Speaker Surround Repair: Revision #7

Here a good video for refoaming  http://www.youtube.com/watch?v=lp1kjymypQc&feature=related

Driver foam surrounds gets old and brittle with use and years, so vintage drivers (normally bass drivers) will need new surrounds, if your speaker has distorted sound in the lower tones, take of the speaker grill (USA "frets") and if it looks like this, its time to start working.

To get the right surrounds you will have to measure your driver, some sellers just sells what they think is right, so check the dimensions before buying.

Your dimensions may be 1-2 Mm different, but try to get as close to the original as possible. For an 8" driver glue strip to the cone should be at least 4-5 Mm. To the basket more like 8-10 Mm.   May be less for very small drivers and more for bigger ones.

The old surround and old glue, will have to come of, the best way to do it is with a hobby knife or razor blade. On the basket you can scrape and cut it of easily, but on the cone (mostly paper cones) you will have to work with care, not to damage the cone, DO NOT USE ANY SOLVENTS HERE. And don't cut of the dust cap, before you finish cleaning and have glued the inner edge of the surround to the cone

With everything clean and looking like new, apply glue to the cone where the inner edge shall go, You may wish to make a pen line all around the cone, marking the inner edge diameter.

Apply glue to the cone and/or surround, according to glue recommendations.

Now place the surround on the cone, carefully press the surround to the cone without pulling or stretching the surround, make sure the surround fits like this all around the cone

Press the surround to the cone with one finger under the cone and one finger over the surround, all around 2-3 times, When properly fitted, find a dish or something circular that fits exactly over the glue strip and put some wight upon it, leave until glue has dried. The pic is just for show, its a finished RL 140 driver.

Glue dry, now cut the dust cap, as close to the cone as possible and nearly all around, leaving a 2-3 Mm bit still attached to the cone

Fix it with tape

DO NOT use cardboard or paper for shimming, like in this photo, its not precise enough and may leave dirt in the voice coil

Now start shimming, You will need some strips of different thickness, clear plastic film or transparencies, I use 0.05, 0.1 and 0.3 Mm, cut 10 x 80 Mm. strips, and start inserting strips all the way to the bottom, in the gap at "0", 120 and 240 degrees, the same count of strips at all 3 points, moving the cone in and out, adding strips until you feel the cone starts moving harder, the adjustment is right when the cone moves hard if an extra 0.1 Mm. strip is inserted at one of the 3 points.

Now add glue to the basket and/or surround outer edge, press the surround to the basket, same way as to the cone, two fingers all around, without pulling or pushing. If your driver has a gasket, place that over the glued surround, find a circular item that fits over it and add some weight to it, leave to dry.

When dry, retract the plastic strips and check moving the cone in and out with 3 finger on the cone, if the voice coil moves freely and without "scratching" sound its OK, glue back the dust cap with just a small strip of glue on the cut.

When the glue is dry, you can connect your driver to the crossover and connect the speaker to an amp for testing, or if you are an optimist, build it into your speaker, connect to your amp and test, start at low volume and let it play for an hour or 2, then gradually increase the volume and bass levels until you are satisfied that it works okay, if you at the same time changed your caps or repaired your crossovers, there will be some "playing inn" time before the speaker will reach the correct sound.