CLSII panels with CLS1 electronics?

[mosttoysrk]

With the end of support for the CLS1 panels, I was wondering what it would take to make the CLS1 electronics compatible with the CLSII panels. Anyone hear of users making this modification or of CLSII panels with CLS1 electronics working?

 

[zaphod]

With the end of support for the CLS1 panels, I was wondering what it would take to make the CLS1 electronics compatible with the CLSII panels. Anyone hear of users making this modification or of CLSII panels with CLS1 electronics working?

i haven't heard tell of that, Jim Powers once told me that they are incompatible. i'd tend to trust his judgement.

 

[MPS]

It can probably be done. I think only things to check / modify would be bias voltage and audio transformer ratio. Anybody?

 

[mosttoysrk]

Dana from ML responded to my question and did confirm that CLS1 electronics cannot be modified to work with CLS II panels. I was also concerned with the failure rate of the CLSI electronics, especially if I planned to store a spare set of panels to be used years down the road. He seemed confident that there would be no problems with purchasing parts from an outside source and would share the schematics, also noting he has seen only 2 CLS I electronics in for service. It seems like a purchase of spare CLS I panels is my only option.

 

[kmanusa]

Dana from ML responded to my question and did confirm that CLS1 electronics cannot be modified to work with CLS II panels. I was also concerned with the failure rate of the CLSI electronics, especially if I planned to store a spare set of panels to be used years down the road. He seemed confident that there would be no problems with purchasing parts from an outside source and would share the schematics, also noting he has seen only 2 CLS I electronics in for service. It seems like a purchase of spare CLS I panels is my only option.

I managed to blow a step-up transformer in one of my CLS 1 electronics modules a few years ago so it can happen. Thankfully, Jim Power was there to guide me in replacing the blown transformer with one provided by ML service. While I think most of the other parts in the CLS 1 electronics modules can probably be found from an outside source, the transformers might be an exception unless one is willing to pay for a custom one-off job.

 

[EdSawyer]

Why would the panels be incompatible?

That sounds like BS to me. From what I have read in the past, the panels were the same between I and II. At least the replacement ones supplied from ML were supposed to be the same, according to multiple sources.

Given the panel is a passive device, what could be different enough to make them incompatible? The only thing I can think of would be bias on the panel, higher in the CLS I might be more than the current panels want to see, but that would be unlikely IMNSHO.

-Ed

 

[robertawillisjr]

AFAIK the design of the panel differs from I to II models.

 

[zaphod]

That sounds like BS to me. From what I have read in the past, the panels were the same between I and II. At least the replacement ones supplied from ML were supposed to be the same, according to multiple sources.

Given the panel is a passive device, what could be different enough to make them incompatible? The only thing I can think of would be bias on the panel, higher in the CLS I might be more than the current panels want to see, but that would be unlikely IMNSHO.
-Ed

Jim Powers who has forgotten more about those panels than any of us, and is infinitely trustworthy has told numerous people, myself included, that the CLS1 and CLSII panels are different and will not work with each other's electronics.

try it if you like, keep an extinguisher handy.

 

[GDSA]

When I got my first replacement panels for my first CLS (1987) in 1992, Jim sent out a PCB mod to do to lower the bias to suit the new (more electrically efficient) mylar.
Bias was reduced from about 5.5kV to 4.4-4.6kV (ideal).
A group of diodes and caps were removed (and a jumper wire fitted) to facilitate this. Any pre 1990 CLS running 700 series replacements should have this done. If anyone needs this, I can post photo of modded board (fax from Jim has only hand drawn diagram and it is pretty faded and tatty now).
I would guess the same circuit board stayed with the CLS till the advent of the CLS2, but the later CLS (after about #3300) that left the factory with the "new" mylar would have had Jim's mod done.
I believe (someone can probably help here) that the bias Voltage from the 2 later power supply units fitted to the CLS2 series would be putting out about the same 4.5kV.
If that were the case I suspect the panels could "play", BUT they will be tone profiled completely differently to suit the difference in the shape and strut positions.

Possibly that is what ML mean when they say they "won't work" . My guess is that they will "play", but they won't sound right with the wrong signal profile going to them.

I have been going to pull a pair old old CLS2 panels out of the shed to try them with the CLS interface, but just waiting till I have one of the CLS apart. (both pairs are in use atm). I will post and let you know if I have music or smoke..LOL

If ML are going to continue to supply the older CLS panel that is great news and this topic is redundant, but it did tweak my interest enough to want to try. Like other members here I am keen to keep these lovely speaker going.

Of all the parts I have tried to buy to rebuild CLS2 boxes, the only one so far I CAN'T get, is the 10kV cap between the panel and earth. The CLS interface components look easily sourced (maybe except the LP trannny).

As far as Panel life..my 1992 (700) panels are still close to mint and sounding as good as some 2004 (700)panels I have here too.
Keeping them covered (UV and dust) regular vac (and wash if necessary).

Components?... Keep an eye on the two ceramic resistors at signal source (1 and 4 ohms from memory), replace the audio line caps at 10 yrs. There is a small socketed (I believe it's an op amp) in the third line of components that can fail. I have replaced all of these..they're cheap as chips. (no pun intended).
cheers,
Greg

 

[bk12]

Hi Greg,

Can you post the information on the bias change?

What is the downside of running newer panels at the older, higher bias?

Thanks!

 

[Oxford]

GDSA, thank you for the informative post! I recently bought a pair of CLS1 so I send a few questions to Martin Logan service. Jeff Dearinger replied that the later CLS II panels are not compatible with the CLS1. The CLS1 stats use a different connector. He also mentioned that using the CLS II panels will not have much bass output when using the CLS1 electronics.

After pondering about the issue about the bass output, I think this might be the reason why. If you look closely and compare the design of the CLS1 replacement panels vs. the latter CLS II panels, you will notice that the CLSII panels have symmetrically spaced horizontal stator bars that are “mirror imaged” from top to bottom while the spacing between horizontal stator bars on the CLS1 replacement panels are spaced further apart on the bottom and then becomes spaced closer together as you approach the top of the panel.

The vertical bars are also different with the CLS1 being symmetrical between its inner and outer border distances while the later CLS II versions have assymmetrical distances between its inner and outer borders. I am also assuming that the electronic modules have different filtering characteristics
to compliment their respective panel designs.

I still don’t understand the role of the higher bias settings on the CLS1 but please post some pictures of what was done to your electronic module to modify the bias settings. Thanks!

 

[GDSA]

Photo of Jim's hand drawn diagram attached.
Modern panels (pretty much includes all replacement panel and OEM panels from early 1990's) had better electrostatic dispersion coatings and didn't need to be charged up quite as high to make them jump when they saw speaker signal.
The connectors difference is nothing..just a plug change (I'll probably just do a temp wiring rather than take the clips off the old CLS panels).
The panel shape and structure will be the major difference (I'm guessing) as to whether they sound "acceptable" or "awful"...the tone profiles (from transformer) going to the panels will be quite a bit different and is probably the main hickup in trying to mix electronic boxes within the CLS/CLS2 models.

re. downside of running new panels on old 5.5kV....Honestly I don't know if there is one.

Possibly: (just thinking out loud)

1/ higher voltage may more quickly oxidize and degrade electrostat ring wire contact ( the screen bias is fed by a U shaped flat copper ribbon between the foam adhesive/packing and the connection to the feed wire from the plug is just "twisted" onto it, NOT soldered.
2/ with the old panels I used to get occasional "arcing" where there was dust build up (this may be just peculiar to the old poorly coated panels)..but increased voltage does add elect pressure to look for areas to short.
3/ Maybe the mylar coating will live longer with the lowered voltage???

Hope it is helpful!
Greg

 

[bk12]

Thanks for the diagram!

 

[Oxford]

Bias was reduced from about 5.5kV to 4.4-4.6kV (ideal).
A group of diodes and caps were removed (and a jumper wire fitted) to facilitate this. Any pre 1990 CLS running 700 series replacements should have this done. If anyone needs this, I can post photo of modded board (fax from Jim has only hand drawn diagram and it is pretty faded and tatty now).



GDSA,

Could you please post a photo of your modded board?

Thanks!

 

[GDSA]

Hi Oxford

Board looks exactly as the drawing above.
I have only just got my new RSA foil cables supported (and burning in), tied to a hole through the top plate and base box and it is going to mean removing my cabling and would rather not just atm. The ends are contiguous milled foil (and contact pasted) and the less movement they get the better..when I shift the 4 CLS and use the CLS2a again it will be easier. If there is a specific area that is troubling you I will try to explain from the diagram.

Sorry and thanks for your understanding.