A much more common problem that happens to even the most careful of audiophiles is that the foam edge (outer suspension or ring) of most speakers will dry rot. The technical name for this part is an annulus. About ninety percent of all home stereo speakers use this material as a suspension. New "high tech" woofers with polypropylene cones and buytl rubber edges will not suffer these problems but could develop others. This dry rot problem is caused by age and certain other environmental factors and has nothing to do with your kids "jamming too loud" or the movers that you think might have busted them in transit. (NOTE: Professional movers might want to print out this page to use it in their defense on the next damage claim). Speakers that have never been used and have been in storage for 20 years will develop this same problem.

This is the most common problem that I see with stereo woofers and can be remedied by replacing the foam edge. Even those of you just browsing this page should take the "pinch test" if your speakers are older than eight years. Place your thumb and forefinger on the foam bump of your speaker and give it a small tug. If it is intact, you are safe but please repeat this test every six months. If the foam comes off in your hand, please drop us a line.

Both of your speakers were manufactured at roughly the same time and will rot at the same rate. I can't tell you how many people call me and initially tell me that only one speaker has a problem. They think I'm The Amazing Kreskin when I tell them about their other woofer. Even the most stubborn of customers eventually bring the other woofer in for repair as the difference is so obvious. As an incentive, I offer a reduced rate if both speakers are brought in for repair at the same time. You wouldn't believe how much time (yours and mine) and paperwork this saves.

The foam edge on a speaker is much like oil is to a car engine. Oil keeps the parts in your engine lubricated so that friction will not build up. If friction occurs in your car, parts rub together and many nasty things will happen --- all of which cost big money to repair. This works the same way with speakers!

When intact, the foam edge keeps the voice coil in alignment and seals all of the air movement into the cabinet. When the foam rots, air leaks out (not in phase with the front radiations) and your bass frequencies cancel with each other. The biggest problem is that the voice coil is not centered, rubs against the magnet (friction), the coil overheats, the varnish on the wires melt, the coils come undone and get stuck in the gap. You then need a much costlier recone. The worst thing that can happen are that the voice coils catch on fire (and you know how fires can spread) or that it can blow up your amplifier with a short circuit (transistor amps) or an open circuit (tube amps).

Just like when the oil light comes on in your car, it means STOP OPERATING AND FIX NOW!!! I have repaired more horror stories than I can tell you about. The basic story is that a person will call me knowing that they have this problem and ask for a quote. After getting my quote they say they will "get back to me on it". More often than not, they (or their kids) will have a party, "crank it up" and blow the speakers --- which normally would have taken the same volume level. The customers are then in need of a much costlier repair. Another case is when the grandchildren come over and the toddler has turned the volume control all the way up (when the stereo is off). The next person that turns on the stereo then destroys the speakers. These are high stakes to be gambling with. If you are going to wait on this repair then at least unplug your speakers and hide them. Even playing them at low volumes is too much of a risk. A car without oil won't blow up if not used but some people will still try to drive it "just down to the store".

The highest risk speakers are many JBL and Cerwin Vega drivers because they are built with extremely tight voice coil gaps (for high efficiency). The smaller the gap, the easier it is for the parts to rub if not centered. There is nothing wrong with these brands but the case is, if you hear a rubbing sound, it may already be too late for a simple foam edge replacement. I keep a blown JBL 122-A cone laying around to show customers. It had to be reconed and cost the customer close to $170! If he had just called me sooner...

My retail warranty on the foam edge repair is five years parts and labor. Just try to find that kind of warranty on anything these days. This covers not only rot, but also if any of my parts come unglued. The refoamed speaker has the same Thiele-Small parameters as new (read the page on box tuning if you haven't already), costs a fraction of the price of a replacement, and has a five year warranty versus the standard ninety day warranty for replacements (over twenty times longer). Now you understand why I say that my repairs are both BETTER AND CHEAPER THAN NEW!

No, sorry, I do not sell do-it-yourself foam edge replacement kits. When I started this business, back in the 1980's, I had a few customers that swore that they could do the work themselves and wanted only to buy the edges from me. I decided to sell them the parts only to find out later (oh yes, they called back) that they didn't do the process right and in at least one case, had destroyed their cones in trying. The companies that sell these kits are in no way responsible if you mess up your speakers. There is of course a short warranty period but they will only replace the parts if defective (not if you broke them through your own fault or ripped them in trying to recenter them). A lot of these "kits" don't even come with the proper parts or directions for installation. The proper adhesives must be used. The wrong adhesives can be corrosive and prematurely rot your new edges. Sometimes, even speaker manufacturers don't get this right: I've seen foams that would have held up many more years that had rotted only at the edge of the gasket because the wrong glue was used to attach the gasket.

Parts have to be aligned with shims to get them centered properly. Most of these kits do no include shims or the proper directions on how to use them. In querying other repair shops around the country, I haven't found one yet that performs this critical process. One shop even told me that "to do that, we would have to charge as much as a recone." I have re-repaired speakers for "professional" companies that couldn't get the speakers aligned. The last time I checked, my prices were only about five dollars per speaker higher than theirs.

Besides the right glue and the proper alignment, there are many other things that can go wrong with speakers when the foam edge fails (especially if not caught in time and their use is continued). Other parts can come unglued, or devlops kinks, warps, and clicks (all of which are audible) and each requires a different adhesive, chemical, or technique which is not available to the general public. There are a few secret techniques that I have invented that no one else has.

Once a speaker is repaired, it must be tested with tones from an audio generator to make sure that there are no frequency dependant problems. Again, another tool that most people don't have laying around.

The process of repairing a speaker is much like surgery. One slip of the knife and the "patient" could die. Oh yes, I can usually resurrect them if reconing parts are still available, but it always costs much more than doing it right the first time. Some exact replacement drivers cost into the hundreds of dollars! There are no such things as "quick fixes" using silicone or nail polish. I don't know who started this completely asinine rumour but I'd love to inform them of the truth. In closing, there is still the matter of the sheer skill it takes to do this process. I've done it for surgeons who didn't feel comfortable with kits. Even the greatest of surgeons won't operate on their own kids, so why would you think about risking the life of your speaker to your untrained hands?

Return to NeviSonics home page