Speaker Foam

I have four infinity speakers. they all need new foam (maybe). infinity say they have no replacement speakers (what?) and offered no repair kits. i do have a few local places that refoam but have not called for prices yet. the speakers still sound fine to me except when there is some low frequency music that cause the speakers to rattle.

1) what is the purpose of the foam? dirt? rattle? 2) how do I measure the speaker to buy a foam kit? speaker diameter? cone diameter? what? 3) if I can live with it, does it further damage the speakers without the foam? 4) what destroys the foam?

If i just want to replace the speakers, what is recommended. Mine are

9 inches outside diameter so should be easy to find replacements. Want good enough sound not expensive.
Reply to
Mark
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As far as I know, it prevents the compression and rarefaction of the air within the speaker from making the air marginally hotter or colder

- the foam doesn't have much thermal mass, but it has quite a bit more than the air itself. There's also an element of damping, which may be what you are missing, though the "rattle" may be the speaker cone running into the end of the hole in the foam that it has dug for itself over the years.

It's suppposed to fill the internal volume of the speaker cabinet The outside dimensions of the cabinet are probably what you want.

I'd be surprised if it did any serious damage. The "rattle" sounds ominous, but the foam isn't stiff, and having the speaker cone slam into what's left of it probably isn't going to break anything.

Oxidation? Insects? Maybe the components weren't properly mixed in the first place and you always had patches of duff foam within the cabinet that broke up more rapidly than thye should have done.

How deep is your pocket? And how golden are your ears? Manufacturers like KEF have always had a good reputation, and everything they sell is good, but you are paying about 50% extra for that reputation. You need to go to one of the audio groups to get this kind of advice, but many of them are dominated by the golden-eared boys who think that valve amplifiers are better than transistor-based amplifiers because they like a bit of third harmonic distortion, so any advice you get has to be taken with a large grain of salt.

If Phil Alison posts a response to this post, take his advice seriously. He's famously irritable, but knows more about audio than anybody else who posts here regularly - much more than I do.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

A quick google will tell you all you need to know (and more). E.g.

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"(Material) for loudspeaker suspension is compressed foam, it is evenly compliant across a wide range of movement and affect the sound of the driver far less than rubber and other less perishable materials, so it is an unavoidable part of a quality loudspeaker, it only down side is that, depending on environment and climate, it will perish and start hardening after 8 ? 12 years."

The surround has multiple functions - maintaining cone alignment is one.

Reply to
Gib Bogle

kits.

The outer foam band seals the inner/outer enclosure. It also is part of the mechanical assembly which plays a role in the Q of the speaker. It also helps keep the cone centered.

Some drivers are different. I would look into model number replacements.

foam?

Yup.

They either rot, or dry out and crack. Or just break down over time. With good foam you can manipulate it with your finger without tearing it apart.

too many variables. Boxes are designed to work with the drivers parameters.

You can search Internet for model number foam replacements. There are sites that specialize in foam replacements or others that also include selling them If you screw up, your screwed.

Greg

Reply to
gregz

I don't think he is talking about interior foam. Foam usually not used, mostly because it's expensive, and depending on enclosure type, polyester, might be better. I often use foam myself, again depending on the situation. Interior foam does not break up as fast as driver foam. Also, sometimes rubber is the replacement outer flexor. As long as it does not change the driver parameters.

Greg

Reply to
gregz

Foam breaks down the fastest from what I've seen. I try to avoid foam drivers. When switching surround types, you can get unexpected results for another reason. The surround is part of the cone surface. It radiates. Sometimes the surround phase will cause peaks or mulls in the centerline response. Foam and folded paper or hardened cloth will radiate upper frequencies better. Rubber does not couple well at higher freqs. If the woofer is not used at upper freqs., it's not going to be an issue. Another good old surround type was treated cloth, which except for the drying out or flow of the gook, lasted a very long time. Many still going good.

Greg

Reply to
gregz

You can get Foam replacements online, jus match your speaker size. FYI, I've replaced the foam on my drivers and used Elmers Rubber cement. It will hold up well, and also allows you to do it over if your alignment is off. The voice coil should move freely. I did the foam replacement over 5 years ago and it's still sticking.

Cheers

Reply to
Martin Riddle

Do they have model numbers? If unavailable, is the speaker cabinet, wood, plywood, particle board, or plastic?

Ummm... this might help: Lots of detail included on the purpose of the foam and its composition. However, for this plastic case, it appears that the foam has to be installed as part of the manufacturing process. The patent indicates that it's urethane foam, the same as used in fence post compound and wall insulation. You might get away with making a mould out of the speaker case and some stiff packing cardboard covered with grease, pouring in the liquid urethane, allow it to expand, and remove the cardboard. There's a description of the manufacturing process and type of urethane used at Page 5, line 46.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

Good to hear. The usual glue is the flexible form of white glue, a copolymer, such as Air flex 400 . I once got a gallon of it. Regular white glue is a mono polymer.

Greg

Reply to
gregz

I thought wrong. stiff glue is homopolymer. ! Not monopolymer.

Greg

Reply to
gregz

"Bill Sloman"

As far as I know, it prevents the compression and rarefaction of the air within the speaker from making the air marginally hotter or colder

- the foam doesn't have much thermal mass,

** The OP is asking about annular foam surrounds for his woofers.

They famously perish and need to be replaced.

If Phil Alison posts a response to this post, take his advice seriously. He's famously irritable, but knows more about audio than anybody else who posts here regularly - much more than I do.

** Nice of you to say so.

BTW:

are you still living in Centennial Park or some other part of Sydney now ?

... Phil

Reply to
Phil Allison

"Martin Riddle"

** A couple of questions:

When replacing a surround, it is necessary ( or a good idea ) to remove the dust cap and shim the voice coil tightly in the gap first ? Or can you just wing it and rely on slow setting adhesives ( like Silastic) to let you fiddle with the new surround till there is no sign of poling?

And do you glue the surround to the cone first or the frame ?

.... Phil

Reply to
Phil Allison

"gregz"

** Isn't long haired sheep's wool supposed to be the best ??

That was THE recommended filling for " transmission line" bass boxes.

I have used " bonded acetate" fibre or white polyester pillow material in the past.

They seem to work OK.

Sheep's wool is a tad exotic.

.... Phil

Reply to
Phil Allison

That foam is the cone suspension, which when done in foam does actually degrade over time and needs replacement. You need to "recone" the speaker by replacing it. Sizes are usually standard therefore it won't be a problem finding spares.

Reply to
asdf

No, I didn't remove the dust cap. The drivers weren't anything special, so I just winged it and made sure there wasn't any binding. I did the frame first then the cone. I think I tacked the cone in 3 or 4 spots checked for voice coil movement then pressed the rest of the surround down. I did have to do it twice on one of the drives, the voice coil was not centered the first time.

There is a 3/16 thk paper ring that sits on top of the surround, that tends to fall off every couple of years using the rubber cement. But the surrounds are still stuck to the cones and frames.

Cheers

Reply to
Martin Riddle

?

In theory, yes - I've even got a NSW driving licence - but right now I'm Christchurch, New Zealand, and will be here for almost another fortnight before we go back to Darlinghurst.

--
Bill Sloman, Sydney (but in Christchurch, NZ at the moment).
Reply to
Bill Sloman

er,

And perhaps a bit labour-intensive. The only hi-fi enthusiast I've known who went to that much trouble with his speaker supported the sheep's wool on nylon fishing line that he strung from side to side every few inches.

I'd have thought that aerogel might have been better, but it might hae been a bit hi-tech for the golden-eared boys.

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--
Bill Sloman, Sydney (but in Christchurch, NZ at the moment)
Reply to
Bill Sloman

I bought some wool once. It does do things slightly different. It was claimed best for transmission lines, but I can't verify. Richard pierce claims the transmission line is just a modified port.

If I'm reducing in box reflections I like foam attached to the walls. If I'm doing a heavy fill in closed box, fiberglass is better than polyester. I also liked the very fine no itch fiberglass corning used to make. Still got some. I've used cotton, foam, various brands of polyester, wool, fiberglass. Sometimes using foam and polyester together.

Greg

Reply to
gregz

I only did a couple surrounds. Shimming voice coil by removing dust cap. I'm pretty sure you do first the foam to cone, but I just followed instructions.

Greg

Reply to
gregz

I have fixed more surrounds than I have replaced them. Using silicone rtv or Airflex 400. Its often a tricky situation. I have probably treated a few dozen drivers, mostly small 4 1/2 inch type. If the foam is completely missing, can't do.

Greg

Reply to
gregz

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