Most guys do when they can.
No but seriously, sounds like the cab was not properly braced by the builder. My guess would be he is more of a guitar cab builder. Get the cab well braced and maybe add some foam if there isn't any.
Enjoy the benefits of a premium membership!
Upgrade Account
-
TalkBass has been independent since 1998. Add your voice.
Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
Join free Log in
Want zero display ads or expanded classifieds tools? Compare plans.
Need assistance with Amp/Cab vibrations
- Thread starter JDLowEnd
- Start date
-
- Tags
- assistance
Most guys do when they can.
No but seriously, sounds like the cab was not properly braced by the builder. My guess would be he is more of a guitar cab builder. Get the cab well braced and maybe add some foam if there isn't any.
There are mats designed for washing machines. It is a hard and dense rubber, designed to absorb vibrations.
You get them basically anywhere you get washing machines.
I cut one of these to size, so I can place a mat below my cab and one on top.
The mat below the cab makes the whole 'amp head dancing around' thing a bit easier and removes a bit of the shaking floorboard thing. The mat on top keeps the amp head firmly in position. Even a light class D one.
You get them basically anywhere you get washing machines.
I cut one of these to size, so I can place a mat below my cab and one on top.
The mat below the cab makes the whole 'amp head dancing around' thing a bit easier and removes a bit of the shaking floorboard thing. The mat on top keeps the amp head firmly in position. Even a light class D one.
Your Dually vibrates that much? Who built it? Have you talked to the builder about it?
A strip of 2" wide 1/2" ply (PL, clamps, stand up the ply horizontally) run a strip centered around the sides, top, bottom; two horizontal strips and a vertical one on the back panel.
Have a look for lining while you're in there, it most likely will benefit from it. Looks like a rear mounted, removable-back -panel cab. How well sealed is the cab rear?
Have a look for lining while you're in there, it most likely will benefit from it. Looks like a rear mounted, removable-back -panel cab. How well sealed is the cab rear?
+1. Cabs that are well braced don't do that, so we know without even looking inside that it's not well braced. Chances are if he doesn't know how cabs are supposed to be braced he made other mistakes too.
+1. The cone is a pump that pushes air. Whatever energy that goes into vibrating the cab is energy that's wasted.
Once (long, long ago) at a band rehersal we cranked up the volume for a rendition of Mississippi Queen and unknown to me (but obvious to everyone else) my Marshall head took a dive off the two 4x12 cabinets. It survived, but for the remainder of my time with that rig I always kept one eye on the head.
Since the subject has come up...
I’ve been doing a LOT of vibration measurements this past month; both beneath the cab and between the cab and the head. I’ll fill in all the experimental details in a separate thread; but, here are some of the spoilers:
Vibration transfer to the stage seems to be dominated by acoustic coupling. I’ve tried everything out there to eliminate it, including the commercially available devices (not just the ones I’ve made); and, it just seems to be a fact of life that if you are moving air at anything over 80 dB, you will cause resonant modes in the stage to vibrate. In my mind, this alone is a good argument for going ampless; but, OTOH, it’s also part of R&R. Anyhow, my finding is putting vibration absorbing devices under the cab doesn’t reduce vibration transfer to the stage.
All cabinets vibrate. Some are worse than others. Well braced cabs simply vibrate more near the edges than in the center of the top panels; but, the amp is still subjected to vibrations. Which may or may not matter to you. There isn’t any correlation between the level of vibration and the sound of the cab. I’m not going to assay every cab out there; but, I’ve looked at enough to see the effects. Large vibrations do not equate to a poor sounding cab. OTOH, very well engineered cabs (meaning more expensive) are quieter; but they still vibrate when you drive them. It’s simple physics. Newton’s Second Law.
Vibration transfer from the cab to the amp seems to be strictly a mechanical coupling problem. Some kind of vibration absorbing pad is a good idea, if you want the amp to stay put, and to reduce fatigue loading on the circuitry. Modern amps are pretty robust to fatigue cycling; but some components, such as tubes, not so much.
@Munjibunga and some others like drawer liner as a solution between the cab and the head. The drawer liner he is referring to is the stuff you get at Sears for tool boxes, and is a thin foam mesh. It actually can work as a vibration absorber on lighter (5 - 10 pound) heads, and it’s a whole lot better if you double it up. The 5 - 10 pound micros kind of squash it at a single layer, which reduces the vibration damping effectiveness, though it will keep the head on the cab. For a 75 pound head, it will keep the head from moving around; but, won’t damp the vibration transfer a whole lot. You can also use those foam kneeling pads you can get in the gardening center at WalMart, Home Depot, etc. or an Auralex. Just depends what you want to drag around with you.
More to come.
I’ve been doing a LOT of vibration measurements this past month; both beneath the cab and between the cab and the head. I’ll fill in all the experimental details in a separate thread; but, here are some of the spoilers:
Vibration transfer to the stage seems to be dominated by acoustic coupling. I’ve tried everything out there to eliminate it, including the commercially available devices (not just the ones I’ve made); and, it just seems to be a fact of life that if you are moving air at anything over 80 dB, you will cause resonant modes in the stage to vibrate. In my mind, this alone is a good argument for going ampless; but, OTOH, it’s also part of R&R. Anyhow, my finding is putting vibration absorbing devices under the cab doesn’t reduce vibration transfer to the stage.
All cabinets vibrate. Some are worse than others. Well braced cabs simply vibrate more near the edges than in the center of the top panels; but, the amp is still subjected to vibrations. Which may or may not matter to you. There isn’t any correlation between the level of vibration and the sound of the cab. I’m not going to assay every cab out there; but, I’ve looked at enough to see the effects. Large vibrations do not equate to a poor sounding cab. OTOH, very well engineered cabs (meaning more expensive) are quieter; but they still vibrate when you drive them. It’s simple physics. Newton’s Second Law.
Vibration transfer from the cab to the amp seems to be strictly a mechanical coupling problem. Some kind of vibration absorbing pad is a good idea, if you want the amp to stay put, and to reduce fatigue loading on the circuitry. Modern amps are pretty robust to fatigue cycling; but some components, such as tubes, not so much.
@Munjibunga and some others like drawer liner as a solution between the cab and the head. The drawer liner he is referring to is the stuff you get at Sears for tool boxes, and is a thin foam mesh. It actually can work as a vibration absorber on lighter (5 - 10 pound) heads, and it’s a whole lot better if you double it up. The 5 - 10 pound micros kind of squash it at a single layer, which reduces the vibration damping effectiveness, though it will keep the head on the cab. For a 75 pound head, it will keep the head from moving around; but, won’t damp the vibration transfer a whole lot. You can also use those foam kneeling pads you can get in the gardening center at WalMart, Home Depot, etc. or an Auralex. Just depends what you want to drag around with you.
More to come.
Last edited:
I say the cab weighs around 50lbs. It's close to the weight of my old Orange OBC115 cab, a little taller, but not as wide. It looks like I can take the rear panel off. I was told the speaker is an eminence 15lfa.
Attachments
Thanks a lot for the information and the science behind it. I have actually followed a few of your posts around the same issue and have a lot of respect for your information. I am worried about putting that heavy tube amp on top with the risk of rattling the tubes around in their sockets. The auralex stuff does seem like something that could work, albeit pricier, maybe an alternative foam solution would suffice. Once I can take the back cover off and take a peak inside I will update and see about bracing. In other posts I have seen people discuss the use of dowels as a brace, but I am thinking something a little thicker like a piece of wood, I guess the idea would be to drill from the outside of the cab to secure. Maybe also take a look about adding some battling if there is none.
- Apr 18, 2008
- 16,004
- 1
- 31,697
- Disclosures
- I'm highly opinionated and extremely self-assured
Regarding cost of the Auralex or any other device for that matter, only you can decide what makes sense. Is a ~ $50 device worth it to protect a ~ $1000 tube amp?
Regarding messing with the cab bracing; I’ve been using a Bergantino HD112 for the majority of my measurements. It is an extremely well braced cab. The top surface vibrates less in the middle than at the edges. But, the amp, a Genz Benz Shuttle 6.0, sits in a particular footprint, and the isolation devices have a slightly different footprint. These are the kind of details you don’t think about; but, which need to be controlled, if one wants meaningful comparative measurements. Anyhow, I also have noisier cabs that sound just fine. A more well braced cab will be quieter for the head; but, can not eliminate the vibrations altogether. As to whether the sound improves with added bracing, I suspect it doesn’t get worse; but, I would be surprised if the fractional energy loss was actually discernible vs porting/tuning. My sense is we are talking about two somewhat different aspects of a complicated system. In any case, I would personally work with the cab builder, if I were going to mess with internal construction. But, that’s me.
I reached out to him through Facebook as he has a public page. I checked the page and he has not posted anything or any updates since early 2017. I did reach out and sent him a message, but he has not responded to me. I can tell that he did "see" the message, indicated through messenger. I hope he is able to respond if not for just providing me with some information about the cab.
The most direct way to attenuate vibrations on opposing panels (in this case the top and bottom of the cabinet are the ones that you'd most like to tame) is to tie them together with a rod from one to the other.
The acoustical pressure in a speaker cabinet tends to push opposing walls away from each other (and then towards each other, depending on which part of the cycle you're talking about) at low frequencies - tying them to each other allows the acoustic forces to fight themselves, reducing the vibrations for the lowest frequency modes of the panels, which helps a lot. If also tends to cancel the acoustical output from those modes, which make the thing sound better as well.
I generally use a couple port cutouts (discs left over from cutting holes in the cabinet) inside of opposing surfaces as pads to tie the rod to (so the rod is coupled to some more area than just its diameter), and then screw a rod to those pads, going through the center of the cabinet on the inside. I run those screws right through the outside of the cabinet - my cabinets have screws plainly visible from outside - its a different look, but so far, so good.
The acoustical pressure in a speaker cabinet tends to push opposing walls away from each other (and then towards each other, depending on which part of the cycle you're talking about) at low frequencies - tying them to each other allows the acoustic forces to fight themselves, reducing the vibrations for the lowest frequency modes of the panels, which helps a lot. If also tends to cancel the acoustical output from those modes, which make the thing sound better as well.
I generally use a couple port cutouts (discs left over from cutting holes in the cabinet) inside of opposing surfaces as pads to tie the rod to (so the rod is coupled to some more area than just its diameter), and then screw a rod to those pads, going through the center of the cabinet on the inside. I run those screws right through the outside of the cabinet - my cabinets have screws plainly visible from outside - its a different look, but so far, so good.
Yes I agree about taking care of the amp itself and it would be worth it, for sure, to spring for the extra money to protect it. I have reached out to the builder but he has not responded to my message.
What are the rods you are using for the braces? Unfortunately I don't have the original cutouts, but I can easily purchase some new wood and secure them to the top and bottom panels.
Add an HPF to your signal chain to remove low end rumble frequencies.
I will just also add that while we have threads showing bracing methods, and the concept makes physical sense, I have seen zero actual measurements of the panel deflections in an A/B sense. While better bracing should reduce the vibrations, they do not IME eliminate them; and when the cab gets rocking above 95 dB, it is unwise to assume the vibrations are zero for a well braced cab. They aren’t.
