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Extension cabinet?

Discussion in 'Amps, Mics & Pickups [DB]' started by wallawallabob, Aug 13, 2012.

  1. I have a Genz Benz 10T, 8 ohm and I am thinking about adding a 12" extension cabinet for more volume. The rig is great for smaller venues (mostly where I play). K&K BassMax with preamp.

    I read the sticky on ohms and watts etc, and I am still confused.

    By adding another 8ohm speaker will the volume increase? The GB is 300 watts with the extension, about half that with the 10" it came with. Should I get a 4ohm?

    Obviously, I am unaccustomed to using electrons....Thanks for your ideas!
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    You can add either another 10T or a 12T, either will work just fine and more volume and low frequency extensin will be possible with the 12-10 combination. This series was designed from the beginning to work well together in a mix & match scenario.
  3. iiipopes

    iiipopes Supporting Member

    May 4, 2009
    I actually use a 1X15 ported cabinet as an extension cab when necessary with my Carvin MB12 on both DB & EB.

    Make sure you use an extension cabinet with the recommended impedance of your particular amplifier. Too low an impedance and you can stress the output stage and cause thermal overload. Too high impedance and you lose efficiency.

    "Louder" depends on the interaction of the output section with the total load, the efficiency of the cabinets and the frequency range reinforcement. I use my extension cab more when I need that lowest 1/2 octave for whatever reason more than to get "louder," although it can.

    Following ohm's law, to some degree, a lower impedance load has the potential from the same output stage to produce more power, assuming the output stage can pass the required extra current, which can help the volume, but unlike with old tube amps and output transformers, it's not as linear due to the internal impedance of solid state output devices.

    The bottom line: if you're adding cabs to get better coverage or change frequency range reinforcement, fine. If you're adding cabs to get more volume, then it's better to look at a line out to a slave head/cab arrangement.
  4. Bob Gollihur

    Bob Gollihur GollihurMusic.com

    Mar 22, 2000
    Cape of New Jersey
    Big Cheese Emeritus: Gollihur Music (retired)
    Stick with another eight ohm cabinet; running the two will result in a four ohm load. Provided the new speaker is has a similar efficiency, you will get more volume as a result of two reasons - you are correct that the amp's wattage output will increase, and you will be moving twice+ as much air because of the additional speaker cone.

    While I can't link directly to it, I've written an article, with illustrations, to explain the whole mess. It's under Upright Bass FAQs on my site; hope you find it illuminating. It's titled:

    OHMS & IMPEDANCE from the OUTPUT (speaker) perspective: What the heck are impedance and ohms, and why should I care?
  5. Matt Ides

    Matt Ides Supporting Member

    May 12, 2004
    Minneapolis, MN
    The Shuttle series works really nice with the matching ext. Cab. Another 10 would give you a mini stack and the 300 watts.
  6. Thanks, all, for the input: a little more insecurity:

    1. Would there be an advantage to adding a 12" rather than another 10" Genz extension cab?

    2. Would any 8ohm speaker be more or less the same efficiency?

    3. What about a decent 15", 8 ohm (Genz Benz Focus-LT FCS-115T Bass Speaker Cabinet (1x15")? I know there will be weight, but I'll have to make another trip anywho.....
  7. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The matching Shuttle 12" will give a bit more LF extension and maybe a dB of additional LF SPL. Otherwise,, it's pretty close. You do want to stay withing a dB or two of the same sensitivity, but when you are looking at high volume performance large signal modeling specs are required but not usually provided because they are very complicated. What is imp[ortant is that at high SPL, the speakers exhibit similar performance and efficiency. Since I did the engineering on our product, that's why I am confident of the combinations. I can't speak for other manufacturers however.

    The Focus 15 is also pretty close using the large signal model, but I would suggest that you give this combination a try because the tomal profile is a lttle different and I don't know your personal tastes.

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