Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Need advice on combo amp construction (Joris?)

Discussion in 'Amps and Cabs [BG]' started by throbbinnut, Dec 6, 2000.


  1. I snagged the chassis from an old Bassman 10 amp, and now I want to build a cabinet for it to make a nice 50Watt tube combo. I have a CTS 15 that I want to use instead of 4-10's. I want to build it sealed, cause I think that's the way the early Ampeg Potaflex B15N cabinet was built and I want to go easy on the speaker(which came out of a Magnavox console stereo from the 60's). Here's a drawing. My question is whether the speaker should be mounted up high (right side pic), or centered in the baffle (left side pic). The box will be 11.25 inches deep.

    Any pointers? I will probably shock mount the chassis to be nice to my tubes.

    [​IMG]

    Thanks,
    Chris
     
  2. Come on gurus (Joris, MikeyD, Brianrost). Give me some input. I'm thinking that up high is better.

    Thanks,
    Chris
     
  3. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    First suggestion is that if you got the speaker out of an old stereo you'll probably blow it pretty quick. Get yourself a driver meant for bass guitar.

    Where the speaker is located on the baffle doesn't matter a lot.

    As far as sealed vs. ported, that depends on the driver specs and what sort of freq response you want. Ported cabs increase low end efficiency at expense of low end extension.
    That is a properly designed sealed cab can go lower than a ported cab but it will not be as loud (to get the low end back you need to boost it with EQ). Ported cabs will give more volume but if you try to boost frequencies below the port's resonance you'll just blow the speaker due to over-excursion.
     
  4. Thanks for the info. As for blowing the speaker, I'm not worried about it for 2 reasons: I got 2 of them for free, and they are CTS square magnet speakers that were mounted in an open stereo cabinet. Check it out. It's the same as the original Portaflex B15N speaker. I'm only gonna be hitting it with 50 tube watts, and with a sealed box, I won't be flopping it around.

    [​IMG]

    [​IMG]

    I was under the impression that mounting the speaker in the center of the baffle would make resonances more prominent (bad) and raising it off the floor would help the speaker "throw" better (good). Could be wrong on both counts.

    Thanks,
    Chris