Martin Logan ESL Expression 13a amp removal, woofer not working

My 13a has front and rear firing 10 inch woofers and one of my rear woofers is not working. It seems intermittent.  I took it out and saw nothing but when i put it back in, it worked!  For a while.

The amp is on the bottom and seems pretty difficult to remove.

Any tips or tricks to removing the amp?  It didn't simply unscrew and pop out easily like I wanted and I certainly don't want to damage any further.



Your woofer cone may be intermittent. Rather than examining the amp, first swap the drivers, see if the problem moves with it.

There are a couple of places where this can happen. The solder to the connectors/tabs can become loose, but the wiring that goes from the tabs to the coil can become lose. The glue can come detached and/or the solder that connects the flexible wires from the tabs to the voice coil wires can fail.

Fortunately this is a case where a simple continuity tester from a multi-meter will help.  If in doubt, hook it up and gently play with the wires see if the resistance or continuity changes.

Call Ron, in service, at ML.  Have your serial number handy.  He is great to work with.

Great thoughts. I was just wondering if this sounds like a common "oh yeah, that's always this fuse, replace and be happy."  

I'll swap the woofers in a bit and see what happens. 

Ok, I swapped the woofers, same thing.. Rear woofer is out and seems to be an amp problem.. Hmm, I'd much rather replace a woofer than take the amp out and send to ML.  

Of course, I would discover this on a holiday weekend and I'm sure Ron at ML will be slammed on Tuesday. 

Easy to remove. Unscrew feet, use 1/2 inch hexwrench to remove where the feet were screwed into. Seperate(easiest if speaker laying on side), disconnect 2 connectors. Vwa lah.

Droleg.  Tried that but feels like it’s connected somewhere else up in there. So I don’t have to remove the side rails?

No. Just the 4 thingys. Then it just jiggles out. Did it on mine several times, for different reason than yours , though.

If you go on ml website/support, you may find the instructions. They sent them to me, but not sure where they are.

I don't know this amp but most subwoofer amps are similar inexpensive class D amps (not critcizing, that is quite adequate for bass frequencies).  I've replaced amps in subwoofers the blew.  I think the one I ordered from HSU was about $250 and took 10 minutes to install.  

I'm guessing something in the channel is overheating.  could be a defective thermal overload ($2 part).   when you get the amp out you may see obvious signs of overheating.  if not, ask ML how much it costs for them to just send you a replacement amp.  You may be surprised.

If it was mine, I would troublshoot it myself and likely fix it for $10 or less but to pay someone to do the troubleshooting will likely cost more than the price of a new amp.  Yes, that is the service industry world we live in.  I recommend every young person study physics and become self sufficient.  I've yet to have one take my advice.