Ampeg 1973 8x10 Cab

Discussion in 'Amps and Cabs [BG]' started by Brian McElwain, Sep 6, 2018.

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  1. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    A friend gave me his 1973 SVT 8x10 cab. It makes a fart like noize when I play a low b or c on a four string bass. I can't tell where its coming from. If its a speaker, which speaker? I'd like to determine the cause and fix it. Should I remove one speaker at a time through a process of elimination to find which speaker is farting at low C? Should I take them all out and test them one at a time?

    I took two of them out and noticed a speaker jack for the lower four speakers had come lose from its mount and had fallen inside the cabinet. Putting the wiring back together properly will be a challenge for me - I've never been good at wiring diagrams.

    To make a long story longer, the cones seem to be functioning well. The paper is in good shape. Only one dust cap is pushed in. Should I have them all re-coned just because there old or should I just re-cone the offending speaker?

    I never thought I would be working on one of these SVT cabs until it fell into my lap for free last week.

    IMG-0262.JPG IMG-0261.JPG
     
    Last edited: Sep 9, 2018
    Bugeyed Earl likes this.
  2. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    Nice! The 26th week of 1973.

    The cab is only rated for 240w, be careful when pushing it hard. This can cause buzzing or distortion.

    Be careful when mounting a speaker. The fasteners should be tightened evenly. Over tightening can warp the frame or over compress the gasket. A loose fastener, or anything else, can cause buzzing. So can the wiring harness up against a speaker cone. There are a lot of possibilities.

    No reason to recone them all if they are in good shape. The wiring is easy, all the speakers are connected in parallel. All the speaker terminals marked [+] (or sometimes labeled with a colored dot) are connected together and go to the jack’s tip. The other side of each speaker are connected together and connected to the jack’s sleeve.
     
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  3. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    Thanks, I noticed that when I hold one of the speakers firmly in place with my hand that the bad noise goes away. I'm going to replace the fasteners with torx screws and make it right.

    I reinstalled the lower jack and tested the speakers with a 9 volt battery. I managed to get all 4 speakers in the top half to move in the same direction. One of the speakers in the lower middle row had the polarity reversed and the other speaker doesn't move at all when tested. Two of the bottom speakers look like they have been re-coned. One of the speakers in the bottom row has a dust cover that's pushed in.

    I reinstalled the lower Jack. I can't remember how they had three connectors each (6 total) on the two positive and negative (4 total) tabs on the speaker that's connected to the side, bottom, and Jack! The Jack is connected to the top as well. Not sure if I should disconnect the top half from the bottom half so that you have to plug them both in, or leave them connected so you can use the bottom jack to connect to another cabinet.

    I'll send the dead speaker off to get a new cone. The top 4 speakers look identical and function well. The lower four all look a little different except for the speaker frames and magnets. I'm tempted to send all four lower speakers in to be re-coned.
     
    Bassbeater likes this.
  4. Bassbeater

    Bassbeater Guest

    Sep 9, 2001
    Before you start opening up the cab, try to determine if it is a speaker or a sealing issue, and which specific speaker.
    Find the note that makes the noise at the lowest volume level and loop it into the amp with software or a looper if you have one.
    With a microphone, go speaker by speaker and record the speaker closely. Call out the speaker number as you go.
    Listen to the recordings.
    If no single speaker is making the anomaly, try using a feather or cigarette smoke and go around the corners of the cabinet while the sound is looping. This is to look for an air-leak.
    Yes, you will need to start smoking.
    Ok, you can use incense if you in insist!
    Good luck!
     
  5. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    I hadn't thought of using my looper. That's a great idea. Too late to not take things apart however.
     
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  6. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    The issue of the non working speaker might be resolved in another way.

    If you have an ohm meter, disconnect the speaker wires and test across the speaker terminals. If you read a resistance in the mid 20’s the issue could be with the wires running to the speaker.

    The “dead” speaker might just need a solder joint reflowed at the terminal. The tinsel wire sometimes has a bad connection at the terminal that affects the signal flow to the speaker coil. Worth a shot.

    Try connecting a good speaker to the dead speaker’s wires and see if it also appears dead.

    Hopefully, the buzzing is just due to loose fasteners. Every speaker has a gasket that compresses as the speaker’s fasteners are tightened. If the gasket is too old and looses it’s ability to compress, it can be replaced.
     
  7. Bassbeater

    Bassbeater Guest

    Sep 9, 2001
    Yeah I saw your post update just after I posted. Hope you sort out the issues. Fantastic cabinet you have!
     
  8. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    So I've spent some more time trying to find the four best speakers so I can play a little on the top two rows. It looks like the installation of the speakers was "gouched" from the beginning. Note the screw in the photo in sideways. I have a photo of the "dead speaker" that is missing the connection to the coil. Were those factory screws?

    In the mean time I was playing through them and found a new rattle at C# on the E string. I'm beginning to wonder if I should just keep this as a collectors item and spend my time practicing instead. This free cabinet is burning a lot of time.



    IMG-0267.JPG IMG-0266.JPG IMG-0264.JPG IMG-0265.JPG
     
  9. Popps

    Popps

    Nov 26, 2009
    In the 8x10 cab that I had from around that era, if memory serves,
    the speakers were mounted with clutch head screws.
     
  10. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    Thanks, yes I think the buzz is due to an old gasket. I'm in the market for new speaker gaskets. I'm not sure if I can fix the missing wire on the dead speaker. I may send a few speakers off to be re coned. It would be nice to send them all off to be re coned but not sure. At least they should come back with new gaskets. And they would all look the same.

    I played my Fender Rumble 4X10 cab and then switched back and forth to the top four speakers on the Ampeg Cab. The Rumble is ported and had an open boominess to the sound. The Ampeg sounded tight and compressed - no boominess. I was playing flat wound La Bella's on a P bass. I'm thinking this may be a worthwhile project after all!
     
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  11. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    For me it would be worthwhile. Those are great cabs.

    Since the speakers work in pairs within a chamber, it is best to have two identical speakers in the same chamber. By identical, I mean the same cone type. If one speaker in the chamber is reconed and the other isn’t, the performance could differ. Original recone kits are not available so something close is hopefully used. The weight, stiffness, etc of each cone should be the same. So if you recone one, it could help to have both in the chamber done.

    If the replacement cone is exactly the same, this isn’t a big deal. It’s best to ask the reconer what they suggest.

    BTW, when they recone, they also change the gasket. All so called soft parts are replaced.
     
  12. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    Can you recommend a reconer? would you drive this with a 300 watt SVT with volume turned down or would you go with a 100 watt V-4B?
     
  13. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    The speakers are conservatively rated and people do use the early cabs with an SVT. Just be careful. A V4B is no problem and these 810’s sound fantastic with that amp.

    Most people don’t want to spend more on the repair that it would cost to buy a modern cab. A recone can cost almost as much as a new modern speaker. But with a recone, the advantage is that you have an original speaker.

    Recone costs go up with shipping to and from the shop. If at all possible, find someone close to home so you can take it there. It depends on where you live. The shop can check out the speaker and maybe repair it without a recone. It depends on the problem.
     
    Last edited: Sep 11, 2018
  14. Brian McElwain

    Brian McElwain

    Aug 12, 2018
    Great advise, thank you!
     
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