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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
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29th Aug 2016, 7:43 am | #1 |
Retired Dormant Member
Join Date: May 2011
Location: Johannesburg, South Africa.
Posts: 32
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Improved sound from old loudspeakers
The sound from older loudspeakers with corrugated cardboard surrounds can be improved by buying plain glycerine in your ladies' beauty section (very cheap) and, using a toothpick or match, spreading a little glycerine over the corrugated surround (not the cone). It soaks into the cardboard and makes the surround much more flexible - improves bass and mid responses - and effectively lasts forever.
I have never had a problem with this technique and it also makes the speaker surrounds last much longer. NB, it is particularly effective on little radio loudspeakers. |
29th Aug 2016, 9:22 am | #2 |
Nonode
Join Date: Aug 2015
Location: Cambridge, Cambs. UK.
Posts: 2,198
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Re: Improved sound from old loudspeakers
I seem to remember reading about the glycerine treatment decades ago, and I did try it.
What I found was that a lower resonant frequency isn't necessarily an improvement. For a speaker in a simple baffle or open cabinet, it can reduce the power handling capability due to the cone 'flapping' rather too freely. Also, beware that glycerine is hygroscopic - that why it's used in royal icing to keep it soft. So your cone surround will be forever slightly damp - and the treatment tends to spread into the rest of the cone. By all means try it as an interesting experiment on an old speaker, but I'd be cautious. Martin
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29th Aug 2016, 11:21 am | #3 |
Heptode
Join Date: Apr 2016
Location: Croxley Green, Hertfordshire, UK.
Posts: 979
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Re: Improved sound from old loudspeakers
I don't like messing about with old speakers if they still perform well.
But occasionally I'll treat a cone to a coating of PVA sealant to stiffen it up if it's become fragile or soft. I did this to a Bush Dac 90a speaker and it really improved the sound.
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Clive |
29th Aug 2016, 1:01 pm | #4 |
Retired Dormant Member
Join Date: May 2011
Location: Johannesburg, South Africa.
Posts: 32
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Re: Improved sound from old loudspeakers
Thanks, great tip.
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7th Sep 2016, 3:51 pm | #5 |
Octode
Join Date: Jun 2005
Location: Sheffield, South Yorkshire, UK.
Posts: 1,227
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Re: Improved sound from old loudspeakers
I have some powdered glycerine , which is used in cooking( jellies etc). I think I will try this as I have 5 small speakers. How does it improve my beauty?
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7th Sep 2016, 4:01 pm | #6 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re: Improved sound from old loudspeakers
I think you'll find what you have is actually gelatine powder - that's a very different material.
Alan |
7th Sep 2016, 4:12 pm | #7 |
Octode
Join Date: Jun 2005
Location: Sheffield, South Yorkshire, UK.
Posts: 1,227
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Re: Improved sound from old loudspeakers
Yes it dissolves in hot water and cools to a gel.
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7th Sep 2016, 9:19 pm | #8 |
Octode
Join Date: Feb 2009
Location: Bletchley, Buckinghamshire, UK.
Posts: 1,223
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Re: Improved sound from old loudspeakers
When I worked for a loudspeaker company, there were various substances used on cones and suspensions. Often referred to as "dope" and usually some kind of plastic dissolved in a volatile solvent.
"Plastiflex" and "opanol" were two trade names that I can remember. There was also a specialist PVA adhesive that came from the book-making trade and had the advantage that it remained flexible after setting. I've never heard of Glycerine being used (and very definitely not Gelatine! ) |
8th Sep 2016, 10:43 am | #9 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
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Re: Improved sound from old loudspeakers
It depends if the corrugation is an extension of the cone material or if it is a separate
fabric or foam. All plastic adhesives end up hardening, One could use a silicon bathroom sealant, but my preferred choice is a rubber solution glue, e.g. Copydex. |
8th Sep 2016, 4:38 pm | #10 |
Heptode
Join Date: Sep 2013
Location: Manchester, UK.
Posts: 862
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Re: Improved sound from old loudspeakers
I've always used Copydex for cone edge repairs and it always works a treat.
Regards, Paul
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8th Sep 2016, 4:42 pm | #11 |
Heptode
Join Date: Jan 2008
Location: Shrewsbury, Shropshire, UK.
Posts: 845
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Re: Improved sound from old loudspeakers
Agreed,
I've used Copydex for over 50 years on speakers that were past their prime. Seems to do the job. Of course this assumes that the formula hasn't been recently changed. Dave. |
8th Sep 2016, 8:05 pm | #12 |
Nonode
Join Date: Feb 2005
Location: Worcestershire, UK.
Posts: 2,535
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Re: Improved sound from old loudspeakers
In pursuit of 'improved sound' from a 1949 Buick Eight's car radio speaker, found to be badly warped (and thus jammed) I detached the cone, lightly soaked it with water and then left it to dry out, clamped between two upturned cereal bowls.
I have now re-attached the 're-formed' cone and all appears to be well. It moves freely. I am hopeful that when the rest of the work on the radio is complete, it will sound fine. Steve
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14th Sep 2016, 9:04 am | #13 |
Rest in Peace
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
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Re: Improved sound from old loudspeakers
Too much PVA on the corrugated rim of a speaker (outer suspension) will cause it to stiffen and severely effect the base response of the speaker. I do use PVA sparingly but I dilute it 50:50 with water so that it forms a thinner coating and helps to bind the paper fibres together. I use paper kitchen towel, it is very strong, as in the adverts. I separate the layers and use just one layer on both sides to reinforce a tear in the diaphragm.
Mike |
14th Sep 2016, 9:46 am | #14 |
Dekatron
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,349
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Re: Improved sound from old loudspeakers
The bookbinding adhesive was probably something like EVA (non-plasticised ethylene-vinylacetate). Neutral pH, archival quality, fast drying, and suitable for gluing spines and linen hinges. £7 for a 500ml tub from Shepherds (London). Evostick also remains flexible, and paperbacks whose spines I re-glued with Evostick in the 1960's are still in excellent condition. I just hope they haven't changed the formula for something more environmentally-friendly but less effective: they did change the solvent a few years ago.
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23rd Sep 2016, 3:33 pm | #15 |
Retired Dormant Member
Join Date: May 2011
Location: Johannesburg, South Africa.
Posts: 32
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Re: Improved sound from old loudspeakers
A little humour - my good lady reminded me that this is probably the only other use for KY jelly that she could think of.
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8th Dec 2016, 10:25 am | #16 |
Retired Dormant Member
Join Date: Dec 2016
Location: Pasadena, California, USA.
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Re: Improved sound from old loudspeakers
This is one great tip thanks a ton!
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25th Jan 2017, 5:34 pm | #17 |
Heptode
Join Date: Mar 2010
Location: Hemel Hempstead, Hertfordshire, UK.
Posts: 848
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Re: Improved sound from old loudspeakers
I use Nu-Skin - pains on to cuts that don't heal. Works well and is very flexible.
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