[Jazz and Baroque]

Is there any reason to prefer foam or rubber as the surround on a subwoofer driver??  Is one more expensive??  Does it affect the sound??

Thanks,
Mike

[jules]

Rubber lasts longer and the last time I priced something with an option, cost more.

Sound ... I don't know 

jules

[Imperial]

Can we ask what specific driver it is? And how it will be placed, say level or on the side or what..

Imperial

[warnerwh]

Foam is an excellent material. Modern foam that is treated will also last a long time. I doubt there's much difference in sound quality. That will be more influenced by the rest of the driver.

If you ever get foam rot if you have old speakers you can just replace the foam surrounds. They don't cost much but are a pain in the ass to change.  After the swap you'd be good for 20 years with modern foams.

[TerryO]

This is a common question and deserves a good answer.

Foam is much, much better for Subwoofers than "rubber".

Not only do the new foam formulas last much longer, but they're a superior product for large excursion drivers. They will allow you to have prodigious Xmax while keeping the cone centered, yet a "rubber" surround that will allow that amount of Xmax needs to have such a tight, rigid spider, that it will either inhibit or limit the Xmax, or if it isn't rigid, then the cone will rock, which can be pretty rough on your voice coil. Foam surrounds also have another attribute that is almost a necessity in a high quality Subwoofer driver and that is, unlike "rubber," you won't get "Suck-back" when the partial vacuum inside the cabinet acts on the surround and causes it to invert at high excursion levels. One other factor, not mentioned often, is that foam is self damping and reduces or terminates standing waves on the cone  much better than "rubber". Finally, the actual cost difference in manufacturing is such an insignificant amount that it shouldn't be an issue.
Soooo...Always remember, foam spelled backwards is... moaf aa.

Best Regards,
TerryO

[Imperial]

Cool! Ok, what great sub drivers use foam then? Which is the better ones?

Imperial

[Jazz and Baroque]

I'm glad I checked back on this.     Thanks TerryO.

Imperial, I don't have a specific driver, but it will be front-mounted when I get one. 

And I am also interested in your request for recommendations for foam sub drivers, 12-inch for me. 

Mike

[Daryl]

Foam is always the safest bet for sound quality but rubber can be made more durable.

You will not get suckback with a properly designed surround for the application.

You used to see suckback a lot when there were few rubber surrounds available and one not up to the task would get used for a particular driver because it was one of the only ones available (especially in bandpass enclosures).

You see rubber surrounds on some of the best subwoofer drivers available.

TC Sounds
Dayton RSS
Peerless XLS
Kicker Solobarik

Among these you have high excursion, high linearity, high cabinet pressures/extreme durability and low Fs so it is not necessarily true that tight spiders are necessary or limited/non-linear excursion will result.

Creep is certainly a concern and clearences must be properly specified for the materials you are using.

For a company with the money to develop and verify the performance of a part rubber is attractive.

If you are small and must choose off-the-shelf parts then foam likely is the safest bet.

I have Lambda Subs with foam surrounds a small company now gone who used to manufacture subs with copper sleeves on hyper-extended pole-pieces.

Most rubber formulations (except those referred to as low damping rubber) become stiff at high frequencies and will damp cone resonances, foam does not.

Foam is very light and has minimal effect upon the motion of the cone and because of it's low mass to loss ratio foam damps it's own surround resonances but not those of the cone.

Rubber is excellent for bass-mids and midranges when used with semi-exponential cone profiles because it's high frequency loss if matched to impedance of the cone will damp the cones resonances and allow it to operate right through and beyond the frequency of the cones resonances.

I have Seas mid-basses with semi-exponential paper cones and rubber surrounds.

So you have two main approaches to driver design...

Straight profile cones with rigid material and low damping surrounds.
Semi-exponential profile cones with soft/high damping material and high damping surrounds.

[Daryl]

The Dayton RSS315HF is among the best drivers available and price is rediculously low.

It has a rubber surround but I see no reason to get an inferior driver just to have a foam surround.

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-464

[TerryO]

Cool! Ok, what great sub drivers use foam then? Which is the better ones?

Imperial

Here's a couple of recently updated versions of two of the best subwoofer drivers ever designed.

Shiva-X

http://www.diycable.com/main/pdf/Shiva-X.pdf

Tempest-X

http://www.diycable.com/main/pdf/Tempest-X.pdf

Best Regards,
TerryO