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Thread: Dali speaker cone repair
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7th September 2009, 06:40 PM #16
The guys were a bit concerned when they saw the speakers.
They told me that there could be damage to the coils/drivers.
Anyway apparently they were fine and they replaced the surround and tested everything out.
I hooked them up and they sound as good as new.
$165.00 sounds like a lot of money for a couple of pieces of foam but I know that materials are a small part of the cost.
I think it is a reasonable cost for a couple of hours by an expert and I have the confidence that the work was done properly.
$20k or $40k is a bit steep for me but I am sure they would be fantastic speakers.
My repaired $2k speakers make enough noise for me and I reckon that I can hear a lot more music with them now.
A friend came around on the weekend and took my didge into the bathroom to play. He said that it is the best room in a house to play them.
Next time I will ask him if he want to play in the WC.
Cheers.Scally
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The ark was built by an amateur
the titanic was built by professionals
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20th September 2009, 10:09 PM #17
I have only done a few, recones/refoams (unlike some of my mates who have done hundreds)... but $165 fo doing what would be 4 drivers.....and dismantle and reassemble boxes........seems quite reasonable.
There are several methods.....some use shims some eye them up.
this is what is involved.
remove the drivers from the boxes
from those available select a surround that is close to original and a matching dust cap
remove the cone from the frame (some don't)
clean up the frame (this takes time)
remove the dust cap (some don't)
clean up the cone and the spider (this takes time and a carefull touch)
fit the surround to the cone (this requires a straight eye and plenty of care)
wait for the glue to go off
trial fit the cone in the frame and cut shims to centralise the voice coil.
remove the cone and apply the glue to the spider and the surround
apply the glue to the frame
depending on the materials ( and the method) a different glue may be required for the spider and the surround......(no solvent bassed glue if it is a rubber or foam surround)
slip the cone into the frame with the shims fitted.....do not allow the glued parts to contact.
with the cone straight cental in the shims....slide the cone into place and mate up the spider and the surround with the frame.
I usualy use a solvent bassed glue on the spider and a specific water bassed glue for the surround.....because you can stick the spider down and it stays and you can then finesse the surround.
examine the speaker from all directions to check that it is straight.
set it aside and hope.
when glue is set......check speaker travel.....gently by hand.....then with amplifier and LF oscilator.........all good... relief............not good.....start again.
fit relacement dust cap and dope surround as and if required.
fit cardboard rim pieces if required
wait for it to dry.
test again......glue dribbles from the dust cap can ruin it all.
refit to boxes..and re test.
explain to customer why a couple of bits of foam cost so much.
seriously.......anything less than $50 a driver for a proper job is more than reasonable.
personaly...I do not believe it is possible to do a proper job without removing the cone and I'll be b###d if I can see how anybody could get a voice coil properly straight and central with out shims.
this is how the pro recones are done.
OH.... anybody who thinks they can make a proper surround out of anything is kidding themselves.......particularly if it is a high power pro audio application.
I do not know of any manufacturer who has made a production speaker with a leather surround........in the older times ( and still) various cloth or papers were used as surrounds.
leather is too unrelaible and inconsistent.
in older times both tannoy and warefedale used to make their speakers from scratch....including their cones and surrounds.
in more recent times all manufacturers either source components externaly or let out the whole job..........
cheersAny thing with sharp teeth eats meat.
Most powertools have sharp teeth.
People are made of meat.
Abrasives can be just as dangerous as a blade.....and 10 times more painfull.
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20th September 2009, 11:16 PM #18
Thanks for the explanation Soundman.
I remember the guy mentioning some of those steps. He has a good reputation so I expect that he did a professional job.Scally
__________________________________________
The ark was built by an amateur
the titanic was built by professionals
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21st September 2009, 10:49 AM #19
Toilet bowls, "The Original Ceramic Speakers".
Buzza.
"All those who believe in psycho kinesis . . . raise my hand".
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21st September 2009, 03:35 PM #20
I fully endorse the thoroughly professional explanation by Soundman, except that he omitted one crucial step.
* Before replacing driver in box
* * Paint "coating goo" on the newly installed surrounds.
* * Apply a second coat of "coating goo".
The "coating goo" is as described in my Tannoy surround kit and is a thickish white liquid that dries clear. Its purpose is to stiffen and deaden the surround to help minimise colouration.
Cheers
Graeme
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21st September 2009, 03:40 PM #21Senior Member
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21st September 2009, 11:32 PM #22
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21st September 2009, 11:35 PM #23
I did mention the doping the surround if required.
quite a few manufacturers are using some sort of dope on or in the surrounds.
the idea is that it dampens standing waves from running across the cone and bouncing off the frame and back onto the cone.....suposedly reduces harmonic distortion and peaky top end response in the cone.
Its pressence needs to be accounted for and it would influence the mass of the cone, stifness and damping of the cone
I did some EV drivers recently and the original drivers had one of the "V"s in the surround filled with dope.
if the original has it you do it if not you dont.
quite a lot of what you do depends on how the parts come to you......at one time most recone kits came assembled......cone mounted to voice coil, with surround and spider attached and all treatments already done....all you did was shim it up and glue it down.....bung on the dust cap......a fast operator could do a 15" recone in 20-30 minutes and slap it back in the box during interval......I can remember helping a bloke replace a blown driver in a rear loaded box while a show was running......it was not uncommon in the days of rock and roll to do recones by the side of stage.
then some of the manufacturers tried to save cost ...shipping was a biggie.....they could ship 10 recone kits for the price of one if they shipped unassembled.....in that case you had to do all the treatments as well as assembling the kit.
if you are using generic surrounds they will come untreated......so you have to eye up the treatment as well as the closest surround.
In the past most pro recones were done with solvent bassed contact type cement....most recones came with a tube of a bostik product........black spray can paint was mixed with the supplied glue when fitting dust caps and for doping cones and surrounds.
Many of the cloth surrounds came untreated and required some form of dope....some used PVA.
with the advent of foam and rubber surrounds solvent bassed glues have gone out of favor........many of the surround failures have been due to solvent bassed glues used in original manufacture.
The water bassed glue, I get from my supplier is used for the dope as well as fixing the surrounds.......it is nowhere near as fast as the solvent bassed glues.........but if handled well is a great product.
Its actual composition has slipped my mind..... but it is an AV syntec product that is only available in 20L drums........EVA rings a bell.....it is much more flexible than PVA.
comes white and dries water clear and a little rubbery.
cheersAny thing with sharp teeth eats meat.
Most powertools have sharp teeth.
People are made of meat.
Abrasives can be just as dangerous as a blade.....and 10 times more painfull.
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21st September 2009, 11:42 PM #24
most pro audio drivers.....like the tannoy, are quite stiffly suspended and the pro audio designs seem tolerate variation much better than the HIFI items particularly those with small drivers.
cheersAny thing with sharp teeth eats meat.
Most powertools have sharp teeth.
People are made of meat.
Abrasives can be just as dangerous as a blade.....and 10 times more painfull.
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22nd September 2009, 12:05 PM #25Senior Member
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22nd September 2009, 12:33 PM #26
yeh lets not get all bitter and twisted about this.
In general terms you do as was done.
But I will say that there is an eliment that seems to think that speakers are a high precision article......nup........there is quite a lot of variation from one driver to another ( in comparison to other enginered items) tolerances are quite wide.........in engineering terms a speaker is a lump of paper glued to a motor........lets not kid ourselves...... ..and i have seen and heard plenty of speakers that have been......um....er.....fiddled.........and lets face it.....it isnt a life and death issue.
so whats the worst that can happen..........OH NO.....he doped the surround... we are all going to die.
cheersAny thing with sharp teeth eats meat.
Most powertools have sharp teeth.
People are made of meat.
Abrasives can be just as dangerous as a blade.....and 10 times more painfull.
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22nd September 2009, 01:17 PM #27Senior Member
- Join Date
- Aug 2006
- Location
- Oyster Bay NSW
- Posts
- 120
I measure speakers (drivers) as part of my professional life, for several companies. I always request that I be supplied at least 4 samples of each driver. One company supplied me with a range of drivers from their supplier in China. The drivers were terrible. Not that their absolute performance was bad (though it was), but that the 4 drivers had critical measured characteristics that were as much as 30% different. Contrast that with typical European drivers which easily exceed 5% tolerance from driver to driver. The same company then provided me with some new drivers, sourced from another company. These were easily as good as anything I've measured from the best European manufacturers. If they are provided with sufficient encouragement, the Chinese can turn out a quality product.
The upshot is this: By mucking about with a driver, by applying goop to the surround, one risks impairing the performance of the driver by a considerable amount. I know this from personal experience. Goop is not a panacea. It should be used when the manufacturer suggests it. It should not be used when the manufacturer does not suggest it. Many years ago, I figured that I would start using butyl rubber surrounds for clients' speakers, as the butyl rubber surrounds are far superior to the plastic ones used by many manufacturers. That idea quickly came unstuck, when several clients complained about the sound quality. The butyl rubber has radically different characteristics to the foam plastic ones. In EXACTLY the same way that adding goop to the surround will have. My desire to provide a superior product to my clients ended up back-firing on my big time. Back in the late 1990s, when I acquired some sophisticated measurement equipment, I measured the drivers and understood why my clients complained. The different surround materials impacted on the measured (and audible) performance of the drivers.
No one said it was. Bad advice, however, is just that: Bad advice.
The worst that can occur is that the speakers can never be returned to their original performance capability and the owner can be dissappointed for a very long time.
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22nd September 2009, 01:25 PM #28
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