Martin Logan Sequel II ESL frequency response and worn-out check

[AndreaT]

Hello Folks, I own a pair of Martin Logan Sequel II.

Anybody of you has a known-good frequency response of the ESL panel?
Better if obtained by driving the ESL panel directly at the input of the T1 high voltage transformer, bypassing the high-pass filter.

Over the time I modified the xover filter, I upgraded the high voltage power supply to the MLPS103 and about 15 years ago I also replaced the panels.
However, only recently I got a professional and calibrated measuring suite.

So, I would like now to check if the panels are still good or needing for replacement, but I lack any reference / known-good response of the original new ESL panels equipping the Sequel II.

Tips on cleaning and "restoration" will be highly appreciated.

Many thanks and kind regards,
Andrea.

 

[Andersonix]

Attached is a screen capture from a recent video showing the FR of the ML Ethos measured during ML QC (I assume). But since the conditions of this test setup are not known, I don't know if you could correlate this (or any) FR test with your own setup.

Please do post your measurements when you run your FR test! I just hope you aren't disappointed -- I've seen other ESL FR tests, and they're surprisingly wiggly...

New panels from ML are now priced out of this world. I have thought that I would extend the high frequency life of my ML panels by using a digital eq and xo (like miniDSP)....

 

[AndreaT]

Dear Andersonix,

thank you, but my very old Sequel II don't use the new ML ES technology equipping the Ethos.

Fortunately, a few days ago, the ML's support replied me in this way:
- they do not have any comparable/usable Sequel II panel freq response
- however, gave me a reference SL3
- explaining me that the panels of my very old Sequel II should begin to roll-off around 4 kHz.

So, I then compared by ES panels response, and personally I figured-out that are mostly still working as new.

Here is the SL3 reference response from Martin Logan:


And herein are my Sequel II ES panel responses before and after washing (yes! I washed these!) - don't care the offset, I used different levels.

Lug 14 are the graphs 1 & 2 BEFORE washing (since 1996 when installed)
Ago 4 (today) are the graphs 3 & 4 AFTER washing (washed yesterday)

Currently I am listening to the new "washed" sound and it seams better, more realistic and brighter ... even if from the measurements it should be the same of before.

Regards,
Andrea

 

[AndreaT]

Dear Andersonix,

I key detail I missed in my previous post is that my ES panel had 3+ dB improved sensitivity after washing.

So, the dirty layered on the mylar over 15 years of work had really impacted, if not the frequency response, the output sound level at least.

Regards, Andrea

 

[liching1952]

Dear Andersonix,

I key detail I missed in my previous post is that my ES panel had 3+ dB improved sensitivity after washing.

So, the dirty layered on the mylar over 15 years of work had really impacted, if not the frequency response, the output sound level at least.

Regards, Andrea

Another usefull upgrade is using a higher eht. Original 2400volt. However when the room is not humid you can increase upto 3600volt with a much brighter sound as result.

 

[AndreaT]

Hello Liching,

how can I get such a kind of EHT?

Then I have also to update all about the washing:
- First I measured only my left panel and I confirm it improved about 3..4 dB
- However, my right panel worsen about 2 dB, so actually I have a very unbalanced system with up to 7-8 dB of difference from left to right

See my post "Problem with one channel after ES panel dismount and washing " here
http://www.diyaudio.com/forums/planars-exotics/208495-electrostatic-speaker-help-trouble-4.html
post #38 and the last #46

Do you know what could went wrong?
Any suggestion on how to troubleshoot the problem?

Many thanks and kind regards,
Andrea

 

[liching1952]

hi, i don know what the reason is for worsening after the washing. May be not dry jet or try a second wash.
About your question how to improve the EHT, On the printed circuit there is already place for 8 more diodes and condensors. I put 4 extra diodes and condensors improving the eht to about 3600volt. Each diode and condensor brings about 300volt extra.

 

[AndreaT]

Hi Liching,

but if you look at my today capacity and resistance measures, these should get away any issue related to washing (please give a look to my post #46 at Electrostatic Speaker Help/Trouble.

Thank you for the trick about how to increase the EHT voltage.
By the way, do you know how many dB each 300V extra increase the output level?

Many thanks and regards,
Andrea

 

[liching1952]

1200volt extra as what I did gives 3db extra.

 

[Andersonix]

AndreaT,
Sorry to read about your low output panel. Also sorry that I cannot help, except to suggest that you keep all posts about this problem in one thread (either this thread OR the other thread where you have also posted) to avoid missing information and the general confusion of cross-posting.