4" Tangbands damaged?

[Kjeldsen]

I have two 4" tangbands. The other day I saw that one is "pushed" almost all the way in, and the other almost all the way out.

They can stille move (and seems to play fine), but it seems that some DC from the amp is triggering this. The very strange thing, is that it does not help removing the cables from the amp. What could have caused this?

[Cal Weldon]

Stacking the drivers face to face and placing them down on one of the magnets for a period. Sounds like sag taken to an extreme.

[Kjeldsen]

They are hanging on a wall, but have been laying flat on top of a subwoofer for 10 minuttes. Could that be it?

[Cal Weldon]

No it would take more like 10 years for that to happen. If it was DC from the amp the voice coils may be damaged and held in place because they partly melted. What happens when you move the cones with your fingers.

[Kjeldsen]

They move fine with no scratch and don't distort. I have been building speaker for 20 years, and have never seen anything like this.

[planet10]

Were they like this from the start, or did it develop?

dave

[Kjeldsen]

Originally Posted by planet10

Were they like this from the start, or did it develop?

dave

it wasn't there to begin with. I have just made some adjustments, and then I saw it. I have been playing around with some different amps, and one amp (class d) began to oscillate (NXD8950th based amp). It happend at night time, so I discovered it after several hours i guess. I didn't notice then, but it could have happend at that time.