Speaker Foam

[Mark]

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.

 

[Bill Sloman]

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?

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.

2) how do I measure the speaker to buy a foam kit?
speaker diameter? cone diameter? what?

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

3) if I can live with it, does it further damage the speakers without
the foam?

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.

4) what destroys the foam?

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.

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.

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.

 

[Gib Bogle]

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.

A quick google will tell you all you need to know (and more).
E.g. http://www.audionote.co.uk/downloads/speaker_foam_replace.pdf

"(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.

 

[gregz]

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?

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.

2) how do I measure the speaker to buy a foam kit
speaker diameter? cone diameter? what?

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

3) if I can live with it, does it further damage the speakers without the foam?
Yup.

4) what destroys the foam?

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.

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.

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

 

[gregz]

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.

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

 

[gregz]

A quick google will tell you all you need to know (and more).
E.g. http://www.audionote.co.uk/downloads/speaker_foam_replace.pdf

"(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.

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

 

[Martin Riddle]

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.

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

 

[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

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

 

[gregz]

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

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

Greg

 

[Phil Allison]

"Bill Sloman"

1) what is the purpose of the foam? dirt? rattle?

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

 

[Phil Allison]

"Martin Riddle"

You can get Foam replacements online, just 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.

** 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

 

[Phil Allison]

"gregz"

Foam usually not used,
mostly because it's expensive, and depending on enclosure type, polyester,
might be better.

** 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

 

[Martin Riddle]

"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

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

 

[Bill Sloman]

"BillSloman"


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 ?

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]

"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.

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.

http://en.wikipedia.org/wiki/Aerogel

 

[gregz]

"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

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

 

[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

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

 

[Phil Allison]

"gregz"

"Phil Allison"

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.

** Richard Small ( of Theile and Small ) made that same observation back in
the 1970s.

Seems he and I were at the University of Sydney in 1972 - though he is a
few years older than me.

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.

** Have you done any testing to verify results ?

I have tried 4 cycle sine wave tone bursts and close micing with some
success - you may need to be outdoors or far from walls to eliminate
extraneous reflections in the scope trace.



.... Phil

 

[Phil Allison]

"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.

** Those 41/2 inch drivers were not Bose by any chance ?


..... Phil

 

[Phil Allison]

"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.

** Shimming sounds like the proper way to do it.

Same as when re-coning.


.... Phil