Hi All

I've just swapped my Martin Logans - Bye-bye Ascents, hello Prodigy. Prodigy was ML's top-of-the-range speaker 15-20 years ago, and these have allegedly recently been re-panelled. Haven't got the placement/bass sorted out yet, but the panel does a lot of the work and they're sounding nice already - I've just dropped them in more or less where the Ascents came out.

However, I may not able to sort the bass out in their current form, and this is where I'll need help. Each prodigy has 2 x 10" bass drivers - one at the front and one at the back. They came out of the factory with an alloy cone at the front and a paper cone at the back. The front cone does the bass "proper", the rear cone appears to be used to cancel some of the rear radiation from the front one. (Martin reviewed it all for HFN 20 years ago and seemed to like it...). Each is in its own sealed compartment.

The rear cones on mine are original but the front ones are clearly polypropylene, so they've been "done" at some point. Googling suggests that alloy-coned woofers weren't one of Scanspeak's brighter ideas in terms of reliability, at least with the glues available circa-2000.

The internet hive-mind suggests that ML have a suggested replacement driver (Scanspeak Classic 25W/8565-00) so I've mailed them to confirm, so I get the correct answer from the horse's mouth. In the meantime, if I get a set of US-sized Allen keys tomorrow (rolls eyes) I can drop out one of the existing polypropylene units and see if it has a name or number on it.

Would I then be right in assuming that if we can find some Thiele-Small parameters for the polypropylene units, you guys will be able to advise as to whether they're "near enough" or whether I just have to stump up the £400 for a pair of new drivers...?

Or is the answer always going to be "buy the scanspeak drivers"? :-)

Thanks!
Pete

Just a thought?

If they are chuffing a possibility it could be the voice coil rubbing? try rotating the drivers through 180 degrees and refit them, may take a day or so to settle down

at risk of boring us all :

The ML electrostatic upper panel is a dipole, directional where the rear sound radiation is out of phase with the front and thus has a characteristic sound in the room.

A box type woofer is omnidirectional ,ie spherical.

Superimposing these two in one loudspeaker is awkward and their sound fields fight.

ML designed a double box woofer where the rear radiation is partly out of phase with the front, more closely aligning with the dipole panel above, and with a more natural sound, but adding power bass.

Martin

Well, I got an hour or two to play with the new toys. I'm clearly going to have to dance my way around the sitting room with them to get some optimal performance, but there's very clear signs of promise.

The bass is by some margin the best I've had in my room; that's not necessarily saying a whole lot, I know, but... With past speakers, walking around the room has yielded plenty of ill-defined bass, but actually getting it to arrive solidly at the sofa has always been problematic. ML's somewhat complex dual-woofer arrangement, that Martin mentioned above, does indeed seem to be doing something useful. The actual forward-facing woofers are still 10" units, the same as in my previous MLs, but what they're delivering is significantly improved - there's real depth, there's clear note differentiation and - based on playing some "Zumba for Kids" (!) from Youtube this afternoon - there's real Slam when the source material has been (over-)engineered for it. Bass is playing tunes, without a whole lot of effort at room placement. It should only get better from here.

The panels are glorious. With a crossover down at a nominal 250Hz, the tonality is gorgeous. Slightly warm and honeyed, at least based on what I've played so far, but that doesn't seem to be a trick pulled at the expense of the treble. Definitely on the warm side of neutral; whether this is an artefact of the speaker in general or of the Acoustic Zen cable, I can't currently say, having stripped the terminations off of my VDH cables in order to terminate the AZ! So it ain't a monitor, but it is lovely. And the layers of detail - singers have lips and teeth and they breathe, and all those sorts of cliches. I'm at a bit of a loss as to why it's much better in this respect than the Ascent was - after all, the panel is the panel, albeit the Prodigy panel is 25% larger (4' high, but 16" wide rather than 12"). I can only assume that it's being held more rigidly, and that more money was spent on a better and more transparent cross-over. But "difficult" voices - Cowboy Junkies' Margo Timmons, or Springsteen, for example - are portrayed very nicely indeed.

Pace and timing, as Martin reported 20 years ago, are good. Dynamics are excellent, they go extremely loud with no sense of strain. Going old-school, Oxygene IV is just a hilarious romp!

So that was the good bits.

I haven't got the positioning right yet; firing straight down the room, I get pace and timing and excitement and a hole in the middle. Toed in a bit, I get lovely spread and great delicacy but a sense of wanting to keep turning it up to wake 'em up some more.

Anyway, promising :-). Have to wait til lockdown is over now until I can find a "dance partner" to help me move them....