Acoustic B115 Mk II cab making irregular vibration noises on certain notes

[FJBass82]

I'm having some technical issues with my Acoustic B115 Mk II cab. Getting several irregular vibration noises on several different notes, though not every note is affected; primarily A and B on the G string, G and G# on the D string, G and G# on the A string, and several notes on the E string. If it makes any difference I mainly play in standard tuning.

If I place my ear up next to the upper front corners of the cab, the vibration noises appear to be most prevalent in those places. I removed the upper three and lower three screws that appear to hold the grill in place but it wouldn't move. I just wanted to see if maybe an internal screw or two had come loose.

Any suggestions? I've had the cab for two years now.

 

[FJBass82]

I was able to remove the cloth grill. Then I removed the speaker. All of the noise-dampening material inside was in tact. I ran my hand beneath it, all around the inside perimeter, but didn't feel anything unusual. I carefully inspected the speaker but didn't see any cracks, punctures, etc. I played my bass while the speaker was sitting outside the cab, and the fuzz-like vibration sounds were still there when I played the notes I said were making the noise, but it wasn't as bad. I also tightened all the screws inside and out. After putting it all back together the fuzz-like vibration sounds are still there, just as bad. I don't know what to do. I don't think that I'll be able to hear the noise while practicing with the band or playing a gig, but it's still annoying when I'm practicing by myself. And I don't like not being able to figure out what's causing the fuzz-like vibration noises.

 

[FJBass82]

I contacted a rep from Acoustic and gave him the information about the problem in detail. He thinks it's a resonant frequency that is vibrating a part of the amp speaker assembly because it's only certain notes that are causing the sound I described. Replacing the speaker would solve the problem.