Is My 1966 Ampeg B-18 Cleveland Speaker Blown?

Discussion in 'Amps and Cabs [BG]' started by OldFenderPlayer, Feb 16, 2020.

  1. I recently had some maintenance done to the head of my 1966 Ampeg B-18N Port-a-Flex, that has its original Cleveland speaker; the amp was working but making static, and before there was no distortion from the speaker - at least that I was aware of; I only took the head to his shop. I can find the tech's notes and post them if it turns out that they are important.

    When I got the head back and plugged it in, it sounds like the speaker is blown because while the sound is powerful, its also very distorted, like an overdrive.

    I moved my 1970s B-15N next to the B-18 and plug it into the B-18 speaker, and get the exact same distortion.

    1. I plug the B-18 head into the B-18 cabinet and its a distorted tone.
    2. I plug the B-15 head into the B-18 cabinet and its a distorted tone.
    3. I plug the B-18 head into the B-15 cabinet and its a clean tone.
    4. I plug the B-15 head into the B-15 cabinet and its clean tone.

    Here are photos of the cabinet: the full front view without the grill; a close-up of the cone; and the two interior connections.

    Does it seem like the speaker is blown? Or could it be related to the recent repair?

    Attached Files:

    Border and dbase like this.
  2. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Ya, it does sound like the voice coil wore out. Push in on the cone gently with even pressure all the way around. If you feel a rubbing feeling, then the voice coil is shot. If not, look elsewhere for the problem.
  3. Thanks Jimmy, I will try that, but on Tuesday. I just put the amp back together and pushed it in a corner. The string band meets here tonight and tomorrow it’s the rock band.
    JimmyM likes this.
  4. Is the Port-a-Flex Club still in existence? I searched for it to post there, but couldn't find it.
  5. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Official Ampeg Portaflex Club

    "Portaflex" is all one word, so that's probably why it wasn't turning up for you.
  6. Boy, so many questions. Let's assume that after 54 years the Cleveland speaker's voice coil wore out.

    > Is this fixable?
    > Is it worth fixing or should it just be replaced?
    >Who does this type of work? Fliptops?
    >Any tips of packing a 50 year-old 18 inch speaker for shipment?
  7. dbase

    dbase Gold Supporting Member

    Jan 3, 2008
    South Jersey, USA..
    The 1st amp I ever owned was a Standel, the 2nd was a brand new 1966 Ampeg B18.. brings back memories .. miss that amp.
    bobyoung53 and OldFenderPlayer like this.
  8. beans-on-toast


    Aug 7, 2008
    Remove the speaker from the cabinet and test it on it’s own. The tinsel might be rubbing and the issue isn’t the coil.

    It’s a very good speaker and not easy to replace with the same make and model. This is a good replacement: Peavey 1801 18" SPEAKER FOR B18, B18X - Product Details. It’s important that the speaker fits with the head flipped.

    Your speaker might be an 8 ohm, or it might be a 16 ohm. Figure out which you have. The same output transformer was used, it was wired differently depending on the speaker.

    When shipping a vintage speaker, I either mount it to a piece of plywood cut to fit the box or I use an expanding foam kit. The foam is best because it is lighter and fills the voids. Some speaker manufacturers use this method, others have custom packaging. For OEM they may ship on a pallet. It really is best to seek out a local re-coner, shipping a speaker costs a lot. Yes, fliptops does recone. I have no experience with his speaker guy.
    Last edited: Feb 17, 2020
    OldFenderPlayer and Jim C like this.
  9. Soulfinger


    Sep 20, 2004
    Houston, TX
    My 2 cents worth is that for a B18 speaker replacement, you're better off fitting a 15" with an adapter plate.
    SherpaKahn and OldFenderPlayer like this.
  10. bearfoot

    bearfoot Inactive

    Jan 27, 2005
    Chittenango, NY
    Beautiful workhorse amp and cabinet, my 2 schillings is to keep it original (repair) , if that is affordable to you.
    It may not sound the same though, as it did before it blew. You'll just have to keep playing another 52 years :bassist:
    OldFenderPlayer likes this.
  11. Eddie LeBlanc

    Eddie LeBlanc

    Oct 26, 2014
    Beaumont, Texas
    Don't create no problem, won't be no problem.
  12. Martin Beer

    Martin Beer

    Dec 4, 2004
    Could it be that the B-18 head is just putting out more power now it's been repaired, and that's caused the speaker to blow?
    bobyoung53 likes this.
  13. SherpaKahn


    Dec 1, 2005
    Bronx, NYC
    There's a JBL K151 on Reverb. I heard tell that it fits in a B18n, and that it's also a rare 18" with a strong "top" end (top for bass guitar). I have one on its way in the mail and will post results somewhere here, once it arrives. My B-18N speaker has a seemingly similar scratchy-sounding output.
    JimmyM likes this.
  14. beans-on-toast


    Aug 7, 2008
    They used either an 8 ohm or a 16 ohm speaker in the B-18. The wiring from the transformer was different depending on which speaker was installed in the combo cabinet. The output transformer has both 8 and 16 ohm taps. Not a big deal to rewire. You should ensure that the wiring in the amp matches your speaker in order to ensure that the impedance is properly matched.
    BassmanPaul and SherpaKahn like this.
  15. SherpaKahn


    Dec 1, 2005
    Bronx, NYC
    Wise counsel. Yep mine is wired for its 8 ohm load, though the internal paper schematic is for the 16 ohm model. The 16-ohm output wiring uses both contacts of the dual-switching TRS jack; the 8-ohm wiring only uses one of the switches. When I first tried to make sense of the wiring in mine, I was losing my mind until I remembered the presence of the isolating fiber washer...So yeah, I'm starting from the 8-ohm setup and staying there.

    Silver lining of the JBL speaker upgrade is that I'll be able to use the b18 cabinet as an extension cabinet beyond 50W. It also reduces my apprehension regarding switching to SS diodes and jumbo-ish filter caps.
    beans-on-toast likes this.
  16. BassmanPaul

    BassmanPaul Inactive

    I wonder if the Tech messed with the wiring of the external speaker jack. If the insulating washer was removed the amp could be working into a short. Whatever the problem is it's up to the Tech to sort it out. the amps doesn't work and he should find out why.
    Last edited: May 31, 2020
    SherpaKahn likes this.
  17. BassmanPaul

    BassmanPaul Inactive

    You probably know but there is a SS unit that plugs right into the rectifier socket.
    SherpaKahn likes this.
  18. SherpaKahn


    Dec 1, 2005
    Bronx, NYC
    Yeah, but if the goal of the SS rectification is power and LF authority, the input filter cap can be brought beyond the limited 30-50uF imposed by the tube rectifier.

    Contrariwise, for those 25" spaghetti-string things of which we dare not speak , I find the overload of the stock setup at full-tilt quite pleasing. Going between the "stiff"/"spongy" power supply setups would warrant frequent surgery, or some well-implemented sturdy switches.

    Side note: I recall a B18n schematic stock with SS diodes. There was a 25R resistor between the rectifier DC out and the top of the first filter cap. Some kind of current/inrush limiting?
  19. beans-on-toast


    Aug 7, 2008
    Voltage spikes when the amp is tuned on and the node A capacitor is discharged are somewhat limited by the 25R resistor. It also will lower the voltage a bit and slow the inrush a bit. Normally the first capacitor has a higher voltage rating to help cope with the initial turnon conditions. An alternative is to place two resistors, one to each plate of the tube rectifier from the high voltage power transformer winding. Some 5AR4 data sheets describe how to calculate these limiting resistors.

    To make the power supply stiffer, it would have been better if they had an inductor in place of the resistor. It allows higher valued capacitors to help the low end. This was done in the Heritage B-15 at the request of Jess Oliver.
    Last edited: Jun 1, 2020
    SherpaKahn likes this.
  20. bobyoung53

    bobyoung53 Supporting Member

    That happened to me with an Ampeg Bassamp.
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

    May 16, 2022

Share This Page