Question for the cab design guys.

Discussion in 'Amps [BG]' started by creis2, Dec 5, 2012.


  1. creis2

    creis2

    Joined:
    Nov 11, 2011
    Location:
    Cambridge, MA
    I've been searching for days and I haven't found much.

    I'm trying to differentiate between sealed and ported cabs.

    Is this correct:

    Sealed needs more drivers for more volume.

    Ported needs less drivers due to the port designs.

    It seems that I'm seeing less sealed 810's on stage and more ported 412's, ported 610's and those fearful designs that have multiple size drivers.


    For example: The ampeg 610 vs 810 (tuning totally aside, that's irrelevant to me for what I want to understand) can put out the similar volume but the 810 needs the extra drivers due to it being a sealed design?

    I'm really trying to understand, if anyone could put it in laymans terms for me.
  2. will33

    will33

    Joined:
    May 22, 2006
    Location:
    austin,tx
    Disclosures:
    Use of this field for any other purpose is prohibited
    Above a couple hundred hz or so, all drivers act as if they are in a sealed box, even if it is ported. The porting affects what's going on in the bass end only. It can make them reach deeper and play louder down there, sometimes by quite a bit, but has no effect on the mids and highs, they stay the same.
  3. low2groove

    low2groove Tyranis 4 / Lower Groove Guitars Supporting Member

    Joined:
    Jan 21, 2007
    Always ported in my book. A sealed design will never have the bottom of a ported design but it will have more overall punch.
    My 4x10 Eden or DNA will push more air and sound better than any 8X10 sealed ampeg cab could dream of.
    There will probably be many more responses to this thread now that I've posted and you may actually get an answer to your question.
    i will also get flamed by the ampeg lovers, Yay!
  4. creis2

    creis2

    Joined:
    Nov 11, 2011
    Location:
    Cambridge, MA
    One of the big reasons I ask, is that I played an Aguilar 412 today and then an Ampeg 810.

    I played all types of setting and different heads. The 412 whooped the 810's hiney.

    Just wondering how this is. I know the Aguilar is ported and the Ampeg isn;t/
  5. fdeck

    fdeck Supporting Member

    Joined:
    Mar 20, 2004
    Location:
    Madison WI
    Disclosures:
    HPF Technology: Protecting the Pocket since 2007
    Broadly speaking, think of the port as giving you a bigger "budget" of low frequency response for a given driver and box, assuming that you've chosen a driver that works in a ported box. What you do with that budget depends on how you want to play other typical tradeoffs, such as low end extension versus overall sensitivity.

    Here's a brief article on a ported design, where I was aiming for a response curve similar to a particular classic sealed cab, but with considerably higher sensitivity and power handling:

    http://personalpages.tds.net/~fdeck/bass/smallbox.pdf

    The article compares two idealized designs, both with the same driver, at opposite ends of the tradeoff spectrum.

    As for your listening experience, you have to watch out, because sealed-vs-ported probably wasn't the only variable in play when you compared speakers.
  6. B-string

    B-string Supporting Member

    Joined:
    Nov 21, 2008
    Location:
    Lake Havasu City, Az USA
    Porting extends the sound pressure level on the low end then drops off sharply. Sealed has a gradual roll off in volume. You could think of a sealed cab like gradually breaking to a stop sign, ported like breaking hard and late to stop. Breaking late you have more forward speed up to the breaking point. Sealed can (as a general rule) actually have a lower usable frequency range, it is just not as loud as ported cab in the frequencies we want to hear most.
    The fact that all speakers are NOT created equal applies. A poorly designed or miss-used 12" can be over-powered by a good 10" used as designed. The 412 may have well beat the paints off the 810 in low end response, but in band use you may find the 810 carries through the mix better. No easy answers!

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