[James Romeyn]

I've been living w/ a rubbing voice coil in a 10" sub driver for some time (easier to live w/ this defect with three other properly functioning subs spread throughout the room).

Removed the problem driver today w/ the intent to replace it.  Whilst thinking about knocking the 40oz magnet off (more junk for the house) I was headed toward the garbage can w/ the cancer-ridden 10, pushing the cone forward WAY beyond the normal excursion limit...and let go just before breaking the cone/VC joint.   

The past few days I've been pushing the cone in/out but within normal limits, like picking a scab, thinking maybe this magical therapy would work out the sprain.  No dice...till now!

Pushed the cone in/out to normal limits...no rub!  Played the FIRST scene of the Star Trek prequel (HIGHLY recommended) w/ 20-something Hz effect...IT'S FIXED!  Jack Johnson is cranked loud right now and never sounded so good! 

Hey, if the driver seems fried anyway, go ahead and try it.  What do you got to loose?  Let go before the cone/VC joint breaks though. 
 

[JoshK]

I once read how you are "suppose to" fix a rubbing voicecoil.  The problem is it isn't centered in the gap.  What you are suppose to do is pry up the back plate (hard if the magnet is really strong) and put little wedges between the magnet and the back plate.  once you have the BP pried up you can slide it into center and then take out the wedges.  This is assuming the pole piece is what was off center.

[Pez]

Thanks for the info. I'm going to try this on my broken ass car stereo speaker. The right side one has been distorting for months.

[James Romeyn]

Josh
Send my dumb advice to the wastebin w/ this thread.  Played the first 10mins of the aforementioned movie up till the "Star Trek" title appears.  During that time a huge explosion occurs, producing the loud familiar "CRACK" from the direction of the same sub enclosure.

Oh well, "Never mind", as Rosanna Rosannadana used to say...sorry...Back to wondering if I should hammer off the magnet when the replacment driver arrives...

[Wind Chaser]

I once read how you are "suppose to" fix a rubbing voicecoil.  The problem is it isn't centered in the gap.

What you need to do is remove the dust cap and insert vertical strips (about 1/8-1/4" wide) of shim material inside the voice coil in between the voice coil and magnet pole piece to keep cone/voice coil assembly centered.  In order for this new alignment to stay in place, you will of necessity have to refoam the woofer.  Since the alignment is out, chances are someone had refoamed the driver but omitted the above step.


along with the rubber / foam surround. 

[James Romeyn]

This particular driver has its original surround/cone.

I did notice that the surround seems to be deformed from its original shape.  Meaning the OEM shape of the normal functioning drivers appear to be a symmetrical 180-degree half rolls, while the shape of this one is non-symmetrical, or of varying radius.  The drivers sat around for about twelve years or so, taped face-to-face as pairs.  The paper gasket material holding the surround to the frame is thick enough to have kept the surrounds from touching, but gravity may have caused the above described deformation.  IIRC the drivers were verticaly sited. 

I may carefully and judiciously apply heat via hat gun to the surround in one last likely vain attempt to reform the surround to its OEM shape.     

[Wind Chaser]

Given the problem as you describe it, the only corrective action is to replace the damaged surround.  There's plenty of instruction on the net that omit shimming the voice coil, but the omission of this step will most likely result in a poor alignment.

http://www.instructables.com/id/SPVB3WDFOVXONT9/

[jneutron]

Is the mounting surface flat?

John

[James Romeyn]

Is the mounting surface flat?

John

Thanks for the heads up.  Never considered that.  I'll check but I'm guessing the mounting surface is flat.  This driver has had symptoms for some time, even in prior boxes. 

As mentioned above, the surround seems to definitely be distorted in shape, which may be related to the symptom. 

Replacement should arrive shortly.  HT really makes quite extroardinary demands on output relatative to music.  Only one or two songs cause the untoward noise, but it's often heard in HT use.

[jules]

From what you say it sounds as though the distorted surround is the problem but it's also possible that you've got blistering of the voice coil. Age and operating heat can combine to form blisters/bubbles that raise the voice coil windings so that they touch the surrounding metal.

jules