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Talk to me about Ported VS Sealed cabs

Discussion in 'Amps and Cabs [BG]' started by spectorbass83, Dec 11, 2006.

  1. spectorbass83


    Jun 6, 2005
    I realize this topic has probably been covered, but after doing a search I could not find the answers I am looking for.

    Based on some of my research I found that Sealed cabs are "faster" than ported cabs..Is this true?

    Do ports help augment low frequencies?

    I have also read on another forum that a sealed enclosure is less efficient than a ported one :confused:
    How can this apply to something like a Schroeder cab, which is sealed but one of the most efficient cabs you can find?
  2. First, the Schroeders are ported... you just can't see the port... it's between the back of the cab and the slanted baffle.

    I'll let others with more technical knowledge answer the other parts of your question.
  3. spectorbass83


    Jun 6, 2005
    Really?! Cool, thanks for clearing that one up.
  4. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    'faster' doesn't define anything. It implies that the driver cone in a sealed box moves faster than that in a ported box, and that's not true.
    Not true, ported and sealed cabs have similar efficiencies, but ported boxes do tend to have higher sensitivity at low frequencies.
    Schroeders are ported and at about 5% are similar in efficiency to other ported boxes.
  5. Craig Phillips

    Craig Phillips Supporting Member

    Dec 6, 2005
    Sacramento, Calif.
    I noticed Carvin is using sealed cabs in their BR line... Does anyone know why? It seems like it would be easy to port... I know weight may be an issue. Seems like sealed cabs used to be used with tube heads?
  6. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    In the last year I've ended up with a couple of sealed cabs (GK SBX 410 and Ampeg PortaBass 210) after years of ported ones (currently, Eden 210 and 15 cabs). I'm not sure how much of what I hear is coming from speaker design vs cab design. What I've noticed is not quite as much low mid, plus more focus. Downside is less efficiency.

    As some have cautioned here, be careful how far to generalize about comparisons, given that several factors come into the final sound outcome.
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The usual reason would be to accomodate drivers with specs specifically tailored to work best in sealed cabs. There aren't many, but there are some. Weight would not enter into the equation.
  8. This is a fantastic post. :D
  9. morebass!

    morebass! I'm all ears Supporting Member

    May 31, 2002
    Madison WI
    +1 sealed seem to be less boomy and more focused to me.

  10. A9X


    Dec 27, 2003
    Ported cabs need to be designed correctly to work at their best, and unfortunately most aren't all that well designed and consequently sound not as good as they could.
    Weight, size and letting the specs and marketing sell the product rather than true performance are the usual reasons.
  11. A ported cab is simply a different style of design where the resonant frequency of the speaker box is harnessed and added to the frequency output of the speakers.

    Factors a designer has to take into account are the speakers themselves (a sealed box offers more resistance behind the speaker cone as it moves and so limits its travel), the size of box, the size and shape of the port, and the length of the port. There are lots of things you have to juggle to get it right and small changes in design can have big effects in performance! That's also why good ported cabs can cost a bit.

    For a bass enclosure, most designers use the port to boost very low end frequency, giving the cab a lower overall cutoff than the speakers or box size will allow. This means you get a smaller or lighter box with better low end bass than you would normally have.

    I have made some gross generalisations because there's a lot you can do with well designed ports, but that's about it.

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