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Refurbishing some Martin Logan electrostatics

Wildcat

Wildcat

¡Que siga la fiesta!
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A few years back, I got ahold of a set of Martin Logan Sequel IIs that were in need of repair--the price was so dirt cheap that I couldn't resist. They were in Connecticut, and I wasn't, so a friend kept them in storage until I was able to pick them up. I finally got them last year in August, and found the problems.

Due to a lack of time, I recently offered up everything I'd accumulated so far as a DIY project, but nobody took me up on it. So due to that lack of interest, I've decided to take the leap and finish this off. I'll be recording progress here. (I"m keeping a journal of sorts and will post links over time.)

The seller mentioned that the panel on one side was dead, and the woofer on the other side was similarly dead. I feared the worst (a problem in the electronics--basically a crossover and high-voltage power supply), but it turned out that the voice coil in the bad woofer had no continuity (an "open" circuit), and the wires on the bad panel had been sheared off right at the panel. What happens on these is that the adhesive holding the panels in place can turn to goo over time, and the top panel will slide down behind the woofer grille (which is the same perforated metal). If it falls far enough, it will break the wires right off. One wire connected to a stator looked to be resoldered, and the wire to the diaphragm was not promising

Unfortunately the wire connecting to the diaphragm did some damage and the Mylar diaphragm is ripped. I had originally planned on separating both panels to revive the conductive coating (these panels get weak over time), but now I have to get some new Mylar, build a frame, tension it in the vertical plane (these are curved panels), and then coat the new Mylar.

I have just ordered some Mylar (6 micron) and already have the conductive coating, foil tape and terminal blocks to redo the diaphragms. I just need some sort of adhesive for the lower spars, and to build the frame.

The original woofers were apparently lacking (according to many others who have owned this model), so I have located some newer aluminum coned woofers that fit right in the cabinet. I may need to modify the cabinet slightly but that is no problem.

The cabinets themselves aren't perfect but I have a few ideas for touch-ups.

I'll keep everyone posted over the coming weeks on the progress.
 
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having owned many Martin Logan speakers and modded them , its not gonna be as easy as just re mylaring them and sprinkling a coating on and walla.. Few have been able to do this with great results.. Much info can be had from the ML forum site.. spar spacing was done for a reason and thickness on the older panels was needed.. clear spar technology is only in the new micro perf panels ... Good luck but there is a value limit as to what it is gonna cost in time and materials as to what it may sound like .. New ones from ML are outrageously expensive for a reason ..FORCED extinction !
 
I've read about a lot of very successful builds of DIY panels, and refurbished ML panels as well, so I am confident this won't be so difficult. The kit I bought to recoat the diaphragm is also proven, and has all the extras to make it work easier than trying to wing it on my onw. The research and trial/error on correct film tensioning, type and thickness of coating (and film), has already been done by others, so I'm learning through their own mistakes. ;) My hurdles were mostly mental. Now that I have a better idea of what the end results need to be (through more hours of reading), I think we'll be A-OK here. Plus, I have enough Mylar to redo my screw-ups a dozen times over, so it's no big deal. :D I am keeping the old spars in place anyway, so no changes there.

There is a rebuilder near Cleveland who has done nice work for others, at a price far less than the $400/panel that ML wants for genuine replacements. (I think he wanted $350 to do the set, which still isn't too bad.)
 
Russ Knotts Just real music is his name and his panels are OK .. NOT as good as ML .. Many have done their own but yet to get any one who did it to my ears.. Its why I left them as they were to temperamental.. When MY CLS was set up its magic.. I just spent a day with the CLX at my buddies house, I am well versed in ML, knowing the old service manager and having been at the plant in Lawrence

Good luck and do post progress and pics if possible
 
nerdorama said:
I'm getting a set of Aerius' soon, so just in case, I'll be very interested in this project. Signing on.
John
Click to expand...

I will post a few things once I get rolling.

There is no way I'd ever afford a new pair of current Martin Logans at the moment, so for me this situation is ideal. Plus, if I find another pair that need a new home, I will already have most of the materials on hand if they need a refurbishment.
 
I'll have a more complete list once I get up to speed (and some spare time), but the Mylar is easily available from a seller on eBay. He offers 3-micron, 6-micron and 12-micron film (I grabbed a 40 meter roll). He also sells the conductive material that needs to be dissolved, then applied to the tensioned Mylar. McMaster-Carr sells a polyester film (which is, essentially Mylar, which is a DuPont trademarked name IIRC) in a 12.7-micron thickness which might work. Many (if not all?) of ML's original diaphragms were 12-micron.

I obtained a kit from ER Audio in Australia that has some conductive fluid, copper foil tape, terminal blocks, and high voltage wiring. I am going to examine these more closely when I get a chance, in case I come across another set I want to rebuild.
 
The Aerius that I'm buying sound great and seem to be working fine. I'm just trying to be prepared for the day when something needs to be done. I might even buy the materials and sock it away so I have it regardless of future availability. I'll use them for a few weeks or months until I decided if they are the goods.
 
One thing I noticed with the one working panel was that there was little output in some spots, while others had plenty. The Martin Logan Owners forum has a few tips re: vacuuming, or even removing the panels to give them a washdown (which I think ML themselves may have recommended--not sure).
 
Update: busy with the holidays, work, taxes, etc. and haven't had time to do anything on this.

I only have to get the wood to build the stretching frame for the mylar. I considered 2x2 lumber, but try finding any that is anywhere close to being straight. 2x3 lumber actually looks attractive at this point; 2x4s might make it just that much heavier that the frame becomes inconvenient to work with. I might also look at 2x2 pressure treated,as I've seen some of those that looked quite straight. (They don't need to be perfectly straight; as long as I cut the ends properly, I'm good. Some, though, are too skewed to be of any use.)

Everything else is apparently in-house now. I am still debating woofers, though, and have a pal of mine helping to decide what to do. I still may get the dead woofer repaired, provided the suspension (surround, spider) isn't tampered with. My last driver repair ended up with a woofer that sounded completely different (far worse) than the original.
 
Whatever is cheap. This is a one-time use. So if it warps more a month from now, no big deal. :D The 2x3s should be straight enough. I just need the ends parallel, that's it.

If I get another set of MLs that need the diaphragms replaced, I might have to rebuild it anyway (if the panel curvature is different). I totally missed out on a pair of smaller MLs that had weak panels for $150 plus shipping. Still kicking myself for that one. They would have made nice rears.
 
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