Audio Research and Martin Logan Montis


My 21 year old solid state amp is developing some hum issues and the price to ship and fix it would be more than the value of the amp. Has anyone had any experience driving the Martin Logan Montis with Audio Research amps.
the Montis is rated at 4 0hms, but it varies widely, down to .5 ohms. It is pretty sensitive at 91 db. Am considering buying a Ref 75 before the upgrade.
Regards,
Robert
tennisdoc40
"03-05-15: Georgelofi

Bfin3
It may sound very good with your 80w tube.
But with this statement for the measured Stereophile tests, it maybe not at it's "best" with tubes."

I haven't read Stereophile in years, but one thing I remember is that you have to watch them with their measurements because the person doing them is usually not the person reviewing them. And when that happens, they don't have listening tests to verify there will be a spec related issue in actual use.

Going by actual experience with ML, and looking at the specs ML lists, I don't see cause for concern. Unlike the SL-3's and some of the other models mentioned, this pair of ML's has a powered woofer. An advantage none of the others had. The amp just has to drive the panel. ML list's the speakers at 91db and recommend a minimum of 20 watts. I've never been one to trust amp specs, but speakers are another matter. They don't want someone to buy they're speakers and have bad results due to low power, so most manufacturers seem to recommend what's really needed to drive the speakers. But also, looking at a recommendation of an amp that puts out 200 watts into 4 ohms, who's watts are we talking about? All the companies measure them differently.
Zd542

This is the kind of non linear frequency response that may happen with a tube amp at 4.5khz with the Montis, -2db!!! because of it's -55 degree phase shift and combined 3ohms load, because the amp can't deliver current.
It has nothing to do with wattage! It's all about current. Not very flat is it?

http://www.stereophile.com/images/archivesart/A88FIG01.jpg

Cheers George
What difference does it make if the system sounds OK?

What about a different speaker like the Prodigy? Would you say the same about that one?
03-06-15: Zd542
What difference does it make if the system sounds OK?

What about a different speaker like the Prodigy? Would you say the same about that one?


Well your not listening to a flat frequency response, it like having a fix tone control embedded, + - 4db from 20hz to 20khz

As for the Prodigy, it too has an evil load, of -55 degrees with 3ohms, but it's further up around 7khz.

http://www.stereophile.com/content/martinlogan-prodigy-loudspeaker-measurements

As for Bfin3 Spire's there is no load v phase angle graph done on these, so who knows.

Cheers George
"What difference does it make if the system sounds OK?"

A technical mismatch does not mean the results will not "sound good". Its a red flag indicating performance as intended may not be optimal. But nothing says optimal "performance" means best sounding to all. Optimal performance on paper is always a good omen though. The sound can always be tweaked to tastes to some extent once one has optimal performance but if not its possible that no tweaks might suffice.

Its more about the selection process and how to be in the best possible position to achieve satisfactory results more so than a question of what might sound good or best to any particular individual.