speaker refoam

[John-Del]

This is a favor for a friend of a friend. I've never done a refoam before but I realize it's not rocket science but there's probably a learning curve. I won't have the option of do a trial run.

These drivers come out of a pair of Infinity Crescendos, and the plastic dust caps seem well bonded to the cone. I'd much prefer to shim the cone before bonding the foams, but I don't know if the dust caps can be removed somehow from the cones without damaging them.

Any advice appreciated.

[tabb...@gmail.com]

shim it from behind the cone, using bent bits of card.


NT

[John-Del]

It's got a cloth barrier running from the basket to the back side of the cone. The VC is completely hidden.

Too bad the dust caps weren't tacked down with hyde glue.

[peterw...@gmail.com]

On Tuesday, November 13, 2018 at 2:06:15 PM UTC-5, John-Del wrote:

> Any advice appreciated.

You will find that if you are exceedingly careful, and use a bit of high-tack contact cement to get things started to center the cone to the foam, that shimming will not be necessary. But, it will help to cure the finished job upside down so that the cone is floating just a bit.

Peter Wieck
Melrose Park, PA

[tabb...@gmail.com]

On Tuesday, 13 November 2018 20:17:07 UTC, John-Del wrote:

cloth airfilter can be cut & replaced without affecting speaker operation.
The voice coil is already centred by the spider anyway, so not convinced you need to shim it.


NT

[Dave Platt]

In article <9174cb59-61f8-44c4...@googlegroups.com>,

SpeakerWorks sells re-foaming kits for a lot of sizes (both foam, and
rubber surrounds).

There are at least three ways to make sure that the cone is centered,
when you do the final glue-down of the surround:

(1) Remove the dust cap, shim, and then re-glue the dust cap
afterwards. Apparently the dust caps can usually be removed
without too much damage by cutting them carefully near the base
with a single-edged razor blade or a sharp box cutter or etc. One
must be careful not to cut the voice coil, damage the voice coil
former, or get debris into the gap between magnet and voice coil.
Lots easier with a paper voice coil than with plastic, I don't doubt!

The instructions which SpeakerWorks provides with their re-foaming
show how to do this, but it is _not_ their recommended approach.

(2) Do it "unassisted". SpeakerWorks shows a procedure where you
press gently down on the dust cap, and carefully manipulate the
dust cap and cone side to side slightly so you can feel the
positions where the voice coil moves in and out freely without
touching the magnet assembly. This is their recommended approach,
and they claim that most customers have no problem with it.

(3) Use electro-mechanical centering. If you apply a small DC voltage
(a single AA cell is sufficient - even 1 volt works in many cases)
it will energize the voice coil, move the speaker inwards or
outwards by a fair percentage of its Xmax, and the force of the
"spider" and the magnetic field interaction between voice coil and
magnet will tend to center the voice coil in the gap.

I used method (3) when re-foaming a pair of Minimus 77 drivers, and it
worked perfectly - no scraping was evident after the repair was done.

I did it again, last night, when gluing new rubber surrounds onto a
pair of Minimus 7 drivers, and it seems to have worked just as well.
After the glue dried I disconnected everything, and gently pressed the
dust caps, and the cones moved smoothly without any sign of rubbing.

The method I used was: apply a positive voltage to the coil, moving
the cone in the "outwards" direction for several millimeters. This
makes it convenient to glue the new surround to the cone, as the outer
edge of the surround will be up above the frame. Let the glue dry.
Lift up the outer edge of the surround, spread glue on the frame,
relax the surround, then turn voltage down to zero (returning the cone
to its rest position), reverse polarity, and apply a small negative DC
voltage. This pulls the cone "inward" slightly and snugs the edge of
the surround down onto the glued frame.

You can do this with just a penlight cell - when I did the Minimus 77
drivers I found that 1.5 volts was plenty, even with the two drivers
wired in series. I took a more delicate approach with the Minimus 7
drivers last night, using an adjustable DC supply (with the current
limit set to about 100 mA just to be safe!).

[John-Del]

Thanks Dave - I really like the idea of adding a bit of DC to the coil. I do have a programmable power supply so I'll be sure not to cook that VC with too much DC.

I was thinking a nice, *slow* setting, syrupy although not too viscous adhesive would allow the cone to self center under the new foam. The kit the guy gave my brother has a small bottle of adhesive (that leaked a bit!). Hopefully it'll be suitable.

[tabb...@gmail.com]

The coil is centred by the spider 100% of the time. What you want to centre is the edge of the speaker at the foam surround. There is nothing in the standard moving coil speaker mechanism that will do this by itself. Method 2 works IME.


NT

[Phil Allison]

** Plenty of u-tubes to be found on speaker repair, including the art of replacing loudspeaker surrounds - whether foam or neoprene / rubber.
This one in about the Infinity Crescendo CS3007 model.

https://www.youtube.com/watch?v=UwVDVQ8_feI


TIP:

Speakers that use rubber roll surrounds last waaaaay longer.



.... Phil

[tabb...@gmail.com]

than what? from what I've seen cloth lasts longer.


NT

[Phil Allison]

tabb...@gmail.com wrote:
>
>
> > John-Del wrote:
> > >
> > >
> > > This is a favor for a friend of a friend.
> > > I've never done a refoam before but I realize
> > > it's not rocket science but there's probably
> > > a learning curve. I won't have the option of do a trial run.
> > >
> > >
> > > These drivers come out of a pair of Infinity Crescendos,
> > > and the plastic dust caps seem well bonded to the cone.
> > > I'd much prefer to shim the cone before bonding the foams,
> > > but I don't know if the dust caps can be removed somehow
> > > from the cones without damaging them.
> > >
> > > Any advice appreciated.
> > >
> >
> > ** Plenty of u-tubes to be found on speaker repair, including the art
> > of replacing loudspeaker surrounds - whether foam or neoprene / rubber.
> > This one in about the Infinity Crescendo CS3007 model.
> >
> > https://www.youtube.com/watch?v=UwVDVQ8_feI
> >
> >
> > TIP:
> >
> > Speakers that use rubber roll surrounds last waaaaay longer.
> >
> >
>

> than what?


** Than the kind mentioned in the *heading* and throughout of this thread - dickwad.

[tabb...@gmail.com]

On Wednesday, 14 November 2018 05:36:10 UTC, Phil Allison wrote:
> tabby:

Expecting people to be mind readers is rather silly.

[gregz]

Applying tones to hear when it rubs works well. You can move outer around
to get centered so the coil is parallel to pole piece. There is also the
way to cut slits in dust cap and insert shims through dust cap. Then glue
up slits when done. And check spiders for sag and securly attached to
frame. Also check tinsel condition. A DC voltage and moving them should
have no noise. When done apply low frequency sine wave and listen or any
noises.


Greg

[Phil Allison]

** Never expecting that.

You a lack the ability to follow the context.




.... Phil

[tabb...@gmail.com]

On Wednesday, 14 November 2018 08:45:04 UTC, Phil Allison wrote:

> tabb...@gmail.com wrote:

> > > > > Speakers that use rubber roll surrounds last waaaaay longer.
> > > > >
> > > > >
> > > >
> > > > than what?
> > >
> > >
> > > ** Than the kind mentioned in the *heading* and throughout of this thread
> >>
> >> - dickwad.
> >
> >
> > Expecting people to be mind readers is rather silly.
> >
>
> ** Never expecting that.
>
> You a lack the ability to follow the context.

your bullsht lately is tiresome

[Phil Allison]

tabb...@gmail.com wrote:

> >
> > > Expecting people to be mind readers is rather silly.
> > >
> >
> > ** Never expecting that.
> >
> > You a lack the ability to follow the context.
>
> your bullsht lately is tiresome

** Piss off to hell - you PITA damn troll.

[Phil Allison]

GS wrote:
>
>
> Also check tinsel condition. A DC voltage and moving them should
> have no noise.
>

** Not too long ago, I had a small woofer that was quite silent.

An ohm meter test showed the voice oil was shorted - however the cone moved back and forth freely under finger pressure. No burnt smell either.

Then I saw it, the tinsel leads had welded themselves together requiring some effort to pull them apart. Later, when the woofer was driven hard on test, the leads vibrated *towards* each other, eventual making a horrible noise when they began touching !!!

Shortening both tinselleads by a couple of cm and twisting them 90 degrees in the solder terminals fixed the problem.

A similar problem happens when both tinsel leads are able to contact the speaker's steel frame in use. Tinsel leads have to be just the right length and oriented correctly.

> When done apply low frequency sine wave and listen or any
> noises.
>

** Agreed.



..... Phil

[Look165]

Try this :

http://www.goodhifi.com/

They are super, rubber rings, diaphragm, special glue.

The prices are quite nice.


John-Del a écrit :

[tabb...@gmail.com]

On Wednesday, 14 November 2018 12:03:21 UTC, Phil Allison wrote:

> tabby wrote:

> > > > Expecting people to be mind readers is rather silly.
> > >
> > > ** Never expecting that.
> > >
> > > You a lack the ability to follow the context.
> >
> > your bullsht lately is tiresome
>
> ** Piss off to hell

you beat me to there

> - you PITA damn troll.

I'm only a pita to people that keep bsing.


NT

[jurb...@gmail.com]

>"Applying tones to hear when it rubs works well."

I do that. I use a function generator on sine and set it to the free air resonance frequency It is easy to see, whatever frequency moves the cone the most. Then I see which way it might have to go to be in the most perfect center. It could be fine without touching it but I push it both ways on both axes to find which way the bent bends. Whichever way I got the most clearance before the voice coil rubs is the direction I "coax" it to before the glue dries.

Once I had to fix one someone else had done. He thought it would require removing the glue and tearing everything out. Nope. I simply bent the frame slightly. Of course this will not work on speakers with cast frames so just be more careful on those.

Actually there is money doing that. I heard of a guy in my state who started doing a few and still worked. In a couple of years he quit his day job to do this full time and makes decent bucks doing it. He can't keep up with the work. I am considering doing it. All you need is a little bit of exposure and a few satisfied customers. And of course I would have a discount for cash... It would tie in nicely with any of my stereo fixing endeavors as well, it would be practically the same customers. And audiophiles go in packs, at least on the internet. Of course some of them will fly cross country to hear another's system, but when your system cost more than a new car you do things like that.

[stra...@yahoo.com]

I've done 6 refoams on Advent woofers and 2 on 6" JBL drivers. The first Advent kit came with shims and new dust caps. I followed the instructions and they worked fine. The next sets came without shims and I did not use any and everything is fine. I know the gap in the Advent drivers is quite large though I don't know if it's different in other brands. I have no idea what the gap is in the JBL but had no problem. As long as the spider hasn't shifted I don't think you'll have problems.

G²

[jurb...@gmail.com]

>"As long as the spider hasn't shifted I don't think you'll have problems"

You can The voice coil could be ike:

|/|_|/| or |\|_|\|

with the top of the coil perfectly aligned but the bottom of it off due to the cone edges not being in the right position I use the generator and find which direction has the most leeway until it rubs and then "coax" it into the best position. This way when it gets pushed and expands thermally the clearances should not disappear.

[Look165]

I did refoam speakers (mainly woofers) 5 years ago for my mother and me
; they work pretty fine (8Ohms 45W and 100W peak).

The only specific check is the centering BEFORE glueing.
The best is to put a cylinder of paper or plastic (about 1 or 0,5mm)
around the bobin for centering (take care not to damage the wiring).
Then glue the foam ring to the cone and the circular skeleton of the
speaker ; NO FORCE TO APPLY ; let everything must rest where it is.
After 2 days, take the cylinder off, clean and glue the diaphram.

Then let rest for at least 2 days.

Goodhifi is a very nice supplier, when you provide the right
informations (manufacturer, exact type - written on the magnet...).
They also provide tutos for operations (see Youtube).
You can get new diaphragms, new cones and the appropriate glue.

Before that, check the wiring is OK ; no enammelled wire damaged.

Forgive my lack of English.

John-Del a écrit :

[Paul Hovnanian P.E.]

I've done a couple of them. As long as there is no need to repair or replace
the cone or detach it from the coil or spider (I think it's called), I
didn't have to shim the coil. The spider held it centered well enough that
as long as no lateral load was placed on the cone during the foam glue
setup, the air gap remained OK.

--
Paul Hovnanian mailto:Pa...@Hovnanian.com
------------------------------------------------------------------
A recent study found that women who carry a little extra weight
live longer than the men who mention it.