Smooth treble

Ralph has a good point. Non musical added harmonics would not be smooth (Amp xover distortion - clipping etc.) Jitter would also not be smooth. The musically unrelated stuff (just like non musical driver resonance) is generally harsh or "etched" sounding. A hypercompressed recording will sound rough too.

Dazzdax, to answer your question about the differences between the Sound Lab and the Apogee, IMO/IME the Sound Lab is likely the better performer of the two, given that you have the ideal amplifier to driver either one, which could be two very different amplifiers!

The reason I say this is that the Sound Lab has a powered system for moving the diaphragm and the Apogee relies on a permanent magnet. All magnets in all speakers have a certain amount of sag when the amplifier puts power to the diaphragm to make it move (BTW this is why Alnico magnets are preferred in cone systems as they sag the least and consequently sound better). IOW the powered electrostatic field of the ESL will not sag while the permanent magnet system will. The cone speaker equivalent of this is the field coil; so far I've not heard of a field coil-powered magnetic planar, and that would be an interesting speaker project...

The powered system offers greater impact and greater detail, often with associated smoother sound, IME.

Otherwise I would expect very similar performance overall, if it is possible to rule out the amplifier in the equation, which I am not sure is possible.

Hi Ralph, my experience is a bit different than yours. More often I hear "softer" (smoother, less grainy) treble presentation with (fullrange) ribbon speakers. For example years ago I heard the Dali Megalines (ribbon tweeter + midrange with cones for the bass) and it was as if there was no treble, at least not the treble we are accustomed of at home. The sound wasn't dull either but quite natural to me. The problem is at home we hear another sort of treble/high frequency reproduction than in the live situation --> live music sounds much more "smooth" and airy in the high frequency department.

Chris

"live music sounds much more "smooth" and airy in the high frequency department."

Depends on where you are sitting relative to the source.

Sit next to a drum set and give the crash symbol a good whack. Chances are it is not so light and airy.

Mapman, yes it is very direct with high energy content (not very good for da ears), nevertheless it sounds very rich with rich overtones and also... airy. You can also hear there is some warmth (paradoxically) in this loud, aggressive and metallic sound of the cymbals.

Chris