Help with weird buzz

[Cretins]

Question...I've got a Celestion Blue 12 made in UK I bought new some 15 years ago and placed it in an Avatar open back 17" cabinet. It hasn't been used much in all that time (20 hours max) and everything looks fine and in excellent shape. The problem I just noticed is that whenever bass notes are played near this cabinet/speaker it buzzes and that is even when no power is applied to the speaker! I've got 4 other guitar amps in the room and any time I'm playing any of them the celestion blue buzzes like it plugged right in with them. I've tried tightening the connections to no avail. I put the cabinet on my coffee table, took the cover off and plucked a low E on my guitar I had hooked up to another amp, sure enough the speaker starts moving and buzzing and when I put my finger on it it stops. The only way I've found to stop the constant buzzing is to move the cabinet out of the room entirely. What could be wrong?

[nickb]

The nominal resonant frequency of a CB12 is 75Hz and low E is 82Hz - very close. When you stimulate something at its resonant frequency it takes very little energy to get things moving and so the cone vibrates. The question is how much? If large you can exceed the design limits of the speaker and that could conceivably cause a buzz. If the movement is slight then the speaker could have a damaged voice coil or something is loose - perhaps the mountings or the cabinet. Try pushing on things to see it anything makes a difference when you play low E. Try gently and evenly pushing the cone in hear/feel any voice coil rubbing without playing.

It's not the number of hours that damages a speaker. A minute of excessive power will do it. The CB12 is only rated for 15W and so it quite delicate.

[nosaj]

just for kicks and simplicity, will it do it unmounted from the cabinet?

nosaj

[Richard]

How does the speaker sound when you play directly through it? I'm guessing that there is something contacting the speaker cone, possibly the tinsel wires from the terminals to the voice coil.

[Cretins]

It actually starts buzzing when I pluck the D string or anything lower than that. I tried pushing and tightening everything and everything seems tight. I just hit a low E on my Tele hooked up to my Pro Reverb across the room and sat in front of the unpowered blue speaker 20 feet away, as long as the note sustained (15 seconds) I could press on the cone and it would stop, release my finger and it would start right up again, and i was able to do that about ten times in one note. I think the speaker is partially blown somehow and I'm just getting harmonics coming through. I'm just relieved that I isolated the problem to that one speaker, before I thought I was having issues with outlet voltage because I'd get the buzz no matter which amp I used.

[Tom Phillips]

Cretins,
It does sound like the speaker is damaged and needs recone. That is, unless you find something touching the cone like the tinsel wires or something between the cone and the grill cloth. If you just wish to silence the buzzing while you figure out what to do about it you might try electrically shorting the speaker terminals. That will dampen the cone movement. This is assuming that the present condition is just the unconnected speaker in the open back cabinet.
Cheers,
Tom

[Cretins]

Sorta sounds like a fuzz box.

[J M Fahey]

The voice coil takes only 15W, period.
It´s made out of thin light round copper wire wound on a single layer paper tube (think thin printer paper) , glued with nitrocellulose lacquer (think transparent nail enamel) .
Since it´s the lowest mass voice coil which can be made, sound is incredibly sensitive and detailed, chime jangle Paradise.

It´s also the weakest one, by far.

Nitro lacquer bubbles above 85C , weakens and becomes brittle above 90C and disintegrates above 100C (boiling water temperature).
Paper also toasts above 100C and becomes very brittle, because paper humidity dissapears .

So your speaker voice coil has one or more bubbles , loose copper turns or both.

Only solution is reconing with original parts or very close copies.

[Cretins]

Okay all, so some part is blown, I can deal with that. What I found incredible is that the speaker itself would influence the tone of any other amp in the room that I happened to be playing at the time. The buzz from that blown speaker would be in the background and would increase proportionally to the volume of any other amp I was playing to the point where I thought all of my amps were screwed up! Is it just because the speaker is blown that it has that characteristic?

[J M Fahey]

No.

Any amp you play in that room, or better said any speaker played there, will vibrate the Blue which will buzz.

Obviously, you will hear "all together" BUT the Blue is not "affecting the others" which of course sound fine.

In fact, you "should" notice that if, say, you are playing into a good speaker on your right and the Blue is on your left , the buzz comes from your left, not your right.

[Cretins]

No? Was that no in reply to "Is it just because the speaker is blown that it has that characteristic?" Because the Blue has always been in the same room but it never buzzed like that before. (Before it was blown.)

[nickb]

No? Was that no in reply to "Is it just because the speaker is blown that it has that characteristic?" Because the Blue has always been in the same room but it never buzzed like that before. (Before it was blown.)

All the inactive cones will be moving, just like your eardrums. Your hear just that one as it's damaged.

[Cretins]

Thanks Nick

[Cretins]

Took it out of the cabinet today and no, to my utter surprise it doesn't vibrate at all anymore. Dead quiet and still. So...is it still blown or has my cabinet somehow gone bad?

[Cretins]

Now with the speaker out of the cabinet and just laying on the table I hooked it up to my 1 watt Blackstar and it sounds great, no more buzz. So now I guess I'll try putting in back in and see what in the cabinet is creating the buzz. Don't know if I can but sure worth a try.