Jono Bolton Posted November 1, 2015 Share Posted November 1, 2015 (edited) I recently picked up an old Peavey 2x15 cab and took it down to my band's practice space to use it in anger for the first time tonight. I noticed while I was playing that there's a very severe vibration, especially when playing round the 7th fret on the A string, and a low D (first fret on the bottom string as we tune to C#). I say a vibration rather than a buzz, rattle or distortion because my head nearly fell off the top of the cab while I was playing. Changing the EQ didn't make much difference; I usually have the bass boosted slightly, the middle set flat, and the treble cut back. In terms of volume, both the input and output controls are set halfway. Reducing the volume isn't really an option as trying to get my drummer and guitarist to be quieter is like herding cats. Does it sound like it may just be a case of tightening screws or adding bracing to the inside of the cab? Edited November 1, 2015 by Jono Bolton Quote Link to comment Share on other sites More sharing options...
casapete Posted November 1, 2015 Share Posted November 1, 2015 Try checking whether the baffle board is loose, maybe get a mate to play your bass whilst you listen or feel for the rattle. Physical vibrations in a cab usually easier (and cheaper!) to rectify than speaker unit problems. As you say, tighten every screw / bolt you can find too Good luck. Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted November 2, 2015 Share Posted November 2, 2015 Bracing in older, and for that matter many newer, cabs is often inadequate, if not missing entirely. That's what I'd check first. Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted November 2, 2015 Share Posted November 2, 2015 My first cab, nice sound, but no fun to carry up a flight of stairs! As I remember they are on castors, check the cab is secure on the floor. You say there is no buzz and mention no unexpected sounds so I'll assume all is working as it should. Are you using a lightweight amp. The amp sits on the smallest most rigid panel so I wouldn't expect it to shed the amp. I never had this problem but was using the Peavey MK 3 amp which was quite heavy itself. Quote Link to comment Share on other sites More sharing options...
Jono Bolton Posted November 2, 2015 Author Share Posted November 2, 2015 [quote name='Phil Starr' timestamp='1446453443' post='2899390'] My first cab, nice sound, but no fun to carry up a flight of stairs! As I remember they are on castors, check the cab is secure on the floor. You say there is no buzz and mention no unexpected sounds so I'll assume all is working as it should. Are you using a lightweight amp. The amp sits on the smallest most rigid panel so I wouldn't expect it to shed the amp. I never had this problem but was using the Peavey MK 3 amp which was quite heavy itself. [/quote] The cab has side mounted feet as well as the castors but even when I lay it sideways on the floor the vibration was still present. The head has just been cleaned out and all the pots cleaned so it's all working, but the noise definitely comes from the cab. I'll check the metal side stripes on the grille as they don't seem to be secured to anything at the front so it's possible they're vibrating. My head is an Ashdown ABM 300 which is reasonably small and lightweight, when I got the cab I tried it out with a Mark IV which may have weighted the cab to stop it vibrating. Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted November 2, 2015 Share Posted November 2, 2015 [quote name='Jono Bolton' timestamp='1446455545' post='2899401'] My head is an Ashdown ABM 300 which is reasonably small and lightweight, when I got the cab I tried it out with a Mark IV which may have weighted the cab to stop it vibrating. [/quote]A heavy head would be less likely to vibrate atop the cab, but nonetheless the cab panels should not be vibrating in the first place. A well braced cab won't even cause a pint to vibrate off. That's how I test my cabs. Of course, you can't take the results of only one test as valid, only after a dozen or so pints can you be sure. Quote Link to comment Share on other sites More sharing options...
3below Posted November 2, 2015 Share Posted November 2, 2015 [quote name='Jono Bolton' timestamp='1446455545' post='2899401'] I'll check the metal side stripes on the grille as they don't seem to be secured to anything at the front so it's possible they're vibrating. [/quote] Metal side strips on my old Peavey did just that. I seem to remember wedging them with sticky velcro or some such. The whole grille frame and metal sides were velcroed (or something like that) onto the baffle. It needs to be pushed quite firmly on from memory. Quote Link to comment Share on other sites More sharing options...
Jono Bolton Posted November 2, 2015 Author Share Posted November 2, 2015 [quote name='3below' timestamp='1446469624' post='2899523'] Metal side strips on my old Peavey did just that. I seem to remember wedging them with sticky velcro or some such. The whole grille frame and metal sides were velcroed (or something like that) onto the baffle. It needs to be pushed quite firmly on from memory. [/quote] Looking at it last night, the grille itself is wedged in pretty well, but the part of the side strips that folds over the front doesn't seem to be attached in any way; it's just the part that runs down the side of the grille. I'm sure that it would emit some sort of vibration, but I wouldn't have thought that it would be enough to move my head across the top of my cab. I may do away with them altogether just to remove any element of doubt. Quote Link to comment Share on other sites More sharing options...
Jono Bolton Posted November 2, 2015 Author Share Posted November 2, 2015 [quote name='Bill Fitzmaurice' timestamp='1446467948' post='2899510'] A heavy head would be less likely to vibrate atop the cab, but nonetheless the cab panels should not be vibrating in the first place. A well braced cab won't even cause a pint to vibrate off. That's how I test my cabs. Of course, you can't take the results of only one test as valid, only after a dozen or so pints can you be sure. [/quote] Agreed, the level of vibration is way too much, given I've used the head with countless cabs over the years and never had this problem. First job is to check all the screws and joins to make sure everything's tight, and then take a look at bracing. Is it worth running a brace from top to bottom? Would I need one running width-ways across the middle to support it? Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted November 2, 2015 Share Posted November 2, 2015 [quote name='Jono Bolton' timestamp='1446472357' post='2899565'] Is it worth running a brace from top to bottom? Would I need one running width-ways across the middle to support it? [/quote]This is what the interior of a well made cab looks like. Few do. Quote Link to comment Share on other sites More sharing options...
3below Posted November 2, 2015 Share Posted November 2, 2015 (edited) You have the answer courtesy of BFM. Having built a BFM cab the method is easy to carry out and works well. You can even glue the bracing strips to each other. My Barefaced cabs had/have a similar but simpler arrangement. How much you need and exactly where can be established by trial and error - just fit the strips / dowels as an interference fit The metal strip is stapled (memory again so may be wrong) to the side of the wooden grille frame. Agree this would not be making the head move, just a possible source of annoying vibration. Edited November 2, 2015 by 3below Quote Link to comment Share on other sites More sharing options...
Jono Bolton Posted November 2, 2015 Author Share Posted November 2, 2015 [quote name='Bill Fitzmaurice' timestamp='1446485189' post='2899756'] This is what the interior of a well made cab looks like. Few do. [/quote] Thanks Bill, I'd seen that diagram a couple of times whilst researching what I'd need to do. I take it that for a cab with multiple speakers I'd need a similar arrangement around each of them? Also, assuming that the cab is completely empty inside, would the vertical rods need to run the full height of it? I would have thought that that length of rod would have license to oscillate from the vibration. That said, I know next to nothing about the subject I guess if the rods are dense enough it wouldn't be an issue. Quote Link to comment Share on other sites More sharing options...
3below Posted November 2, 2015 Share Posted November 2, 2015 Time to get some bracing material and trial fit it. See what happens Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted November 2, 2015 Share Posted November 2, 2015 [quote name='Jono Bolton' timestamp='1446496506' post='2899874'] assuming that the cab is completely empty inside, would the vertical rods need to run the full height of it? I would have thought that that length of rod would have license to oscillate from the vibration. [/quote]With rods, and they can be square or round, of an inch diameter oscillation isn't an issue, as there are no forces in that direction, it's all tension and compression. FWIW I only use 1/2 inch plywwod, even with concert grade subs, and they don't vibrate. This illusltrates why: Using only the single red brace to connect opposed panels the vibration resistance of a 1/2" plywood panel is the same as a full inch of unbraced plywood. Using the blue braces as well increases the stiffness to the same as two inches of unbraced plywood. Commercial cabs tend to use thicker materials with inadequate or even no bracing, as that greatly reduces labor costs, and when corners are cut it's usually inside the cab, where it can't be seen. Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted November 3, 2015 Share Posted November 3, 2015 [quote name='Jono Bolton' timestamp='1446455545' post='2899401'] The cab has side mounted feet as well as the castors but even when I lay it sideways on the floor the vibration was still present. The head has just been cleaned out and all the pots cleaned so it's all working, but the noise definitely comes from the cab. I'll check the metal side stripes on the grille as they don't seem to be secured to anything at the front so it's possible they're vibrating. My head is an Ashdown ABM 300 which is reasonably small and lightweight, when I got the cab I tried it out with a Mark IV which may have weighted the cab to stop it vibrating. [/quote] Ok if I have this straight then your head is moving on the top of the cab and you have an audible vibration? My thought is the two may not be caused by the same problem. They may be of course. I had an unpleasant buzzing noise from mine. Upon examination the dustcaps in the centre of the speaker were loose and there was some separation of the corrugated surround from the cone. Not unusual in speakers of this age as teh adhesive becomes brittle with time. I carefully removed the dustcaps and glued them back down with Copydex, which is latex based adhesive. I then stuck the surrounds back with more copydex and used a paintbrush to then seal the whole circumference to the cone with more copydex. The speaker is still working after several years. You should be able to remove the whole grille assembly including the silver strips and operate the speaker without these. That will eliminate them as a cause. You can also remove the speakers which will allow you to go round tapping bits of cab to see where they are loose, if at all. Whist in there check the speaker cables inside aren't buzzing against anything. Quote Link to comment Share on other sites More sharing options...
Jono Bolton Posted November 7, 2015 Author Share Posted November 7, 2015 Having taken the grille off the front, I don't believe the vibration is to do with bracing; inside is split into two 1x15 enclosures by a shelf (for want of a better word) between the two speakers connecting the front baffle to the rear panel. There also a T-shaped brace running from the bottom of each enclosure halfway up the rear panel. It all seems fairly solid. One of the screws connected the bottom driver to the baffle wasn't tight and the screw holes on the speaker don't match the holes in the battle so it's not got a full compliment holding it in; as a result almost the whole left side of the bottom driver wasn't secured. I've tightened the loose screw and I'll have a go with the cab at next practice and see if it sorts it. Eventually I'll have to try and sort the screw holes so that both speakers are fully secured in place. Quote Link to comment Share on other sites More sharing options...
3below Posted November 7, 2015 Share Posted November 7, 2015 This sounds promising (pun unintended). My experience of Peavey cabs (early stuff, can not comment on newer kit) is that they are built like the proverbial outhouse. I unwittingly destroyed a BW driver when the cone to frame glue joint failed (old age). If I had been a bit more astute I could have saved the driver with Copydex as suggested above. Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted November 8, 2015 Share Posted November 8, 2015 [quote name='Jono Bolton' timestamp='1446929549' post='2903635'] One of the screws connected the bottom driver to the baffle wasn't tight and the screw holes on the speaker don't match the holes in the battle so it's not got a full compliment holding it in; as a result almost the whole left side of the bottom driver wasn't secured. [/quote]That would be problematic to say the least. The driver frame could vibrate against the baffle, with the same effect as rapidly whacking it with a hammer. Quote Link to comment Share on other sites More sharing options...
Jono Bolton Posted November 8, 2015 Author Share Posted November 8, 2015 [quote name='Bill Fitzmaurice' timestamp='1446990888' post='2903931'] That would be problematic to say the least. The driver frame could vibrate against the baffle, with the same effect as rapidly whacking it with a hammer. [/quote] When my head was moving forward off the cab, it was the left side moving forward rather than the right side, and that's the side of the speaker that wasn't screwed down. As the screw holes of the speaker overlap the screw holes in the baffle (but don't line up), what would be the best way to secure the speaker in place? Quote Link to comment Share on other sites More sharing options...
3below Posted November 8, 2015 Share Posted November 8, 2015 (edited) [quote name='Jono Bolton' timestamp='1447014006' post='2904199'] When my head was moving forward off the cab, it was the left side moving forward rather than the right side, and that's the side of the speaker that wasn't screwed down. As the screw holes of the speaker overlap the screw holes in the baffle (but don't line up), what would be the best way to secure the speaker in place? [/quote] T nuts will be the usual method since you can not access the back of the speakers. Pictures if poss to show the non lining up would help. You may need to glue dowels into the existing holes and redrill to fit new T nuts in correct place. Edited November 8, 2015 by 3below Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted November 8, 2015 Share Posted November 8, 2015 [quote name='Jono Bolton' timestamp='1447014006' post='2904199'] As the screw holes of the speaker overlap the screw holes in the baffle (but don't line up), what would be the best way to secure the speaker in place? [/quote]Pull the driver, fill the old holes, rotate the driver position 30 degrees, drill new holes. Quote Link to comment Share on other sites More sharing options...
Jono Bolton Posted November 8, 2015 Author Share Posted November 8, 2015 [quote name='Bill Fitzmaurice' timestamp='1447016570' post='2904225'] Pull the driver, fill the old holes, rotate the driver position 30 degrees, drill new holes. [/quote] I spent 20 minutes discussing this with my father and we didn't come up with anything as straightforward as this. It's embarrassing really. Quote Link to comment Share on other sites More sharing options...
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