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Old 1st February 2011, 06:43 PM   #1
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Default Focal Tweeter Repair

Some of the four Focal T120 1” tweeters in each of my pair of VMPS Super Tower IIa/R speakers are showing deterioration in the foam surrounds. There is not yet any apparent deterioration in the sound (at least that my old ears can detect). I have had good luck with diy replacement of the foam surrounds on other speakers but have not yet found a source for the repair materials for these tweeters. The pictures show one of the most damaged tweeters. Any ideas or suggestions greatly appreciated.
Jim Gregory
Sausalito, CA
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File Type: jpg Tweeters.jpg (94.9 KB, 584 views)
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Old 20th December 2012, 08:49 PM   #2
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any news?
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Old 21st December 2012, 03:32 AM   #3
laverda is offline laverda  United Kingdom
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Focal do repair kits (which is the dome and coil) for their TC90 & TC120 tweeters not sure they would suit your 120's but may well be worth an email.

or these may do the business....

http://reconingspeakers.com/products...td5-diaphragm/

but needs some clarification if they are compatible.

Last edited by laverda; 21st December 2012 at 03:40 AM.
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Old 23rd December 2012, 06:21 AM   #4
laverda is offline laverda  United Kingdom
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Strassacker: Loudspeaker, Coaxial speakers, Driver, Tweeter, Mids, Woofer, Subwoofer, Components
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Old 23rd December 2012, 04:51 PM   #5
JMFahey is offline JMFahey  Argentina
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Those are not foam "surrounds" at all, the domes have a (usually) Kapton or Mylar suspension.
Those are foam absorption or damping rings, to absorb whatever little sound is reflected on the speaker cabinet surface, causing dips in the frequency response.
They don't move, of course.
That deterioration you see will not impair their function (there still more than 90% original foam, after all) but if you want to, you can carefully scratch old foam (which must be crumbling anyway) and glue new rings, cut by hand with scissors out of a similar foam sheet.
You can even use felt or cloth similar to what stuffed toys use.
Not critical at all.
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Old 23rd December 2012, 05:43 PM   #6
sreten is online now sreten  United Kingdom
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Quote:
Originally Posted by JMFahey View Post
Those are not foam "surrounds" at all, the domes have a (usually) Kapton or Mylar suspension.
Those are foam absorption or damping rings, to absorb whatever little sound is reflected on the
speaker cabinet surface, causing dips in the frequency response. They don't move, of course.
Hi,

That is not the way they are usually described. They are part of the
dome assembly, they are attached to the dome and they do move.
They are the suspension. There is no sign of the suspension you
describe. I've never seen a dome with a sub-suspension.

rgds, sreten.

Click the image to open in full size.
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Last edited by sreten; 23rd December 2012 at 06:05 PM.
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Old 24th December 2012, 05:30 PM   #7
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by sreten View Post
Hi,

That is not the way they are usually described. They are part of the
dome assembly, they are attached to the dome and they do move.
They are the suspension. There is no sign of the suspension you
describe. I've never seen a dome with a sub-suspension.

rgds, sreten.

Click the image to open in full size.
Dear streten, I don't know how they are "usually described" and couldn't care less about Marketing Dept babble.
*They* can call it anything they like
I am referring to the picture kindly posted by timthedog
Click the image to open in full size.
1) I am referring to the 2 foam rings clearly visible in the picture.
I must think you also refer to the same, since you use the word "they".
a) the larger one, brownish colour, 100mm outer , 65mm inner diameter is clearly glued to a silver or white ring, part of the whole tweeter structure, and of course is not a moving part. So the larger one is already discarded as "suspension".
b) the smaller one, dark greyish, 42mm OD, 30mm ID, is also glued to a non moving part , lighter grey or darker silver, which is the magnetic system front plate *or* a plastic ring where the diaphragm is mounted.
It does not qualify s a "suspension" either, being a rigid part.
c) now to the diaphragm itself.
To begin with, I've never mentioned any "sub-suspension"
In dome speakers (tweeters or midrange), the diaphragm can be divided in 2 parts: the dome itself, and its edge or suspension, which flexes and allows movement.
Pro drivers , which must be strong, usually are made out of 2 materials, commonly aluminum or titanium for the dome, and Kapton/Mylar for the edge/suspension. No need for an additional sub-suspension.
Cheaper drivers or tweeters, as the one in the picture, are often one-piece, to save on cost and complexity.
So the edge/suspension material will be the same as the one in the dome.
In the picture you can see that the dome proper is 25mm diameter , then you clearly see a 2mm wide ring around, same material, looks flat, which is the real suspension, and which by flexing allows for back/forth dome movement.
That edge must be somewhat wider, of course (the dome is not "floating " in mid air, after all) , typically 5 or 6mm wide, and that "extra" diameter is glued to the light grey ring.
We can't see it, of course, because the dark grey foam ring is glued on top of it.
See that anyway it does not reach the dome edges, you need those 2mm around free to move unimpeded.
So the only other function possible for that foam ring is what I described, as an absorbent of waves reflected around the dome.

As a side note, *there are* speakers with "foam" surround , typically woofers or midrange speakers, *never* tweeters, and they use relatively stronger *closed cell* foam (meaning air is trapped in bubbles which do not communicate between them, and air cann not pass through the foam, while the acoustic foam we see in the pictures is *open cell* (it can easily be seen).
No tweeter designer in his sane mind would use open cell foam as a dome/diaphragm suspension, doubly so because voice coil centering must be kept under *very* close tolerances; tweeter gaps are much narrower than those used in woofers.
Now, if you say that the smaller foam ring partially covers the (glued) outer edge of the suspension, I can agree with that

PS: and in the picture you posted, maybe you *could* say it has a "sub-suspension"
The dome there (which is more complex) shows the dome, then a flat ring around which is the actual suspension, then an outer mounting ring (often metal+cardboard) for easy replacement without gluing.

Last edited by JMFahey; 24th December 2012 at 05:35 PM.
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Old 24th December 2012, 09:19 PM   #8
sreten is online now sreten  United Kingdom
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Quote:
Originally Posted by JMFahey View Post
1) I am referring to the 2 foam rings clearly visible in the picture.
Hi,

Except the foam rings you now say you are referring to are not the
foam rings described in the original post, which is clearly referring
to the tweeters foam ring suspension, a feature of most Focal
inverted domes, and they don't have Mylar or Kapton suspension.

You have got the wrong end of the stick, and posted a load of
tosh regarding the original post, though I agree about all your
comments regarding the larger faceplate acoustic rings.

rgds, sreten.
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Last edited by sreten; 24th December 2012 at 09:26 PM.
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Old 24th December 2012, 10:45 PM   #9
JMFahey is offline JMFahey  Argentina
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Quote:
Except the foam rings you now say you are referring to are not the
foam rings described in the original post,
"You now say?" From the beginning I have been referring to the same ones the OP is *showing* and taking about, the "damaged foam rings" clearly visible in the picture.
Don't you see them?
I even gave the measurements (the OP shows measurements too) so we all talk about the same.
And no, those are not "suspensions" at all, because they don't move.

Confirming this, there *are* replacement foam rings available, which can be replaced by the user *because* they are not that critical.
While if they were suspensions, it would imply a very complex dome replacement and realignment, a critical task.
Why? ... because the dome is suspended from the suspension (that's why they call it that name )

As of the material suspensions are made of, of which you are trying to make a point unsuccessfully, I said
Quote:
the domes have a (usually) Kapton or Mylar suspension.
Noticed the qualificative "usually"?
Which means: "in a small dome the suspension is usually made out of the same material of the dome itself" , which is easy tu understand, because dome and suspension, all one single continuous piece, are molded/pressed out of a flat sheet of suitable material.
Most common and abbundant, are domes made out of some kind of Mylar (by far the most popular) or Kapton (a very similar product) in a few more modern ones.
In this particular Focal tweeter they are made out of another modern plastic material (kudos to them): kevlar.
But never ever foam. Never.
Why would they use such a poor material?

So I'll spell it to you, to avoid misinterpretations:
If the dome is made out of ... the suspension will be made of ...
Dome .............. Suspension
Mylar ............. Mylar
Kapton ........... Kapton
Kevlar ............ Kevlar
Silk ................ Silk
Phenolic cloth .. Phenolic cloth
Foam ............ well, no domes are made out of foam so I guess suspensions are no made out of foam either. Sorry.

By the way, the OP does not use the word "suspension" anywhere.
And if he thinks they are so, he can be forgiven, nobody is born with knowledge, which is acquired through hard study and experience.

Foot note: before you try to crucify me because I suggested even felt can be used, please read this, pasted straight from Audio Asylum speaking *specifically* about these tweeters:
Quote:
REVIEW: Focal Tweeter Model T-120 FC Speakers Review by roberts@bandstand productions at Audio Asylum
208.149.44.174
Bought 6 sample units for testing and evaluation. Overall a great sounding tweeter simalar to what Wilson uses in their designs. Huge motor assembly and tiny voice coil gives fantastic speed and transparency. Dispersion is good to very good...needs treatment to control dispersion for proper imaging within a system. A felt ring did the trick, and kept standing waves from bouncing back and forth from the flange to the diaphram , Plus giving the window more control
What more can I say?

Oh yes, here the important guy is the OP.

Dear timthedog, as post #5 suggests, your foam rings can be home replaced .
And as the Audax Forum says, they have a home repair kit available, with 3 different ring sizes and a small contact cement tube.
No mention of centering shims, which would be needed if you had to replace the suspension, of course.
They speak of "moisse plat" which means flat foam, and "colle néoprène" which is contact cement.
I'd use the kind without Toluene or Xylene or it will try to "eat" the foam.
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Old 24th December 2012, 10:55 PM   #10
sreten is online now sreten  United Kingdom
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Hi,

This is getting very sad. You made a mistake, admit it.

rgds, sreten.
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