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Speaker Clearances & Why We MUST Use Shims
First of all, shims are thin pieces of material (usually plastic) used to space the voice coil and pole piece during speaker assembly. There is a very good reason that all our kits have
dustcaps & plastic shims included. Most modern speakers have very tight clearances in the voice coil gap area. Specifically, the space between the voice coil and the pole piece (the area we will be working in) is usually ONLY 5-15 THOUSANDTHS of an Inch! There is very little “slop space.” IF the voice coil is not EXACTLY centered AND kept vertical, it WILL rub... unless you are very lucky! This is why you MUST use shims if you wish to do the best possible job of properly supporting the cone and keeping the voice coil centered AND square in the gap!
Although the spider centers the cone, it allows too much TILT without the surround attached. You should always remove the dust cap and shim the voice coil & cone for proper support
while gluing the surround... otherwise, you can’t expect a quality repair. Also, since the cone and/or frame may not be perfectly concentric, you must let the cone find it’s own
natural fit... from the center out. Trying to set the cone by hand, will almost always allow the voice coil to tilt in the gap, and rub. IF you don’t use shims, you can’t expect your speaker to be free of voice coil rubs & scratches. So Please use shims.
Folks often ask, "but why can't we just use paper for shimming?" The answer is pretty simple... Shims need to be fairly tight to hold the assembly properly, yet still able to slip when you want them to. Paper isn't as stiff yet slick like our special plastic shims, and most importantly, paper shims can kink & tear and can get stuck inside the gap making lots of extra work! Use Plastic Shims for best performance and least risk!
Therefore... ALWAYS REMOVE/REPLACE THE DUSTCAP &
USE SHIMS TO CENTER/SQUARE THE VOICE COIL & CONE!
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When Removing the Woofer
When you remove your woofer, be sure to make note of the wiring. Also, IF your old surround is badly rotted, please use EXTREME CARE not to further damage the cone and/or voice coil assembly by allowing it to flop around. Without the support of the surround, the voice coil assembly can be easily damaged by tilting of the cone. Take care to carry the speaker by the frame with two hands with the cone facing up, to help it stay centered. On badly rotted surrounds, it may help to remove the dustcap asap, and shim the voice coil to help prevent any further damage/galling of the voice coil.
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Prepare Your Tools & Work Area
The first step in doing any repair is to prepare your work area. You will be working with glue(s) and there will be a certain amount of debris, so you should cover your work surface to prevent damage. In addition to the items supplied in the kits, you will also probably need a very sharp knife. We like to use both scalpels/Xacto type knives for work with the foam and dustcaps, along with a utility/box cutter type knife for cutting away the gasket. The very sharp thin blade of an Xacto allows you to cut without putting excessive pressure on the VC assembly, and thereby avoid potential damage. The heavy duty cutter allows for safer removal of the gasket and glued foam. You may also need some clamps; clothes pins or large document clips can be used. Knives & clamps are commonly available at hobby shops, WalMart and from our ebay store. In working with the adhesive/treatment, we find it best to keep a small cup of water nearby. We like to use old spray paint can tops, as the separate compartments are handy to dilute the glue, and for a supply of fresh water for cleaning the brushes. Paper towels and/or tissues & a damp sponge or cloth are also handy to have nearby. Further, a vacuum is almost essential for keeping a clean workplace and speaker.
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