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Ported vs. non ported cabs

Discussion in 'Amps and Cabs [BG]' started by ardorx, Dec 8, 2004.


  1. ardorx

    ardorx

    Sep 23, 2004
    Sugar Land, TX
    I have a genz benz 410, and it has 4 ports behind the speakers on the back. It has good low end, but i want more punch. Would covering the ports on the back help with this?
     
  2. Sundogue

    Sundogue

    Apr 26, 2001
    Wausau, WI
    No. Ports are there to tune the cabinet to a specific frequency, which is determined by the speaker's T/S parameters.

    Worst case scenario...closing the ports would tune it higher and you'd risk blowing out the speakers by sending too much low end into a cab that now would be tuned too high.

    Best case scenario...it would simply sound like crap.
     
  3. ardorx

    ardorx

    Sep 23, 2004
    Sugar Land, TX
    haha. thanks. I don't think I'll do that. But what do you mean by "tuning"?
     
  4. Sundogue

    Sundogue

    Apr 26, 2001
    Wausau, WI
    Every speaker has what is called T/S parameters (which are the specs determined by two guys, I think from Australia, Thiel and Small). These parameters allow cabinet builders to design cabinets to the exact specs of those speakers.

    Not only are watts and ohms important, but things like the best volume size of a cabinet for speakers, the frequency response of those speakers, etc.

    Cabinets are designed specifically to those speaker specs. Tuning is done by the use of ports of a particular diameter and length to get the cabinet to "tune" the cab down to the best frequency for a given speaker(s).

    For instance your speakers might go down to 40Hz and the cab might be tuned to 39Hz. Low E is 41Hz, so if you never play anything below low E, you probably won't ruin your speakers. I say probably, because other things factor into that.

    But the cabinet is "tuned" to a certain frequency, through porting, so that it maximizes the effectiveness of the speakers in that cab. If you block the ports, the cab will be tuned higher than it should be for those speakers.

    It really is a science...it's not just throwing any old speakers into any old cab and cutting a few holes in it.

    Do a search here for "Cabinet Design 101". I built a cab recently and I'll tell you, every bass player should know what goes into cab design...it really opens your eyes. After going through that, now I not only know what sounds good to me, but why!
     
  5. Closing the ports wouldn't raise the tuning frequency, it would just make it a sealed cab, and sealed cabs dont have a tuning frequency. But yeah, it would most likely sound crappy, because speakers that are normally put in sealed cabs are designed for that purpose with a low efficiency bandwidth product.
     
  6. Sundogue

    Sundogue

    Apr 26, 2001
    Wausau, WI
    Well, right you are! I was thinking that if he only closed a couple, or just messed around with the ports, it would change the tuning.

    But, yes, if he closed them all off completely, it would be a sealed cab, and thus the tuning of the cab would be whatever the speakers themselves deliver. If they are drivers with a higher frequency rating than what the cab is tuned to, it would be higher. But more importantly, as you said, those speakers were designed to be in a ported cab, and would probably not work well in a sealed cab.
     
  7. geshel

    geshel

    Oct 2, 2001
    Seattle
    Yes, actually closed cabs do have a resonant frequency. And, closing the ports would likely raise it. However, it behaves a bit differently than the resonance in a ported cab.
     
  8. Zooberwerx

    Zooberwerx Gold Supporting Member

    Dec 21, 2002
    Virginia Beach, VA
    Don't mess with it. Enjoy the durn thing!

    Riis
     
  9. ardorx

    ardorx

    Sep 23, 2004
    Sugar Land, TX
    I agree.
    Thanks for the input guys!