1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
     
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

Help Me Mod My Cab

Discussion in 'Amps and Cabs [BG]' started by The WideBody, Jan 22, 2012.


  1. The WideBody

    The WideBody

    May 18, 2008
    Blew a speaker in my bassman 50's 2x15 cabinet yesterday. Measured the internal volume and intend to do some speaker shopping. The internal volume is about 3.75 cu ft. Much too small for the 2x15 that it was. I want to do a single 15 lfc and at least a smaller mid bass driver. I dont want to do to much deconstruction or reconstruction and need to use an off the shelf passive crossover. I hope to either find a suitable sealed back mid driver or convert the vacant 15" opening to a small sealed area for the mid driver but that would eat up about a full cubic foot.

    My budget is $200 so i am considering the eminence alpha line. I figure the crossover to be $50 so the remainder will have to be split between the drivers.

    Please suggest the following:

    Driver combo

    Tuning freq

    Lfc port diameter and length

    Thanks for your input.
     
  2. will33

    will33

    May 22, 2006
    austin,tx
    Look at the emi. Legend CB158 or Beta 15A, with the Beta8A or la6cbmr.

    off the shelf crossover should be the 800hz 2-way. It'll play a lot better with the beta8 than it will with the closedback.....impedance curves.

    The mid only needs to be in a little sealed box. .1 - .15 cu.ft.

    Box tuning 45-50 hz.

    My .02 as far as cheap but effective.

    I'd let a few more folks throw some ideas out there before you go buying anything.
     
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    What amp? That's just as much part of the equation as the rest. With low power a ported cab is usually not the best idea.
     
  4. The WideBody

    The WideBody

    May 18, 2008
    Bassman 50 - by all accounts a low powered amp. So ports are out?
     
  5. chadds

    chadds

    Mar 18, 2000
    Sell it and get something else. I had one with JBLs. The design is very poor. By the time you take out the baffle you could have bought something else.
    There are many single 12"s now that will spank it.
     
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Vented isn't worth the effort. You also want a 4 ohm load. I'd use a pair of Beta 12, using reducer plates to adapt the 15 holes. Be sure to beef up the cab bracing and line it with polyester batting. Forget the mid driver.
     
  7. The WideBody

    The WideBody

    May 18, 2008
    Great! Where do i find these reducer plates?
     
  8. Arjank

    Arjank

    Oct 9, 2007
    Above Amsterdam
    What are your arguments?
     
  9. will33

    will33

    May 22, 2006
    austin,tx
    You'd make them out of a piece of 3/4" plywood. Basically fill in the current speaker cutouts, then re-cut them for 12" drivers.

    And yeah, better to have a 4ohm load for your bassman.
     
  10. The WideBody

    The WideBody

    May 18, 2008
    Unfortunate (for me) story. I had a buyer lined up. The night before the buyer was to come i thought that i would fire it up one last time. I must have burnt out the speaker at that time cuz when the buyer showed up - the only tunes that would come out of the cab were early sabbath stuff!
     
  11. Arjank

    Arjank

    Oct 9, 2007
    Above Amsterdam
    :bassist: great sense of humor!
     
  12. The WideBody

    The WideBody

    May 18, 2008
    Please point me at a tutorial or something so that i don't have to reinvent the wheel.

    Wouldn't a single fifteen and a smaller mid bass driver add up to the 4ohm load. Missed that day in math class when they showed us how to figure impedance.
     
  13. will33

    will33

    May 22, 2006
    austin,tx
    No, it'd be 8ohms on both sides of the crossover. I didn't think ahead to ask you what amp you're using.

    I'll see if I can dig up a pic of an adapter ring. Basically, cut circles the size of your 15" holes, cut circles in those to mount the 12" drivers and glue them in.
     
  14. will33

    will33

    May 22, 2006
    austin,tx
    It'll look sort of like a donut, 15" ring with a 12" hole in it.
     
  15. will33

    will33

    May 22, 2006
    austin,tx
    Have you looked into getting your JbL's reconed rather than all this modding? They might be worth more out of the box than they are in it.
     
  16. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Put your 15" driver onto a piece of ply. Draw around it with a pencil and then mark the eight mounting holes. Cut around the outside of the circle and drill out the holes. If you draw lines connecting each hole with its opposite you'll find the centre. Mark and cut the appropriate sized hole for the 12" driver. Drill and mount T nuts 10x32 for the 12" driver. You can mount the ring into the cabinet using the original hardware. attach some weather stripping to act as a gasket. Repeat for the other driver. 1/2" ply should be fine for this.
     
  17. The WideBody

    The WideBody

    May 18, 2008
    Pulled one out. I don't know what make it is. It has a fender sticker on the back. I will try to upload pics.

    image-3846860850.
     
  18. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    At your local lumber yard, disguised as sheets of plywood. All you need to do is to remove the excess.
     
  19. 1n3

    1n3

    Sep 13, 2007
    USA
    So, not a JBL. Eminence or CTS, I would guess. If you're pretty sure it's only one speaker, I'd try to repair it. Should be cheaper than replacing two speakers, and easier than modding a cab. And the cab might be more valuable if left original, though I don't know that.

    I'm a little skeptical that it's blown. The storyline doesn't fit well - 50w head, hasn't been used much... an inspection would be in order. Look for cone tears, loose surrounds or spiders, voice coil leads touching the cone, etc.
     
  20. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Back in the day I blew Fender 'special design' drivers regularly with a 50 watt Bassman. The only thing 'special' about those drivers was the sticker, and until at least the mid 70s Fender used guitar drivers for both guitar and bass on standard versions. Unless JBL or EV they're not worth reconing.
     

Share This Page