Audio Research and Martin Logan Montis

Zd542

The Montis is a harder load at 4khz. than most other ML's
I'm not saying good tube amps won't drive them Zd, and they may sound very good. But if you want to get 100% drive capability and sound out of them then tubes will struggle a little at the presence region of 4khz as I outlined above.

Frequency (Hz)
Octave
Description
2048hz to 8192hz 8th to 9th octave. Gives presence to speech/music, where labial and fricative sounds lie.

Cheers George

I had spires driven with 80 watts tube power with no control issues whatsoever. The montis should be easier to drive than the spires

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.

"Stereophile: Either way, that this speaker is a difficult load for the partnering amplifier to drive is compounded by the high electrical phase angle.
The shape of the impedance trace will result in the Montis's top octaves shelving down when the speaker is driven by a tube amplifier having a high source impedance."

Cheers George

"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