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Vibrating Noise

DerHoggz

DerHoggz

I like cats :|
Inactive
Feb 13, 2009
1,704
1,037
33
Western Pennsylvania
#1
My combo amp vibrates at certain frequencies, F# and G to be exact. What is it, I'm guessing resonant frequency since it is only around those areas. I can still hear the note, but it sounds like something is flapping around.

It has a crappy little horn in it, could that be the problem.
 
#3
Check the snugness of the screws holding down the drivers and handles if any. If the cabinet has sockets for plug-in casters, remove one and check for little openings/slits. I have found that air escaping through the slits causes a lot of strange sounds. One more thing... If there is a wire going through the cabinet to the speaker, stuff a little piece of foam into the hole which is usually much larger than the wire. I have also found that wires running from a crossover in the cab can vibrate if they are touching something... same for wires in the head. Good luck.
 
#7
Yeah, loose wires can cause problems. Make sure they don't touch the speaker loosely in any way. Shorten them by doubling up some of the wire and keep it together with a zip-tie or electrical tape or even a twisty-tie.

You should be able to slide the head out if you suspect the vibrations coming from there. Should be four screws on top of the amp or on the side. I had a Peavey MicroBass that had a loose component on the board that just needed to be snapped in. It caused the speaker to sound like it was blown. All was good after the fix.
 
#8
Thanks for all the help so far.

I got the head out, nothing looks messed up, anything specific I should look for befre I put it back in? Once I do that I will shorten the wires. I thought it might have been the sound isolation stuff on the inside, so I stapled it sown, but that didn't help.

I disconnected the horn but it still happened, so that isn't the problem.
 
#9
Where does the vibration sound like it's coming from? Have you tried the amp in a different room. Sometimes something in the room can vibrate and it can sound like it's coming from the amp.

You could also try cleaning all the jacks with some Deoxit or contact cleaner. Spray a little on a jack plug and run it in and out of all the jacks especially the send and return jacks in the back. I have had situations where it sounded like a vibration but was actually a buzz on certain notes because of oxidized connections... maybe worth a shot.
 
#11
No, don't use WD-40. You can get contact cleaner at Radio Shack or maybe even a hardware store. A music store would probably carry Deoxit.

I'm not sure what other suggestions to offer. It is sometimes very difficult to pin point a vibration. You could try laying the cab in it's back, front and sides and see if the vibration is still there. Get a long cardboard tube and have someone play the notes and use the tube like a stethoscope. Of course don't play so loud as to blow out an eardrum while listening through it. :D

You're sure it's not the diver?

Edit: One more thing to check. The two wires that come off the speaker voice coil that go to the connectors on the speaker frame. Check to see that they do not touch or rub the speaker cone. They will surly make a vibration/distortion noise if they do. You can gently bend them away if they do. When replacing the driver, turn it to make sure the wires hang away from the driver.
 
#12
Alright, I pulled the driver out with it still connected and played through it, there was no noise. So, the amp and driver are not to blame, it must be something in the box or the box itself.

Could it be the sound insulating junk, its about 1/4" thick and loose and like pulled apart cotton swabs. I might just rip it out.

It has a port, I held the port while playing to stop it from virating in case that was the problem, but it didn't stop the noise.

I'm leaving for a weeklong gig tommorrow at 5 AM, so hopefully you can get back to me before then.
 
#13
it could still be the tweeter! I know you've already checked it but Ive had the same problem and it was the piezo tweeter (even tho I could still hear the noise with the tweeter turned off).
something inside the plastic tweeter was resonating at certain frequencies. The only way to rule it out is to remove the tweeter from the box and temporarily seal the hole with a scrap of wood.

Sounds like your being very thorough. Good luck.
 
#16
Rattle chasing is a PITA sometimes. New environments always help, though, so maybe getting out for a few days with it will make a difference. I wouldn't worry too much about it at this point, though. It'll be fine for a few days...the drums will probably drown the worst of it out.
 
#20
Ya, been there many times with cash. Maybe it's just an interaction with the rooms you've been in, or maybe you just need to back down on the volume a little. Either way, you'd be surprised how much stuff gets buried. And even if it doesn't, just blame it on something in the room rattling ;)
 

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