Ampeg 8x10 Cab Malfunction

Discussion in 'Amps and Cabs [BG]' started by Brian McElwain, Oct 18, 2018.

  1. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    This is the "free" 1973 cabinet a friend gave me. I replaced the speakers, and it still makes a bad noise when I play a low C on the E string. I think I know where the noise is coming from now.

    I used a freeze pedal and played the low C on the E string. That allowed me to investigate the noise hands free. I noticed it stopped when I applied pressure to the bottom of the top left speaker, but is also stopped when I applied pressure to the wood face between the top row and the next row down.

    It appears that the wood face and the top partition is loose and vibrates at and around low C on a four string. But how to fix it? I was thinking of putting a few screws through the face and into the partition. Is this too crude a fix for an old cabinet? Any suggestions would be appreciated!

    Before I replaced all the speakers with new ones, I wish I would have just bought a new cabinet!
    Last edited: Oct 18, 2018
  2. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Is that the only note you're having trouble with? There are other possible causes, too...hard to say without seeing it. Wouldn't be looking to drill any holes or add screws just yet without investigating fully.
    Aqualung60 likes this.
  3. bobyoung53

    bobyoung53 Supporting Member

    It is likely the baffles between the 4 sets of speaker pairs. I used drywall screws on one of mine, no more noise. No one ever sees it unless you take the grille off.
    ObsessiveArcher and sissy kathy like this.
  4. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    Notes on either side of low C will get the same noise, but it fades off when you get farther from C. I agree, I don't want to rush into it until I know for sure. This is what I've done so far:
    • Tried tightening all the speakers down as much as possible.
    • Replaced all of the 1973 Alincos with new Eminance B810s. (I returned the Alincos to the guitar player that gave me the cabinet - he didn't know he was giving away 8 1973 Alincos until I showed him what was inside).
    • I noticed that all 8 speakers where wired together and the jack for the bottom four was wired but hanging loose in the third row down. I installed the jack in the metal plate in the bottom half of the cabinet where it looked like it was supposed to be.
    • I checked the wiring to make sure it wasn't vibrating on the speakers.
    • I used a 9 volt battery to make sure all the polarity was correct. (one of the original speakers had reversed polarity).
    After every attempt the same noise seemed to be coming from the same place when playing a low C on the E string. At first I thought it was a bad speaker, then a loose speaker. Now I think its the face plate vibrating against the partition cause when I push on the face plate at that location the noise stops. I don't know what else to check for.
  5. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    I'm tempted to throw a few screws in there. I have an outdoor gig on Saturday. Sure would be nice to show up with this cab and an SVT CL on top.
  6. bobyoung53

    bobyoung53 Supporting Member

    I did mine about 15 years ago, have had no rattles since then. You can hardly see them even standing right in front of it with the grille off.
  7. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    How long is a drywall screw?
    bobyoung53 likes this.
  8. bobyoung53

    bobyoung53 Supporting Member

    There are different lengths, I think I used maybe 1 1/2", could have been 2" but either way they go in quickly especially if you use a drill and a screwdriver bit but even by hand they go in easy, mine are flat back cabs. I bought one cheap because of the noise and figured it couldn't be too hard to fix. I went crazy with them, did the sides and everything, wasn't until I was almost done that I realized it was just the baffles vibrating against front of the cab, maybe they are originally glued to the front? Easy fix though.
  9. They come in a wide variety of lengths. I'd think 2" would do. But drill clearance holes through the baffle first. Otherwise the joint might not pull together tightly.
    zoonose, BadExample and sissy kathy like this.
  10. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    Right on, I'll give it a go. Maybe I can find some black screws to match the plate.
    bobyoung53 likes this.
  11. Most of them are black already.
  12. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    I'll drill holes first and get long screws.
    rufus.K likes this.
  13. bobyoung53

    bobyoung53 Supporting Member

    I wouldn't drill holes with those, they are made with their threads very slanted (don't know the correct word) and screw in very easily, they might not even hold if you drill pilot holes, buy some and check them out first, they go in very easily with no pilot hole and have a very sharp point, also start very easily. Once in though they will tighten up firm and don't come lose, like I said mine have been in at least 15 years. I think 2" would probably be best.
  14. Drill small pilot holes first, to full depth. Then enlarge ONLY the baffle portion to clearance. This will give the best result.
    Last edited: Oct 21, 2018
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  15. bobyoung53

    bobyoung53 Supporting Member

    You don't need pilot holes with Drywall screws in fact they would probably be detrimental, these screws are made to quickly drill into a wall with no pilot hole, they are thin screws with large slanted threads.

  16. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    OK good to know. I think I've used something similar on framing material. I also built a long fence once with screws and no pilot holes.
  17. 2tonic


    Dec 22, 2015
    First, try moving the offending spkr to a different location in the cab.....see if the noise moves with it or stays in the same place on the baffle board.
    If it stays in the same location THEN use screws/ glue to tighten it up.
    Yes, drywall (sheetrock) screws have a very steep pitch to the threads, which is why you DO want a pilot hole in the baffle only. Here's why.......
    Unless you have clamps and cauls to lock the baffle and partition tightly together (150~200lbs of force) , or you can lay the cab on its back and stand on the loose part of the baffle while you drive in the screws, then the screw won't pull the parts into secure contact, it will leave a little freeplay between the two pieces you're trying to lock up. If you drill a sufficiently large hole in the baffle ( just so the screw shank can pass through cleanly) then when you tighten it down it will pull the baffle board into hard contact with the wood behind it.
    Clutchcargo, SoCal80s, five7 and 4 others like this.
  18. mwbassace


    Jul 26, 2010
    N.W. Ohio
    +1 on the above post.
    What happens to cause that gap is the screw is biting into the 1st board then pushes the 1st board slightly away from the 2nd board as it tries/starts going into the 2nd board & never fully pulls the 2 together. Drilling the hole in the 1st board assures that the screws curved shank & head is what grabs the 1st board while the threads grab the 2nd pulling them tight.
    This isn't an issue when using them for hanging drywall & isn't always necessary, but in this case I'd drill the hole.
    I'd recommend a 2" long screw & an 1/8" drill bit for the hole.
    Clutchcargo, 2tonic and agedhorse like this.
  19. john m

    john m Supporting Member

    Jan 15, 2006
    Use a better screw than a drywall screw.
    Many better construction grade screws are available in the orange or blue store, or any other handyman source.
    seamonkey and InhumanResource like this.
  20. BadExample


    Jan 21, 2016
    1/16" PILOT hole full depth, 1/8" CLEARANCE hole for just the baffle. Lest you split the 45 year old wood that you are driving the screw into on edge. Without a pilot hole, the wood has to expand to make a hole for the screw. Good for hanging drywall, not so good when driving into old plywood on edge.

    Baffle thickness plus 3/4" is a good screw length. The average person can't drill a 2" deep 1/16" hole into wood without breaking the bit and making things worse, and 3/4" into wood will hold just as good as going any deeper. Get a 1/16" wood bit for drilling and pull it out every 1/4" to 1/2" to release the saw dust. The 1/8" clearance hole needs to be drilled 2nd with a regular metal type bit. Lower drill speed, light pressure. Like marriage, practice on scrap if not very experienced.
    pht2356, five7 and mwbassace like this.