Repairing an expensive speaker

[Ron]

On 09/07/2010 19:36, TMI wrote:

This is a horse of a different color.

You can't repair a cracked magnet and get the same flux in the gap
because the crack adds extra gaps. Getting the magnet to crack in the
first place usually means something horrible happened to the driver.
Buy a new one.

Cracked ferrites _are_ repaired but only as a last resort in cases where
there's no alternative. We've been through this recently on another n/g.
It's not recommended, but it can be done.

According to a large professional loudspeaker repair company I contacted
on the subject, de-magnetising and remagnetising also is to be avoided
as it loses flux.

Ron(UK)
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[TMI]

This is a horse of a different color.

You can't repair a cracked magnet and get the same flux in the gap
because the crack adds extra gaps. Getting the magnet to crack in the
first place usually means something horrible happened to the driver.
Buy a new one.

If you ever tried to assemble something with a charged magnet,
particularlly something with a gap you did not want to close, it would
make a lot more sense. The assembly acts to protect the charge from
being deminished by nearby magnets. It also allows you to achieve the
specified flux in the gap of the assembled speaker, where the rubber
truly meets the road.

Tom Maguire
TMI Engineering

Interestingly, a similar discussion has been going on over in
alt.audio.pro.live-sound, tho mainly concerned with repairing cracked
magnets.

I was surprised (after seeing a program on tv - to find out that
ferrites are magnetised _after_ assembly with the motor and basket assembly

Veejo here

http://www.youtube.com/watch?v=VN0tmyyC0ak

Ron(UK)

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[John]

On Fri, 9 Jul 2010 08:22:27 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

This has been a very interesting and informative discussion
but until now nobody has answer my original question that
was the type of glue to use to glue the coil to the 2" tube.

But the question /has/ been answered -- contact the manufacturer and ask it
what the appropriate adhesive is.

You want us to give you the answer you'd like to have -- and I, for one, am
not going to do it. The manufacturer should know best.

That was the first thing I did and the answer from Tannoy was:

"We don't have the kit but you may get it from company x. Then send
the complete assembly to the closest Tannoy service center (200 miles
from my residence) and we will do the reconing.
We don't recommend changing the coil."

The installation of the kit is easy. It is self center and it doesn't
have play adjustments.

In order to do a god job, I should order 2 cone kits from England but
the total cost including transportation, duty an taxes will be more
than $1k.

The speaker with less damage has about 6 turns dislocated as a group
from the rest of the coil that looks solid.
I am going to read again your recommendations about the glue, paint
the 2" tube with that glue and slide the 6 turns group into their
previous position.

If this works I may try to rewind the other coil "fat chance"

Then I may order one or two kits from England and do the reconing
myself.

Thanks for all your help.

John

 

[Jeffrey D Angus]

Cydrome Leader wrote:

http://www.youtube.com/watch?v=VN0tmyyC0ak

hahaha. Skip to 2:10

they magnetize the ferrite with the operator panel from a reel to reel
tape drive or some washing machine sized hard drive, and by pushing the
Fault button.

Yeah, I thought the button legends were a bit odd.
Equally funny is watching the whole thing jump in the fixture.

Jeff



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http://www.stay-connect.com

 

[Cydrome Leader]

Ron <ron@lunevalleyaudio.com> wrote:

On 09/07/2010 16:33, TMI wrote:
When voice coils are wound the former which you refer to as a 2" tube,
is placed an a mandrel with an expanding collet. In better speakers,
it is "wet wound" in glue under precise tension onto the former to
create a mechanically homogeneous coil, using a precision "coil
winder" which advances the width of the wire for each turn of the
mandrel. Without the mandrel and the collet, you cannot apply the
correct tension to the wire, assuming you knew what it was.

Old cones are not good cones and become tired, particularly after an
event like you describe. New cones have a break-in period of several
months until the spider and surround stabilize at their nominal
compliance.

Tannoy speakers are high efficiency with relatively small magnets
which point to a tight gap. This is very unforgiving with respect to
egging the coil and former, extra glue from the repair, misalignment,
debris, nonlinearity of the reworked spider, surround and cone.

You do not mention centering the coil in the excursion, which is
critical for low distortion and is 90 degrees away from the shims.
Since this alignment opposes the spring action of the suspension, the
cone and spider must have no glue grooves to the former.

In short, buy the cone kits or better still, ship the drivers to allow
someone who does vintage Tannoy work to install them and preserve
those $5,000.00 speakers through restoration. A top notch shop may
also have a magnet charger to restore the specified flux density to
the gap.

Tell you friend that there are few "Vintage" cassette decks and for
what this repair is going to cost he should look for something newer.

About glue....a bit of acetone can be used (in areas other than the
coil where it may create a shorted turn) to rewet and bond glue that
has cracked. GC Radio and TV Service Cement was the old fashioned
method used by TV repair shops. Real speaker reconers use the OEM
glues.

Adding epoxy to a solvent based glue joint is a cobblers repair.

Using epoxy in place of a solvent cement is better, but still
different. While tougher, epoxy often lacks the Q of a solvent cement
joint that has aged, particularly when mixed and applied by hand which
yields entrapped air and sloppy nonuniform ratios.

These observations do not apply to modern 1KW drivers used in PA
systems and beaten to death every weekend. Your friend's solution is
perfectly valid in this application and a little DEVCON goes a long
way toward a reasonable operating cost.

Tom Maguire
TMI Engineering


Interestingly, a similar discussion has been going on over in
alt.audio.pro.live-sound, tho mainly concerned with repairing cracked
magnets.

I was surprised (after seeing a program on tv - to find out that
ferrites are magnetised _after_ assembly with the motor and basket assembly

Veejo here

http://www.youtube.com/watch?v=VN0tmyyC0ak

hahaha. Skip to 2:10

they magnetize the ferrite with the operator panel from a reel to reel
tape drive or some washing machine sized hard drive, and by pushing the
Fault button.

 

[TMI]

I'll bet they don't have the machine required to degauss and
remagnatize your speaker. Or you are talking to a salesman trying to
manimize profit. There is no loss of flux with the correct size
equipment. In fact, there will be more flux in a newly charged magnet
compared to one that has been in service for a while.

In the macro economics of it all, a reconer has to charge you so much
to repair that magnet that it exceeds the value of a good basket core
(speaker without the cone/voice coil). It will never be exactly like
the uncracked one on the other side. No used speaker is worth more
than a core + the recone job and that is very close to the cost of a
new speaker.

Now there are some unique drivers out there that are not available
anymore but in most cases it makes real sense to measure the TS
parameters of the remaining driver and make a good substitution using
those numbers if a true replacement cannot be found.

Someone who is REALLY into restorations might have a similar piece of
ferrite or other magnetic material to replace the cracked magnet.
There is NOTHING wrong with repairing a magnet that way, then charging
the assembly.

I have been doing this for 4 decades and that is my professional
opinion.

Tom Maguire
TMI Engineering


On Jul 9, 4:08 pm, Ron <r...@lunevalleyaudio.com> wrote:

On 09/07/2010 19:36, TMI wrote:

This is a horse of a different color.

You can't repair a cracked magnet and get the same flux in the gap
because the crack adds extra gaps. Getting the magnet to crack in the
first place usually means something horrible happened to the driver.
Buy a new one.

Cracked ferrites _are_ repaired but only as a last resort in cases where
there's no alternative. We've been through this recently on another n/g.
It's not recommended, but it can be done.

According to a large professional loudspeaker repair company I contacted
on the subject, de-magnetising and remagnetising also is to be avoided
as it loses flux.

Ron(UK)
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[N_Cook]

Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:tVKZn.17551$c85.7376@newsfe15.ams2...

"Meat Plow" <mhywatt@yahoo.com> wrote in message
news:3t44sc.v8m.19.13@news.alt.net...
On Fri, 9 Jul 2010 01:45:22 +0100, "Arfa Daily"
arfa.daily@ntlworld.com>wrote:



"Meat Plow" <mhywatt@yahoo.com> wrote in message
news:3t2ats.t4n.19.4@news.alt.net...
On Thu, 08 Jul 2010 20:48:38 +0100, Ron
ron@lunevalleyaudio.com>wrote:

On 08/07/2010 20:15, root wrote:
Meat Plow<mhywatt@yahoo.com> wrote:

Seek out a professional reconing shop. You need some specialized
tools
of the trade and some talent to recone. My good friend did it for a
living until he passed away recently. He would advise the same even
if
you didn't chose his service.

You can buy kits for reconing speakers. It isn't a
hard job. You remove the flex outer rim from the
cone. Then you cut out the bulge covering the voice
coil and put shims (supplied with the kit) in to center
the cone. Then you glue new flex material around
the cone, and wait overnight. Then you remove the
shims and seal up the bulge with glue.

Apart from the overnight wait for glue to dry, it
only took me about half an hour the first time.
With practice I might be able to get it down to
10 minutes.

And that takes care of the knackered voice coil does it?

Ron(UK)

The 10 minute recone part really bothers me. Sure with production line
jigs, shims, guides and people who do maybe a 100 per day that is a
tangible goal. But for an average Joe buying reconing parts and being
successful is not the average outcome. Sure there are exceptions so if
you want to try it on your own good luck.


Interestingly, I was discussing exactly this issue with the owner of the
music shop that I do a lot of work for, just this week. He rents a lot
of
biiiiigggg PA equipment out - kilowatt amps and 4 x 15 bass cabs and
such.
These get damaged by inept users all the time, apparently. I suggested
that
it must cost him a fortune in replacement speakers, but he said "Oh no -
I
just re-cone them". I asked him how long he had been doing this and he
said
years, but I had never seen this going on in his shop. Anyway, I asked
him
how long it took, and how hard a job it was, and did he have lots of
specialist shims and feeler gauges and jigs and what have you. Nope, he
said. He reckons it takes him but a few minutes (literally) to do the
job.
He says that the most time consuming part is making sure that all the
crud
from the burnt up voice coil, is removed from the airgap. He uses a
combination of compressed air, and sticky tape to do this. As to
centering
the new cone's voice coil, he says that most replacement kits come with
a
set of four plastic spacer shims, but that many modern designs are
fundamentally self - centering anyway. He reckoned that it was basically
a
piece of piss job that just needed a little care, and that much bollocks
was
talked on the subject. I might ask him to let me know next time he's got
one
to do, as I would like to watch him at work ...

Arfa

I've been around when my buddy Bart reconed some pro-audio speakers.
It all comes down to people doing it the way they have learned. It's
not as easy as you think but it isn't hard either. He chose to buy
specific tools and glues and treatments not relying on kits for shims
and glues. He knew what he was doing and reconed all my speakers.
Never had a re-run because of a botched repair. Hey if you can learn
the essentials and want to give reconing a try go for it. Maybe it's
for you maybe it's not.

I don't reckon I've got the patience, Meat. I had always thought that it
was
quite a tricky and skilled job, so I was just interested to have a watch
next time Dunc does one, as he reckoned it was so straightforward !

Arfa

Reading through this I see no ref to 3 or 4 slices of credit card to align
voice coil with the slot, maybe an omission or another reconing job I'm
remembering

This is my experience of reconing a Peavey Black Widow speaker
Not made for the UK climate, stored in a (normal for UK) damp garage for 3
years, came out making nasty "amp clipping" noise.
I don't know how general this is for different manufacturers but for
unsticking the contact adhesive of the original cone and spider skirt.
I tried hot-air gun , oven cleaner and acetone but the one that worked on
the one I did this week was petrol. Some strips of tissue paper soaked in
petrol and covered with some circular strips of plastic and leaving for half
an hour to soften the glue
Now it is totally apart, small bits of aluminium oxide in the voice coil
slot were causing the distortion along with loose skirt biased to one still
retained side. 15 inch size with aluminium basket.
The voice coil is in perfect condition and no imperfections to the cone
despite 30 years old.
Prior to me getting to look the owner had removed the 3 magnet retaining
bolts and removed some perished foam filter from inside under the mesh cover
and squirted in WD40.
The white oxide formations had burst the glued skirt off , about 80 percent
of its rim, and the same for the cone rim (after removing the periphery
bolts) and nothing much holding on the remainder, easy to prize off.
masked off the central voice coil slot area before
abraiding back the lands to take contact adhesive to replace the skirt and
cone. Then air blast and run thick plastic around the slot to clear any
crud. The magnet does not seem to be corroded, shiney, no obvious rust
spots.
The 0.08mm thick aluminium dome must have been press-formed
or by metal spinning with a cylinder
extension to the dome and the cylinder section is glued to the inside of the
VC former. So had to cut around the dome to remove and hope the
final gluing-back holds up against the air pumping process.
I just used 4 ball point pens in the rim
mount holes for rough alignment and some clothes pegs to give a bit more
clearance gap for laying down the glue. Removed them prior to dropping the
cone in case they gave some bias.

 

[TMI]

FYI.....

HI Tom,
We only recone with authentic Tannoy parts returning the speaker to
exact new condition. I haven't priced this kit recently, but about one
year ago, charges for us to recone the low frequency were $440.00
each. I can check the price on Monday to make sure there haven't been
any major changes, but generally there are only a few dollar
differences or none at all. The more important question will be
availability and if you are interested, I will pursue that too.
I'm glad you saw our Over the Tannoy Post. What did you think of it?
the website?
Cathy Satin The Speaker ExchangeŽ
1250 E. Hillsborough Avenue • Tampa, FL 33604
Phone:1-800-849-6972 • 1-813-237-4800
Fax: 1-813-238-3558 cathy@speakerex.com Mon-Fri 10-5:30 est, 1st Sat
of e month 10-3:00
AIM:cathyspex Skype: speakerex http://www.twitter.com/speakerex

Speaker Sales, Service, and all your repair needs since 1977

Please send us your impressions, comments or suggestions concerning
our new improved site www.speakerex.com
SHIPPING instructions and REPAIR FORMS: http://tinyurl.com/2c3e27k



On Jul 9, 9:31 pm, TMI <audio...@hotmail.com> wrote:

I'll bet they don't have the machine required to degauss and
remagnatize your speaker. Or you are talking to a salesman trying to
manimize profit. There is no loss of flux with the correct size
equipment. In fact, there will be more flux in a newly charged magnet
compared to one that has been in service for a while.

In the macro economics of it all, a reconer has to charge you so much
to repair that magnet that it exceeds the value of a good basket core
(speaker without the cone/voice coil). It will never be exactly like
the uncracked one on the other side. No used speaker is worth more
than a core + the recone job and that is very close to the cost of a
new speaker.

Now there are some unique drivers out there that are not available
anymore but in most cases it makes real sense to measure the TS
parameters of the remaining driver and make a good substitution using
those numbers if a true replacement cannot be found.

Someone who is REALLY into restorations might have a similar piece of
ferrite or other magnetic material to replace the cracked magnet.
There is NOTHING wrong with repairing a magnet that way, then charging
the assembly.

I have been doing this for 4 decades and that is my professional
opinion.

Tom Maguire
TMI Engineering

On Jul 9, 4:08 pm, Ron <r...@lunevalleyaudio.com> wrote:



On 09/07/2010 19:36, TMI wrote:

This is a horse of a different color.

You can't repair a cracked magnet and get the same flux in the gap
because the crack adds extra gaps. Getting the magnet to crack in the
first place usually means something horrible happened to the driver.
Buy a new one.

Cracked ferrites _are_ repaired but only as a last resort in cases where
there's no alternative. We've been through this recently on another n/g..
It's not recommended, but it can be done.

According to a large professional loudspeaker repair company I contacted
on the subject, de-magnetising and remagnetising also is to be avoided
as it loses flux.

Ron(UK)
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[John]

On Fri, 09 Jul 2010 17:15:17 -0400, John <Ya@you.com> wrote:

Some one made some reference to the use WD40 to melt the glue

I had an interesting experience with that powerful staff:
The spring load cover of an outdoor power outlet that I have, made a
screeching noise when lifted. I sprayed it with WD40 and the cover
toke off like an Arab rocket.
Einstein once defined a stupid person the one who does the same thing
and expects a different result so I did the stupid thing of
installing a new cover and spray again with WD40 and obviously the
result was the same.
Installed another cover and no more spraying. The nasty WD40 melted
the plastic holding the spring.

Ref: Material to hold the coil in position :
I used, 65 years ago, strips of plastic from photographic film
negatives.
Boston Acoustics sells a speaker with a removable voice coil and
attached to the cone by screws. There is a metal ring with threaded
holes glued to the cone.

Thank you to everybody . Fantastic help

John
>

 

[John]

On Fri, 09 Jul 2010 17:15:17 -0400, John <Ya@you.com> wrote:

Some one made some reference to the use WD40 to melt the glue

I had an interesting experience with that powerful staff:
The spring load cover of an outdoor power outlet that I have, made a
screeching noise when lifted. I sprayed it with WD40 and the cover
toke off like an Arab rocket.
Einstein once defined a stupid person the one who does the same thing
and expects a different result so I did the stupid thing of
installing a new cover and spray again with WD40 and obviously the
result was the same.
Installed another cover and no more spraying. The nasty WD40 melted
the plastic holding the spring.

Ref: Material to hold the coil in position :
I used, 65 years ago, strips of plastic from photographic film
negatives.
Boston Acoustics sells a speaker with a removable voice coil and
attached to the cone by screws. There is a metal ring with threaded
holes glued to the cone.

Thank you to everybody . Fantastic help

John
>

 

[GregS]

In article <ilnb361h0p8jm7btj7jolui1l27cf5becn@4ax.com>, John <Ya@you.com> wrote:

I am repairing two 15" Tannoys of the Gold series. A $5k unit if we
could get them.

Un oscillation in a cassette deck I was using, produced a very lowed
sound that damaged the speakers.

One of them has 6 turns of the voice coil, lose and can be glued back.

On the old days I used to repair speakers using the same type of glue
that was used on the assembling of models. A type of glue that use
acetone as a solvent.
Today we have better types of glue like epoxy and I believe the harder
the glue the better the performance, the disadvantage is that using
epoxy will make a future repair very difficult.

Any suggestions ?

The coil on the second speaker is open and in very bad shape. I am
looking for a replacement.

Tannoy does not carry parts for this type of speaker but there is a
place in England that will sell me a cone assembly for about $300 usd.

I noticed Parts Express also does reconing. Pretty cheap.

greg

 

[Ross Herbert]

On Thu, 08 Jul 2010 10:40:20 -0400, John <Ya@you.com> wrote:

:I am repairing two 15" Tannoys of the Gold series. A $5k unit if we
:could get them.
:
:Un oscillation in a cassette deck I was using, produced a very lowed
:sound that damaged the speakers.
:
:One of them has 6 turns of the voice coil, lose and can be glued back.
:
:On the old days I used to repair speakers using the same type of glue
:that was used on the assembling of models. A type of glue that use
:acetone as a solvent.
:Today we have better types of glue like epoxy and I believe the harder
:the glue the better the performance, the disadvantage is that using
:epoxy will make a future repair very difficult.
:
:Any suggestions ?
:
:The coil on the second speaker is open and in very bad shape. I am
:looking for a replacement.
:
:Tannoy does not carry parts for this type of speaker but there is a
lace in England that will sell me a cone assembly for about $300 usd.


Are these the speakers? http://www.44bx.com/tannoy/gold.html#anchor2238478

If so then they should be fairly easily repaired. A good repair shop will remove
the surround and the spider (probably with acetone) and they can re-attach the
winding or rewind if necessary.

Where I am in the most remote capital in the world we have a repair shop who
could do it http://www.shortfuse.net.au/ He is frequently asked to perform this
type of repair on Altec, Goodmans, Wharfedale etc.