Voice coil rub

[MysteryFever]

Hey folks,
It seems I may have driven my new Celestion blue a little too hard and now there's a buzzing sound whenever I play through it. I'm sure the voice coil must be warped, I've checked the cone for tears and debris that could be causing noise but it's clean. I'm considering removing the dust cap and reforming the voice coil but I'm naturally a little hesitant to take a knife to my $280 speaker. Anyone done this before? Any tips or cautionary tales would be most helpful.

[jjman]

I would verify the rub by gently and evenly pressing the cone to feel for the rub. Or use it on a different amp to verify.

I did my 1st recone recently and had to do it twice. It was rubbing and I did not adequately clean the gap of the contamination the 1st time. If it's rubbing there is likely some contamination.

How do you reform a voice coil w/o doing a full recone?

[amplifiednation]

I just cut the dust cover off an ev12l only to confirm there was......coil rub!

As stated above you should be able to feel the friction when you push the cone in straight if it is rubbing.

Did you try a different amp or cabinet? I would do some elimination before cutting the speaker open.

In reference to reforming the coil, there are kits you can buy that have small plastic shims that you gently place in-between the magnet and coil, wait awhile (like a couple weeks) and see if the coil reforms into a circle with even clearance, and if it does, install new dust cap. I have not actually done this successfully yet though.

[Scumback Speakers]

If the voice coil is bubbled from too much heat (power sent to the speaker) you won't have much luck with reforming the coil since the tolerances are already compromised.

There's only about .005 clearance in there on the gap.

But I wish you luck.

[MysteryFever]

hmmm... I'm not feeling or hearing any friction when I press down on the cone. The full guitar signal is still coming through beautifully but the buzzing seems to have been added to it. Is there anything else it could be?

[amplifiednation]

Did you try other guitars? Other amps? Other cabinets? Those are all things it could be.

I thought my cabinet was buzzing last winter and then i found that the misses had put a whole bunch of metal shelving in a drawer of the corner of the basement and IT was buzzing!!!

[MysteryFever]

The easiest thing I could do was simply try a different speaker with the same amp and guitar. It sounded normal... plus the buzzing just sounds like it's being generated at the speaker locally to my ears. It can't be anything close by rattling or the cabinet because I've held the speaker in my hand while picking a note and still heard the noise!

[amplifiednation]

That's the exact same thing my EV12 was doing...and exactly how I tested it to finally make the decision to open it up.

I heard that buzzing coming right out of the speaker. It's a really bad sound. My thread was exactly like this one. A couple of the guys chimed in and I came to the assumption that it was vc rub.

Here's my thread in case you want to read through some of the info. I have some pictures showing whats underneath the dust cover (I never knew).

https://tubeamparchive.com/viewtopic.ph ... e+coil+rub

[jjman]

I've had some speakers with rubs that could not be felt. Others that could be felt. An amp problem can cause a noise that sounds like a rub. I've had that problem too. Also had rubs that sounded like a harsh amp.

[Scumback Speakers]

In my experience, speakers can have voice coil rub under a load (amp sending a signal to the speaker) but not when you do the four finger test without a signal.

There are way too many factors...heat, how far the cone travels, if the voice coil expands with a signal (which generates the heat that expands the coil), etc, etc.

If you heard it separately by isolating the speaker by holding it in your hand, then it probably only shows up under a load, and not when out of the cab on a bench. Had that happen many times.

Sorry!

[Bob-I]

The method I use to determine there's a rub is to take the speaker out of the cab, connect a signal generator and sweep through the full range of the speaker. Youll hearmthe rub easily.

Don't have a signal generator, google it, there's many available for the pc, some with free trial periods.

[Scumback Speakers]

For those who want to know what voice coil rub sounds like, here's an mp4 of one:
http://www.scumbackspeakers.com/wbq/J75 ... rbuilt.mp4

Here's the same speaker frame rebuilt correctly and how a speaker should sound on a sweep generator:
http://www.scumbackspeakers.com/wbq/J75CAbuilt.mp4