Repairing Gummed Up Drivers

A common fault with Minstrels is the gumming up of their drivers. This also affects other models that share similar drivers (Doublets, Envoy etc). The coating on the driver cone is, intentionally, ever so slightly viscous and can ‘run’ into the voice coil, preventing the free movement of the cone. Often occurs with speakers left unused in storage or in a hot climate. This gumming can be remedied by carefully cleaning the gum away from the voice coils. You may need to regularly apply this procedure as more gum seeps through.

Before you begin
Firstly: have a look at a basic driver internal diagram picture (cross section) so you know more aware of what you’re doing before. i.e. you need the pole piece & the surrounding adjacent aluminium cylinder (which holds the delicate coils around its rear) completely free of one another; this is where the gum collects.
See here and here.

Speaker Cone Cross-section
Speaker Cone Cross-section

Secondly: just be aware of the 2mm gap in the aluminium voice coil cylinder, where you can just see the coils behind:- DON’T poke at these (common sense will kick in re this, I’m sure).

Procedure
Piece of paper, cut a 4 x 1 cm bit, you will GENTLY insert the shorter end in so make it long enough to hold. Curve it slightly so it matches as accurately as you can the gap curve (see photo). Now just gently go in and just prise out a tiny bit at a time the black gum. Work round the pole, careful enough not to force the gap anywhere at all. You can go deep, but remember the diaphragm (rubbery concertina’d affair) is at the bottom so don’t dig in and you should be OK. As the paper gets covered in gum, replace it with a fresh piece.

Once the cone is able to move move freely of the pole piece, use a cotton bud dipped in alcohol, nail varnish remover or something sensible, to gently remove the thicker blobs of gum from around the pole piece. You can depress the cone gently, by pressing on either side of it near the rubber surround. This will expose the sides of the pole (see photo), for you to clean, they should have no black gum on them, just bear metal.

Pay attention to the metal at the base of the cone, closest to the centre pole, this often has a tiny gap where it joins, which is often where the worst of the gum seeps through. On some Royds this metal points straight outwards (as in photos below), on others it has been snipped and splayed out flat against the cone.

Just progress slowly, go gently, keep checking how freely the cone moves, repeat the above steps again if needed.

Further discussion on this subject can be found these Pink Fish Media threads here, here and here.

I’d like to thank ‘The Captain’ (PFM) for his contribution to this article.

Disclaimer:
www.roydaudio.com accepts no responsibility or liability for damage incurred as a result of following the above procedure. Use your common sense!