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Will a pair of Manley tube amps be a good match for Martin Logan ESL 11A's?

I have been looking into the Manley power amps to drive a pair of Martin Logan ESL 11 A's. From Manleys specs they report a speaker load of 5 ohms is recommended. The Logans are rated at 4 ohms.
pvmike
jafox
1,466 posts
 
In general its frequently thought tubes are a bad amp for electrostatic speakers.
I never heard this before.  Perhaps this is true for amps with rather  output transformers.  But any speaker that dips down to 2 or even 1 ohm is going to cause a lot of amplifiers, tube or SS some serious pain.

I have run Sound Lab A1's for 13+ years, and these too dip to nearly 1ohm at the higher frequencies.  The 220w Wolcott tube amps drove these speakers incredibly well.  And then I changed to CAT JL-3 amps, 150w rated, which also do not have multiple output taps, and the result is stunning.

Make a call to ML as well as VTL to learn if a particular VTL amp would be a good match for the 11A's.


bdp24's avatar
bdp24
9,923 posts
 

@georgehifi has given you a good lead in the Music Reference RM-200 Mk.2. It is the only tube power amp I know of that puts out 100 watts at both 8 ohms and 4 ohms (do the McIntosh amps also?). The common wisdom used to be that OTL amps were a great match for ESL’s, and the Futterman amps were often paired with old Quads, single and stacked. Lots of Atma-Sphere amps on Quads and SoundLabs as well.

MR’s Roger Modjeski, a very opinionated designer/builder, disagrees (and has no axe to grind; he builds OTL’s himself). If interested, go to the MR website for more details, and read Michael Fremer’s review of both the original and Mk.2 versions of the amp in Stereophile (and equally important, John Atkinson’s bench test reports).

bdp24's avatar
bdp24
9,923 posts
 
Oops, neglected to include the matter of tube amp output impedance. Many tube amps have a high enough figure to cause considerable roll-off or boost at either the bottom or top (or both) of the audible frequency range when paired with speakers themselves having very low or high impedances at some frequencies, ESLs being exhibit number one. 
mijostyn's avatar
mijostyn
8,570 posts
 
bdp24 and georgehifi are absolutely correct. You may want to read Roger Sanders white papers to get a contrasting view. I personally am not a big fan of using tube amps on ESLs which like jafox I have been running for decades. One transformer is bad enough. Two transformers is really uncomfortable for my brain. Now OTLs get rid of the second transformer and Atma-Sphere amps have a storied history with SoundLabs but I have not heard this combo yet so I can not speak from personal experience. But I have had numerous amps in my system and as a rule Class A SS amps fair the best the two outliers being The JC-1 and strapped AHB2s. I also cross to subwoofers at 125 Hz so the ultimate low bass performance is not an issue for me. You also cross to woofers I think it is somewhere around 250 Hz but don't quote me on that. Biamping would be a consideration but that still does not negate the issue with low impedance at high frequencies. Trick: put a 1 ohm 200 watt resister in series on the + side of the speaker. This will not decrease the efficiency of the speaker all that much and frequently makes the amp more comfortable with the high end. Digikey has them. These are not little devices. They are mounted in 3 inch X 2 inch heat sinks. I always do this if I have trouble with amps overheating and it solves the problem 100% of the time.
bdp24's avatar
bdp24
9,923 posts
 

The following may appear to contradict what I said about Modjeski's opinion of OTL's paired with ESL's: Roger is making his own ESL loudspeaker (which includes an 8" woofer for each side; another pair can be added, of course). But dig this: he is also offering it with a direct-drive OTL amp for extra $. "Direct-drive"? The mono OTL for each speaker has no output transformer, of course, but the ESL has no input transformer. The OTL output tubes drive the ESL panels directly!

Modjeski worked for Harold Beveridge, who had Roger redesign the power amps that were integral to his ESL, also direct-drive. So this is not new to Roger, but it sure is unique. It takes a lot of engineering knowhow to pull off, involving the disciplines of power amps, tubes, transformers, ESL design and construction, and extremely high (lethal) voltages. No kids or pets allowed in the room ;-) .

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