Also, I have to hop on the earlier conversations about electrostatic speakers. One poster said he'd moved on from them, finding them dynamically unconvincing - not 'pressurizing the room' the way box/dynamic speakers do. I moved on from electrostatics (Quade ESL 63s) for the same reason! I was for a while seduced by that particular boxless 'transparent-sounding' aspect of the electrostatic sound. But it seemed after a while to have a sort of ghostly, removed character, as if I were listening to a performance happening through a window in a different room.
When I'd throw in my older smaller box speakers (a pair of old Thiel 02s) it's like the room came alive with the energy of musicians. Drums, bongos just seemed to "whap!" the air right there, like someone was in the room playing the instrument. It just seemed more palpable and dynamic and affecting.
I added the gradient sub to the Quads - some may remember it was a dipole sub designed specifically to match the radiation pattern of the Quads, and the Quads sat on top making for a seamless monolith. They remain to my ears the most seamless combination of dynamic sub with a panel that I've heard. Yet, I still found the 'problem' above persisted and I moved on to box speakers, never looking back.
I've heard a great many Martin Logan hybrids over the years, and my friend owns a pair of ML hybrids as well. Every time I'm struck by the same impression: wow at that cool electrostatic presentation in the mids up, but that same old weightlessness. I get why some people think that adding a dynamic driver in to the design for the lower frequencies gives back some dynamic palpability. But what I always hear is a discontinuity: instruments ranges covered by the dynamic driver have some weight and air-moving drive - e.g. bass instruments - but as the range moves to higher frequencies there is that weightless quality. My friend thinks his MLs rock just fine because once he feels those bass notes hitting from the woofer section, well....there you go! They rock! But for me, it just doesn't work as I find the rest of the spectrum dynamically bereft. Put on Rush and geddy lee's bass can be felt, but Lifeson's guitars don't seem to have the same drive - they are more like a sonic mist you could just walk through rather than the killer impact you hear from a guitar through their cabinet amplification.
So, I get both the anti-panel and pro panel opinions. I enjoy visiting panels - and in fact would own Quad ESL 57s if I had the room to store them when not listening. But it's more a nice place to visit than a place to stay for me.