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In Reply to: Foam or rubber surround? posted by sser2 on February 22, 2007 at 13:30:10:
Foam speakers usually will rot out after 15 years or so...often sooner!
I have 40 year old speakers, with rubber surrounds, that sound as good as the day they came from the factory....with NEW capacitors of course.
Foam surrounds are cheaper than rubber surrounds...pure economics.
Follow Ups:
Just because a material is more durable does not make it better. Infact, at on time the cheapo speakers of the 70s had a lock on rubber surrounds while the high end speaker employed foam.There are extremely expensive speaker manufacturers that have elected to use foam on selected drivers for reasons of sound and transient response. For example, in the *same* system the low frequency driver will employ a rubber surround while the upper bass driver will employ a foam surround. It was compliance and transient response issues that lead to the decision not the minimal cost difference.
To be sure, in recent years as rubber and other materials have been fashioned that match (or perhaps exceed) the behaviorial characteristics of their foam counterparts foam (with good riddance)has become less used (although new treatments for foam can extend life to more than twenty-five years.
Robert C. Lang
Indeed. Foam generally does a better job of damping sound waves so they don't reflect back into the cone, edge termination as it's called.Believe me, JBL didn't use foam on LE-14 and LE-15 woofers because it was cheaper. There was NOTHING cheap about those things.
Because of it's higher elasticity, rubber does a far superior job of 'edge termination'. Besides the small difference in cost, the down side of rubber is mainly that it is heavier than foam, thereby reducing the speaker's efficiency.Foam surrounds can also easily be made stiffer than rubber, and are therefore better suited for certain applications.
The new-age material for surrounds is a Thermo-Plastic Elastomer -
Santoprene. (www.santoprene.com). This offers advantages of both rubber (better damping, longer life), and foam (lower weight, controlled stiffness & lower cost).
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