Amp for Martin logan CLS Originals


I have been considering a couple of amps to pair with Martin logan CLS originals.

Any thoughts on the Mcintosh 2205(or other 200+ watt Mcintosh Solid states), Mark Levinson 23, Harmon Kardon 7.1 ?

Advice would be greatly appreciated.
I would go with either the McIntosh or the Levinson, if those were my only choices. You might want to check out the Sanders Sound System ESL amp or an older InnerSound amp in addition.
A friend of mine has ML CLS speaker for as long as I can remember and has used Pass amps. He is very an.. about those speaker, you may want to try Pass.
Mac 2205 will NOT drive the CLSs.
The original CLS is a solid state amp killer.
Most of the freq impedance curve runs between 16 and 32 ohms.

Just as some amps double their output when the impedance drops (8 - 4 ohms) they will also cut their output in half when the impedance is doubled (8 -16 ohms).

I drove my CLS's with a Classe CA400;
400 watts @ 8 ohms
800 watts @ 4 ohms
1.6k watts @ 2 ohms
and 1 ohm stable

With the CLS's that turns into;
200 watts @ 16 ohms
100 watts @ 32 ohms

When you factor in that the CLS is not the most efficient speaker, maybe actually 82 dB, 100 - 200 watts is not much power.

I could drive the CLS's just so far, then either the speaker or the amp ran out of steam.
The stators were also the newest generation.

A 200 watt tube amp would be a better choice.
I agree with Mrderrick to some extent.
20 years ago my friend Richard had the original CLS's which sounded just sublime driven by Audio Research amps (D115 I think from memory).
I never heard them with solid state amps so can't really help in that direction.

To this day, there are things that the original CLS speakers could do that I've never heard bettered by ANY speakers anywhere.
VTL or Manley monoblocks will drive these wild. I cannot imagine driving this speaker with anything but tubes. They are too revealing and tubes just make them sing. Long interconnects to monoblocks, short speaker wire runs.

"To this day, there are things that the original CLS speakers could do that I've never heard bettered by ANY speakers anywhere."

I could not agree with you more! I dont't believe they are the best speaker in existence, just one of the best. Frequency extremes may be a problem, lower octaves can be supplemented with a lightening fast sub if you can find one that will keep up with the el stats. However, at the price they go in the used market + cost of replacing panels you will be hard pressed to find a better loudspeaker, nothing even comes close in my opinion. CLS overbuilt originals are something special.

I have heard them extensively, driven with a HK Citation XX. This amp is unattainable, for those that do not know about it, it was an amp originally designed for the president of the company in a virtually limitless budget project. only a few had access to it, namely the executives of HK. Oh yeah and it was brought to earth by Dr. Matti Otala the guy that discovered transient intermodulation distortion. Let's keep it simple and just call it audio-un-obtanious. It was rated conservatively @ 250 watt into 8 ohms and drove the speakers absolutely insane. I have heard the same system driven by a pair of 200 watt heavily modified Bogen mono block amps powered by some monster 8714 tubes. It was like heaven on earth..yeah the audience sounded like it was behind me as did the clinking tea cups in Jazz at the pawnshop.

I am no expert, and I know that for some reason 250 watts is different on each amplifier, but I thought an amp like the 200+ watt Macs, Levinson, or Citation 7.1 might drive the CLS. Very interested in hearing from you guys on this, please keep posting.
I have tried a wide variety of solid state amplifiers with the original CLS and none of them came close to the performance of tubes. 100 watt tube monos are ideal. I had great success with Quicksilver, VTL and Audio Research.
I've tried them with amps 100W and up from VTL, Threshold, and Pass Labs with excellent results. My personal preference are with the Audio Research tube amps.

I agree with Reylon, the Macs is not a favorable match for the CLS.

I had the CLS2Z for about four years. Most of that time I drove them with an ARC VT130. I also tried the Pass Alpha 100 watt mono-block and thought that worked extremely well with the CLS2Z. One thing to remember regarding usage of tube amps, because of the difficult load they put on the partnering amp, they eat through output tubes real quick.

I find it funny (odd) that the bass is an area of performance that the CLS got criticized for by most people, and in a certain aspect of bass performance I believe rightly so, but at the same time, I always felt that the bass that was there was some of the most detailed, quickest, transparent bass I've yet to hear. I think that revealing nature of the CLS bass performance was the hardest thing for me to get past when moving on to other speakers.

Up until now I have only considered solid state gear. Based on your feedback I might want to check out 100+ watt Audio Research tube. What do you guys think of the rogue M120 Mono blocks?

Great suggestions in terms of tubes, however on the solid state side anyone with good results/suggestions?

Ultimately I would prefer to go solid.
Hello Dfelkai,

I would look into either Pass or BAT if you're thinking solid-state. Good luck and enjoy the search.


You may try Spectron amps too as highly recommended by a friend who uses them to drive Analysis Audio panels with effortless authority and neutrality.
I agree that tubes are ideal.

If you must use solid state a used Innersound amp or new Sanders Sound amp will work well. They are designed to work with electrostats.
Please go to my system page and, specifically, read the short history of my system (starting in 1990 when I bought the CLS II's (now IIz).

Since I strongly disagree with about 80% of the previous posts' contents, I'd rather not add to them; however if you have specific questions about my system's evolution, my choices, etc, I'd be happy to respond -- either here or offline.

Nsgarch, I understand. Thanks for the help.
The first thing you need to understand is the original CLS is a completely different animal than the CLSII and IIz. I ran the original CLS with 60 watt tube monos and they played loud enough that snare drum wacks would make you jump. They also produced enough bass with 90 watt tube monos to jar my listening room door.

Keep in mind these speakers are not designed to be used on stands. The stands raise the speaker off the floor distancing the speaker from a critical room boundry and thereby affecting the bass in a negative way. The speaker is designed to be tilted back for proper tonal balance just like Maggies, however, the stands do not allow for this. Once the speaker has been placed on stands the tonal character and presentation has been completely altered and not for the better in my opinion.
Rrog, your information is incorrect. If you'll send me your email, I will scan/attach a copy of a MartinLogan factory memo to CLS owners dated Feb. 12, 1992. Among other things, the factory recommends (and explains the reasons for) the use of Arcici stands, co-developed with ML.

This memo also documents the technical evolution from the CLS-I through the CLS-IIz. I owned all four versions, and the only one with a performance glitch (in the upper midrange) was the CLS-II, quickly remedied with the "a" mod. But it still dipped to .6 ohms at 18KHz. The IIz mod took care of that. You can drive all four at 4 ohms, with 100W (+/--) of tube power, or 200W (+/--) of ss power.

Arcici no longer makes CLS stands; but Sound Anchor currently makes much better ones (IMO), and the current price is ony $575/pr. (I think ;--)
Nsgarch, The topic here is the original CLS. I purchased Arici stands direct from Ray Shab before the stands were discontinued and my experience with the original CLS includes time spent with and without the stands. Associated equipment included Audio Research D-115 MKII, Quicksilver 8417 monos, Quicksilver Silver 90 monos, VTL Ichiban monos, Audio Research SP-8 MKII, Quicksilver full function preamp, Audio Research LS-2B, VTL Ultimate preamp, Ocos, Magnan and Audioquest cables. A Muse Model 18 subwoofer with CLS performance card also spent time in the system.

It should be noted the Arcici stands were recommended after the update to the CLS II and the major change in the CLS II was the increase in bass. As I previously mentioned, the original CLS in a differnet animal from the CLS II. Associated equipment that works well with one may not work with the other and that includes stands.

In associated equipment I did not include the wide variety of solid state amplifiers that spent time in the system because none of those amplifiers came close to the performance of tubes.

The original CLS is an amazing speaker and most amazing speakers are very demanding. Reviewers, dealers and owners struggled with these speakers because they were so sensitive to everything in the system. The change of one wire and the system could fall apart.

In my listening room measuring 15'X20'X8' the original CLS sounded best without stands. They also sounded better without a subwoofer. Because of the speaker's revealing nature the simpler the system the better the sound.
Rrog - just out of curiousity, what SS amps did you try?
Rrog: You are correct about the CLS-zero (if you want to call it that ;--) which panel was only divided vertically, and the (two) bass sections were in the middle (halfway between the top and bottom of the speaker.) The stand recommendation came after the 'zero', and applied to all subsequent models (starting with the CLS-I)that had the full-height bass sections on the left and right side of the panel, and a full-height high/mid-frequency section.

Indeed, it was quite common for people to 'tilt' their original CLS's back a bit. However, in that case it was in order to get the bottom high-frequency section better pointed at the listener, and with carpeted floors, to keep its HF output from getting soaked up by carpeting! If you recall, the original Statement (the Fabio model ;--) had the same panel layout as the first CLS, however it came with factory stands. When I enquired why the Statement had stands and the CLS didn't, I was told the Statement's greater overall height meant if it was tilted, the HF radiation from the top of the panel would be lost to the listener -- so it was decided to get it off the floor a bit and not tilt it.

But your points are well taken; frankly these days when someone says "CLS", I assume (perhaps wrongly) they mean the CLS-I which had horizontal AND vertical spars like subsequent models; I suppose because it's so rare to find an original CLS-zero, and rarer still to find one with a panel in good condition -- no sags or ripples in the mylar, and a viable conductive coating. Nevertheless, I probably should have asked Dfelkai which one he actually has!

I do know one person who recently had to replace his CLS-zero's panels (no longer available,) with modern panels, and said the improvement was astounding -- although that was likely because the original panels were so far gone at that point ;--))
I have owned 12 pairs of Logans and three pairs of various CLS
and always felt they sounded much better with tubes. Various trials with Levinson, Perreaux and others always sounded dry in my opinion.

I had great luck with various ARC amps in the day including Classic 120's etc.
Its always a pleasure sharing thoughts with another CLS fan. The CLS is an amazing speaker that takes the right person to make it sing. Once you have experienced a properly set up CLS nothing else will do.
Once you have experienced a properly set up CLS nothing else will do.
If you are brave you could try the NYAL OTL3 that is for sale now.
I bought Stax F83's years ago (in the eighties) and tried many many amps before settling on this one. Head and shoulders above everything else I tried, including Counterpoint, Audio Research, and several solid state amps.
The tubes for these are no longer available, but the seller is including a new spare set, and they seem to last forever. Of course, the Stax's have an even higher impedance that the Logans, so it may not be quite such a dramatic difference.
The tube suggestions make all the sense in the world, but curiously enough way back when, ML used Thresholds for shows and Threshold used ML's amongst others when developing their amps. Go figure?
Unsound, ML used ss amps for shows in order to insure good solid controlled bass. However this meant forfeiting the incredible silky highs and delicate, lifelike mid-range of which almost all stats are capable when driven by tubes. The alternative would have been for ML to drive all their hybrid models bi-amped -- which I bet they rejected fearing it would turn off a lot of customers because of the cost(s) they'd incur.

However, the CLS's, the original Statement, and the CLX are ONLY stats -- no cone woofers! So there is absolutely no reason IMO to drive them with ss amps; none! And if required, the lowest two octaves can be provided by a ss-driven sub.
Celtic66 is dead on accurate. I owned CLSiiz's and used a vast variety of SS amps, namely Plinius SA250, BAT VK500, Pass Aleph 2 monos, but the best overall performance I experienced was after mating the CLS's to a pair of Manley Ref 450 mono's, that I of course acquired used. Those speakers came alive and sang with joy from power o' plenty!
The CLS 1 (the original) had a high impedance and was a match made in heaven for tubes, even OTLs.

The CLS 2 was an example of Martin-Logan's attempts to make ESLs compatible with transistors. It was very low impedance, 0.5 ohms at 20KHz. Almost any amplifier sounds better on it if using a set of ZEROs to help with the impedance.

The CLS Z and later models do show some moderation with regards to impedance, but still are built to favor transistors.

Its hard to make transistors sound right on a full-range ESL due to the impedance curve. There is a tendency to be weak in the bass and too bright in the highs. As a result many ML owners place the speaker fairly close to the rear wall to try to get back some of the bass, but it is often one-note bass due to the placement (ESLs need to be out in the room at least 5 feet).

But the CLS 1 (which, BTW, it sounds like ML still has parts on hand to build them) is an easy load for most amps and IMO the best of the lot; of course I have a bias :)
Atmasphere, you have the impedance thing backwards ;--) The original CLS, CLS I were .5 ohm. The CLS II/IIa were .6 and 1.0 ohm respectively; and the CLS IIz is 1.5 ohm

In all models, this "low impedance" occurred only above 15KHz. Raising it initially resulted from adding a second transformer to the electronics module, starting with the CLS II/IIa. The electronics module for the CLS IIz was a complete re-do and included a more sophisticated crossover network (filter network) and a 'signal sensing' circuit which turned off the high-voltage circuits when the speaker was idle -- a great idea for keeping dust from accumulating on the panels, but a disaster in terms of performance! It takes overnight for an electrostat to fully charge, or "form" -- it's just a big capacitor after all -- so most owners have probably never really heard what a IIz can sound like (unless you keep it playing music 24/7!) People with IIz's who know about this, defeat that function so the speaker is always charged up and ready to go. I never had a dust/smoke problem anyway; and Jim Power at ML said that a dry climate is the most important factor in panel longevity.

The later models were (sligntly ;--) easier on ss amps, but the changes to the electronics module were for the purpose of reducing the high end brightness and improving the upper mid-range. Even with the (1 ohm) impedance increase, you still had to buy an unnecessarily high-powered Krell, Threshold, Bryston, etc. to insure they wouldn't see the low impedance as a short! Tube amps by contrast, can handle shorts, but don't like open outputs (ie, nothing connected to the speaker terminals.)

I actually have a 1992 ML factory memo detailing most of these points, including a recommendation that the CLS be placed on stands.
Nsgarch you know who atmasphere is right?
No. Why do you ask?
Atmasphere is one of the top 5 amplifier manufactures in the audio industry in my opinion;Ralph Karsten produces tube pre amps and OTL amplifiers for over 30 years.I would find it hard to believe that Ralph would be incorrect in the impedance of these speakers.
Google Atmasphere in St.Paul Mn;Ralph has several good white papers to read and his website in quite informative.
Atmasphere's description of the various models is dead-on right. I was an original owner of the first version of CLS stats, and followed the so-called upgrade path step by step to the CLS-Z. The original CLS was a very easy load for tube amps. I used them mostly with an RM-9 Music Reference, which was a great match, but I also tried them with some Dyna mods (Mk. 4 and ST-70) and they worked great as well. The CLS-II was quite a different story. It had a punishingly low impedance at some frequency due to a notch filter in the crossover. Supposedly it made the speakers more compatible with Krells and Mark Levinson amps, but it didn't like tubes at all. Things got better with the CLS-Z. Unfortunately for me, I was fed up with the CLS by that time. I found I was no longer playing music I liked, just because it didn't sound so good on the CLS. I opted instead for cone speakers that are more universal in terms of music playability, but it is true that the CLS has a special magic on the right types of recordings that none of the cone speakers I've used since then can equal.

Rleff, yes, I know Ralph Karsten -- and I like his amps. BUT, nevertheless, he still has the impedance history backward. Why would you not give precedent to the MartinLogan factory information? You think I'm pulling your leg? I'll make a note to send Ralph a copy of the ML memo. Anyone else who wants one please send me your email address.

Whatever ;--))
Nsgarch thats ok I just thought you weren't familiar with Ralph's products and knowledge of the industry.
The evidence is in:

The ML memo supports Nsgarch 'specs completely. Is it possible Ralph has been misquoted here, for clearly Nsgarch's specs are dead on accurate with ML's memo.

Is this like one of those Bill Clinton definitions where there's more than one definition of IS? :)
Thank you Greg ;--)

In the famous words of Robert Duvall:

"I love the smell of Napalm in the mornin', and the sound of vindication in a public forum."
Well, perhaps I've taken more than a few liberties with the quote, but you get the gest I'm sure ! ; )

Neil thanks for saving that memo. Now, where the heck do I find a pair of Arcici stands for CLS's that were so heartily recommended in the memo? They'll be enroute next week.
If you click on my system, you'll see I have the Sound Anchor stands which are still in production at ~ $575 a pair I think. I like them better than the Arcicis (aesthetically, and structurally) although I think you should ask SA to make your stands about 4" shorter (they're OK the way they come if you are sitting way back; otherwise they're just a bit too tall ;--)

If you like the way the Arcicis look, I can email you the address of a CLS owner who made (much nicer) copies of the originals; you could probably get him to make you a pair for a reasonable price.
It may well be that the original CLS 1 had a lower impedance at high frequencies. Usually how that behaves with any tube amp is that the amp will be rolled in the highs.

Our amps did not roll off with the CLS 1, the same as with other tube amps, but when you put those same amps on the later CLS models, they all rolled off.

So empirically it is logical to assume that the original model had a higher impedance. Based on this experience, I am inclined to think that ML's history of their products is not accurately portrayed, but if it is, then they had something quite unusual- perhaps an increase in efficiency that compensated for the lower impedance.

At any rate: the CLS 1 was an easy load for tubes where none of the succeeding models were.