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cabinet port ??'s

Discussion in 'Amps and Cabs [BG]' started by rdcalab, Jul 7, 2005.


  1. rdcalab

    rdcalab

    Jan 10, 2005
    San Diego
    I have an old peavey 115 p.a. cab that i put a madison executioner into. this thing has 6 ports all about 2 1/2 in. in diameter and a 4 x 4 hole cut for the horn. Question.. is this way too much porting? What would the difference in sound be if I say, closed them up, maybe leaving 1 or 2 open? thanks ryan
     
  2. Cover some with a piece of wood and try different combinations.

    To find the answer, you need a bunch of parameters from the speaker, the volume of the cabinet, volume/area of any ports. Some speakers in that cab would need more ports, some would need less. Depends on resonant freq, compliance, whole bunch of things.

    Randy
     
  3. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Don't get bamboozled by the number of ports. What matters is the frequency to which the cabinet is tuned. If you want to tune a cab to, say, 40Hz, there's a myriad of different porting combinations you can use to achieve 40Hz. Generally speaking, the more ports you add, they have to be either deeper or smaller to maintain the same frequency. Chances are the same porting result could have been achieved with one port on this cab, but it would have had to be considerably larger in diameter, maybe too large for the amount of space available on the baffle.

    If you start to close up ports, you're effectively lowering the tuning frequency of the cabinet. doing so makes you cab start to lose bottom end earlier, but is reduces the slope at which the bottom end falls away. So you're basically getting a higher -3dB point in exchange for a lower -10dB point.

    Is that good or bad? I don't know. I'd need the speaker's Thiele/Small parameters. I'd also need to know the dimensions of the cab, and the depth of those 2.5" ports.