3, Low frequency rattle

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Anthony Palmer2004-05-18 04:44

Hello. I\'ve was lucky enough to inherit a pair of Model 3\'s about five years ago, and have been extremely pleased with them. However, one of the speakers has developed a rattle at certain bass frequencies. At first I thought it was a ruptured membrane, but the rattle doesn\'t occur at loud volume, only certain frequencies even at low volume, and seems to be coming from the top left of the speaker. Also, I\'ve noticed three screws on top of the speaker, the middle and right screws are tight, but the left screw, the one above the rattling panel, doesn\'t tighten at all. In fact, the rattle seems to get worse when the screw is turned. I have zero technical abililty, but I would like to stabilize the panel without ruining the speaker. Any advice before I start would be appreciated. Thank you.

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Andy Szabo2004-06-08 18:39

Rattling panels is fairly common, but the good news is that the problem is easily remedied. You’ll need to remove the grille cloth, so read my Technical Bulletin “Grille Cloth Removal, Cleaning, and Replacement”, located under the subheading “Refurbishing”. A rattling panel is usually caused by a lack of tension in the Mylar diaphragm, and/or a foreign material caught in the stator-to-diaphragm gap. I suggest you follow these steps once you have the grille cloth removed (or at least pulled down far enough to access the entire panel area). All of these steps should be performed with the panel disconnected and fully discharged. 1) Tighten all of the screws that secure the panel to the wood frame. If these screws are not tight, the nylon bushings under the screw heads can vibrate. 2) With an open hand, gently bang on the entire surface of the panel, in an effort to dislodge any foreign material that may be in the gap. If you have a source of compressed air available, you might also try blowing out the panel, front and back. Then, vacuum the entire panel surface, front and back. 3) You may need to re-shrink the Mylar. This can be done with a high-powered hair dryer, or, with caution, an industrial heat gun. The idea is to evenly heat the entire surface of the diaphragm, without overheating it. The Mylar cannot be over-stretched, but if you overdo it in the extreme, the Mylar can melt. Just make sure to always be moving the source of heat so as not to overheat a small area. My final suggestion is to leave the panels exposed until you are sure the problem is solved. The processes described above may need to be repeated several times to cure the problem, but they are almost always successful. The loose screws you mentioned, I believe, are the ones holding the metal plate on the top of the frame. This plate’s purpose is merely to hide to attachment of the grille cloth. If one of the screws is stripped out in the wood, you can try injecting a bit of wood glue, or a bit of tissue paper in the hole, to tighten up the connection.

Anthony Palmer2006-04-24 19:19

Hello again. I finally got around to trying to solve the rattling panel problem as per your instructions - thank you. The problem had \"solved\" itself for awhile becuase I started using an older pre/pre with a fixed 80hz crossover; the rattle pretty much disappeared at the expense of not being able to run the panels at full range. However, I\'ve recently upgraded to aother pre/pro with a variable crossover, and I\'ve been crossing over to the sub at 40hz. The sound is more natural, but the rattle returned. Now I could even cause the panel to rattle just by shaking it. Before I tried your recommendations, I noticed that hitting the top of the panel caused the rattle to go away for awhile. Very strange. I tested this method for weeks and it never failed. But in an attempt to remedy the problem for good I followed your instructions. After using the blow dryer I shook the panel and it seemed to be quiet. I then plugged the panel back in and the rattle came back, So I repeated the process and now the panel seems even looser than before I started. Everything seems better until I plug it in then the mylar seems to loosen up again. Should I continue the shrinking process? Also, should I place a nail in the top of the frame since pounding the top seemd to quiet the panel? Thanks again for your advice on this matter.

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