

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

I’m happily using ICEpower based monoblocks on a pair of 4 ohm rated floorstanders with 12" woofers. I drive these hard, without a hiccup from my amps. However, they are a traditional design, not electrostats.

I’d listen to Erik, he tends to know of what he speaks.

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

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

Anyone have experience running them with Quad electrostatics, which go down to 2 ohms in the high frequencies.  Considering for a pair of stacked quads.

Most Class D amps behave as voltage sources, which is to say that they can double power as the impedance is cut in half.

This does not work in your favor in the case of ESLs, the reason being that the typical ESL has an impedance curve that varies by about 10:1 from the bass to about 20KHz. In addition, the impedance curve is not based on a driver in a box as you know.

When the impedance curve **is** based on a driver in a box, the impedance curve is also a map of the efficiency of the speaker; so for example the resonant peak of the driver in the box will be a peak in the impedance curve.

ESLs have their impedance curve based on a capacitor so its not a map of the efficiency of the speaker. IOW, the speaker has the same efficiency from the bass all the way to 20KHz or wherever it rolls off.

We all know that solid state amps and also class D amps can often double power as impedance is cut in half. Think about that happening over a 10:1 range- the amp will be making about 8x more power than it should at high frequencies. This is why solid state amps often sound bright on ESLs.