Refoaming an Electro-Voice PL10

I bought an Electro-Voice PL10 a couple of years ago. The element always rattled around inside because the interior foam was completely degraded. I finally decided to do something about.

Materials

I got in touch with a guy who works on old EV mics and he told me just to do it myself. He was really great and told me which types of foam to get and where I might be able to get them. The keys for the material are 20-60 PPI foam and 1/4" thick.

The main foam cup that the capsule sits in is 60 PPI reticulated open cell foam. I was told to just cut down an RE27 windscreen to the right size. For the front blast filter, I was told cutting down an RE50 blast filter did the trick, but Full Compass didn’t have that in stock, so I just went with the RE20 pop filter. The pop filter for the RE20 is 20 PPI reticulated open cell foam.¹ I also ordered the rear foam piece for the RE20; it ended up coming in handy. So, the parts I got were:

• 78233 - windscreen
• 78232 - rear foam
• 78231 - pop filter (for the front)

I also purchased Frost King 1524 air conditioner filter material. It was $1 at Home Depot. It’s not quite the right stuff, but it could work. It came in a 24"x12"x1/4" sheet and appears to be about 30 PPI. One last source that I didn’t fully pursue was a sample pack of reticulated foam from McMaster-Carr, part number 2195K99, which gives you 3’x3’x1/4" each of 30 PPI and 60 PPI foam for about $7. Next time, I’ll probably give the foam from McMaster a shot and see how it turns out.

Procedure

Disassembly and Cleaning

All in all, it was pretty straight forward. To disassemble, remove the XLR plug in the rear by means of the small flathead screw. Once the screw is fully tightened into the XLR plug, the plug should pull out. Desolder the wires, making note of the connections.

Next, unscrew the front cap. Once it’s off, you should be able to pull the capsule out. If it’s still sitting snuggly in its foam, use a pencil or something inserted in through the XLR hole to push the capsule out. The capsule has a plastic shield over the diaphragm, so it is somewhat protected. I’m glad this piece was there, since the foam in mine had completely melted all over it.

Now that the mic is disassembled, it’s time for cleaning. I used an old toothbrush to clean the casing and a bunch of q-tips to swab off the capsule. Whenever the melted foam was sticky, I used a little bit of isopropyl alcohol (just over the counter rubbing alcohol; unfortunately I no longer have access to the lab grade stuff). I dipped my swab/brush into it and then worked on the foam; I didn’t dump the alcohol directly onto the mic.

At this point, I realized there was a little black plastic ‘hubcap’ over the front of the element. On my mic, it popped right off, which enabled me to really clean off the stuck foam. It’s directly below all the foam in the following two pictures. After cleaning, I put it back onto the mic capsule. It seems to be held on by the tiniest lips of tape ever, but it did seem to be semi-secure.

Reassembly

Once everything is cleaned, it was time to construct the new foam filter and put it all back together. I took the main RE20 filter, cut off the bottom disc, and then sliced it down the side. This gave me a rectangle of foam. Then I trimmed it to the right size, which ended up being 82mm x 110mm. That second dimension is a rough estimate—the foam ends up being pretty stretchy. Then I rolled it into a cylinder along the 110mm axis and used a little hot glue to glue up the seam. This left me with a 82mm tall tube of foam.

For the bottom of the tube, I used the RE20 ‘rear foam’. I didn’t bother glueing it to the main tube. I just dropped it into the bottom of the mic case. Then, I folded up the cylinder I just made and inserted it into the case as well.

Initially, I had tried to put the capsule into the foam, and then insert capsule+foam all together into the mic case, but it was just too tight of a fit. Inserting the capsule into the foam+case was much easier. Before I inserted the capsule, I fed a piece of string through the mic. To the front end of this, I taped the capsule wires, enabling me to pull the wires down through the mic body and the hole in the rear foam. Then, I started to insert the capsule.

The capsule went in pretty easily up until the rounder head. The head is big enough that it just started to push the foam down inside of the body instead of insterting into the foam. So I cut a couple of strips of card stock, inserted them in between the foam and capsule, and then tried again. The card stock acted as a skid for the capsule to slide down without grabbing on the foam.

Now that the capsule was fully inserted, I cut a little biscuit out of the RE20 pop filter (12mm thick) and dropped it in front of the capsule. There was a little empty room in front of the filter due to the grill shape, so I cut an additional small disk out of the Frost King foam for the very front of the mic. Then, just screw the front on.

Lastly, solder the wires back onto the XLR and insert the connector back into the body. Tighten the screw, and your mic is refoamed!