Woohoo! (I think) I fixed my ML ESL

Sorry to be incommunicado for a while, but my right channel was getting flaky on me for the last few months. Martin Logan Spire speakers, BHK 250 amp, BHK preamp, DS DAC. At first I thought it was tubes in the amp. Swapped those out, but the problem returned a while later (seemed like a signal loss in the right channel, as if one half of the balanced channel went dead all of a sudden, then came back on line.) Trouble is, it wasn’t consistent, some days it’d work, some days not.

After changing the tubes, it reappeared, so I swapped speaker cables at the amp so right channel was driving left speaker and vice versa. Behold! The problem stayed with the speaker! OK, now we’re getting somewhere.

But while swapping the speaker cables the terminals on the BHK 250 stripped, so that had to get sent back to Boulder to fix. Gaah. OK, pull out the Streets 950 from the closet and continue. (Hey, it still works after 34 years!)

So I remember the factory rep when I bought the speakers visited my dealer (Pete Soderberg) saying that after a while dust builds up on the ESL and the best way to clean them is to take the panel off, wash it in the shower, let it dry for 3 days and then reassemble. While waiting for the panel to dry I contacted ML support (who said he wished I hadn’t done that) and sent me the service manual for the removal of the internal components of the speaker.

Ugh. Getting too complicated. Should I just get new speakers?

When the panel was dry, I put it back on, but the problem remained. Following the manual, I removed the back cover plate (This holds the woofer amp) and poked around the system. Some of sound deadening foam had come loose from around the woofer, so I put it back in place. The unit then ran fine for a week or so, then started to exhibit the failure again. The support tech suggested I swap the ESL panels from right to left speaker and see if the problem moved with the ESL panel or remained with the electronics. I tried that, and sure enough the problem stayed with the electronics (the base of the unit).

OK, now we’re getting somewhere. I checked to see how much it cost to replace the various boards in the base. There are 3 PWB boards: back panel with woofer amp, crossover board, and ESL power supply. Not cheap, even for the few remaining units they had left. (I bought them 9 years ago)

Listening to the unit, I’m thinking “This sounds like a bad solder joint.” You know, sometimes it works, sometimes it doesn’t, and because the PWB is sitting in the same box as the woofer, sound from the woofer will cause the failed component to shift and cause the wire lead on the component to shift in the PWB through hole and cause an intermittent contact. sometimes loud passages seemed to make it worse. So I disassembled the woofer base again and pulled up the PWB’s to check underneath for a fractured solder joint and tug at every component on the PWB for looseness that would indicate a bad solder joint.

As I’m doing this I note that one of the wire leads from the crossover to the ESL power supply board is a little loose in the terminal block. I can move it with light pressure in the terminal block itself. Lifting up the PWB reveals no obvious solder joint damage, but what the heck, get a screwdriver and torque down the loose leads on the terminal block. It actually took about a full turn or more on the setscrew to clamp the wire down as much as the other terminals. (I don’t know why ML didn’t use a connector here, but decided to use instead a terminal block using a setscrew on each wire) Huh. I wonder if that was it? There were only 2 loose wires out of the 8 terminals on the ESL power supply board, but the loose ones were really important: getting the signal out of the crossover and into the ESL! If there’s no signal, there’d be no sound.

Put it all back together and fired it up. It seemed fine (well, as much as the Streets could be as I wait for the BHK 250 to come back) Ran some loud bass through it. Put 3 hours on it last night, and there are no problems so far.

So that may be it. Don’t have to ship the units back to ML (My dealer closed 5 years ago) No $$ expended yet.

More testing to come. But who’d-a-thunk a loose wire can drive me batty enough to think about replacing the speakers for $10k?


This is quite a story. I hope you found the problem.

I soooo have my fingers crossed! I’ll run it for another few hours today (while wife is at a local comic con) and see what happens. Hope that’s it.

Held up just fine today during the music in the first atmosphere-processor scene in “Aliens” (halfway through) when Ripley takes over command of the APC when the marines get their butts kicked by the critters and Lt. Gorman just sits there. . . . (That was a nice, loud passage. Thanks, James Horner.) :slight_smile:


I’m glad it was that easy to track down, Streets. I wish my Quads were as easy to work on as your MLs (and that when they periodically die the problem was as simple as a loose wire!). Thank you for sharing your story.


PB, it wasn’t easy to track down, it was easy to fix once I found it. The problem has been ongoing and intermittent for the last 6 months or so, sometimes never really being in ‘failed’ mode long enough to troubleshoot. Sometimes the speaker would sputter, sometimes it ran fine. Sometimes it wasn’t a binary “on-off” failure (i.e., level would drop 6 to 10 dB, then bounce back up again, sometimes up to 3 times a second.) I tried changing tubes, and that seemed to work for an hour or two, then it would manifest itself again. It wasn’t until Friday it dawned on me that it could be a ‘bad solder joint’ so I dove into the woofer chassis a second time yesterday to actually look for a bad solder joint and that was when I found the loose wire. But before I hadn’t thought to look for it and was pondering buying all 3 PWB boards and shotgunning the repair without really knowing where the fault was. Fortunately I came up with the idea before ordering the spare parts.

So, no, not easy to track down as I pondered for months on end and went down a lot of rabbit holes to dead ends. But once I considered the loose wire as possibility it was very easy to fix once I found out where it was.

Well done!

I just wish it was a process resolved in a weekend, not over six months.

Congrats and thank you for sharing this SSW!

Listening to ML Spires for years and very happy with them. Also spotted the cleaning tips showering the panels but I would never have the guts to do that myself. Taking the power of the stats for at least 24 hours before cleaning the panels with a vacuum cleaner two times a year should be enough to prevent building up too much dust on them.

I would choose to bring the Spires to the ML certified support tech for repair whenever failures would arise, lucky to have him within reasonable reach. However reading your experience I will check for loose wires before going that route.

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Thanks wijber! Washing the panel wasn’t too bad, I just had to have the discipline to let it dry for 3 days before reassembling it onto the base. Also, I kept the water off of the electrical connector and held the panel upside down in the shower to let the water run toward the top of the panel, that way I could control how much water got into the wires. But the woofer was pretty dusty after 9 years, so at least the water cleaned off the grill and I was able to wipe off the woofer with a damp rag once the panel was off.

Really, it wasn’t tough to do.

And it ran fine for another hour last night as we watched another episode of Black Mirror, so it’s fixed or the process of going through the motions tweaked the real fault enough to make it work. Should find out after another 25 hours or so (only 5 on it so far)