Martin Logan Quest Z Bass - can it be fixed ?

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.

Mikey44, the ML's are bear to drive, puny amps need not apply. These measurements suggest that the specs don't really indicate just how difficult:
http://stereophile.com/content/martinlogan-quest-z-loudspeaker-measurements
My suggestion is to buy amplifiers for speakers, not speakers for amplifiers. Most of the speakers you seem to be considering are not easy loads. Think in terms of total system synergy.

Well, I hate to burst the bubble of all the Xperts here, but at this very moment I'm filling the room at 85dB volume driving a pair of CLSiiZ's with a small 10 watt Class A SET integrated. These panels have the reputation for being atrocious to drive. So much for reputations.

I've owned Aerius I's, SL3's, Quest Z's, Requests, and now working on my second pair of CLSiiz's. I've also owned the third generation Vantages. Best overall sound production to be had from any of these for me were in the order: CLS, Vantages, Requests, SL3's and so on.

I don't do heavy rock so perhaps my listening patterns don't have the same performance issues critics experience with ML's. A simple 50 watt Class A solid state amp will drive any of these speakers to satisfying levels. A 200 watt Sunfire will also do the same trick. They love current to be sure, but as I opened, even a 10 watt Class A 300B SET integ will do the trick...if it's the right one. Take a glimpse for the integ is currently on ad. I'm about to pull the ad for the integ's too good to sell.

As in all things audio your room, your taste in music, your needs will be different than mine therefore just because this works for me doesn't mean your experience will equal mine. But CLS's are worth the time to invest in getting them properly set to any room. Good things truly come to those that wait. What's the rush?

12-09-10: Johnsonwu
>Adding a sub makes it worse. It's a phase coherence issue.
The "speed" of the panel and that of the cheap cone are vastly different.

No. It's a power/polar response issue.

The panel is a dipole, with 4.8dB of directivity and a cosine-alpha polar response which plots to a figure 8.

The woofer is a monopole, with 0dB of directivity and polar response which plots to a circle.

The two don't match.

The problem is that each octave below where their outputs match a dipole requires 2X more displacement than a monopole. Given equal output at 160Hz (not unreasonable for a domestically acceptable speaker), the dipole requires 2X more output to match the monopole's SPL at 80Hz, 4X at 40Hz, and 8X at 20Hz.

Martin Logan's compromise through most of their range was monopole bass which has sonic problems where they're starting (a few hundred Hz) but comes in a small package with high output. Full-range ESL panels like the CLS/CLX compromise towards better sonics but reduced output and larger size.

Better solutions are dynamic driver dipoles like the Martin Logan Statement bass units or Audio Artistry series which get more output for a given footprint than ESL panels but can still be objectionably large (the Beethoven has a stack of 4 12" woofers behind each speaker) and dynamic driver assemblies which transition from dipolar to monopolar at lower frequencies like the Summit X.

You could build a Linkwitz style H frame.