It’s been about 15 years since I’ve done any electronic work, let alone wield a soldering iron. After a lot of research into the audiophile world and slowly gathering ideas for projects, it was time to finally get back into the swing of things with a simple project, and upgrading the capacitors in my Martin speakers seemed like a great project to do so!
Since electrolytic capacitors degrade over time, some research showed that a Polypropylene replacement would best be suitable. The price range abounds on these, and I settled on Dayton’s PMPC line, purchased from Parts Express. I was not only impressed with the 1% tolerance rating they have, but they also came in the closest ratings I needed. I didn’t want to have to piggy-back capacitors as much as I needed to.
The Martin 4050′s use the following three capacitors:
Overall the project was a success! Nothing exploded or caught on fire! This is good news! I am starting out with just one speaker and will give the capacitors burn-in time for comparison to see if this upgrade really does deliver a sound difference.
So let’s start with the first speaker.
The crossover, all snug in its bed.
The design of these 4050′s has a seperation between the upper and lower woofer. The top woofer needs to be removed to get access to the crossover. From there, three screws hold it in place.
Since all the connections for the various drivers & connections are soldered onto the board, I decided to to the replacement with the board in place. If you remove the lower driver, you can push the wires underneath up through the wax molding to get a bit more slack to angle the PCB into a position suitable for the procedure.
After 15 years or so, it seems my de-soldering skills are still quite good! Of course this is due to a lot of reading up on the process and watching YouTube videos. I spread a bit of flux using a toothpick onto the connection before applying the de-soldering strip and iron. Temperature of the iron was set at 700F.
Now that the old capacitors are removed, it’s time to size up the newer, larger ones and create a battle plan.
I’m not sure if Polypropylene capacitors are naturally larger than Electrolytic ones or not, but regardless, there’s an obvious challenge of dealing with the size difference.
I placed each of the new capacitor onto the board, planning out how to bend the wires to ensure none of them would touch anything. It wasn’t too difficult, about 10 minutes of work. Thankfully it was possible.
I pre-assembled a 47uf and 1uf Dayton capacitor after configuring the wire on the larger 47uf capacitor by wrapping the wire and soldering it in place. Seems to hold well. I placed a sticky felt pad between the two to prevent the top smaller one from vibrating around.
Here’s what the final installation looks like with the new capacitors. The angle of the photo is somewhat misleading, none of the cables are touching anything and have a good clearance between themselves and the inductors.
Because I had positioned the 12uf capacitor you see on the far right to lay off the PCB somewhat to create room for the larger 47uf capacitor, it meant that the PCB no longer would align tot he existing screw holes. Having pushed some of the cabling up through the wax hole on the board, I got enough movement to reposition the board as needed.
Some of the sound-proofing material also had to be cut because the 47uf capacitor needed all the room it could get to fit next to the board running down the center of the casing.
After testing the PCB connections, and speaker input with a multimeter, it was time for a test on the stereo. Success! Nothing exploded, smoked, smelled or caught fire!
And now some additional information and photos.
This guy held up impressively well for being 40 some years old!
Here’s some additional close-up photos of the components found on the crossover as well as the driver used, a Seas 25F-EWX 8hm driver.