Wear Mark on Speaker Cone

Paul Hutzler · Post by **Paul Hutzler** » 8 Jan 2019 12:43 pm

What is this wear mark on my 20 year old JBL K130 15"? Or was it put there by the manufacturer?

Erv Niehaus · Post by **Erv Niehaus** » 8 Jan 2019 12:54 pm

It almost looks like a water stain.
Erv

Godfrey Arthur · Post by **Godfrey Arthur** » 8 Jan 2019 7:52 pm

Erv Niehaus wrote:It almost looks like a water stain.
Erv

Or dope from the surround

Craig A Davidson · Post by **Craig A Davidson** » 9 Jan 2019 7:26 am

I would say it is where the speaker wires are connected to the cone.

Godfrey Arthur · Post by **Godfrey Arthur** » 9 Jan 2019 9:48 am

Craig A Davidson wrote:I would say it is where the speaker wires are connected to the cone.

That too or this happened:

Paul Hutzler · Post by **Paul Hutzler** » 9 Jan 2019 11:09 am

Its not a water stain. Nor is it a lead wire. Its a wear mark...

Paul Hutzler · Post by **Paul Hutzler** » 9 Jan 2019 11:20 am

Its not a water stain. Nor is it a lead wire. Its a wear mark...

Godfrey Arthur · Post by **Godfrey Arthur** » 9 Jan 2019 11:21 am

Paul Hutzler wrote:Its not a water stain. Nor is it a lead wire. Its a wear mark...

You mean from the metal frame rubbing?

Erv Niehaus · Post by **Erv Niehaus** » 9 Jan 2019 11:34 am

Where is it, I don't see it?
Erv

Godfrey Arthur · Post by **Godfrey Arthur** » 9 Jan 2019 11:40 am

Erv Niehaus wrote:Where is it, I don't see it?
Erv

Erv Niehaus · Post by **Erv Niehaus** » 9 Jan 2019 11:48 am

Water stain, it's even blue.
Erv

Godfrey Arthur · Post by **Godfrey Arthur** » 9 Jan 2019 12:03 pm

Erv Niehaus wrote:Water stain, it's even blue.
Erv

Dog peed in the pool, Erv...

Jerry Overstreet · Post by **Jerry Overstreet** » 9 Jan 2019 12:13 pm

I would venture a guess that it's just discolored in that area from paper or cardboard on that area while being packaged or stored for a long time. JMO.

Paul Hutzler · Post by **Paul Hutzler** » 9 Jan 2019 12:34 pm

Look up chladni plates on youtube. I think what I'm looking at is a wear mark from a standing wave on the speaker cone.

Godfrey Arthur · Post by **Godfrey Arthur** » 9 Jan 2019 12:44 pm

Paul Hutzler wrote:Look up chladni plates on youtube. I think what I'm looking at is a wear mark from a standing wave on the speaker cone.

Interesting. But what material is being sonic-ally acted upon to create the mark?

Paul Hutzler · Post by **Paul Hutzler** » 9 Jan 2019 1:06 pm

Thanks for posting that GIF. I think the material being worked on is the paper cone itself.

Godfrey Arthur · Post by **Godfrey Arthur** » 9 Jan 2019 1:12 pm

Paul Hutzler wrote:Thanks for posting that GIF. I think the material being worked on is the paper cone itself.

Yeah, could be minerals in moisture absorbed by the paper cone and then acted upon by the sound waves over a period of time.

Paul Hutzler · Post by **Paul Hutzler** » 10 Jan 2019 3:36 pm

At this point, I'm convinced that the wear marks on the speaker cone are from something over driving the voice coil. What happened is this voice coil traveled so far that it pushed the paper speaker cone up and wrinkled it. It created the weird wavey pattern just because thats the way the paper cone will fold when its shoved forward. Make sense? This is all from the amp tech too by the way.

Jack Hanson · Post by **Jack Hanson** » 10 Jan 2019 4:09 pm

Does the speaker sound okay? If so, it would be a moot point with me.

Makes for an interesting discussion, however.

Donny Hinson · Post by **Donny Hinson** » 10 Jan 2019 6:55 pm

Paul Hutzler wrote:Look up chladni plates on youtube. I think what I'm looking at is a wear mark from a standing wave on the speaker cone.

Except that I don't think you'd see a standing wave-shape like that on a conical surface. Besides, any "wear mark" would likely have degraded the fragile surface of the paper cone. The surface of the cone (in the area under discussion) looks to be almost pristine? I think it's possibly the result of someone using a liquid (alcohol?) to clean/polish the aluminum dust cap, and capillary action spread it through a larger area.

Erv Niehaus · Post by **Erv Niehaus** » 11 Jan 2019 8:38 am

I'll bet some little boy peed on it!

Ervf

Stephen Cowell · Post by **Stephen Cowell** » 12 Jan 2019 9:17 pm

Probably dust. Are there marks on the back?

Donny Hinson · Post by **Donny Hinson** » 13 Jan 2019 8:16 am

Paul Hutzler wrote:Thanks for posting that GIF. I think the material being worked on is the paper cone itself.

I doubt that. Thin metal plates are the most commonly used materials for this type of standing wave demonstrations, and they use black plates because the table salt they normally use for a vibration medium will show up better.

Carl Mesrobian · Post by **Carl Mesrobian** » 16 Jan 2019 7:15 pm

Migrating oils from the adhesive from the dustcap ?? Has the dustcap been recently reglued?

EDIT - Is the surface of the cone wavy or smooth?

Paul Hutzler · Post by **Paul Hutzler** » 17 Jan 2019 3:36 pm

The wavey line is from "over excursion." The amp was cranked very loud at some point. The voice coil traveled too far. The paper speaker cone got squished as the voice coil pushed forward. The paper cone creased into the weird wavy line pattern.