Make Speaker Gaskets with Neoprene or EPDM Closed Cell Tapes
When constructing loudspeaker cabinets it is important, (for their correct operation), that an air-tight
seal is achieved between the Loudspeaker driver and it's cabinet. Failure to do this may alter the
enclosure performance and introduce unwanted noise. Most production volumes of Loudspeaker gaskets are stamped. For
DIY use it's relatively easy to make these gaskets from either Neoprene or EPDM closed cell foam tapes.
Professional manufacturers often have custom gaskets sourced for use with their drivers but it is rare in the DIY world that the purchase of drivers is accompanied by a gasket of any variety whatever. Occasionally a strip seal may be provided but not often.
QTA Systems can provide closed cell tape / foam strips with a self-adhesive backing using either NEOPRENE or EPDM The Neoprene or EPDM strips are available in 3 widths and 2 thicknesses for users to construct their own loudspeaker gaskets. There are some quite major differences between the two materials, mainly in their temperature performance and resistance to solvents. However, for domestic use as loudspeaker gaskets the two materials have near identical sealing properties.
There are a number of adhesives which can be applied to the reverse of
the closed cell strips. This is application dependent. The backing release papers are coated with an aggressive / high tack
adhesive which once applied may be difficult to remove. This depends upon surface characteristics and works well
with clean MDF.
MDF is a fibrous material and wood particles shale off easily. This reduces adhesion so it is best to remove all wood dust or debris. Sticky tape is good for this, eg sellotape.
The thinner width materials, 5mm may be better suited for tweeters as the narrow tape width allows easier flexing / placement around smaller diameter cut-outs. This has smaller flexing forces and remains in place whilst you position your loudspeaker driver.
(1) Without removing the backing paper, use the Neoprene or EPDM strip to measure around the edge of the cut-out. Note the tape is placed on edge for this measurement as it then flexes around the bends better. See fig(1). The strip should be cut marginally longer than the required length leaving about 20mm overlap of the two cut ends. This allows the use of a splice / diagonal cut through the tape giving a better air-tight seal than a straight butt joint. Using a pair of sharp scissors cut through both pieces of Neoprene at once. This will give matching material edges.. As an alternative a sharp scalpel blade or craft knife will do the same job.
(2) Peel off the backing strip and position the tape in place, fig(2). Ensure the tape passes on the inner side of any screw holes used to fix drivers to their cabinet, (a source for potential leaks, as air can leak through the screw threads.)
(3) Using a sharp scalpel or craft knife make a diagonal cut / splice through both pieces of gasket material. fig(3). You really do need a sharp blade for this to achieve a good flush joint. Remove the waste pieces of material from both strip ends.
(4) Butt the two angled / spliced ends together and press the whole tape firmly into place. Fig(4) shows the final result.
Under normal compression the material will compress to around 10% of its original thickness, so, for a 5mm thick strip, this will compress to around 0.5mm. This information may be helpful if you are machining driver cut-outs for a flush fit, otherwise....... it's no real problem.