The surround is the flexible ring that joins a woofer's cone to its metal frame. It lets the cone move in and out while holding it centered, and on a lot of vintage speakers it's the first part to fail. If you shop for older speakers, you'll spend a lot of time squinting at woofer edges. This guide covers what they're made of, how rot shows up in photos, how to judge a refoam, and what to make of torn cones and dented dust caps.
What surrounds are made of
Surrounds come in rubber, polyester foam, treated paper, or a ring of corrugated, resin-coated fabric. Foam is light and economical, but it breaks down with time, sunlight, humidity and heat. Polyurethane also reacts with moisture in the air, and it discolors as it ages, going from off-white to yellow to reddish brown. One maker of repair kits puts the typical life of a foam surround at ten to fifteen years. That's one vendor's figure, and climate and storage matter a lot, but most restorers assume original foam from the 1970s is finished unless the seller says it's been redone.
Rubber ages differently. Ozone can crack it, and the cracks run across the direction of stretch. Butyl rubber resists this better than natural rubber, though it isn't immune. Cloth is different again. Early AR-3a woofers, built from 1967 to 1969 with Alnico magnets and cast frames, used a cloth half-roll surround coated with butyl latex. In 1969 AR moved to a ceramic-magnet woofer with a urethane foam surround and a reddish-orange Masonite ring outside it, so an AR-3a can have either depending on when it was built.
The cloth ones look wrinkled, and that's normal. The Restoring the AR-3a guide on Classic Speaker Pages says the cloth-surround Alnico woofers are often fine, though the coating can need renewing to stop air leaks. Its check is to press the dust cap gently and feel for the seal. Leaks matter in a sealed box, and the guide notes they can also come from a missing driver bolt, a loose control shaft or missing gasket putty.
Foam was everywhere else in this era. AR says the AR-5 pioneered its urethane surround, which later spread across the line, and the 1975 to 1977 AR-11 woofer has foam too. The Advent Loudspeaker's woofer has what Advent called a thermally formed, fiber-reinforced polyurethane outer suspension. JBL's literature doesn't say what the L100 woofer surround is, but collectors widely report refoaming them. We couldn't confirm the woofer surround material for any Klipsch, Altec or Infinity model, so trust the photos over any listing that promises no rot.
How rot shows in photos
Ask for photos with the grilles off, lit from the side, with a close-up of each woofer edge. Then look for these signs.
- Crumbling or powdery edges, or cracks running around the roll.
- Missing chunks, or gaps where the foam has pulled away from the cone or the frame.
- Black or sticky residue on the surround.
- Foam dust in the bottom of the cabinet or caught behind the grille.
Color alone doesn't settle it. Yellowing is normal aging for polyurethane, but a surround that has gone dark brown and sticky is near the end. Ask to see the whole circumference of every woofer, since one photo can hide the bad side. On a speaker with a passive radiator, like the Klipsch Forte, check its edge as well.
When a pair arrives, press gently and evenly near the dust cap with your palm. Foam that feels stiff, sticky or flaky is due for replacement. A healthy surround has an even, intact roll all the way round, still flexible, glued cleanly at both edges, and made of the same material on both speakers.
What a good refoam looks like
A refoam replaces only the surround. One repair shop lists the steps. Remove the old surround, scrape the old foam and glue off the frame, clean it with rubbing alcohol, glue the inner edge of the new surround to the cone and the outer edge to the frame, then refit the gasket. The new surround has to overlap the cone on the inside and the frame on the outside, and the glue is matched to the cone, latex for paper and nitrile for plastic.
The hard part is centering. The surround and the spider hold the voice coil centered in a narrow gap, and if they're off, the coil rubs against the magnet. Shops do this by lifting the dust cap and setting shims in the gap. Many restorers instead play a low tone, around 20 to 40 Hz, at low level while the glue sets so the cone finds its own center. Either can work, so ask which was used.
In photos, a good refoam shows a neat, even glue line at both edges, the same surround profile on both woofers, a round, unmarked dust cap and no glue streaks on the cone. Both woofers should be done at the same time with the same kit, in the original material. One kit maker warns against swapping foam for rubber or the reverse, because it changes the sound.
Most restorers name the same signs of a poor job. Listen for scraping or buzzing on bass notes, and look for a surround that sits too tall or too short or rolls the wrong way, glue smeared onto the cone, a crooked or crushed dust cap that was lifted for shimming and refitted badly, or one woofer done differently from the other. On arrival, push each cone gently and evenly at several points around the dust cap. It should travel smoothly with no scraping. Then play something bass-heavy at moderate volume and listen close to each woofer.
Torn cones and pushed-in dust caps
The dust cap has a real job. It keeps dirt, and especially magnetic debris, out of the voice coil gap, which is why a torn or missing cap deserves a question. A pushed-in cap is a common sight on old woofers. Many hobbyists pull a dented cap back out with a loop of tape or, very gently, with a vacuum hose, and most say a dent doesn't change the sound unless the cap is creased or torn. They skip that trick on fabric or vented caps, and AR's sealed designs vented through cloth dust caps, so leave those alone.
Domes deserve a look too. The AR-3a's midrange sits behind a mesh cover, and the restoration guide calls small dents in that cover common and harmless. A dent in a tweeter or midrange dome itself is a different matter, so ask about it.
Cone damage is a bigger question. Shops treat a refoam and a recone as separate jobs, and a recone replaces the cone, spider and voice coil together. Restorers often patch small tears in paper cones with tissue and glue or a thin coat of cone dope. A big tear or a warped cone usually means a recone, and on a collector pair a reconed driver isn't the same as an original one. Tide-line water stains or rippled paper suggest damp storage, so look for rust on the frame and magnet as well.
What to ask the seller
- Original or refoamed. Ask whether the surrounds are original. If they've been redone, ask when, by whom and in what material.
- Both woofers. Ask whether both speakers were refoamed together with the same kit. The two surrounds should match in profile and color.
- Centering. Ask how the voice coil was centered. Shims or a low tone are both normal answers.
- Rubbing. Ask whether either woofer scrapes or buzzes on bass. The answer should be a clear no.
- Cones and caps. Ask about tears, repairs or pushed-in caps, and where the pair was stored. A dry room is the answer you want.
For the rest of the inspection, see how to check a used pair, read up on Acoustic Research, or browse the speakers we track.