speaker refoam

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 du st caps seem well bonded to the cone. I'd much prefer to shim the cone bef ore bonding the foams, but I don't know if the dust caps can be removed som ehow from the cones without damaging them.

Any advice appreciated.

Reply to
John-Del
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e but I realize it's not rocket science but there's probably a learning cur ve. I won't have the option of do a trial run.

dust caps seem well bonded to the cone. I'd much prefer to shim the cone b efore bonding the foams, but I don't know if the dust caps can be removed s omehow from the cones without damaging them.

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

NT

Reply to
tabbypurr

ore but I realize it's not rocket science but there's probably a learning c urve. I won't have the option of do a trial run.

c 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.

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

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

Reply to
John-Del

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

Peter Wieck Melrose Park, PA

Reply to
peterwieck33

efore 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.

tic dust caps seem well bonded to the cone. I'd much prefer to shim the co ne before bonding the foams, but I don't know if the dust caps can be remov ed somehow from the cones without damaging them.

cone. The VC is completely hidden.

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

NT

Reply to
tabbypurr

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!).

Reply to
Dave Platt

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.

Reply to
John-Del

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

Reply to
tabbypurr

** 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.

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TIP:

Speakers that use rubber roll surrounds last waaaaay longer.

.... Phil

Reply to
Phil Allison

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

NT

Reply to
tabbypurr

** Than the kind mentioned in the *heading* and throughout of this thread - dickwad.
Reply to
Phil Allison

Expecting people to be mind readers is rather silly.

Reply to
tabbypurr

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

Reply to
gregz

** Never expecting that.

You a lack the ability to follow the context.

.... Phil

Reply to
Phil Allison

your bullsht lately is tiresome

Reply to
tabbypurr

** Piss off to hell - you PITA damn troll.
Reply to
Phil Allison

** 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.

** Agreed.

..... Phil

Reply to
Phil Allison

Try this :

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

The prices are quite nice.

Reply to
Look165

you beat me to there

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

NT

Reply to
tabbypurr

On Wed, 14 Nov 2018 13:34:56 +0100, Look165 wrote as underneath :

Informative site on the subject , thanks! C+

Reply to
Charlie+

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