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
That should work fine. I had my VT-100 on my SL-3's and had no problems. The model you have is easier to drive. Actually, I saw a couple of VT-100 listed here in good shape, at reasonable prices. You would probably be happy with the combo.


I drive my Martin Logan SL3s with an Audio Research Ref 110, and before that a VT 100. Martin Logan speakers work really well with tube amps. But they can sound a bit closed in with out enough power. At one point I had a VT 200 in my system. The SL3s opened up a bit more but not enough for me to justify doubling the number of power tubes. The Ref 110 was a huge improvement over my VT 100.

I know, I have heard how powerful the Ref 75 is. Still if it were me I would opt for the Ref 150. If possible though I would like to hear both amps with the Montis.

The whole Audio Research Ref line of amps is about to be replaced with new SE versions this month. it should be easy to find a good deal on either amp right now.
Jump on ARC asap would be great!!
The whole Audio Research Ref line of amps is about to be replaced with new SE versions this month. it should be easy to find a good deal on either amp right now.
Really? Dump a REF for REF SE with HUGE loss basically for a set of KT150s? Can't upgrade?

03-01-15: Ebm
Jump on ARC asap would be great!!
I rather dump, I meant jump on Magico asap would be greatER!!
I remember going to a demo that was showcasing top end Martin Logans with Bryston (solid state) vs the same Martin Logans with Jadis (tube) equipment. The Bryston gear was good no doubt, but the Jadis was magical.

I would be wary of any tube amp with these speakers to make them perform at their absolute best.
As at 4khz they give a nasty 3ohms and -55 degree phase angle. Which would be more like a 1-2ohm load as seen by the amp.

An amp that "almost" doubles it's wattage for each halving of load impedance down to 2ohm would be the amp to look for.
EG:
8ohms - 100watt
4ohms - 200watt
2ohms - 400watt

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

Cheers george
"03-02-15: Georgelofi

I would be wary of any tube amp with these speakers to make them perform at their absolute best.
As at 4khz they give a nasty 3ohms and -55 degree phase angle. Which would be more like a 1-2ohm load as seen by the amp."

Shouldn't be a problem regardless of what the specs are. I drove my SL-3's with my VAC amp that puts out 32watts/channel.

Also, if you'll remember back when these speakers were current, Stereophile put together a recommended system with the ML Aerius powered by an ARC VT-50. The Aerius was a little easier to drive than the SL-3, but still, they weren't too far off. And the VT-50 had half the power of the 100.
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
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.
"03-06-15: Georgelofi

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"

In order to have a situation like that, some pretty big assumptions have to be made. All the other components in the system, including the room will have to be neutral and deliver a frequency response that is flat, in order for that one issue listed above to manifest itself as a specific problem. By the time you're done picking matching components and setting them up in any given room, another component could balance the imperfection in the FR out, or even make it worse. None of this happens in a vacuum. Its a challenge getting all the components in a system, set up and working well, given they're flaws as well. Not to mention, planer speakers, in general, don't measure well to begin with. They never have and its something you really have to accept when you buy them.

The reason I asked about the Prodigy was was that, when it first came out, I was invited by my dealer to attend the new product seminar that ML gives when a major product is released. I'm not sure if they do this for all dealers, but the one I used to go to was very big and did a lot of volume. At the seminar, they selected some components in the store to do the setup, and the ML rep. (Gayle Sanders), picked an ARC VT-100 to power them with. He could have chosen anything. The store had no shortage of big, powerful solid state amps. And the Prodigy looks to be a much more difficult load than the Montis that we're talking about here. So, if an amp like that is OK for the guy who designed the speakers, I'm OK with just leaving it at that. But that's my own personal decision, and I won't try force it on anyone else. To be fair, I've heard ML sound great with Krell, Threshold/Pass, Counterpoint, McCormack and ARC solid state amps. There's no shortage of good choices regardless of personal preference.

All I can say to that is, "why do all equipment manufactures strive for a flat response?" And give +-db frequency response measurements points in their specifications?

If they wanted to have it altered all over the audio spectrum because of external loads, they wouldn't be bothered to list those specs to start with.

Need to look at the graphs closer, as the Montis is the harder load as it's bad phase/load point is at 4-5khz (the presence region), the Prodigy is up much higher at 7-10khz, as for the rest of it down low, it is a benign 4-6ohm load, with no - phase shifts to add to it.

Cheers George
hi everyone,
I have an opinion about the above technical aspects which senior fellows here were discussing. I have no electrical background but wish to express something which maybe important and overlooked.

We had seen many varieties of impedance coupled with varying phase angles charts, especially from ESL speakers when they behave like a giant cap into high freq.
When some audiophiles describe tubes amp suit well for ESL, we are assuming the tubes would handle the voltage & current needs well, at a certain range of frequencies. because, generally tubes cannot provide enough high current into magnetic coils when required for high excursion of speaker drivers into low bass.

Now, I do not know how tubes behave given the ever changing phase angle in relation to impedance,(voltage leads or lags before/after the current), but I suspect that tube can offer more "fluctuation" or "more tolerant" to out of phase signals when required by the speaker to produce music. I believe tubes are naturally more "forgiving"(tubes can give more voltage without rising current) as compared to output transistors when facing these out of phase requirements posed by speakers, especially ESLs. I guess transistors usually have a tighter range to work with electrical signal. transistors are generally linear devices am I right? my bet is that transistors work best when voltage and current are output simultaneously(meaning linear), to provide the power needed by speakers, so if transistors need to work beyond its specification(non-linear), it would clip even before it reaches its full rated power(watt).

base on above assumption, I perceive that tubes would better suited for ESLs but there are caveats, that's the songs the listener is playing should not contain low bass & high notes i.e. no punching bass, no high pitch like triangles or in harps/flutes etc.. (please also bear in mind tubes are slower in response, transistors are faster)

just my two cents.