Apogee vs Soundlab

Jafox, what make of selector switch did you use on your SL?

Dazzdax, one thing you might try is to put a resistance in series with the speaker. Two to four ohms ought to do (some audition might be a good idea), but it should handle high power. This will simulate an amplifier with a higher output impedance and will substantially reduce the power doubling problem. A fair amount of power made by the amp will be absorbed by the resistor, so this is not a very efficient means!

The impedance curve of the Quads is bit different from the Sound Labs, if I recall right the Quad matching transformer operates full range (the Sound Lab is a full-range diaphram driven by two transformers which are crossed-over to operate two frequency bands). I doubt that it has the same bandwidth as a result.

Chris, before you start a process that will likely never get you to the desired result with your ss amp, you need to take more seriously Atmasphere's comments regarding the SL's performing at their best with a tube amp. With this said, I can drive the A1's with a Counterpoint NPS400 and there is no brightness nor fatigue at all; I just don't have the degree of detail and refinement in the trebles and the rest of the range for that matter.

With the adjustable 0-to-2 ohms selector, I run it right in the middle. Going to 2 ohms has a significant reduction in treble level. A 10-ohm resistor in series with the SL's treble circuit will have a MAJOR subtractive impact.