66 B15n with vibration on G

[Jimmyupstairs]

Just put Eminance Beta 15A in my Ampeg 1966 B15-n and it vibrates and rattles when I play a G. I can damp out the vibration by placing my hand on the back of the cabinet and apply pressure but I am not sure what the permanent solution is. We play in G a lot so it would be nice to find a solution.

 

[BadExample]

If you can get a 1 x 2 cut about 1/4" shorter than the cab's internal width, and get that in through the speaker hole, you could put a heavy bead of PL on that and set it in place overnight (with the cab on its back). Then you could run a bead around all edges of the stick once it's cured and solid, including the gaps on the end. That should hold the back in place pretty well. You could measure, mark and use some black 1-1/2" drywall type screws from the back, but the PL alone is probably enough. Just make sure you have several inches between the magnet and the back of the cab so you can get the speaker back in place. PL is forever!

 

[Jimmyupstairs]

If you can get a 1 x 2 cut about 1/4" shorter than the cab's internal width, and get that in through the speaker hole, you could put a heavy bead of PL on that and set it in place overnight (with the cab on its back). Then you could run a bead around all edges of the stick once it's cured and solid, including the gaps on the end. That should hold the back in place pretty well. You could measure, mark and use some black 1-1/2" drywall type screws from the back, but the PL alone is probably enough. Just make sure you have several inches between the magnet and the back of the cab so you can get the speaker back in place. PL is forever!

What is PL some type of glue /epoxy ?

 

[bobyoung53]

The vibration could be from somewhere else though, I would be careful before gluing anything in a B-15.

 

[Bill Whitehurst]

If putting your hand on the back of the cabinet stops the vibration
there is a good chance the back is vibrating.
If you can get at the glue joints for the back,
maybe you can lay it on it's back and convince some glue to run into
any cracks you find.
If it just started after changing the speaker, I'd make sure
there are no loose speaker screws.

 

[JimmyM]

If putting your hand on the back of the cabinet stops the vibration
there is a good chance the back is vibrating.
If you can get at the glue joints for the back,
maybe you can lay it on it's back and convince some glue to run into
any cracks you find.
If it just started after changing the speaker, I'd make sure
there are no loose speaker screws.

No disrespect intended, Bill, but I would do anything else I could before gluing the joints again. Not in a B-15N.

I'd invite you to check out the Portaflex Wiki, where there is a whole section on Portaflex de-rattling. Many times, what is rattling is not what you think is rattling. The latches are especially prone to it. And yes, first thing to check since you just changed the speaker is all the screws. Snug but not overtightened. But it's darn tricky to de-rattle an old Portaflex. So many possibilities. Good news, though, is you can do it. Patience is key.

 

[Bill Whitehurst]

No prob Jimmy, just trying simple logic.
Rattles can be hard to find.
I had one that turned out to be stuff in the room rattling.

 

[BadExample]

What is PL some type of glue /epoxy ?

What all the kids are using these days. Just be careful, it's a lot easier to glue the wood than unglue it with this stuff. It usually comes in a caulk type tube, local at any DIY store. It holds forever, so be careful of that! If you do a rib on the back, you don't need to worry about clamping it, no nails or screws needed. If I were adding the rib, I would probably put a 1/4" bead on one edge of the 1 x 2 after getting it in the box, flip it over and press down until the PL starts to come out a bit, eye ball center the wood side to side, dry overnight, then lay a bead on both sides where the wood joins and fill in the gaps on the ends. Just remember, PL is forever.

 

[beans-on-toast]

I would try to narrow it down further. Pressing on the back can affect things that are seemingly unrelated because everything is connected.

It could be something loose inside the cabinet. It could be a leaking gasket under the lid. There are many possibilities. As Jimmy suggested, follow the links at the top to the Ampeg Portaflex Wiki. Here is the cabinet checklist: Cabinet Rattle and Buzz Checklist.

Your '66 cabinet should be what is called a single baffle unit. There are details in the wiki technical cabinet section that shows how the single baffle is constructed. Sometimes the baffle fasteners can be loose and it results in a vibration. I would check this first. Of course, it could be the speaker. Don't over tighten the speaker nuts. Again there are guidelines in the wiki.

 

[JimmyM]

No prob Jimmy, just trying simple logic.
Rattles can be hard to find.
I had one that turned out to be stuff in the room rattling.

I've had that, too! Drove me nuts for a week till I found it.

 

[Jimmyupstairs]

Duh problem solved...it was that vertical screw that secures the dolly to the cabinet that simply needed to be finger tightened. Thanks for all the help. I am not too familiar with these amps even though I’ve had this one for 12 years. The cabinet checklist was helpful because I had inadvertently over torqued the speaker bolts so they are finger tight plus 3/4 turn now

 

[beans-on-toast]

You got off easy! Cabinet rattles can drive you nuts.


Feel free to stop by the Portaflex Club: Official Ampeg Portaflex Club

 

[JW56789]

When I was constantly doing 6 and 7-night-a-week gigging, every six months or so, I'd go 'round every fastener on my cabinets and snug everything up. It's amazing, but those long wavelengths at relatively high SpL's will tend to find low torque and the F-Clef Elves will begin to loosen everything when you're sleeping . . . . . . .

 

[beans-on-toast]

That’s true. Seasonal changes with the expansion and contraction of the wood can also cause fasteners to loosen.

 

[beans-on-toast]

I've had that, too! Drove me nuts for a week till I found it.

Those dang dishes and Hummels.