Soundtechguy
Active member
Hello All!!!
I recently saved a pair of Martin Logan Quest speakers from meeting their fate of the landfill. They were removed from service due to failure and were beside a dumpster at my local Hi-Fi shop. The Hi-Fi shop gladly gave them to me as I work in the pro-sound industry and certainly know which end of a soldering iron to hold (lol). I figured "worse case scenario" I would either fix them for myself or part them out if necessary. I'd like to introduce myself as David from CT and post my findings in case anything here helps others on this site.
After verifying their current state of disrepair (one unit had a dead panel and the other unit had a panel that worked, but faintly), I disassembled both units. The first thing I noted was that the terminal block located below the panel was badly damaged on both units. I don't know if this condition was caused by overdriving, but my educated guess is that the terminal block either loosened or tarnish a bit causing resistance and heat buildup. I'm guessing this condition snowballed until the connection was overwhelmed and damaged completely. I replaced both terminals with Phoenix block connectors which made both speakers functional, but problems persisted.
I removed both power/amplifier units for inspection and found that the similar terminals that connected the feed wires to the panel suffered heat damage as well. I replaced the connectors and chose to replace the wiring between the amp module and the panel as well. This effort was an improvement, but more issues where still noticeable.
I then removed the panels, washed them and inspected them for any obvious damage. With the panels cleaned and reinstalled, a great improvement was made. The speakers functioned 90% better then when I got them! I must say... the imaging and details is breathtaking! The only thing I now note is that one panel is a few db less than the other for some unknown reason. I swapped amp modules between the two speakers and the problem stays with the panel which points the finger at the panel itself.
Lastly, although the amp modules seem to work properly, there are two porcelain resisters mounted to the under side of the crossover that took some heat. I found it interesting that all surface mount parts are located on top of the PCB with the exception of these two. If I had to guess, maybe Martin Logan opted to located these parts underneath the board to keep them away from the fiber matting in the woofer baffle due to the heat they may generate. The downside is the being sandwiched between the underside of the PCB and the rear panel of the amp module the heat buildup burnt the PCB. Although the tracer was still conducting, I jumped it to ensure a solid connection.
I contacted Martin Logan and went over all my repair work. They stated that I pretty much found and correctly repaired the weak links of the ML Quest. They stated that the minimal difference in level between the two is not unusual and that if the difference is just a db or two... I'm doing great for 20 year old stators. The last hurrah is the dreaded Nextel finish that has decayed to a sticky goo. I found that the Nextel does not hold up to denatured alcohol. I guess the next step is to strip off the Nextel and then recoat the cabinets with Duratex. I have used that product on pro boxes with great success. If you thin it out on the last coat, you can obtain a nice fine textured finish that is incredibly tough and attractive.
Greetings from CT!
I recently saved a pair of Martin Logan Quest speakers from meeting their fate of the landfill. They were removed from service due to failure and were beside a dumpster at my local Hi-Fi shop. The Hi-Fi shop gladly gave them to me as I work in the pro-sound industry and certainly know which end of a soldering iron to hold (lol). I figured "worse case scenario" I would either fix them for myself or part them out if necessary. I'd like to introduce myself as David from CT and post my findings in case anything here helps others on this site.
After verifying their current state of disrepair (one unit had a dead panel and the other unit had a panel that worked, but faintly), I disassembled both units. The first thing I noted was that the terminal block located below the panel was badly damaged on both units. I don't know if this condition was caused by overdriving, but my educated guess is that the terminal block either loosened or tarnish a bit causing resistance and heat buildup. I'm guessing this condition snowballed until the connection was overwhelmed and damaged completely. I replaced both terminals with Phoenix block connectors which made both speakers functional, but problems persisted.
I removed both power/amplifier units for inspection and found that the similar terminals that connected the feed wires to the panel suffered heat damage as well. I replaced the connectors and chose to replace the wiring between the amp module and the panel as well. This effort was an improvement, but more issues where still noticeable.
I then removed the panels, washed them and inspected them for any obvious damage. With the panels cleaned and reinstalled, a great improvement was made. The speakers functioned 90% better then when I got them! I must say... the imaging and details is breathtaking! The only thing I now note is that one panel is a few db less than the other for some unknown reason. I swapped amp modules between the two speakers and the problem stays with the panel which points the finger at the panel itself.
Lastly, although the amp modules seem to work properly, there are two porcelain resisters mounted to the under side of the crossover that took some heat. I found it interesting that all surface mount parts are located on top of the PCB with the exception of these two. If I had to guess, maybe Martin Logan opted to located these parts underneath the board to keep them away from the fiber matting in the woofer baffle due to the heat they may generate. The downside is the being sandwiched between the underside of the PCB and the rear panel of the amp module the heat buildup burnt the PCB. Although the tracer was still conducting, I jumped it to ensure a solid connection.
I contacted Martin Logan and went over all my repair work. They stated that I pretty much found and correctly repaired the weak links of the ML Quest. They stated that the minimal difference in level between the two is not unusual and that if the difference is just a db or two... I'm doing great for 20 year old stators. The last hurrah is the dreaded Nextel finish that has decayed to a sticky goo. I found that the Nextel does not hold up to denatured alcohol. I guess the next step is to strip off the Nextel and then recoat the cabinets with Duratex. I have used that product on pro boxes with great success. If you thin it out on the last coat, you can obtain a nice fine textured finish that is incredibly tough and attractive.
Greetings from CT!
