Advice using electrostats with tube amp.


I'm currently using a Cary Rocket 88R amp with Serie Reference 3A speakers which I like very much but I have an opportunity to buy back my pair of Martin Logan Theos speakers that I sold about a half year ago. I used Martin Logan speakers for many years having had the Odyssee's in the system for 14 years. Now that I'm using the tube amp, I'm wondering how the pairing would be in consideration of the current demand of these speakers at certain frequencies. I was made aware on these forums of impedance dipping below 1 ohm with the Odyssee's at least. Would the Ethos present as drastic a drop and, if so,  can this Cary handle it. 

broadstone
A quick Google shows the Theos go down to 4 ohms, so they should be okay, but I think the speakers would do better with a higher powered amp.
I don't know Cary amps well, so others may have better info. Perhaps you should contact Cary directly?
Bob
I have been running ML Summits with a pair of Cary 211AE's for over 5 years now. Wonderful sound !
Gdnrbob, thanks but I reviewed the Odyssey's before i bought them new and the info I found indicated somewhat the same thing as you found. However, multiple knowledgeable members here provided information that certain conditions can result in impedances  <1 ohm.  I know that there are those using tubes with electrostats but ive not heard of any in combination with my model amplifier. Also, I'm not aware if the Ethos has this same dramatic impedance dip as the Odyssey under similar conditions. 
As long as you don't have a really big room and listen at high volumes, you should be fine. More people probably use tubes over SS with ML.
Sfall, the room is about 15X20' with 8.5' ceiling but my listening position is only about 13' from the speakers and i dont listen at high volumes. I agree withyou, then, that it should be fine but because the purchase is not a small one for me, I'm trying for all the advice I can get. Thanks
I wouldn't go with the Cary if I were you.
My former e-stats also had a significant impedance swing from 1 to 6 ohms. They sounded terrible with my 50w p/p tube monoblocks - even with zero-autoformers.  Very tinny - not even close to musical.  Yet, they did sound great with my 300w ss amp that doubled-down.  For any amp that you might purchase, I highly recommend a home trial with the actual speakers.
Stringreen, I already have the Cary so that's the starting point for my inquiry because it will probably stay in the system.   It'd sure be interesting to know the basis for your advice though as it may help with the decision re the electrostats. 
I have tried quite a few different amps with my JansZen hybrid electrostats. They are 87db sensitive and it's been dificult finding the right amp to mate with them until I tried the Linear Tube Audio ZOTL40. No impedance problem here. The beauty of tubes and speed of SS and the most powerful 40 watts I've ever experienced. I still have plenty of headroom.
The Theos has an impedance of .8 ohms at 20khz. It’s not a 4 ohm speaker. Still many people like using tube amps with MLs. I don’t think it would hurt to try your tube amp with them, but I would try to get my hands on a solid state muscle amp for comparison.
"Sfall, the room is about 15X20' with 8.5' ceiling but my listening position is only about 13' from the speakers and i dont listen at high volumes. I agree withyou, then, that it should be fine but because the purchase is not a small one for me, I'm trying for all the advice I can get. Thanks"

You'll be OK. I've powered ML's in a room that was a little bigger, and with an amp with less power than yours.
I need to make a correction.  Although it would have no bearing on the subject of impedance, the speakers in question are the Ethos (not Theos) which, as well as with the Odyssey's before them, I had been using with the Peachtree 220 amp. Today I'll be transporting the Cary to the guy's house who has my old  Ethos for a trial. Room acoustics there are significantly different than mine but I should get some idea about the overall sound. Also, I've been running the amp in triode mode with the reference 3a's and someone suggested that that switching to ultra linear may make a better match. Using the 4 ohm posts also came up in that discussion.  BTW, I've used mostly panel speakers for over 40 years (Acoustat, Magnepan and ML) so my familiarity with them is the only reason I'm even at trying this. I really thought my current setup would be the forever one. We'll see. 

I believe Ralph of Atma-Sphere recommends using a Zero Transformer when running difficult loads. He has a FAQ page on his website that will link you to it. Let me know if you can't find it.
B
I'm guessing you have an issue with high frequencies. If that's correct, I think the ML's are a pretty good choice. Personally, I find the main reason I'm drawn to an esl speaker is that they don't have a tweeter. The highs are much more realistic and natural sounding.
Jim (Broadstone), an impedance curve for the Ethos can be found on this page. My guess is that given the relatively small amount of energy that most music has in the top octave the 0.8 ohm impedance at the upper end of the spectrum won’t **in itself** be a problem, provided that you use the 4 ohm tap on the amp. And, as you mentioned, operating the amp in ultra-linear mode might turn out to be preferable.

However, I suspect that what stands a greater chance of being an issue is the effects on tonality of the interaction between the amp’s output impedance (which will differ between triode mode and ultra-linear mode), and the wide variation in the impedance of the speaker, within the range that is handled by the panels. Specifically, if you see this post prior to today’s audition I would suggest looking for signs of over-emphasis of the mid-range (where the impedance rises to around 18 ohms at 1 kHz), relative to the treble region (where as you realize the impedance gradually descends to very low values).

That interaction, btw, will vary widely among different tube amps, due to the widely differing output impedances among different tube amps. And given also that the output impedance of the 88R does not appear to be specified, nor does its damping factor from which output impedance can be calculated, it’s particularly good that you have an opportunity to audition the specific amp/speaker combo.

Best regards,
-- Al

Thanks, Al. I was hoping you'd see this post. As always you provided exactly the kind of direction that I needed. I wasn't specifically looking for the potential of generally over emphasized mids, but I did detect a hint of that in the lower mid frequencies that you suggested and that I had also experienced with the Odysseys using Rogue and Peachtree  solid state amplification. This issue is not significant enough to affect my decision to buy them back and I did just that. Not just from a budget standpoint was this a very hard decision but stepping away from the Reference 3A's is particularly distressing. I hope i can get a reasonable offer for these amazing speakers. I did the audition using the 4 ohm posts and tried it on ultralinear as well as triode settings. As with the Serie's i found the triode mode somewhat more pleasing.

BTW, because i have a loaner pair of Cary made AES SET2 monoblocks currently set up I tried them with the ML's also. Theyre ok but the Cary is a bit warmer sounding to me.  Thanks once again, Al.       Jim

Sounds good, Jim.  Enjoy!

Best regards,
-- Al
 
Atually, the "warmth" that I heard and generally favor with the triode mode
was a bit too warm approaching somewhat dull. I switched to ultralinear for overall improved upper mid detail. Just an FYI.