Have my CLS I electronics modules been tweaked?

[slownlo]

I tried putting this in the Tweaks area but its actually not a tweak...I'm just trying to find out if it is or not....(huh?)

I bought these used a few days ago so I am discovering things as I inspect them very closely..

I attached a pic for reference. Looks like the panel voltage has been intentionally lowered...? I think there are some caps missing (caps 8 & 9) and Diode missing, a jumper that shouldn't be there, and a diode that has been inverted...

I measure about 2.2kV DC at the HV pin to the panel, which is about half of what it should be yes? (5kV DC)...

How do I get this back to spec...?

I hate mods I didn't do myself.... )

And it may explain why my CLS's sound "soft"...

:bowdown:

 

[Bernard]

................
How do I get this back to spec...? ............

Email Jim Power of ML at [email protected]. He will send you schematics; he responds very quickly.

 

[slownlo]

I've got the schematics...

....thats how I figured they may have been tweaked.

But....manufacturers change aspects many times during the life cycle of a design...the schematic will only show a snapshot of the design at a certian time and may not reflect manufacturer changes afterwards...its a bit of a crap shoot...

I spoke to Jim and he was as perplexed as I was...

I'm hoping someone out there in the forum is familiar with this "tweak" if it is one...

:bowdown:

 

[Bernard]

Then I suggest that you post the serial numbers and if someone here has speakers with serial numbers close to those, they could perhaps send you a picture; yes, I know, hard to go by pictures, but better than nothing.

I'm surprised that ML do not have detailed schematics for every iteration of their speakers.

 

[slownlo]

The serial numbers are...

Panels: CS1EG716/717
Modules: 1178/79

 

[kmanusa]

I don't think you have problem. The modifications done to my CLS power supply appear very similar to yours-- there are "missing caps" and diodes and a jumper added. I emailed Jim Power a picture of my CLS crossover and he indicated that ML had modified the power supply. Jim told me that the mod is to lower the high voltage in the CLS power supply. Here is an excerpt from an email he sent me on this issue.

"... The early original CLSs tended to be a bit high on the bias voltage sometimes (6KVDC or so). The panels are really much happier at around 4.5 KVDC. If you would like us to modify your interface boxes to calm the bias a bit, we can. Essentially we would simply bypass the last couple of stages of the doubler circuit...."

I am attaching a photo of my power supply. Sorry for the poor quality...

 

[kmanusa]

I measure about 2.2kV DC at the HV pin to the panel, which is about half of what it should be yes? (5kV DC)...

:bowdown:

To get an accurate measurement, you will need to use a voltmeter rated to measure in the kilovolts and a HV probe...

 

[slownlo]

"... The early original CLSs tended to be a bit high on the bias voltage sometimes (6KVDC or so). The panels are really much happier at around 4.5 KVDC. If you would like us to modify your interface boxes to calm the bias a bit, we can. Essentially we would simply bypass the last couple of stages of the doubler circuit...."

Yes, this is what I needed! Thanks for the photo. So they were "tweaked", but by ML... This is exactly what I meant about how manufacturers sometimes make unrecorded changes. The schematic for the CLS I doesn't reference this at all...and I am wondering if ML started actually building them by default with this voltage drop going forward? I wonder what they meant by the "panels being happier"? Was this a design flaw effecting panel longevity,...or did the higher voltage make the panels too bright for some users?

In any event I am going to take them back to original and see how they sound...

Thanks for taking the time to help me out with this!

 

[kmanusa]

...and I am wondering if ML started actually building them by default with this voltage drop going forward? I wonder what they meant by the "panels being happier"? Was this a design flaw effecting panel longevity,...or did the higher voltage make the panels too bright for some users?

Thanks for taking the time to help me out with this!

Glad to help, I wondered about mine too when I opened them up. I don't know why they dropped the HV-- maybe it was because the panel output was sufficent at the lower HV or maybe there were problems with migration of charge on the panel at the higher HV. I guess we will never know...

 

[slownlo]

I dunno,...I think this may have been done to tame the hi-frequency response for owners who thought it as too bright. The reason I think this is because just about every review I've read about the CLS mentions how bright/harsh they were out of the box,....:

Stereophile (John Atkinson CLS review)
http://www.stereophile.com/floorloudspeakers/650/

I think these mods were in response to owners who thought so too...but,... as these speakers get older, taking the voltage back up to spec may actually help in giving them some of their original "spark" back...(pardon the pun)...

...check out this thread in the tweaks section:

More volts = better sound?
http://www.martinloganowners.com/forum/forumdisplay.php?f=58

I've never heard a brand new pair of CLS's before (and never will since they no longer make them), but I do know that all it takes is a single complaint from a respected reviewer (Like John Atkinson) and "Voila", like lemmings owners send their modules back to ML to lower the HV to get rid of the subjective brightness...

 

[nsgarch]

I dunno,...I think this may have been done to tame the hi-frequency response for owners who thought it as too bright. The reason I think this is because just about every review I've read about the CLS mentions how bright/harsh they were out of the box..

Are you referring to the original CLS's or all the CLS models?

 

[slownlo]

I'm refering to the original CLS...

no text...

 

[nsgarch]

OK, that's what I guessed, because the CLS II and IIa and IIz modules had a softening switch to roll off the highs, along with (very slightly) more impedance at high frequencies which also helped to tame brightness. Using a tube amplifier provides the best solution to the problem however.

I'm not sure I agree lowering the HV would affect the frequency response curve very much. It would more likely reduce the sensitivity.

 

[slownlo]

Yep,... and sensitivity has a bearing on how...

...loud the panel plays given the same amount of amplifier power. The higher the sensitivty,... the louder it will play being fed the same watt...so given the complexity of electrostat's is there anyway this can somehow translate into the harshness or brightness described by reviewers?

 

[nsgarch]

...loud the panel plays given the same amount of amplifier power. The higher the sensitivty,... the louder it will play being fed the same watt...so given the complexity of electrostat's is there anyway this can somehow translate into the harshness or brightness described by reviewers?

The characteristic "brightness" attributed to stats generally is due to the fact that they present a capacitative load to an amplifier, rather than the resistive/inductive load (reactive load) presented by electrodynamic drivers. If you're interested, you can educate yourself quite well on these matters using Google and the internet. Naturally it will require some time and study on your part