Speaker surrounds, material types???

[kenratboy]

I am aware of the three main types of surrounds on speakers.

1. FOAM - yuck

2. RUBBER - good stuff

3. ROLLED PAPER/CLOTH - professional or Third World

Why use one type over another. Foam is cheap and easy to work with, so why does Velodyne and Atlantic Technology put it on $1500 subs? Rubber is the more expensive choice, like what Klipsch uses, it doesn't rot and is more stable. Last, my professional JBL subwoofer uses rolled paper, WHY? Why don't they use rubber on pro speakers? The woofers cost $350 each, so its not cost. It doesn't have anything to do with compliance, as the Klipsch Reference subs are lower compliance than my JBL's, so what is it? Anyone know, have comments?

THANKS!!!

[mike stehr]

Okay, I'll give it my best, which is pretty bad.

Foam rots, doesn't last long, Your right. YUCH!

Rubber is great for the application, and can be used for long throw subs.

I guess because it can stretch for the massive movement required. Xmax.

It's probably second after Foam for life factor.

Cloth or treated Cloth(some have this black gooey stuff on them)will last a long time.

Now, Cloth surrounds are usually used in high effciency loudspeaker woofers and do not have much movement compared to a long throw sub. Xmax.

But like your JBL's they have a large voice coil, 18'diameter cone, they don't need to move much to do the job.

This is why high Effciency woofers with less Xmax are used in folded horn loudspeakers, like the Klipschorns, the horn is doing the bass chore.

(Or a ported design, as well.)

My Chorus woofers use Cloth, which I think is a EV varient or something.

Hopefully Tom Brennan can give us some good answers for the both of us, you got me curious now.

THANX!

This message has been edited by mike stehr on 02-25-2002 at 05:46 PM

[TBrennan]

The outer suspension on a woofer has 2 main jobs: to determine the compliance of the driver and to damp the wave after it reaches the edge of the cone. When a wave traveling outwards from the center of the driver reaches the edge it can "bounce" back and travel inwards again, this is not good and will cause spikes in the frequency response. Foam surrounds are very compliant and do an excellent job of damping the wave, if they didn't rot they'd be the perfect surround for high compliance woofers. Rubber surrounds are less compliant then foam and don't damp as well but are longer lasting. If a designer wanted a highly compliant driver but not so compliant as with foam rubber is a good choice. When a stiffly suspended driver is wanted then the corrugated cloth surrounds are the way to go. They can provide good damping (and many are treated with "goo" to aid damping) and provide excellent control on the driver's voice-coil position. (though most of the actual suspending of the cone is from the spider, not the surround). The designer can control the amount of compliance by the shape and number of corrugations. So the type of surround used depends on the driver's application, no one type is really superior. For a great deal of info on the whys and wherefores of woofer construction go to www.audioheritage.org Go to the library section, then to JBL articles, then to the article on T/S specs.