Martin Logan Quest Z Bass - can it be fixed ?

you must protect the panels from bass energy.
Drive full range = disaster.
YOu may disable the woofer and custom build a woofer for it.
The SL3 is the most successful in mating a relatively quick woofer for the panels.
Not so with Quests and Monoliths.
Crossovers can be fixed with better resistors and better inductors to give it more speed and make it less lossy.
Very very involved work with lots of listening required.

The only ML's I've liked are the ESL's sans dynamic drivers. As much as I like to listen to them, I couldn't live with them. Please keep in mind, like most panels they can sound very different in different rooms, and they can be quite fussy about set up. Not the easiest or cheapest to amplify properly either.

Did Martin Logan fix what?

It's nice to get advice from people that know more about Martin Logan speakers than Gayle Sanders himself. With all of this advice I am surprised nobody mentioned the OP's choice of amplifier and how his Onkyo M-504 will alter the speaker's sound quality while trying to deal with the Quest Z's wicked impedance curve while it drops to 2 ohms.

Rrog - are you saying the M-504 cannot handle low ohm loads ?
Guess I never really looked that deeply into 'engineering quality' specs.

From AK:
"No problems with low impedance loads. A very fine, dynamic amp."

I tend to think, from what I've read re the 504 over the years, that at my volume levels, it'll have no trouble.

Should I think differently ?

I think IF I get them, maybe I'd try upgrading the x-overs...not sure.