View Full Version : Let's talk cabinet noise and rattle.
11-11-2011, 05:44 PM
I have had noise issues from cabinet throughout my years of guitar playing. Some rattle, some just make weird noises at certain frequencies.
I just put a bigger speaker in a small combo and it is getting a weird noise/vibration on low G notes. I am sure everyone has experienced something similar. How did you go about diagnosing what was creating the problem and how did you end up fixing it?
Share the knowledge.
11-11-2011, 06:06 PM
well...put the earplugs in, turn it up so that you can get the rattle with your fretting hand and start pushing on stuff in the cabinet with your picking hand. I found an OT rattle this way. I added some foam in between the iron and the chassis and it helped. You have to make sure you don't get burned or zapped....
11-11-2011, 06:21 PM
well...put the earplugs in, turn it up so that you can get the rattle with your fretting hand and start pushing on stuff in the cabinet with your picking hand.
I used this method to find a rattle in my Ampeg bass combo. Pressing on the baffle in just the right spot stopped the rattle, and a little Elmer's and a well placed extra screw took care of it permanently.
11-14-2011, 03:00 PM
Come on guys, there have to be a lot more secrets to finding these cabinet noises. Share your remedy's.
11-14-2011, 05:42 PM
You're battling a resonance issue. Everything has a resonant frequency that it vibrates at most efficiently...the speaker has a resonant frequency, the box has a resonant frequency and components of the box may also have their own resonant frequencies. In a guitar amplifier speaker box, all these resonances have to work together...when they don't, you get things such as buzzes, rattles, boominess and boxiness.
You're kinda stuck with the resonance of the speaker as the basis to build your box on so I encourage you to play with the other parameters:
Box cubic volume: even in a combo amp this can make a difference. I use gallon milk jugs filled with water to experiment with box volume; two gallon jugs in a combo amp can really alter the response.
Box material resonance: this is the natural frequency the box itself vibrates at. You can knock on the box an get an idea of where that frequency is in the spectrum. If you secure mass (blocks of wood or metal) to the box itself, it will lower the resonant frequency of the box; larger or denser objects resonate at a lower frequency. Individual components of the box (baffle, back panels, etc) may have their own frequencies that need individual treatment. It's virtually impossible to secure a 1/4" or 3/8" panel securely enough to make its resonance common with other, thicker components.
Open back cabinet port size: this is probably going to be the least well received info I have to offer here. The opening in the back of a combo amp can have an effect on resonance. I find that an opening that is between 125% and 150% of the speaker cone area gives the best dispersion and the flattest response. Varying this figure can tune the box to a certain degree.
There are some decent box formulas out there that can give you a very good idea what is going on in your box as it sits but you have to mathematically extrapolate the figures since the TS parameters of guitar speakers are well outside what typical box formulas are written for.
Good luck and have fun experimenting.
11-14-2011, 11:32 PM
Run a tone through it , sweep up and down in freq till you find the rattle then start pressing on things. Simple.
If you don't have a tone generator there are a few available online as freeware.
11-15-2011, 06:15 AM
Yep, run tone. This is where a signal generator or at least a test CD with different frequencies and sweeps comes in handy. Find the frequency that causes trouble and push and shove on things until you find the culprit.
One low end manufacturer's central tech guy would run music and start going around the cab with a fist full of finishing nails and a hammer until he found it and literally nailed it down. Then he'd drive the heads down under the tolex or rat fur. (Disclaimer: No don't do this, I don't)
11-15-2011, 12:48 PM
See I knew you guys had your ways of doing things. Thanks so much for the input.
11-15-2011, 11:13 PM
iPhone makes a great signal generator for this purpose.
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