Loudspeaker driver surrounds DIY

From a Resource: Speaker Design Course Notes + video materials

In the past, speaker repair services were scarce, often expensive, and replacement surrounds for DIY nearly impossible to source. The web has improved this, surrounds are widely available, but of variable quality. Even so, for a few vintage Hi Fi drivers of unusual size, suitably sized good quality generic surrounds or reasonably priced OEM parts aren't available.

Loudspeaker surrounds made of foam, decay eventually, especially in hot humid conditions. Less often, rubber ones can perish or split. Recent surrounds are sometimes made resistant to UV and tropical climates. When faced with high labor costs, many are prepared to tackle DIY replacement, and OEM or generic surrounds, as well as how to guides, are available on the web. If doing a full restoration, the cost of an OEM part (surround, recone kit, or driver) can be justified, for highly prized vintage models. Exotic full range drivers and Sound reinforcement speakers generally require specialists.

For otherwise good systems, of no particular worth, and where a suitable replacement, can't be found, making the surround itself, can be considered. It can't be justified in $ terms but it can be approached as a one off learning experience, useful recycling and a new skill set, or a potential supply of beer from others if word gets around that you've become good at it.

The driver may not perform exactly as the original, but in the cases tried here and most others the resonant frequency and response were close, due to some experience in what to look out for. The surround is material impregnated from one side (the non gluing side) with a small amount of silicone rubber just sufficient to be air tight and formed in a mould with a release agent so it doesn't stick. Making the mould requires access to some machinery and takes the most time but having done it once it can be reused for the same type of driver. The drivers shown here are 80's vintage; a Technics SBX model and a Dynaudio 21W54, good drivers in their time. Some drivers eg vintage JBL have quite small voice coil clearance, that may require dust cap removal and use of shims for precise centering.

If a system has an unknown history or hasn't been used for a while it's worth checking crossover components, and other system drivers initially. Establish there is no damage to the voice coils before proceeding. Practicing on a non critical driver, and making a new surround when a previous attempt hasn't turned out as expected, before assembly is worthwhile. Removing all remnants of the old surround and glue is worth giving close attention to, for a good looking result.

Step 1 Preliminaries

If the old fragile surround is mostly intact, you can estimate its thickness and measure its 4 dimensions, typically A B C D on a web guide, to set up the mould inner and outer roll diameters as well as the width of the flat parts. The width of the roll is important but If the surround is absent, estimate C and B as accurately as possible with an adequate A and D for attachment purposes. Some web research or enquiry to audio forums, might turn up images or dimensions to go by. Heavy cones from a 3 Way with longer cone travel (Xmax) might have rubber surrounds or of somewhat thicker foam. with a wider roll, compared to narrower rolls on lighter cones with an extended response and of lower Xmax from say 2 way vented systems. Exotic / vintage full range drivers are best left to specialists or dedicated DIY online forums
C sometimes has a small deliberate overhang beyond the cone edge for performance reasons. Note the polarity of wires before removal from box.
For those with the equip, and curious about before and after comparisons, measuring the driver res freq out of the box and response in the box, with and without the crossover in the mid and upper range notwithstanding the likely air leaks can be done. But isn't mandatory just to get a system going again.

In most instances if the inner flat is not angled it can still be satisfactorily be glued to the upper or underside of the cone when the glue (PVA from speaker repairers) is in the tacky stage.

Comments

[abadfart]

am i getting that this is how to make a diaphragm for a speaker?

[strmrnnr]

I am not sure what the product name was, but I believe it was a spray on latex. Our supply man at work found it to repair the foot bellows used to blow up a raft for back up. It was very flexible and creased and uncreased very well without cracking. The dry time was also long. I am thinking a piece of cloth sprayed with this, installed in your mold, and then vacuum bagged overnight would produce a nice, lightweight, gluable ring that would last a long time.

[strmrnnr]

I am finding the silicon outlasts latex, but is easier to play with.

[Da Nugesta]

very good. nice instructable.