Channel Imbalance on Martin Logan sl3s

[ck102020]

’ve been experiencing some channel imbalance with my Martin Logan’s. When changing the speakers it follows the issue, I assumed it was the room acoustics for awhile. It’s not the pre or power amp. What could cause a channel imbalance on a speaker? Maybe I got a bad panel? I got replacements a few months ago.
I had this sensation prior to recapping and repaneling them. I got the power supply board completely refreshed by a highly regarded tech in my area. I assumed it was a bad cap or bad panel. The one side that I thought was quieter before the work and panel replacement (left side) was the same after replacing everything. I switched speakers today in my room and it followed to the opposite side. I had a channel imbalance before fixing them up completely and now still have a channel imbalance.

Both woofers work properly. Directions were closely followed when installing new panels. Power supply board was professionally worked on. Issue follows when changing the speakers around in my room.

I contacted Martin Logan and was told it could be the following-

1) Bad internal HV power supply not putting out the correct voltage
2) Loose connection of the stat wires on the panel
3) Bad panel

I was informed to change the panels around which I did.

I switched the louder panel on to the other speaker. The louder panel now became the quieter one. So the culprit is the speaker, not the panel. I forgot to plug the speakers into the wall at first and the channel imbalance seemed to be solved. After plugging the speakers into the wall the imbalance came back. I changed the power cords between speakers and nothing happened so it isn’t the cords. I cleaned both of the areas where power cords connect and nothing happened. I’m unsure what to do next. I believe the issue is an internal part of the speaker of the power supply board.

Also, various parts of the speakers are different in small ways even thought they have the same serial number. The power supply boards were slightly different and the connectors that connect the panel to speaker were different as well. Very strange seeing they are supposed to be the same as a pair.

I’ve become very frustrated with the ownership of these speakers due to how much they cost to work on and how many issues and headaches I have had with them. I just want these to be working properly and have done everything possible to make sure of it. I have invested thousands of dollars and countless hours of time only to run into other problems and expenses. Any help to resolve this would be much appreciated, I love these speakers so much but am getting rather discouraged. I contacted the tech as we work closely together on many different things and I am learning how to fix up audio, I am in college and have no experience doing so. He has been helping me in the process but wanted some other input. Thanks!

Connor

 

[Robert D]

Did you buy the speakers new, or were they used? What model?
From everything you say, it seems the problem must be the the internal power supply. One idea, does the sound level difference seem to be the higher frequencies and the bass is normal?

 

[ck102020]

Did you buy the speakers new, or were they used? What model?
From everything you say, it seems the problem must be the the internal power supply. One idea, does the sound level difference seem to be the higher frequencies and the bass is normal?

Hello, I bought them from the first owner. There are sl3s. There is just a noticeable difference in loudness for the channels. From the panel and from the bass.

 

[Russr]

If it were me (and I WILL be doing this with my SL3's), i'd get to a pooint where I know the Panels and power supplies are solid, and then go with an active crossover setup, as @Brandon Hartwick did with his Aerius i's in the post below:
https://www.martinloganowners.com/threads/how-to-active-bass-section.19237/There are multiple threads here where folks have gone with active crossovers @ separate bass/panel amps driven by the active crossovers.

What amp(s) are you currently using?

 

[ck102020]

This is something i eventually plan to do. Currently I am running a sunfire cinema grand with a Parasound P5 as preamp. Right now my main priority is to fix the imbalance. I am in college and this has all been expensive enough as it is so this project will be for a couple years out of school I just want the imbalance fixed. They’re great otherwise.

If it were me (and I WILL be doing this with my SL3's), i'd get to a pooint where I know the Panels and power supplies are solid, and then go with an active crossover setup, as @Brandon Hartwick did with his Aerius i's in the post below:
https://www.martinloganowners.com/threads/how-to-active-bass-section.19237/There are multiple threads here where folks have gone with active crossovers @ separate bass/panel amps driven by the active crossovers.

What amp(s) are you currently using?

 

[Tosh]

https://www.martinloganowners.com/threads/aerius-low-output-possibly-hit-by-surge.19874/
My SL3 also had that happen, and it turned out to be that T1 was broken. But in the thread above it was just the opamps...
But yes, something on your HVPS board is not working: opamps for MS, T1, Triac are the simple things to check.

 

[ck102020]

https://www.martinloganowners.com/threads/aerius-low-output-possibly-hit-by-surge.19874/
My SL3 also had that happen, and it turned out to be that T1 was broken. But in the thread above it was just the opamps...
But yes, something on your HVPS board is not working: opamps for MS, T1, Triac are the simple things to check.

https://www.martinloganowners.com/threads/aerius-low-output-possibly-hit-by-surge.19874/
My SL3 also had that happen, and it turned out to be that T1 was broken. But in the thread above it was just the opamps...
But yes, something on your HVPS board is not working: opamps for MS, T1, Triac are the simple things to check.

I will keep this in mind when opening them on Monday to try and find the issue. Hopefully I can locate the issue and fix it quick and cost effectively. Thanks for this info, helps a lot!

 

[Brandon Hartwick]

It definitely sounds like a power supply issue if you've replaced the panels and the volume imbalance is still there. You should check the bias voltage coming out of the power supply, you will need a volt meter and a resistor in between the positive lead and the power supply to bring the voltage down to a measurable level with a standard meter. Measure both power supplies and compare, I do not remember what the rating of the resistor needs to be but someone else here will likely chime in and what it needs to be and where exactly to measure.

Unfortunately these ESL's have a bunch more going on than your ordinary speaker and as they get older there's a lot more than can go wrong. Martin Logan does tend to have good tech support in my experience and they are usually happy to provide documentation and information to help get these older speakers running again. Keep in mind replacement parts can sometimes be totally unavailable or cost more than just finding another used set of Martin Logans.