Speaker Cones

[the_wonderchild]

What type of material is best suited for a speaker cone, as i have read of different materials such as carbon fibre, paper and polypropelene being used.

Which material is the best for a speaker cone and which is probably the worst?

Also does the material used for the cone make a difference in the sound produced by the speaker and what type of material should surround the cone (is rubber better than foam etc.)

Thanks

[454Casull]

You will never have 100% of the audio population agree on one best material, either in general or for specific types of drivers (i.e. tweeters or subwoofers).

I'll skip over the best/worst choices for cones, because you can check out this site: http://ldsg.snippets.org/appdx-b.php3 which will give you an overview of the different cone materials available. However, I think that crystalline diamond is the best tweeter diaphragm material currently available...

As for the surround, rubber lasts much longer than foam, and I think both can be engineered for any level of damping/stiffness. No idea about the different sound they impart.

[kelticwizard]

I think foam has theoretical advantages, but it rots over time.

I disagree with many people about how long it takes to rot-I have seen foam speakers last near 20 years in good shape.

I think a lot depends on whether the speaker is placed near heat, or in the sun.

By comparison, rubber is forever, usually.

There are so many highly rated speakers which use rubber surrounds, that I would say that sonically, there is little difference.

Foam came out at a time when the normal speaker surround material was woven cloth. The "phenolic" treatment of this cloth, to prevent leaks, was similar to Elmer's Carpenter's glue! Those woven surrounds were known to be leaky. Foam is not leaky, so that was a big advantage at the time.

The rubber surrounds came out later. They are not leaky and have much of the flexibility of foam. But some manufacturers still prefer to go for the best combo of flexibility and airtightness, which is foam.

I lean toward rubber, if the driver is available. But I wouldn't reject foam categorically.

[noodle_snacks]

I seem to remember adire mentioning in one of their white papers that they used a foam surround on the shiva or tempest because they couldn't get a rubber surround with the right compliance and size to work or something

[Steven Kephart]

For cones, in general paper offers the best stiffness to weight ratio, especially when also considering price. But speaker building is a game of compromises. So it might be best in a design to compromise on one aspect to gain in another by using a more exotic material.

As for the surrounds, foam seems to be the best choice for subwoofers. This is because of a much better stiffness to weight ratio. Rubber has a problem of puckering, and to get rid of this you have to make it thick. This means added weight. Also, with modern treatments foam lasts much longer than rubber. This is because rubber tends to stiffen up over time, thereby effecting the performance of the driver.

Again, this is all general. The actual better choice for a given design will depend on the design goals. That is why you can never have a "best in all situations" answer.

Steven Kephart
Adire Audio

[Brushpilot]

Steven,
So is it safe to assume that most foam surrounds currently produced by the top speaker manufacturers are using this new technology and that rotting foam is a thing of the past?

[Pan]

"rubber tends to stiffen up over time,"

Are you saying that new modern synthetic/semi synthetic rubber gets old like natural rubber?

/Peter

[Magura]

Originally posted by Pan
"rubber tends to stiffen up over time,"

Are you saying that new modern synthetic/semi synthetic rubber gets old like natural rubber?

/Peter

Theese days synthetic rubber is a very reliable product. I would believe that even under the worst thinkable circumstances (heat and sunlight), such a material would not change any during 25 years. The carbon percentage used today is so high that you can allmost dismiss the uv issue.

Magura

[Kittle]

Just for the record,
my drivers with rubber surrounds are still going strong after 10 years of steady use and 5 trips in moving vans.

[Bull]

How about cloth[plasticised linen cloth sometimes] surrounds as used on pa speakers.
These are very tough.Although someone gave me some old Gauss pa speakers with white die cast aluminium frame and cloth surround;where both the cloth surround and cone had fallen apart due to years of use in direct sunlight.

I got them reconed now are are lovely pa speakers!

And a pic of the lovely Gauss too!