So, I'm having this really weird behavior from a sub I just rebuilt:
I was breaking it in with a sine wave at Fs for the whole night, and at the morning it suddenly started doing a cackling sound, characteristic of a misaligned voice-coil rubbing against the top plate.
I then switched off the amp to see in what direction it was misaligned, but as soon as I switched it off, it would no longer sound like it was rubbing on anything, even if I forced it to tilt with my hands, by applying more force to one side than the other. Seemed very properly aligned.
Then I figured it could only be because of the amplifier being on, I switched it on, and it began doing this rubbing noise when moving the cone.
I took it off from the amp and shorted the voice-coil, and again, it began doing this sound.
So, whenever there's a low-impedance circuit closed on the coil, it does that.
But my question is: WHY?
I don't understand how more damping can cause the voice coil to rub against the walls.
The only thing I can think about is that, when I'm pulling it by the cone with my hands, and the voice coil is shorted, the damping force on the voice coil is misaligned with the force the cone is imprinting on it, and the resulting movement is skewed.
But then again, the weird thing is, that no matter to what radial direction I force it, or tilt it, this rubbing sound never goes away, never improves substantially.
If I force it even more, then another, stronger rubbing sound comes on, making it even look like that only then it's actually rubbing against something.
I don't quite understand why this only began after hours of operation, perhaps because it heated and softened the glues, but the voice coil didn't even felt substantially hot either.
I'm just worried I'll have to rebuild the entire thing just because of this.
And by the way, it's not quiet enough to be ignored, it's clearly audible.
I was breaking it in with a sine wave at Fs for the whole night, and at the morning it suddenly started doing a cackling sound, characteristic of a misaligned voice-coil rubbing against the top plate.
I then switched off the amp to see in what direction it was misaligned, but as soon as I switched it off, it would no longer sound like it was rubbing on anything, even if I forced it to tilt with my hands, by applying more force to one side than the other. Seemed very properly aligned.
Then I figured it could only be because of the amplifier being on, I switched it on, and it began doing this rubbing noise when moving the cone.
I took it off from the amp and shorted the voice-coil, and again, it began doing this sound.
So, whenever there's a low-impedance circuit closed on the coil, it does that.
But my question is: WHY?
I don't understand how more damping can cause the voice coil to rub against the walls.
The only thing I can think about is that, when I'm pulling it by the cone with my hands, and the voice coil is shorted, the damping force on the voice coil is misaligned with the force the cone is imprinting on it, and the resulting movement is skewed.
But then again, the weird thing is, that no matter to what radial direction I force it, or tilt it, this rubbing sound never goes away, never improves substantially.
If I force it even more, then another, stronger rubbing sound comes on, making it even look like that only then it's actually rubbing against something.
I don't quite understand why this only began after hours of operation, perhaps because it heated and softened the glues, but the voice coil didn't even felt substantially hot either.
I'm just worried I'll have to rebuild the entire thing just because of this.
And by the way, it's not quiet enough to be ignored, it's clearly audible.
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Never mind, I just found out the actual issue: One of the lead wires was not properly soldered to the lead and it was intermittently disconnecting and reconnecting while the cone is moving.
This causes a quick variation in the current through the voice coil, which produces this sound. It isn't rubbing against anything, lol.
This causes a quick variation in the current through the voice coil, which produces this sound. It isn't rubbing against anything, lol.
