How to Re-Edge Your Speakers

A good set of speakers is one of the few hardware items you can buy that can last several decades.  While the speaker cone is pretty reliable, you will eventually have to service the foam that surrounds it.  Over time, the foam becomes brittle and flakes off, or (in my case) you have some pesky children who think it’s fun to pick all of the foam away.  In my case the destroyed speaker was a Kenwood SW-300 subwoofer, which had the 10″ cone demolished.

Regardless of how you got to this point, you have two obvious choices: either buy a new speaker or replace the entire driver assembly.  The hidden option number three is to repair the speaker yourself.  As long as the paper cone isn’t damaged then really all you have to do is replace the foam and gaskets around the paper cone.  This could save you a lot of money, especially the bigger and more expensive your driver is.  In my case, I could not locate the specifications on this speaker, so there was a possibility of a mismatch if I chose a third-party driver.  The exact matching Kenwood cone cost over $100.  For around $15 and a little time I was able to repair my driver and salvage my expensive subwoofer.

All the parts: Busted driver, replacement foam, four paper gaskets, a brush, and Elmer’s Glue

Doing repair on your speaker may be intimidating to those that aren’t experienced with such things, but it is very easy.  Let’s face it; this isn’t rocket science and you don’t have to do anything electronic.  If you’ve ever glued popsicle sticks onto construction paper in kindergarten then you’re more than qualified to re-edge your speakers (but you may need help with the Safety Scissors).

On to the prep work!  Step 1 is on the next page…

Step 1: Locate the replacement parts.  I found my re-edge kit at Orange County Speaker.  There are several other vendors, which I’m sure you can find by hitting up Google with “speaker re-edge kit” or “speaker repair“.  The kit comes with two sets of foam surrounds, gasgets, glue, and an application brush.  Oh, and you’ll want to take a screwdriver to your speaker and remove the damaged driver assembly.  Make note of the positive and negative leads (if they aren’t already marked).

Step 2: Remove the previous foam and gaskets. Before you can repair your speaker, you must remove all previous foam and glue from the paper cone and metal housing.  For this you will need a utility knife, chisel, or some other metal tool.  First scrape off all of the remaining foam from the paper cone (you’ll have a naked ring around the edge).  Then use your knife and scrape off the gaskets and foam. You really have to go deep, until you hit the metal.  Then work your knife around until you remove the entire gasket.  Don’t be timid.  As long as you don’t rip or puncture the paper cone then all will be well in the end.   You may have a little bit of glue that you can’t get off but this is ok.

Here is my 10-inch driver after it has been prepped.  Since kids have messed with it, the center dust cover was pressed in as well.  I just used a vacuum hose attachment to pull it out again.

Step 3: Place the new foam. I’d recommend doing a “dry run” before putting any glue down.  Place the foam around the speaker cone and frame to size it.  See if you have to trim the foam at all, but it should fit if you chose the appropriate kit for your cones.  Most speakers have the foam glued to the top of the cone, but some are glued behind the cone.  You’ll want to glue your foam surrounds wherever you have exposed paper.

Place the foam to ensure a proper fit

The next steps are to glue the foam surround to the cone and frame, but do not do this at the same time.  If you mess up, or if there are pockets where something didn’t glue down right then you’ll have a heck of a time fixing it.  Glue the cone first, wait for it to dry thoroughly, and then glue the frame.  I’ll explain why later.

On the next page we resume with Step 4…

Step 4: Glue the foam surround to the paper cone. Many cones have a glossy protective coating, and you’ll see a ring of matte paper where you removed your previous foam: this is where you want to glue.  Place drops of glue on the matte part of the paper cone, and then use the included brush to make a smooth, uniform layer.  Then place the foam surround on the cone and press down.

Have a moist paper towel ready to mop up any glue that seeps out as you apply the foam.

Since you’re curving the foam down, it will likely pop up and you’ll have to keep pressing it down until it sticks (when the glue is really tacky).  This part may get a little messy, as glue will get on the cone and probably on the foam.

Apply glue to the cone’s edge and smooth it out with a brush

It doesn’t have to look perfect in order to sound perfect in the end.  As long as you clean up what you can and don’t have huge globs on the rounded part of the foam then you’ll be fine.  You’ll want to let this dry thoroughly before you glue the other side to the frame, because you may have to pull the cone for a proper alignment and if the glue isn’t secure then it will come undone.  It should be dry enough to move to the next step in about 4 hours, but a 24 hour cure would be best.

Step 5: Check voice coil alignment. We need to check the alignment of the cone to the voice coil before you start glueing the other edge all willy-nilly.  A speaker moves forward and backward, and there is a metal part that fits right down the center of the voice coil.  If you were to pull the cone even slightly to any one side, then the metal would scrape against the coil.  If you press straight down on the paper cone, you will see that there is no scrapeage.  Tilt it to the side and you’ll hear some scraping.  This is what you want to avoid when you perform the next step.

Left: the inner ring has cured.  Right: Gluing the outer ring and tapping down

Step 6: Glue the other side of the foam to the metal housing. Apply dots of glue to the metal frame.  Use the brush to make a nice even layer.  Now that you understand why you shouldn’t pull the cone in any direction, just tap the edge down onto the glue.  Don’t pull it or try to make it “look” symmetrical.  The important part is that the coil is aligned, not if the foam circle is completely centered in the frame.  Press straight down on the cone and verify that there is no scraping sound.  If not then continue to the next step.

On the next page we complete the speaker repair…

Step 7: Glue the gaskets. You can attach the gaskets as soon as you’re comfortable that the foam is placed properly.  Take your glue and apply some to the underside of your gaskets, then make it even with the brush.  Place the four gaskets between the metal edge of the housing and the rounded part of the foam.  The goal here is that the gasket covers the flat edge of the foam, and the curved part of the foam is free to move.

Apply glue to the underside of the gaskets and smooth

Make sure no glue touches the “domed” part of the foam.  The gaskets have notched areas where the mounting screws will go, so please observe them and make sure your mounting holes are visible.  Once this is done, place your speaker upside down to apply pressure to the gaskets and wait at least 12 hours for the glue to cure (24 hours would be best).

out

Attach the gaskets and place upside down for pressure

Step 8: Re-assemble your speaker. Attach the leads from your speaker to the driver assembly and screw everything back into place.  Go test it out and I’m sure you’ll find that the speaker sounds as good as new.

Even if you did a sloppy job with the glue, your speaker will probably sound as good as new.  My home theater subwoofer  is over 15 years old and has resumed its bass-shaking purpose in life. There is no distortion or any other auditory anomaly to indicate that repair was not a smart choice.  For $15 I saved myself from purchasing a new $600 unit.  If your cone is just damaged then you may need to purchase new drivers, but this is still favorable to buying entirely new speakers.  By purchasing an inexpensive re-edge kit, you can salvage your existing home theater speakers instead of buying whole new equipment.

Now onto the next project: building a booby-trap to encage any infants that come within close proximity to my subwoofer.