Replacing the foam speaker surround on my JBL speakers

About ten years ago, I bought a pair of used JBL J520m bookshelf speakers. They have nice, wood cabinets, a great-sounding woofer and tweeter, and a classic look (they don't really look dated, like 90% of 80s and 90s-era speakers).

JBL J520m speaker wall mounted with grill cover next to TV
Doesn't it look stately?

Whenever you buy used speakers, you should check the woofer cone and foam surround, as these are usually the first parts to deteriorate and cause terrible distortion in certain situations. In my case, the speakers had been stored in someone's garage for a few years, so I knew the foam wouldn't last long. When purchased, the foam flexed okay, but this year I noticed both speakers started making funny noises during explosions or low bass notes during movie and music playback.

JBL J520m speaker foam woofer surround dry rot gap
A sure sign of dry rot—and flaky sound!

Instead of purchasing two entirely-new speakers (and dropping another $200+ on my home theater system!), I looked into my options for refurbishing my older speakers (since I was happy with their performance and look):

  1. I could replace the foam surrounds with new foam or rubber.
  2. I could replace the entire woofer speaker assembly.

Option 1 is definitely cheaper—for almost any popular speaker brand, there are foam or rubber surround replacements for $25 or less, shipped. In my case, I found a Speaker Foam Edge Repair Kit for JBL by Simply Speakers, and the kit comes with two foam surrounds, a tube of seriously sticky foam glue (it's almost like superglue!), and some instructions.

Option 2 is more expensive—and depending on your speaker, it might be impractically so. After only finding single woofers here and there (in varying states of decay) on eBay, I decided to see if I could get replacement woofers (JBL part number P205G/76431), and I was lucky to find a company that builds reproductions (the original woofer isn't manufactured anymore), Midwest Speaker Repair. They sell a replacement almost identical to the original woofer, model #MW-5050.

But I thought the DIY foam replacement route seemed easy enough, so I started with option 1. I had the best intentions.

Things were off to a great start after I had the foam in hand:

JBL J520m speaker woofer connections
Unscrew and unseat the woofer, taking note of the positive/negative connections...

JBL J520m speaker wood cabinet woofer removed wires and holes with insulation inside
Pull the connectors and now the speaker cabinet is about 2 lb. lighter!

The first step in replacing the foam is the removal of the old foam. In my case, I used my fingers to grab away the majority of the foam, then I used a cotton swab to soak the remaining foam in 91% rubbing alcohol, and carefully scraped off what I could from the metal ring with a sharp wood chisel.

JBL J520m speaker woofer foam scraped off
So far, so good!

The next step is to put a ring of glue on the edge of the cone, then quickly message the inner part of the foam onto the top surface of the cone. This went pretty well, though there was a bit of glue that would get stuck to my fingers, so I got a little on the cone itself. Not too bad, but could've done better:

JBL J520m speaker new foam glued to cone
A little messy, but nothing detrimental to the sound quality...

After waiting an hour for the glue to dry on the cone and inner part of the ring, I went to work quickly getting down some glue on the woofer's metal mounting ring, then squishing the outer part down flat.

This is where things started going off the rails:

JBL J520m speaker new foam glued to metal - badly
That is not how the speaker looked in the videos!

What happened? Well, first I put down a light layer of glue on the metal ring, then I worked my way around pressing the foam down. But since the cone made the foam itself want to warp slightly upward, I was fighting against the foam's natural desire to stay at an angle.

So then I had the bright idea of putting down a little more glue, and holding it in place for a little bit. That didn't really work out. Instead, I got glue everywhere. It starts to dry pretty fast (less than a minute), but before it fully dries, it turns into a tacky, sticky mess... and that's how you end up with the result in the picture above. Here's a demo video of what the speaker sounded like before (with dry rot/original woofer) and after the #diyfail, and then after installing a brand new aftermarket woofer:

Note: The demo song is Knick Knack Paddy Whack by SteveSongs. When you have kids, you can't demo your sound system with the grungy rock and hip hop songs you used to use :)

After trying out the speaker (with the cover back on—nobody wants to see that messy woofer!), and finding it to be much worse than before the foam was connected at all (I must've messed up the cone's alignment so the voice coil hit the cone during louder notes), I decided option 2 might be the better course.

JBL J520m speaker with new woofer replacement
Not an exact match for the originals, but they look and sound pretty good!

So now I have two new woofers, both with rubber surrounds. Hopefully they take these speakers from the 80s into the 2040s and beyond!

Comments

You used too much glue and didn't center the surround using a tone generator while gluing.

I have used Parts Express's foam kits, and had success. I agree that the kits from Simply Speakers include glue that makes you work FAST. It is indeed possible to do the job though! It takes practice to get good at it.