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 is the perfect starter!
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:
These are being replaced with:
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, but regardless, there’s an obvious challenge of dealing with the size difference.
I placed each of the new capacitors 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 configured the leads on the larger 40uf capacitor by running them through the PCB board, using a needle-nose to make initial bending adjustments, then pulling it out to refine and perfect the bends. Then, I pre-assembled the 40uf and 8.2uf capacitors by piggy-backing them, using a needle-nose to bend and wrap the leads on the smaller 8.2uf to the sides of the 40uf capacitor, giving a slight space so it wasn’t touching the actual siding. Seems to hold well. I placed a sticky felt pad between the two to prevent the top smaller one from vibrating around, and soldered the leads.
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 positioned the 12uf capacitor you see on the far right to hang off of the PCB to create room for the larger 40uf capacitor, it meant that the PCB would no longer align to the existing screw holes. Having pushed some of the cabling up through the wax hole through the cabinet’s dividing board separating the two woofers, I got enough movement to re-position the board as needed.
Some of the sound-proofing material also had to be cut because the 40uf 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! Immediately I heard a subtle difference in the sound, with the high range standing out as being am improvement. Overall, it wasn’t a significant difference, more of a cleaned-up positioning. It would be the second speaker that showed the most improvement.
I waited a week before changing the capacitors on the second speaker. The sound quality had been noticeably weaker here, the highs were harsh and the amplitude comparatively lower. The new Dayton capacitors really brought this Martin back to life. It took about two weeks for them to equal in sound and response. The highs really showed the most improvement being without a harshness that had been bothering me before the upgrade. This was demonstrated with Miles Davis’ Agharta album. My copy demands a good quality needle and a clear soundpath to be played without any distortion occuring. I don’t know if this is due to a poor quality recording, pressing or stereo configuration, but with the upgraded speakers, any hint of distortion in the music has disappeared. Success!
And now some additional information and photos. The driver used in these Martins is a Seas 25F-EWX 8hm driver.