Originally Posted by malthuse
I would add as an aside my esl63s continue to perform in exemplary fashion. Even when the 2905s are playing fine they seem a little strident and shouts compared to the 63s. Is it just me?
The guts of both speakers are effectively identical. There have been different types of passive components in the circuitry over the years. And the original clamp circuit was a bit different if your 63's are not the very latest revision. The speakers after the 63's use a grille which is perf-metal and is not as open as either of the 63 grilles. That could lead to a bit of a cavity resonance effect, but that would be a quite high frequencies.
So in general, I can't point to any one thing that could be causing the differences, but I can believe there is a difference.
I'm a big fan of the original 63's, they are cheap these days and to my eyes look the best. They blend into the surroundings better than 2805's or 2812's. The giant quads like the 2912's just CAN'T blend due to their insane size.