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check out rogue audio they make a hybrid 8ohm 250watt , 4ohm 400watt class D integrated amp.
That certainly sounds promising... have you auditioned it for yourself? If so, how did you find the overall performance and sound?

When I refer to "promising " I can think of just one brand. There are no Class D amplifiers that fully engaged me to the music. It nearly sounded Hi Fi right along...

However, I must say Jeff Rowland Design has come a long way. His would most probably be the only Class D amps I would consider, if I were to go that route. JR and his team have really pushed the boundaries into Class D operation and they've made some serious gear! His preamps are really tops as well and the pricing isn't too shabby.

I've compared Devialet, and two other amps (can't even remember the brand for crying out loud... goes to show they weren't upto par), the Devialet was superior all round. Then I got a chance to audition the JR Designs, and wow! That was in a totally different league! No comparison at all.

Sounds promising to see Rogue taking up Class D, I guess they need to expand their reach. Especially when most people don't have much space to fill their entire living area with audio gear, Class D makes sense I guess.

On my next travels in July, if I do come across the Rogue Class D gear, I'll make it a point to have a listen. Certainly something new to learn.

*forgot to mention * the speakers used during this demo / comparison on Class D amps, were the Ethos, Montis and 11A's.
Cheers, RJ
 
However, I must say Jeff Rowland Design has come a long way. His would most probably be the only Class D amps I would consider, if I were to go that route. JR and his team have really pushed the boundaries into Class D operation and they've made some serious gear! His preamps are really tops as well and the pricing isn't too shabby.
I believe Jeff Rowland has gone back to class AB for all the flagship models. I personally haven't heard any of the newer Class D offerings, I have the Model 1 that runs Class A/AB and it's so good that I'd like to pickup a couple more of them if the opportunity ever presented itself at the right time.
 
There's also your own home-market Audio Research offering, the DSi200 integrated. I'm using one over here in the UK with my Summits and I'm impressed. Being their own bespoke circuit design rather than an off-the-peg module it sounds far more musical than a lot of early Class-D amps did. You also had the benefit of the more powerful stereo and mono power amps in the same Definition series - I don't think they were sold over here but I'd like to hear them if the chance ever comes around (personal import, perhaps)
 
Hi. I've followed this thread for quite some time. I may have contributed to it earlier, but I have mentioned here or elsewhere how pleased I've been with a single Benchmark AHB2 driving my pair of Montis ESLs in a sizeable living room.

I'd like to add some additional remarks concerning what, IMHO, ML ESLs need, and perhaps what they don't need or can't use.

I'd like to offer a pair of useful articles. The first is a multi-page review of the ML Montis speaker by Stereophile's Robert Deutsch with measurements by John Atkinson:

https://www.stereophile.com/content/martinlogan-montis-loudspeaker
Note particularly the Specifications page and the Measurements page.

First, it's important to remember that, for most ML ESLs, the bass is handled by its own self-powered woofer amp. Over the bass frequency range (from 20 Hz to, say, 200-300 Hz), the ML ESL presents to the outside amplifier a nearly ideal flat resistive load that is a pussy cat for the outside amp to drive. The real delivery power comes from the ML ESL's own built-in bass driver amp.

On the Specifications page, the indication is the ML Montis has a sensitivity of 91 dB.

Benchmark Media provides a useful whitepaper with calculators concerning System Performance Calculations:

https://benchmarkmedia.com/blogs/application_notes
With 100 watts of input and a speaker sensitivity of 91 dB, the Montis pumps out a sound pressure level of 111 dB SPL. At one meter distance, this is the level of an active jackhammer or power saw, certainly not levels that should be tolerated without ear protection.

Said another way, 100 watts is plenty to drive the Montis to levels beyond hearing safety.

Now look at the measurements. Notice that, at frequencies at or above 1 kHz, the Montis driving point impedance resembles a capacitor: the impedance drops inversely as the frequency rises, and it actually drops to as low as 0.5 ohm at the upper end of its range.

IMO, the best sort of amplifier for this type of load is one that is both tolerant of wide swings in impedance, AND that can deliver large amounts of clean current at high frequencies, which the AHB2 is designed to do. In fact, the AHB2's power output goes up beyond the nominal 100 watts per channel as the load impedance drops.

I'm not saying the AHB2 is the only amp that works well the the ML ESLs. I can tell you from my experience that it does work well, that its output power is more than adequate and its operational properties work with this ESL as a load. I don't think it's necessary to use more power than the speakers will ever be capable of processing and delivering. I've tried to explain why, but I know others may feel differently.

I've used other amps as well, notably a custom modified ADCOM GFA-555, a refurbished pair of McIntosh Mc60s (6550 tubes with a unique multifilar output transformer and wiring topology) and a Marantz 8B (EL34s). The tube amps had difficulty driving the ESLs at the upper frequencies (the speakers sounded sweet but dull), while the GFA-555 isn't nearly as clean and well behaved as the AHB2.

I do own an NAD M33 with a pair of Purifi Class D power amps. I have listened to the M33 a great deal with Dynaudio loudspeakers (remarkable results) but I have not tried it with the ML Montis.

It's worth taking a look at how the AHB2 has measured up. It's one of the most carefully measured amps out there. I'm not saying measurements are everything, but it is one of the cleanest, quietest, lowest distortion amplifiers in production.

There are good reasons for buying a specific amp or pair of amps -- pride in ownership, for one -- and far be it from me to be critical of any one else's favorite choice as being just that. In terms of what the ML ESLs actually need to work at their best, to achieve what really makes them sing, is not as elusive a matter for deliberation as it might have been in the distant past.

Many dealers offer extended try-out periods offering full money back (less shipping) if the performance proves unsatisfactory.

As always, these comments are just my two cents.
 
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Note particularly the Specifications page and the Measurements page.



On the Specifications page, the indication is the ML Montis has a sensitivity of 91 dB.
[/QUOTE]

and this is where the 'trickery' begins ! A good article in Feb TAS explains............

Simply put when a 4ohm speaker is given a sensitivity rating driven by 2.83 volts rather than 1 watt it dissipates TWO watts of power. Thats's dbl the power , which is equivalent to 3db. Thus making the speaker appear to be 3db more sensitive than it is.

I'm not implying 100 watts can't provide satisfactory power but I will say again as I stated many times before an amps ability to 'dbl down' is a very good measuring parameter for use with stats
 
"... and this is where the 'trickery' begins ! ..."

I meant no trickery. twich54's comments about caution as to what the sensitivity spec really means are valid. Still, I'd like to point out a couple of things.

It can be seen from John Atkinson's impedance measurements vs. frequency that the speaker impedance is not the simple constant 4 ohms that Martin Logan's data specifies:

https://www.martinlogan.com/en/product/montis
Sensitivity91 dB/2.83 volts/meter
Impedance4 Ohms, 0.52 at 20kHz. Compatible with 4, 6, or 8 Ohm rated amplifiers.

From 500 Hz to 2 kHz, the impedance is actually in excess of 7 ohms. Above this range, the impedance is an entirely different story altogether. It's very low and drops as frequency rises.

Yet, the anechoic response from 500 Hz to 15 kHz and beyond is remarkably flat.

So, if one really wants jackhammer or power saw levels across the entire spectrum, it may indeed be necessary to aim for a higher available power capability than, say, 100 watts a channel.

Consider further, as shown on Benchmark's website, the following:

https://benchmarkmedia.com/collections/all-products/products/benchmark-ahb2-power-amplifier

AHB2 Continuous Average Output Power

< 0.0003 % THD+N at full rated power, 20 Hz to 20 kHz
100 Watts per channel into 8 Ohms, both channels driven
130 Watts per channel into 6 Ohms, both channels driven
190 Watts per channel into 4 Ohms, both channels driven
240 Watts per channel into 3 Ohms, both channels driven

So, the AHB2 ultimate delivered power capability actually compensates somewhat for the pesky impedance drops. Said another way, the AHB2 has the kind of reserve twich54 calls for. And, might I add, at brilliantly low distortion.

And, as I said earlier, if it's more peak bass power one wants to pursue, the external amplifier doesn't have the final say. It's the Montis' own built-in woofer amps that define that limit.

The elephant in the room is, of course, Are you sure you really want to achieve levels at or even near a jackhammer or power saw? Is breaking glass or eardrums really your goal?

I'm not twisting anyone's arm about this. I don't work for Benchmark and I'm not a dealer. I'm just an enthusiast. It's what makes you happy that matters most. What I've said is just my two cents.
 
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The specs on the Benchmark power amplifier look quite good. Although specs do impress, sometimes when you actually audition the gear, it's a totally different story... which most of the time is quite disappointing.

I've come across those amplifiers who have real value specs and when auditioned, they've equally impressed. I mean really gripped full range stats and large ribbon panels extremely well, an effortless full authority kind of sound, where nothing was forced. Just to mention a few, Dartzeel, Vitus, Pass Labs, CH Precision, Solution, Boulder, ARC, CJ, VTL, VAC, Jadis and Aries Cerat. These were my favourites amongst many others and really really impressed. There was absolutely nothing to fault in any of them other than the damn pricing on some gear. On some of the top line stuff, like the Dartzeel monoblocks, that pricing was half the cost of our house when we purchased in 2018. Hot damn!

The Benchmark seems to do things right on paper... so hopefully it also works well driving stats regardless of impedence swing. Watts and sheer power, although important, isn't everything. High current and stable voltage is the key, and most amp brands specs don't even show these figures in terns of amperage or voltage. So who knows what's going on in the specs, until you listen.

In general though, I've found that a much higher powered amp will give more of everything or at least it should. In terns of more power, there should also be much larger power supplies, which means more current capacity and higher voltages. Although we simply cannot continuously listen at 100s of watts (we'd go deaf!), the amp is simply cruising along during difficult loads. It's more power will also mean far more headroom and higher capacity to handle notorious impedence swings that are typically found in stats.

If you've been enjoying your music with the power amp/s that you have and they fully grip the stats well, that's all that matters regardless of brand / type and spend. However, things start to make more sense only when you actually start comparing different brands. The one that you thought was great was only just ok when you tried out a different one, that not only fully gripped your stats but also improved its performance onto another dimension! Now that's an impressive amplifier, and if I can afford it, thank you kindly I'm keeping it!

Cheers, RJ
 
"... and this is where the 'trickery' begins ! ..."

I meant no trickery.

Rascal, I was not implying trickery towards you, rather towards Martin Logan and any other speaker mfg that uses the '2.83 volt spec' for a nominal 4 ohm speaker
 
Roger Big Dog RJ on amps that cost the same as the house. ;)

For me, “fully grip”, with respect to my experience with the AHB2, has meant attaining a natural, transparent and effortless delivery and an uncanny ability to handle complex music passages with little or no interaction or blurring of one instrument or voice by others. It’s not a flashy drawing attention to itself. Prior to using the AHB2, I had the feeling the Montis were held back (distorted) because the membranes had a limited range of excursion, but through use of the AHB2, which is utterly clean and I believe is better suited to driving this sort of load, that impression is totally dispelled.

Roger twich54. Thx. And indeed, you’re correct.
 
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Oh, one more thing:

I think I’ve found the plural for Montis, which means Mountain in Latin. It’s Montium! How ‘bout that! ;)
 
That certainly sounds promising... have you auditioned it for yourself? If so, how did you find the overall performance and sound?

When I refer to "promising " I can think of just one brand. There are no Class D amplifiers that fully engaged me to the music. It nearly sounded Hi Fi right along...

However, I must say Jeff Rowland Design has come a long way. His would most probably be the only Class D amps I would consider, if I were to go that route. JR and his team have really pushed the boundaries into Class D operation and they've made some serious gear! His preamps are really tops as well and the pricing isn't too shabby.

I've compared Devialet, and two other amps (can't even remember the brand for crying out loud... goes to show they weren't upto par), the Devialet was superior all round. Then I got a chance to audition the JR Designs, and wow! That was in a totally different league! No comparison at all.

Sounds promising to see Rogue taking up Class D, I guess they need to expand their reach. Especially when most people don't have much space to fill their entire living area with audio gear, Class D makes sense I guess.

On my next travels in July, if I do come across the Rogue Class D gear, I'll make it a point to have a listen. Certainly something new to learn.

*forgot to mention * the speakers used during this demo / comparison on Class D amps, were the Ethos, Montis and 11A's.
Cheers, RJ
PS Audio makes nice amps in several different flavors; some very affordable.
 
PS Audio makes nice amps in several different flavors; some very affordable.
I've bought a PS Audio S300 Amp along with a PS Audio GainCell DAC some time ago to drive my Martin Logan Montis. The S300 was being sold at a promotional discount at the time the GainCell DAC was purchased. The GainCell DAC worked adequately but I recall running into problems with its Home Theater operating mode. The S300 power amp was disappointing and not something I would recommend to others to feed the Montis. I returned both of them.

I was considering the PS DAC and amp as a replacement for a Parasound Halo 5 (John Curl amp design), a well-built reliable powerful integrated amp with a well behaved Home Theater mode and other nice features. The Halo 5 was ultimately bettered by and replaced with the Benchmark DAC3 and a succession of power amps (McIntosh MC60s, Marantz 8B, modified ADCOM GFA-555 (Nelson Pass design)). This, in turn, led to the testing and adoption of the AHB2 amp as by far the leader of this pack.

I have read and watched excellent glowing reviews of PS Audio BHK (Bascomb King) amps, including one by Arnie Nudell, but I don't have direct experience with them.
 
Thought I would add my own experiences here regarding my journey with the ML ESL11’s and amplifiers used.

As my original post I have been using a JS audio upgraded Musical Fidelity Tri-Vista 300, this is a monster of an amp but drives the ML’s effortlessly, the only downside is form factor and user interface.

The amp is monstrous, and doesn’t really fit racking that well, also the remote is the most useless remote I think I have ever come across, so it’s manual operation only! (I know tough burden!!)

But it sounds fantastic, so I wanted to stick with a linear amp and reading various forums decided to go for a used Magtech which came up for sale and although large-ish, would fit into my racking with the speaker leads connected and seemed to have all the right attributes.

This amp is good but not on a par with the Musical Fidelity, it sounds flat and lacklustre in comparison so this was swapped out for a pair of Nord Hypex NC500 amps which is part of a 10 channel active system using the LX521 open baffle speakers (one of the best systems I have heard to date and my current reference) . Unfortunately, these were not good at all, sounding somewhat worse than the Magtech, seemed like all the life had gone out of the speakers!

The Hypex NC500 appear to be exceptional with the LX251’s but in all fairness, I haven’t had the opportunity to try something like the Musical Fidelity on the LX521’s as 10 channels needed! (This is something that I will now need to try if circumstances permit, to see whether it is just a switching amp thing with electrostats or whether there is a significant increase in SQ to be gained on the LX521’s by going linear!

So to recap final order of preference in my ML system thus far:
  1. Musical Fidelity Tri-Vista 300 (by a good margin)
  2. Sanders Magtech (Much better than the following 2 options)
  3. Linn Klimax Solo’s
  4. Nord NC500 (Hypex)
Happy listening!
 
Thought I would add my own experiences here regarding my journey with the ML ESL11’s and amplifiers used.

As my original post I have been using a JS audio upgraded Musical Fidelity Tri-Vista 300, this is a monster of an amp but drives the ML’s effortlessly, the only downside is form factor and user interface.

The amp is monstrous, and doesn’t really fit racking that well, also the remote is the most useless remote I think I have ever come across, so it’s manual operation only! (I know tough burden!!)

But it sounds fantastic, so I wanted to stick with a linear amp and reading various forums decided to go for a used Magtech which came up for sale and although large-ish, would fit into my racking with the speaker leads connected and seemed to have all the right attributes.

This amp is good but not on a par with the Musical Fidelity, it sounds flat and lacklustre in comparison so this was swapped out for a pair of Nord Hypex NC500 amps which is part of a 10 channel active system using the LX521 open baffle speakers (one of the best systems I have heard to date and my current reference) . Unfortunately, these were not good at all, sounding somewhat worse than the Magtech, seemed like all the life had gone out of the speakers!

The Hypex NC500 appear to be exceptional with the LX251’s but in all fairness, I haven’t had the opportunity to try something like the Musical Fidelity on the LX521’s as 10 channels needed! (This is something that I will now need to try if circumstances permit, to see whether it is just a switching amp thing with electrostats or whether there is a significant increase in SQ to be gained on the LX521’s by going linear!

So to recap final order of preference in my ML system thus far:
  1. Musical Fidelity Tri-Vista 300 (by a good margin)
  2. Sanders Magtech (Much better than the following 2 options)
  3. Linn Klimax Solo’s
  4. Nord NC500 (Hypex)
Happy listening!
Certainly looks like the Musical Fidelity amp was the clear winner. Should have kept it...
Goes to show the amp to speaker matching importance. It's so critical to get that combination right, and once you've found it, just leave it! The moment you alter that synergy, everything goes out of whack. Changing gear once again and end up in circles, unless you were going for a complete overhaul. That would include changing the front-end and back-end gear.

In most cases where I've come across a slight mis-match, has the system either under-amped and over-speakered or over-amped and under-speakered. It's crucial to strike a balance between the two, all other gear will fall into place. Another common component generally overlooked, even though the gear is mighty fine, is the room! The room parameters and its characteristics are just as important as any other component in the system.

I've learned over the years to find the right combination of amplifiers that deliver the most natural affect, without pushing or forcing anything. The room has to allow you to relax and be engaged in the music, not keep you on the edge of your seat all the time. Once you've found the right combination, easy flowing tunes, very easy to relax and a totally immersive experience, that's pretty much it! Regardless of price or SOTA gear, you'll know it when you hear it.

Always liked the older MF A1000 series, and the huge SA470 power amps. That was a phenomenal unit way back then. One of the systems- Drove the Mission 753's and Infinity's IRS 1B's extremely well. Partnered with a Meridian disc player, it was tops! Those were the good old days.
Cheers to Musical Fidelity!
RJ
 
Certainly looks like the Musical Fidelity amp was the clear winner. Should have kept it...
Goes to show the amp to speaker matching importance. It's so critical to get that combination right, and once you've found it, just leave it! The moment you alter that synergy, everything goes out of whack. Changing gear once again and end up in circles, unless you were going for a complete overhaul. That would include changing the front-end and back-end gear.

In most cases where I've come across a slight mis-match, has the system either under-amped and over-speakered or over-amped and under-speakered. It's crucial to strike a balance between the two, all other gear will fall into place. Another common component generally overlooked, even though the gear is mighty fine, is the room! The room parameters and its characteristics are just as important as any other component in the system.

I've learned over the years to find the right combination of amplifiers that deliver the most natural affect, without pushing or forcing anything. The room has to allow you to relax and be engaged in the music, not keep you on the edge of your seat all the time. Once you've found the right combination, easy flowing tunes, very easy to relax and a totally immersive experience, that's pretty much it! Regardless of price or SOTA gear, you'll know it when you hear it.

Always liked the older MF A1000 series, and the huge SA470 power amps. That was a phenomenal unit way back then. One of the systems- Drove the Mission 753's and Infinity's IRS 1B's extremely well. Partnered with a Meridian disc player, it was tops! Those were the good old days.
Cheers to Musical Fidelity!
RJ
Not to worry, I did keep it and it is now back in harness driving the ESL 11’s, can’t see me ever selling it to be honest, it’s built like a tank and performs well beyond anything I have yet been able to try.

I wouldn’t be looking for anything else if it was a little more compact and had a usable remote, as it is it’s in the middle of the room on it’s own support as it will not go in the rack ( ideally needs 600mm front to back to clear the rear connections, also lifting it into place is a challenge unless you can just drop it straight down, attempting to slide in or manoeuvre between shelves is asking for trouble!)

Looking to try alternatives over the next year targeting Benchmark, Bryston, Devailet being some of the recommendations used by others.
 
Not to worry, I did keep it and it is now back in harness driving the ESL 11’s, can’t see me ever selling it to be honest, it’s built like a tank and performs well beyond anything I have yet been able to try.
... Looking to try alternatives over the next year targeting Benchmark, Bryston, Devailet being some of the recommendations used by others.
Hi. Inspired by your post, I decided to learn more about the Musical Fidelity Tri-Vista 300. In so doing, I learned a bit about Musical Fidelity as a company. I know you're pleased with the Tri-Vista 300, and it received excellent reviews from others as well. Thanks for bringing it to my attention.

Musical Fidelity has had an interesting history, beginning as a preamp company. They experimented and built many preamps and amps with Nuvistor (RCA) or sub-miniature (Raytheon) vacuum tubes as gain stages. ("Nuvistor" is the basis for the MF product moniker "Vista," though I think the Tri-Vista uses subminiature style tubes rather than Nuvistors.) Ultimately, I believe, Musical Fidelity is now a part of Pro-Ject.

As with owners of any electronics that depends on vacuum tubes, the last few years have been harrowing, as production sources have been caught up in turmoil. I'm not faulting "tubes" for this -- it is, after all, not a technical, electronics matter, but it is nevertheless something to understand and deal with.

Best of luck with exploring alternatives (if for no other reason than the fun of exploring). You mentioned you tried the Hypex Nord amps -- You might want to try newer, more advanced Class D power amps including the Purifi Eigentakt designs. Among these are the NAD M33 and M23. I own an NAD M33 I can tell you it's an astonishingly well behaved, clean, powerful amplifier. My M33 currently powers a pair of Dynaudio Heritage Special speakers -- the combined results are fabulous. I have not tried the M33 with my ML Montis ESLs yet but I probably will. As I've mentioned before, I have an Benchmark AHB2 driving the Montis ESLs now and I'm very pleased with how they get along with one another and with me.
 
I am using a 400W/ch Eigentakt amplifier (the Audiophonics HPA-S400ET) and for the price, I bet nothing really can actually beat it. Other amps might be 'different' though. I am extremely pleased with this amp and homemade loudspeaker cables make from Mogami 3082 wire. It bettered some much higher priced AudioQuest cable by some margin.

I am curious with your experiences comparing the Benchmark to the M33! The M33 uses much the same technology as my amps, but a slightly more high-end implementation.
 
I am using a 400W/ch Eigentakt amplifier (the Audiophonics HPA-S400ET) and for the price, I bet nothing really can actually beat it. Other amps might be 'different' though. I am extremely pleased with this amp and homemade loudspeaker cables make from Mogami 3082 wire. It bettered some much higher priced AudioQuest cable by some margin.

I am curious with your experiences comparing the Benchmark to the M33! The M33 uses much the same technology as my amps, but a slightly more high-end implementation.
Hi! Very cool to hear about your equipment and experiences. The Audiophonics HPA-S400ET has been reviewed by Amir at Audio Science Review:
https://www.audiosciencereview.com/...ics-hpa-s400et-review-stereo-amplifier.32014/The amp works well, it's a real bargain, and good looking, too!

VTV also makes and sells Eigentakt amps as finished boxes, with a variety of buffer choices and at very competitive prices:
https://vtvamplifier.com/product/vtv-amplifier-purifi-eigentakt-stereo-amplifier-based-on-eval-1/I seem to recall the folks at Audio Science Review reviewed this version of the Purifi Eingentakt amps as well.

I realize I'm waxing enthusiastic about amps (including my M33) that I haven't actually tried with my Montis ESLs. However, as I said, I have listened extensively to the M33 through other speakers, the Dynaudio Heritage Specials. I promise I'll try out the M33 with the Montis (and some other interesting loudspeakers as well) and report when other pressing matters are dealt with.

These amps and speakers really do benefit from quality speaker cables. Good to hear about your experience with Mogami. At Benchmark's suggestion, I've been using the Canare Star Quad cables with special clamping banana terminations, and I hear a marked improvement over my old home-made cables. Benchmark Media sells Canare cables with terminations for the AHB2 at fair prices, and Blue Jeans sells them as well. There's an interesting article on the Benchmark website that talks about the the (measurable as well as audible) importance of the cable terminations and how they attach to both the amps and the loudspeakers. There's more to Neutrik connectors, for example, than just a quick compact disconnect and a pretty face. :)
 
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