Speaker cone - UK Vintage Radio Repair and Restoration Discussion Forum

ms660 · 5th Dec 2011, 7:05 pm

Anybody do speaker cone/diaphragm repairs (vintage)?

Lawrence,

Herald1360 · 5th Dec 2011, 9:15 pm

If it's a paper cone and not too bad, tissue paper and diluted PVA is quite effective.

ms660 · 5th Dec 2011, 9:43 pm

Thanks, heres an update....I have an old loudspeaker where 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 diaphragm has obviously come away from the frame, the cone has a rip in it and a couple of creases.
Disaster...well not entirely. I managed to get the cone back over the pole piece after a few careful attempts. The diaphragm is now sitting back on the frame and the cone has resumed its shape, the tear in the cone has more or less settled back insofar as the frayed edges of the tear are neatly overlapping each other.

I powered the speaker up expecting the sound to be the worst ever,
but it's not too bad, the only problem (bearing in mind the diaphragm 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 centre.

I would like to glue down the diaphragm back to the frame but I am concerned that if I disturb it, it might make matters worse.
Sadly the pole-piece is not removable (no screws on back of magnet) otherwise I would glue the diaphragm down and shave a few microns off the pole-piece and reassemble.

Lawrence

dseymo1 · 5th Dec 2011, 10:31 pm

Standard procedure is to shim between the voicecoil and the polepiece with thin card before glueing the spider and surround. Depending on the design, you may need to carefully remove any central dustcap / dome to do so. It's worth running a bit of adhesive tape, doubled-over so that the sticky bit's outside, round the gap before starting, to remove any debris.

ms660 · 5th Dec 2011, 11:04 pm

I tried pulling off the dust cap originally but it's well glued on, the cone is around 70 years old and very "dry". The cap is a circular piece of felt/cloth.
I could cut the cap to gain access but I will have use a new razor/scalpel blade and take it carefully as my eyesight ain't what it used to be. I will have to repair the tear in the cone first.

Lawrence.

geofy · 6th Dec 2011, 10:59 am

All you do is hold the cone with finger and thumb to feel that the coil is free to move so the position is correct. Repeat the process after putting on the adhesive and then put the surround into position, again checking that the cone is still free. You could try just a couple of spots of adhesive at first before applying the rest, repair the tear afterwards. Make sure any rear suspension is fixed as well.

5th Dec 2011, 7:05 pm	#1
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Speaker cone Anybody do speaker cone/diaphragm repairs (vintage)? Lawrence,

5th Dec 2011, 9:15 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Speaker cone If it's a paper cone and not too bad, tissue paper and diluted PVA is quite effective. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

5th Dec 2011, 9:43 pm	#3
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Speaker cone Thanks, heres an update....I have an old loudspeaker where 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 diaphragm has obviously come away from the frame, the cone has a rip in it and a couple of creases. Disaster...well not entirely. I managed to get the cone back over the pole piece after a few careful attempts. The diaphragm is now sitting back on the frame and the cone has resumed its shape, the tear in the cone has more or less settled back insofar as the frayed edges of the tear are neatly overlapping each other. I powered the speaker up expecting the sound to be the worst ever, but it's not too bad, the only problem (bearing in mind the diaphragm 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 centre. I would like to glue down the diaphragm back to the frame but I am concerned that if I disturb it, it might make matters worse. Sadly the pole-piece is not removable (no screws on back of magnet) otherwise I would glue the diaphragm down and shave a few microns off the pole-piece and reassemble. Lawrence Last edited by Mike Phelan; 6th Dec 2011 at 5:28 pm. Reason: Typos corrected.

5th Dec 2011, 10:31 pm	#4
dseymo1 Retired Dormant Member Join Date: Dec 2007 Location: Shropshire, UK. Posts: 3,051	Re: Speaker cone Standard procedure is to shim between the voicecoil and the polepiece with thin card before glueing the spider and surround. Depending on the design, you may need to carefully remove any central dustcap / dome to do so. It's worth running a bit of adhesive tape, doubled-over so that the sticky bit's outside, round the gap before starting, to remove any debris.

5th Dec 2011, 11:04 pm	#5
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Speaker cone I tried pulling off the dust cap originally but it's well glued on, the cone is around 70 years old and very "dry". The cap is a circular piece of felt/cloth. I could cut the cap to gain access but I will have use a new razor/scalpel blade and take it carefully as my eyesight ain't what it used to be. I will have to repair the tear in the cone first. Lawrence.

6th Dec 2011, 10:59 am	#6
geofy Retired Dormant Member Join Date: Jun 2006 Posts: 1,798	Re: Speaker cone All you do is hold the cone with finger and thumb to feel that the coil is free to move so the position is correct. Repeat the process after putting on the adhesive and then put the surround into position, again checking that the cone is still free. You could try just a couple of spots of adhesive at first before applying the rest, repair the tear afterwards. Make sure any rear suspension is fixed as well.