Speaker advice /suggestions

[pwdrive]

Hello, I have an old loudspeaker where the cone has been pushed out, the cone has been pushed out so far that the voice coil has come right out of the pole piece and jammed across it, the diaphram has obviously come away from the frame, the cone has a rip in it and obviously a couple of creases.
Disaster...well not entirely, I managed to get the cone back over the pole piece after a few carefull attempts. The diaphram is now sitting back on the frame and the cone has resumed it's shape, the tear in the cone has more or less settled back insofar as the frayed edges of the tear are neatly overlaping each other.
I powered the speaker up expecting the sound to be the worst ever,
but it's not to bad, the only problem (bearing in mind the diaphram is not glued down) is a small grating noise at low volume and some rattling at high volume ie, symptomatic of voice coil being off center.
I would like to glue down the diaphram back to the frame but I am concerned that if I disturb it it might make matters worse.
Any ideas/suggestions?

Lawrence.

[Paula A]

Righty.. my field of expertise.

The rubbing noise may be due to damage to the edge of the coil former rubbing on the pole.. What is the usual course of action is to slide some thin but rather stuff plastic down between the coil and pole and leave it there for a while so it can all settle. After a while of that (couple of days) repair the rip in the cone and once that dries damp it all down (not soaking but a good dose of damp) which will allow the cone to destress and recentre.. wait for it to dry, remove the plastic and give it a go. If it's good then put the plastic back in and glue it all up.. if still rough it's possible to actually remove the whole diaphragm and cone and investigate further..

I used to recone power drivers on the rig on a nearly weekly basis and though the replacement cones always said "must use (expensive) manufacturers jig", I had no problems at all just using some strips of thin plastic (margarine tub actually) and working by eye. Even put higher rated hand rewound coils on some nice old Fane 18" but only 25 watt drivers taking them up to closer to 100 watt handling. Don't forget.. when it's stuffed theres nothing to lose having a go.

[pwdrive]

Thanks Paula A, I have looked into re centering, the main problem is getting the dust cap off, the speaker is only an 8" but it's 70 years old, the cone is very "dry" the cap is cloth/felt, I will try and cut the cap out, leaving a rim just befor the glue line, then it's out with the fag papers, then glue the diaphram back down, once done i can cut a new slightly larger diameter cap out of some suitable material and glue that on.
i did a smaller speaker last week that was rubbing, it was very fragile so I broke all the rules and un did the screws holding the pole piece asembly, withdrew the pole piece and took a few microns off it with some fine emery... It works fine now.
I will sort it all out one way or another.

Lawrence.