Here's a picture example of why I don't trust the longevity of Poly speakers...

[Harvestor]

https://answers.yahoo.com/question/index?qid=20101228122803AA85JUo

 

[Harvestor]

http://audiokarma.org/forums/index.php?threads/how-do-i-repair-a-split-polypropylene-woofer.231423/

 

[Harvestor]

https://www.overclock.net/forum/18-...fix-cracked-cone-2.html#/topics/471940?page=2

Quick internet search brings up many many people with the polypropylene woofers cracking..
Seems my suspicions are correct..

 

[Guest159]

There are reasons nobody builds speakers with plastic cones anymore. They don't sound good.

 

[Tom Brennan]

There are reasons nobody builds speakers with plastic cones anymore. They don't sound good.

Well, I’m glad that’s settled.

 

[teal'c]

There are reasons nobody builds speakers with plastic cones anymore. They don't sound good.

https://www.amazon.com/Polk-Audio-F...0272258&sr=1-28&keywords=polymer+cone+speaker

• Dual 7" Polymer Composite Cone Drivers With Rubber Surround
• 6.5" Polymer Midrange Driver
• 1" Silk/polymer Dome Tweeter

https://www.parts-express.com/morel-msw-168-shallow-classic-series-6-dpc-cone-woofer-8-ohms--297-006
Shallow profile Damped Polymer Cone


https://www.parts-express.com/faita...ompression-horn-driver-8-ohm-4-bolt--294-1023
Ketone polymer dome diaphragm

 

[onwardjames]

This thread exposed a distant memory. When I bought my ESS 1B monitors (I was a saleseman at the time) my brother just HAD TO have the same speakers. About a decade later, he noticed one of his "bextrene rubber" woofers making a funny sound. I pulled the dust cap off and it had developed a crack going straight out from the center. I applied a thin line of JB weld, put the dust cap back on, and it never had another problem.

That's some good ol' Kentucky boy ingenuity!! Rock on, Rpb, lol. (inside joke, ya'll).

Well, I’m glad that’s settled.

Ahhh, Tom. Your subtle humor always makes me smile.

 

[Ross6860]

You were taught many things in school that no longer apply. As we grow, so do our definitions.

Like that sun going around the earth thing...

 

[Ohighway]

Well I have plenty of speakers with poly cones that seem to be getting along just fine.

That being said, I did run into a problem with a set of midrange drivers ( Elac 4/200 from IMF Supercompact II) that I discovered when doing a refoam. At first it appeared that the edge of the poly cone was brittle, but as I inspected further I found the poly cone was cracked near the voice coil. Seems the entire poly cone got brittle over time.

I see some have suggested yours having been overdriven or hundreds of watts poured into them. Maybe , maybe not, but certainly my midrange drivers did not have the problem of high wattages hitting them or massive amounts of excursion causing the cracking.

Finally got some pictures of what I was talking about here FWIW. You can see the big crack on the edge of the cone, and see where it cracked off near the voice coil. There was no warping nor any discoloration of the voice coil that would lead me to believe it was overdriven and/or overheated.

 

[Lavane]

Maybe the coils are pumping to hard? It might be a design flaw. I can see where if the coil is moving the cone far enough that the surround won't let the cone travel any more and flexes the cone at the coil end. Over time the cone would fail. I didn't own my CV's long enough to see this happen. I did have another set of speakers with translucent poly cones I used for 20 years. The surrounds finally rotted, but both the woofer and mid cones held up fine.

 

[Skywatcher]

Just because you can't appreciate something doesn't mean it isn't good.

True, a lot of people can't stand Rush.. I feel sorry for them.

 

[Harvestor]

True, a lot of people can't stand Rush.. I feel sorry for them.

Who wouldn't love a guy with half his brain tied behind......

Oh not that Rush.....

 

[Old Guy8]

I'm not going to be around in 40 years, to have concerns.

 

[drumbum]

The paper cone CV's are prone to buckling under the dust cap also.

The cyanoacrylate treatment is warrented.

 

[JimPA]

Most polypropylene cones have a number of minerals added during the manufacturing process now a days.

Over time many types of plastic do dry out and become brittle.