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Building a cab

Discussion in 'Amps and Cabs [BG]' started by spalka621, Feb 14, 2006.


  1. spalka621

    spalka621

    Jul 26, 2005
    Sioux Falls, SD
    Dont' know if i can ask this here but im building a guitar cab, a 4x12 in my wood shop class in school and i am wondering if i have to put a port in it. I have run the specs through a program but i have no idea what the graph is telling me. Any advice would help alot, thanks.
     
  2. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Traditionally guitar cabs are usually either fully sealed (Marshall), or have a partially open back. Sealed cabs tend to produce more lows, but they tend to only radiate them to about 6-8 feet. Any further away and they're like a laser beam of midrange. Open back cabs are brighter but tend to sound similar on the dance floor as they do on stage.

    Of course this is just my opinion based on the equipment used by the guitarists I've worked with.

    As for porting, I don't know if it will be of any benefit given the very small x-max of a typical guitar speaker. Porting is used among other things to control speaker movement. Cone breakup is bad for a bass cab, but guitarists expect it. As a result guit speakers tend to have very small x-max but a fairly generous X-mech. This means they'll distort nice and early, but they won't fall appart if pushed into distortion.

    What speakers are you using?
     
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Porting has no effect above 100 Hz, and guitar doesn't extend below 100 Hz, so don't bother.
     
  4. didier

    didier

    Aug 4, 2005
    NC
    hmm... the guitarist I play with has an E string at around 83 Hz (on the occasions when he's tuned recently)

    but we'll agree that porting isn't really important here.
     
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    You'd find on doing and RTA of a guitar signal that there's very little below 100Hz. As with the bass the 2nd and 3rd harmonics swamp the first octave fundamentals, and that's with a clean signal. The more overdrive the less fundamental and the more high harmonic content there is. Most sealed guitar speakers run an f3 around 200Hz, though with sealed cabs the rolloff is first order. Open back cabs tend to have f3s around 120-150 Hz but drop like a stone below that.
     
  6. spalka621

    spalka621

    Jul 26, 2005
    Sioux Falls, SD
    Thanks for the help, it looks like this is going to turn out to be a nice cab.