The problem with dipoles' rear wave is not just the delayed sound, it is also the comb filter effects.
So...
Music is distortion. Musical instruments get their "tone" from varying levels of harmonic distortion.
How to measure whether what we play is distorted is not so easily determined as the basic THD measurement.
IMD uses two sine tones.
THD + N (noise) adds calculation for sound that is not in the harmonic series.
So, make of that what you want, it's something I know.
I'll show something else in a minute.
I have 2 sets of Martin Logans, and 3 different dynamic speakers lying around (2 sets of Dynaudios, both active and passive, one set of little JBLs actives), so this is not coming from a lack of comparisons.
I didn't say dynamic limitation (somebody else did), I said somatic feel.
I'll pick a classical example, since that's your genre:
If I play Dvorak's 9, New World, 4th movement, I get more of a somatic effect from dynamic speakers than I do from my ML's.
The ML's have a bigger, more lifelike soundstage, but the dynamic speakers have more impact in the orchestral power zone (upper bass / lower mid).
Why even talk about THD when IMD is the real bad guy?
Are box speaker monopoles just exciting more room modes giving a heavier thump and thwack to the low end?
The problem with dipoles' rear wave is not just the delayed sound, it is also the comb filter effects.
Just posting off the top of my head. I have never decided which it is. Subjectively the panels sound like what they are in the upper bass lower mids which is soft and billowy lacking genuine firm impact. When considering the lower frequencies are partly cancelling each other out it sort of makes sense. The harder they move air the more the front and back wave cancel. So they would be soft in a sense. On the other hand, that type speaker with the cancellation of dipole nature does not excite half the room modes. Are box speaker monopoles just exciting more room modes giving a heavier thump and thwack to the low end? Or some mixture of both effects?
Instead of trying to make panels bigger to make them reach lower, we should them from the midrange on up, maybe even in a 3-way system.
Mine is a two way cross to a 12" sealed woofer at 180Hz, and I've added the four 15" CheezeWoofers to move more air down low low.
Here's my completely out-of-my-ass amateur hypothesis:
Real life instruments with a lot of energy in the upper bass / lower mids (bass, drums, timpani, lower piano registers, etc.) do excite room nodes in real life. We also experience (at least sometimes) those instruments not just as sound, but as physical experience - surfaces can vibrate and resonate around us, in addition to the room nodes. If we were cats, I'd say we experience this with our whiskers.
Thus, the monopoles excite more room nodes, it matches closer to our real life expectation.
In contrast, instruments that are in the upper mids / treble are things we "hear" as opposed to "feel", and they lie within our most sensitive hearing range, and also in the area where our lizard brain impulse response sensitivity to snapping twigs is most acute. In this area, electrostats, with their faster impulse response and lower inertia can sound more realistic.
So here's the weird paradox in my SWAG hypothesis:
If I'm correct, the whole hybrid electrostat hierarchy (pay more money, get a bigger panel with lower crossover to the woofer, more full range, and a bigger woofer) is wrong. Instead of trying to make panels bigger to make them reach lower, we should use them from the midrange on up, maybe even in a 3-way system.
IMD 83 dB listening position
I've never asked, but is there a high pass filter between the CheezeWoofers and the ML's? Or are the ML's still running full range?
That was basically Mr. Sanders idea, and he is not alone in that. Makes perfect sense, except those have been the least satisfying panels I have heard. Never gave all that much thought to why. In the ML line the wider panels have sounded better to me than the narrower panels. That is nothing definitive. It may just mean no one has done it right as it does make plenty of sense. Of course I did have an active DIY friend who thought the best rig would use huge panel woofers (big enough cancellation of front to back happened below 50 hz) coupled with very nice controlled directivity horns for mid and treble. Minimize the room influence and maximize what was on the recording to our ears.
I'm hoping the new 7-series JBLs give me a bit of the best of both worlds.
The cross is at 1.9khz on the 705p and 1.7kHz on the 708p.
On the 4367 it is 700Hz, and on the M2 800Hz.
I like my 180Hz cross.