Thumping in my 2x12 cabinet, what might be the cause?

[ryanm74]

I have a 2x12 cabinet with two vintage EV SRO speakers in it. When I play through it, I can sometimes hear a "thump". Typically it is when I play a muted low note. If I play and immediately mute, I can often make the "thump" happen. It does not seem isolated to one speaker or the other. Could this be the cab making the noise? Would a board (ala Marshall) from front to back help with this? It does not seem like the speakers, but is that something anyone has had happen to them? I am asking this before I go to the trouble of removing the 76 screws (exaggeration) that hold the back on and trying different speakers. I would really appreciate any help. The cab sounds excellent besides this, and it is not always noticeable. If it makes any difference, I usually use a Super Reverb head with this cab.

[Milkmansound]

make sure all of the screws that mount the speakers to the baffle are torqued evenly - think of it like tuning a drum head.

I usually use my little Bosch cordless screwdriver to accomplish this - I start at 2, and then cycle up the clutch until I reach 4 or 5, going around the speaker clockwise (or counter clockwise). You don't want to go too tight, but you do want to ensure that they are even and won't loosen back up (which can create an annoying rattle as a Keps nut vibrates around on the screw)

[RevD]

It's possible a board front to back could help. I had a 78 4 input master volume 100 watt marshall JMP that was plexied. I had a 2x12 Fender from the 90's and I put a pair of Eminance Wizards in it. That poor old Fender bottom wouild rattle and thump something terrible at even medium volumes. I never solved it because I didn't want to mod the cab so I went back to one of my 4x12's. It is possible to have the baffle resonate and if your game it's not a huge thing to try adding a cleat from front to back to give it a try. It just needs to be solidly connected to the baffle and sufficiently long enough when you put the 800 screws back on. Just an opinion but I know what I heard with my cab. It not only thumped but resonated the jack plate. (It was a VERY healthy Marshall I might add ) Good luck with it. As far as the cause, I'm not a speaker expert but I suspect in my cause I had two efficient speakers (103 db @1 watt etc is the Wizard's spec) and its cone movement wqs such that it was resonating the baffle and back of the cabinet. That's what it sounded like to me anyway.

Regards,

Don

[M Fowler]

When I play through it, I can sometimes hear a "thump".

That's your room mate indicating that you need to turn that thing down.

[ryanm74]

I should have also mentioned that the thump happens a moment after the sound comes from the speaker. So like this, I hit a low E, then mute. A moment later I hear the thump.

[Marioverkill]

Did you try another cabinet or different amp in that cabinet ?

Mario

[ryanm74]

I tried the amp with another cab and didn't have the problem.

[Reeltarded]

Yah, that's wood knock. There is no center post? You are completely beating that poor little cabinet to death.

Most modern Marshall cabinets do this until I tune the center post. (read shim with wedges and a mallet)

[ryanm74]

Thank you for the replies, the situation is fixed!

[amplifiednation]

what was it that fixed the problem?

[M Fowler]

It needed a support post to prevent the it from flapping. More common in 4x12 cabs then 2x12 cabs.