Vibration from thr cab!!??

Jd261808 · #1 03-21-2011, 04:15 PM

I have a 2x15 bass cab and when I play it vibrates like crazy. It almost sounds like the one speaker is blown. But they are brand new. Also, when I take the back off, the vibration is gone when I play. What can I do to get rid of this terrible noise? Any suggestions? So when the back is off it sounds fine and when the back is on it's vibration is bad. What you think?

billfitzmaurice · #2 03-21-2011, 04:21 PM

Quote:

Originally Posted by Jd261808

I have a 2x15 bass cab and when I play it vibrates like crazy. It almost sounds like the one speaker is blown. But they are brand new. Also, when I take the back off, the vibration is gone when I play. What can I do to get rid of this terrible noise? Any suggestions? So when the back is off it sounds fine and when the back is on it's vibration is bad. What you think?

I think your cab lacks bracing. Do not play with the back off, blown drivers can result.

JimmyM · #3 03-21-2011, 04:25 PM

what kind of cab is this that has a removable back?

**mikeddd** · #4 03-21-2011, 04:27 PM

What Bill said, absolutely! No offense, but going by what you posted, you have a lot to learn about speakers, cabinets and how they interact. Unless you want to be buying new speakers on a regular basis, I suggest you don't randomly do things like take the back off the cab and play it that way. The cab has a back for a reason.

For grins, what cab is this? Can you post pics?

**mikeddd** · #5 03-21-2011, 04:28 PM

Quote:

Originally Posted by JimmyM

what kind of cab is this that has a removable back?

Once he broke out the cordless drill, it became a removable back cab. Just guessin'

Jd261808 · #6 03-21-2011, 04:35 PM

Yeah I do not know anything about speakers. This is an Emperor 2x15 with Eminence Legends in it.

Calaverasgrande · #7 03-21-2011, 04:50 PM

My guess would be that you have the bass knob too far up on your amp.

Jd261808 · #8 03-21-2011, 04:53 PM

I dont get why that would happen? Never happen with any other cab with the bass knob up?

Robby Hoinsky · #9 03-21-2011, 04:55 PM

Sometimes small air leaks can sound like big rattles, check that it is sealed around the back, use some caulk or weatherstripping if you have to.

Tune your bass as low as you can and play the lowest note you can through it and get your ear right up to the seams and listen for leaks.

Robby

Jd261808 · #10 03-21-2011, 04:58 PM

Ok I could try that. I had tons of bass cabs in my life and never seen this before.

Jd261808 · #11 03-21-2011, 05:20 PM

Why also does it have that sound when I hit some notes and not all notes?

billfitzmaurice · #12 03-21-2011, 05:38 PM

Quote:

Originally Posted by Jd261808

I dont get why that would happen? Never happen with any other cab with the bass knob up?

Lack of bracing, as I already said.

Quote:

Why also does it have that sound when I hit some notes and not all notes?

Is the cab lined with damping? If not response will have all manner of peaks and valleys, and the lack of adequate bracing will be more apparent at some frequencies than others.

Jd261808 · #13 03-21-2011, 05:48 PM

The backing has a felt all around the piece that comes off. Perhaps it is not enough of a sealant and is letting air out?

Jd261808 · #14 03-21-2011, 08:15 PM

Ok so whom I bought it from, he said he thinks that the grill cloth was streched over the baffle and that is why the noise is heard. This make sense?

JimmyM · #15 03-21-2011, 08:21 PM

Quote:

Originally Posted by Jd261808

Ok so whom I bought it from, he said he thinks that the grill cloth was streched over the baffle and that is why the noise is heard. This make sense?

possibly. i've had rattly grillcloth before on my b-15 cabs.

will33 · #16 03-21-2011, 08:55 PM

As has been said, the cab may be a weak build that can't take it when hit with power and/or pumping speaker excursion, add to that lack of damping, etc.

Also you say these speakers are new or have been replaced....if they were not replaced with the same original spec speakers or something else that would work well in that size cab, with that particular tuning, this may not be your only problem, just your first one.

So what are we working with here in the first place, ie: cab type/model/measurements, tuning, speakers, etc.

Jd261808 · #17 03-22-2011, 05:01 AM

Well he did replace the one speaker with the exact same one. Maybe it's not installed correct. And, now that I have the cab he will not answer my email. Looks I been taken for a ride.

Arjank · #18 03-22-2011, 05:32 AM

Quote:

Why also does it have that sound when I hit some notes and not all notes?

Thats what is called resonance frequency. All objects have a resonance frequency, thats the frequency at which a certain object starts to vibrate with putting the least energy into it. Same as with car tyres, when they are not balanced well things start to shake and rattle at a certain speed. That certain speed "feeds" the resonance frequency of the unbalanced tyre which makes it shake.
So in your case it's a certain frequency produced by the speaker via your bass and amp that "feeds" the resonance frequency of one of the panels from the cabinet. Like Bill said, bracing will minimize this issue.
It might also be something else then the panel, maybe a screw or the speakerbasket buzzing against the baffle of the cabinet.