Speaker surround foam - is there a real difference?

[dzkfraser]

Long term is the only way to validate the quality of the foam, as for audible differences, that is very subjective and you would need to be able to do an original vs replacement comparison. My rule of thumb, cheap drivers get cheap foam, decent ones get decent, i.e. more expensive, or matching original. My 2 cents

 

[spkrdtr]

I see, so where does his foam come From? Not China? Usa made to more critical standards? I have never tried those Chinese cheaper surrounds, but they look identical to ones I got from Rick before. Don't look like it needs to be cut or anything. Just wonder.

Next time you do a refoam, order from Cobb and also the same size from Mat Electronics. When you get them, do a touchy, feely comparison.

 

[Chris Brown]

is there real evidence that cheaper surrounds are indeed of poorer quality? If is it a myth that people buy into and after a while it becomes "the truth".

There are more variables at play than just the surrounds themselves. It's entirely possible that many of the foams found cheap directly from china are in-fact the exact same as the foams sold by traditional well-respected vendors. There is more to it than that though. You still need to select the correct foam.

When I ordered the refoam kit for my JBL 128H woofers. Rick Cobb asked that I measure the cone size. Prior to that I did not even know that the 128H woofers came with slightly different cone sizes, some 9 3/8", some 9 5/8". Despite that small variation, where a generic foam would likely have worked fine on either, Rick Cobb's standards are high enough to the point where he actually cared and wanted to make sure I got foams that were exactly the right size. He also sells foams as kits, which include glue, etc.

It's this extra service, more-so than the actual foam, that is worth paying extra for. Even in regards to the foams themselves, while it's certainly possible that you can get high-quality foams ordering from generic Chinese vendors, you KNOW that you are going to get high-quality foams from vendors such as Rick Cobb.

 

[gdmoore28]

I actually was thinking to do just that, but thought I would ask here first. However, it seems that questioning "traditions" is a no-no here....

Krosya, I'm glad you asked the question, and yes, questioning some of our "traditions" does tend to raise people's hackles. But your question is valid, and well worth exploring.

And without the direct input of Rick Cobb, anything that anybody says here is pure assumption, nothing more or less.

With that in mind, may I offer my own assumptions? I'll wager that Rick's surrounds are made in China by the exact same folks that make all the others that sell much cheaper. I'll bet the reason that Rick's services are so good lies in his research and in his experience in mating the correct Chinese surrounds to the correct speakers. Buying the generic surrounds may or may not produce an optimum match. Mr. Cobb has obviously used his experience to make sure that we get an exact match every time. Doing it right involves lots of research, and that is what we pay for when buying Rick's surrounds.

One additional possibility: Having dealt with Chinese vendors personally, I can tell you that they are quite responsive to customer requests. If one is willing to buy in bulk, they will deliver exactly what you order - cheap and dirty, or perfect and correct. So, it is quite possible that Mr. Cobb has corresponded directly with the Chinese manufacturers and specified exactly what he wants in his products. (And you can be sure that the vendors will use the knowledge they gain from customer requests and incorporate that into everything they manufacture. I've watched it happen.)

Once again, this is all conjecture on my part, but I think it makes sense. I'd love to hear "the rest of the story" from Rick Cobb himself.

GeeDeeEmm

 

[leesonic]

You can also try Tom at myaudioaddiction. He managed to find a set of surrounds that fit the Infinity CS-3007 midranges perfectly.

Lee.

 

[Blue Shadow]

And without the direct input of Rick Cobb, anything that anybody says here is pure assumption, nothing more or less.

GeeDeeEmm

Hey, I had a little bit of fact in my posts. Something I said was assumption but not anything (everything) I said!!

 

[Putterman]

Alright, I'll put some 'fact' into a post. I've used the generic foams from Mat. For most speakers including EPI's it didn't appear to make a difference, but for a pair of Boston Acoustic A70's one speaker had noticeable distortion when cranking the Cream reunion DVD on my home theater system. While not definitive proof, another poster mentioned having a similar problem in another thread.

The 'definitive proof' would be a full workup of frequency response and distortion measurements of the speakers with both a generic foam and a more specialized foam. Everything else is just opinion and hearsay. People who buy expensive foams want to feel justified in their just as people like me want to feel they're getting a bargain.

 

[Collin1141]

Alright, I'll put some 'fact' into a post. I've used the generic foams from Mat. For most speakers including EPI's it didn't appear to make a difference, but for a pair of Boston Acoustic A70's one speaker had noticeable distortion when cranking the Cream reunion DVD on my home theater system. While not definitive proof, another poster mentioned having a similar problem in another thread.

The 'definitive proof' would be a full workup of frequency response and distortion measurements of the speakers with both a generic foam and a more specialized foam. Everything else is just opinion and hearsay. People who buy expensive foams want to feel justified in their just as people like me want to feel they're getting a bargain.

A foam surround is not part of the radiating area, all it does is minimize reflections back into the cone, center it, and provide an air tight seal, that's it
The surround has nothing to do with the driver's T/S parameters beyond Xmax
A driver relies on the spider, the coil and the mass and profile of the cone for the low frequencies and mid band response, that plus the gap and box volume
Quality replacement surrounds like Rick Cobb's are always the best way to go and give you the best shot at getting things as close as possible to back where they belong specs wise, but all the cheap stuff that's close enough can or might alter is the Xmax of the driver, not create distortion
Meaning if it fits dimension wise
Changing the Xmax of the driver could change the driver's frequency response without a doubt, but if you do a refoam job with cheapie surrounds and get any other sort of audible distortion, and not just a change in response, then something else is wrong
It's not the cheap surround's fault

 

[gdmoore28]

Hey, I had a little bit of fact in my posts. Something I said was assumption but not anything I said!!

Those darn generalizations - they come back to bite me every time. Sorry, Blue.

My penitence:

GeeDeeEmm

 

[Collin1141]

Wrong. The foam DOES affect the physical parameters of the driver. Each driver has a unique amount of flex, change that and you change the physical parameters of the driver.

That is why one should buy the foam surrounds for the exact speaker they will be used in.

I think maybe you should take another look at my post
I addressed Xmax in detail, see below
Feel free to point out any errors, and why they are errors, in my original post and I will make the requisite corrections
One's never too old to learn new tricks!

Changing the Xmax of the driver could change the driver's frequency response without a doubt, but if you do a refoam job with cheapie surrounds and get any other sort of audible distortion, and not just a change in response, then something else is wrong
It's not the cheap surround's fault

 

[colohiker]

Almost any Advent is worth getting the proper surround,.

In general I'd agree but in my neck of the woods, the prices of vintage speakers is so low that it's hard to justify the expense. In the last couple of years, I've sold a pair of Advent Prodigy and a pair of Advent Legacy for $40 & $50 respectively. Both pairs were in excellent shape with new foams and caps.

 

[Collin1141]

I was just trying to make it simpler. Sometimes audio geek speak doesn't help.

You've lost me here

 

[NH-MAN]

I Think what the OP might be wondering is there are probably not many manufactures of speaker foam so there is probably a great chance that most are the same given the same dimensions unless bought from a specialty manufacturer.

 

[spkrdtr]

Wrong. The foam DOES affect the physical parameters of the driver. Each driver has a unique amount of flex, change that and you change the physical parameters of the driver.

That is why one should buy the foam surrounds for the exact speaker they will be used in.

Agreed. Both the surround (rubber or foam) and spider impact the cone's compliance characteristics. Compliance is among the T/S paramaters. Cms and Kms are both compliance parameters that quantitatively express how much energy it takes to move the cone. The more supple the foam and spider the better the compliance number that impacts resonant frequency and quickness of response. Studies have shown the spider controls about 70% of total compliance and the surround, the remaining 30%.
Put a cheap, stiff Mat foam on an 8 inch Snell mid-woofer and there goes the midrange performance and bass extension will suffer.
I personally worked with the U.S. largest supplier of speaker parts to the trade (like Cobb and most of the others) to specify a foam they ended up sourcing from Europe for those Snell Vifa and Seas 8 inch woofers. c

 

[Collin1141]

KISS - Keep It Super Simple Many people don't understand all the audio 'geek speak' when they come to this site. They eventually learn it , but initially not so much.

I don't know what your deal is with the "audio geek speak"?
Woofers have parts, those parts have names
Woofers, as do all transducers, have electromechanical parameters
Discussions of woofer parts, like surrounds, re-cone kits, spiders, voice coils etc, and how they relate to performance, requires that those parameters be expressed
This is a thread about one of those parts and the functional role it plays AND the possible impact it can have on performance
In lieu of mathematics and actual measurements, there's not a whole lot you can do to "make it simpler" than to call things by their names
Pretty simple
Nothing "geek" about it
You said I made an error in my post, that it was "wrong"
What do you disagree with in post 28?

 

[Collin1141]

Agreed. Both the surround (rubber or foam) and spider impact the cone's compliance characteristics.

That was never in dispute or doubt
My post was in response to this

Alright, I'll put some 'fact' into a post. I've used the generic foams from Mat. For most speakers including EPI's it didn't appear to make a difference, but for a pair of Boston Acoustic A70's one speaker had noticeable distortion when cranking the Cream reunion DVD on my home theater system. While not definitive proof, another poster mentioned having a similar problem in another thread.

Here it is again, in the context that it was intended

A foam surround is not part of the radiating area, all it does is minimize reflections back into the cone, center it, and provide an air tight seal, that's it
The surround has nothing to do with the driver's T/S parameters beyond Xmax
A driver relies on the spider, the coil and the mass and profile of the cone for the low frequencies and mid band response, that plus the gap and box volume
Quality replacement surrounds like Rick Cobb's are always the best way to go and give you the best shot at getting things as close as possible to back where they belong specs wise, but all the cheap stuff that's close enough can or might alter is the Xmax of the driver, not create distortion
Meaning if it fits dimension wise
Changing the Xmax of the driver could change the driver's frequency response without a doubt, but if you do a refoam job with cheapie surrounds and get any other sort of audible distortion, and not just a change in response, then something else is wrong
It's not the cheap surround's fault

Note "but for a pair of Boston Acoustic A70's one speaker had noticeable distortion when cranking"
That was the what and the why of it, that whatever that distortion was he was hearing, IT WASN'T THE SURROUND'S FAULT
And from only ONE of his boxes
I never said surrounds would not or could not change the driver's FREQUENCY RESPONSE, that would be absurd. I SAID, IT WAS NOT THE CAUSE OF THE DISTORTION HE WAS HEARING
Being misquoted or accused of saying ridiculous things I did not say really drives me up the wall
I actually try to read for comprehension other member's posts

Changing the Xmax of the driver could change the driver's frequency response without a doubt, but if you do a refoam job with cheapie surrounds and get any other sort of audible distortion, and not just a change in response, then something else is wrong
It's not the cheap surround's fault

 

[SoundsAlike]

Rick Cobb's and MAT foam rings are identical. I would not pay the difference -- personally. The CD that is included isn't necessary, either. Rick Cobb is a great salesman.

 

[Collin1141]

Rick Cobb's and MAT foam rings are identical. I would not pay the difference -- personally. The CD that is included isn't necessary, either. Rick Cobb is a great salesman.

No, they are not
Rick's prices are right in line
Order up some surrounds for a LE10H-1 from Rick and compare it to what your guys would send you and then you'd understand
What's the problem with using a test tone VC alignment?

 

[spkrdtr]

The surround has nothing to do with the driver's T/S parameters beyond Xmax

I may be nit picking here but I disagree with this one sentence in your post #28. While the spider and surrounds extension capabilities can and will under certain circumstances limit Xmax when stretched to their limit, Xmax can fall short of that mechanical limit due to limited coil winding length on the former. As I noted in post #37, Mms and Cms are indeed T/S parameters and they can be affected by the surround's basic compliance characteristics.

 

[Collin1141]

I may be nit picking here but I disagree with this one sentence in your post #28. While the spider and surrounds extension capabilities can and will under certain circumstances limit Xmax when stretched to their limit, Xmax can fall short of that mechanical limit due to limited coil winding length on the former. As I noted in post #37, Mms and Cms are indeed T/S parameters and they can be affected by the surround's basic compliance characteristics.

You're not reading my posts, more importantly, what that post was in response to, but it doesn't matter, I'm tired of repeating myself
And, with this one, you're just agreeing with me, I think?
But yeah, no kidding, excursion limits can ultimately be determined by how much wire is on the former or if the former were to hop out of the gap, or if the VC ran out of windings beyond the pole piece during hyper-overdrive destructo-turn it up to eleven mode, then, all of this circular conversation misread misquote would sorta be irrelevant now wouldn't it?
But there CAN even be other scenarios besides that, ultimately defining Xmax on any given woofer
There's magnets and stuff to consider..............
But none of that changes the rightness of what I did say, or attempt to anyway
We're done, pick away
Maybe I just suck as a writer, it's a definite possibility
It's all good!

Carry on