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  • Vibrating back panel

    This is a speaker cab, custom made for me for a 12" speaker. The back has two wood panels. The top panel is vibrating when guitar is played (low notes).
    I already tried attaching two strips of thin foam tape to the panel. It helped but hasn't stopped the vibrations completely.
    Right now there are just countersunk wood screws holding the panel to the back.
    I'm going to the hardware store now to get flat screws and washers.

    Any other suggestions to stop the vibes?


  • #2
    Maybe you can take a Pic and post it. I have a few ideas that might work but I don't want to advice on something that might not help.

    In the mean tine, a couple of questions. do these panels form a closed back or do that allow a semi open back. Next what type of wood and what thickness is this panel.

    The main reason that panel is going to vibrate and make noise is because it's actually resonating at the same pitch as the notes you're playing.
    Its scientific term is called sympathetic vibration. https://en.wikipedia.org/wiki/Sympathetic_resonance

    In essence that panel of the box is vibrating like a drum head. The way you get rid of it is by detune the panel by adding Mass,Rigidity and Absorption.

    Its super simple too.

    You need a wood strip a couple of inches wide, maybe a half inch thick at the most. The Wood they used for molding can be found at home Depot or Lowes hardware. Then you apply a heavy layer of 100% silicone calking on the strip (which you can also buy at the hardware store) and simply tack it down to the inside of the panel maybe an inch from the lower side where that panel vibrates the most and that should lower the pitch of the panel low enough to be out of the range of the guitar notes being able to make it resonate.

    In essence you're putting a soft pad over a drum head to keep it from vibrating.

    Just be sure the strip is out of the way so it can be mounted on the cab without touching anything. You want to use silicone over wood glue or builders adhesive. You don't want it to dry rigid and possibly add to the problem.

    You could probably do the same thing loading up a piece of felt with the silicone and gluing it to the panel but the wood will add more mass and its stiffness sandwiched between the silicone will have a much better wave canceling effect.

    Last edited by WRGKMC; 03-01-2018, 06:11 AM.

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    • #3
      Another option is to reinforce the vibrating panel with a strip of wood or even metal. You can attach it with screws, nails, glue or whatever. Put it on the inside and make sure it won't touch the speaker's magnet or frame. It will make the panel more rigid and add mass so that the resonant frequency is lower. I'm going to guess the two panels are different sizes because otherwise both would be vibrating. As it is, one has the right (or wrong depending on your POV) resonant frequency and the other doesn't. If it's a semi-open back cab with a gap between the panels and the offending panel is larger than the other, you can have it cut down so it's the same size as its non-vibrating sibling with the same resonant frequency.
      Official HCAG “Theory-Challenged Hack”
      Member of the IBANEZ ACOUSTIC ASSASSINS
      Proud Member of The Alvarez Alliance
      Member of the Schecter Society
      Person-2-Person on the Web

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      • #4
        Thanks WRG and DeepEnd for helping out with this one!

        Since I wrote and before I read your replies today I decided take another approach.
        There are two back panels. It is an open back speaker cab.
        The two panels are 5/16" thick.

        I checked my Princeton II and the panels are 8/16" (1/2") so I thought why don't I change
        the offending panel to 1/2"?

        I picked up a 1/2" plywood piece and had it cut to match the panel.
        The only thing I'm currently waiting for is my friend to drill the proper size hole
        to mount the hardware for the speaker jack.

        In the meantime I am finishing the panel the same as I finished the rest of the cab.

        I'm not sure exactly where you are suggesting I put the small piece WRG? It wasn't clear.

        Hopefully this thicker panel piece will fix the problem.
        It is strange that only the top panel was vibrating and not the bottom one.
        But then, it is the top one that has the jack connector and maybe that plays a role.

        While I was testing the vibrations, one time it was centered right at the jack where the
        wire was coming in. When I held the jack, the vibration went away. Other times it was the wood panel
        itself, and when I held the panel the vibrations stopped.

        I just made an interesting discovery right now.
        This speaker cab was made by the same company that made the primary cab for my
        amp. They messed up on my original order request and so sent the second cab as
        a 'replacement'.

        When I was comparing the panels on the back I noticed right away that the original cab
        had two additional screws on the back panels (at the top of the top panel and the bottom
        of the bottom panel). So the panels have 6 screws in total each.
        Whereas they only put 4 on the second cab they made for me.

        I won''t be able to add screws where they put them because they didn't add wood bars
        at the top and bottom of the second cab.

        Here are some photos of the panels. The original is there with the hole I had drilled.
        And the new has a marking where I will drill the new hole (off to the side).

        Click image for larger version

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        • #5
          i just removed the panel on my deluxe clone.
          the vibration and noise it made with it was too annyoing and nothing seems to fix it. yes i need to be more carefull when moving the amp, but it does not happen a lot so its not an issue to me

          Comment


          • #6
            Now that I can see, its obvious with the panels are only held in place at the two ends. Fender used to do that with baffles on some older amps, the theory being the entire baffle would move with the speaker and produce more tone. There is a difference in tone between thin and thick baffeling but for durability and minimal vibrations I'd rather have all 4 sides secure

            By the way, Using that thinner piece of plywood is only going to make your problem worse not better plus it looks awful compared to solid wood. Thin wood vibrates more then thick wood.


            There is a fix for this which is very simple.

            They didn't put a strip along the top because they cut corners. get some solid wood (not plywood because it will split apart) Cut yourself some wood strips for the top and bottom, glue and screw them into place then screw the top of the top panel and bottom of the bottom panel to them. Use at least 3 screws for each panel beginning about 3" from each side and one in the center. Problem solved

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            • #7
              Originally posted by WRGKMC View Post
              . . . By the way, Using that thinner piece of plywood is only going to make your problem worse not better plus it looks awful compared to solid wood. Thin wood vibrates more then thick wood. . . .
              The thin panel is the original, the thicker one is the one the OP proposes to replace it with. It's plywood. No, it doesn't look too good but it has more mass and it should be more rigid.
              Official HCAG “Theory-Challenged Hack”
              Member of the IBANEZ ACOUSTIC ASSASSINS
              Proud Member of The Alvarez Alliance
              Member of the Schecter Society
              Person-2-Person on the Web

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              • Jazzer2020
                Jazzer2020 commented
                Editing a comment
                Yes DeepEnd you are right about the panels. You can see a thinner and thicker one in the last photo.
                I am still waiting for my friend to cut the hole so I can test it out.

                In the meantime I also bought a couple of solid wood bars to mount at the top and bottom of the cabinet just in case the thicker panel alone doesn't solve the problem. I'll report back on how it goes as soon as I can.

                I wouldn't be at all surprised if the tolexed panels on most amp/speaker cab backs were plywood.
                Last edited by Jazzer2020; 03-04-2018, 10:51 PM.

            • #8
              Well now I'm Royally pissed!
              I got the hole drilled and attached the back panel.
              Plug her in and no sound!

              I start tracing the wires with the multi-meter.
              Connections make sense still.
              But no sound!

              I decide to de-solder and solder the speaker jack again.
              I don't like the wires I have nor the jack (it's got three leads instead of two)
              but it was working before (with my vibrating back panel).

              So now re-soldered, I decide to plug her in before I fasten the jack to the back.
              Sound is there!

              So I fasten the jack to the back panel and plug her in.
              No sound!

              I change speaker cab cord. Still no sound!

              Unfastened the back jack and try her again.
              No sound this time.

              Tomorrow will be a busy day, won't have time to do any work on this.

              I just want to SHUT UP and PLAY MY GUITAR! arrghhhhh!!!!











              Comment


              • #9
                Sorry to hear about your continuing cab issues. If it's a standard 1/4" jack, that three conductor jack is a stereo jack like for headphones. It will work in a pinch but it's not the right one. At a guess, I'd say the jack is damaged somehow and needs to be replaced. If you're near an electronics store or a music store that sells amp parts you should be able to pick up a new one that's the correct model. My alternate guess would be a broken wire from the jack to the speaker, possibly from getting kinked when you replaced the back panel. Best of luck and keep us posted.
                Official HCAG “Theory-Challenged Hack”
                Member of the IBANEZ ACOUSTIC ASSASSINS
                Proud Member of The Alvarez Alliance
                Member of the Schecter Society
                Person-2-Person on the Web

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                • #10
                  Weather stripping.
                  --------------------------------
                  www.VerneAndru.com

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                  • #11
                    OK time for an update. Good news!

                    First of all, I changed the speaker jack from stereo to mono, as it should have always been.
                    Which involved re-soldering, which was likely the source of the sound/no sound problem.
                    So that was taken care of.

                    Next the vibration issue.

                    The new, thicker panel seemed to fix the vibration issue. All except for a slight vibration when
                    I played the low E string open.
                    This vibration was probably always there, I just lumped it together with the other vibrations.
                    But since the other vibrations from the back panel were fixed, this one now stood out.

                    Hmmm..... where was it coming from. It was easy to track it down to the front of the speaker cab.
                    Pressing the top front wood of the cab stopped the vibration.

                    I had a hunch of what was going on.
                    This cab was made for me with a gap at the top front, about a two inch gap.
                    When I got the cab I compared it to a closed front cab and preferred the closed front sound.
                    So I made wood plug and screwed it in place (good thing I didn't glue it).

                    So when I was trying to track down the front vibration the first thing I decided to do was remove this front
                    wood plug.
                    Bingo! The low E string vibration went away.

                    And as a bonus, I actually liked the open sound now! So no need for the plug and fighting with the vibration.

                    Now I can finally shut up and play my guitars again.


                    Comment


                    • #12
                      Glad to hear you got it fixed. Now rawk on!
                      Official HCAG “Theory-Challenged Hack”
                      Member of the IBANEZ ACOUSTIC ASSASSINS
                      Proud Member of The Alvarez Alliance
                      Member of the Schecter Society
                      Person-2-Person on the Web

                      Comment


                      • Jazzer2020
                        Jazzer2020 commented
                        Editing a comment
                        Thanks Deep! Or Jazz on as is my case.

                      • DeepEnd
                        DeepEnd commented
                        Editing a comment
                        Okay then, Jazz on! (Unfortunately I don't know how to add a "rawk" smilie to a comment so this will have to do.)
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