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cab sensitivity when using 2 cabs?

Discussion in 'Amps and Cabs [BG]' started by Andrew Jones, Apr 4, 2002.


  1. Andrew Jones

    Andrew Jones Banned

    Feb 28, 2001
    Northampton Mass
    HI


    The sensitivity spec goes up when you use two cabs right ?How much?I have 2 bergantino 112 97db each what do you think they are in a pair?


    thanks
    AJ
     
  2. The general rule of thumb is that the sensitivity goes up 3dB when you combine two identical cabinets.

    Mike
     
  3. Yep, you'll get about 3 dB due to the cabs coupling. If your power amp is solid state you'll probably get another couple dB due to the fact that SS amps can deliver more power into lower impedences.
     
  4. From an SWR faq:

    There is an interesting phenomenon known as "coupling gain". This effect happens when like speaker
    cabinets are placed next to each other or on top of each other, causing the cabinets to "couple", creating
    a situation where the whole becomes greater than the sum of the parts. You get a "free" 6 decibels of
    gain when the cabinets are placed together. If you normally play at or around 100 dB and you place an
    identical cabinet on or next to the original you will more than double the volume to the human ear. Split
    the cabinets and you'll hear the volume decrease.
     
  5. Actually, efficiency given in units of dB per watt at 1 meter, so that extra 3dB/w/1m of efficiency is there whether you're getting extra power out of the amp or not.

    Likewise, I'm not really sure the extra 3dB is due to coupling so much as it is to simply having extra drivers to handle the power, same as going from a 2x10 to a 4x10 (which also typically yields about 3dB extra efficiency, all other things being equal....) I'm not sure if I'd call that "coupling" or not.

    Mike
     
  6. Actually, 10 dB more is "doubling" the volume (takes 10x more power), and 3dB difference is what you get when you double the power. I see the SWR FAQ, but it's incorrect--the relationship between power, efficiency, and perceived volume is pretty much basic physics. Weird--I wouldn't have expected to see that kind of mistake on the SWR site.

    Mike
     
  7. That's effectively what I said. :D You get 3dB purely due to the effects of acoustic coupling. You also get some phase anomolies/comb filters, plus some directivity in the midrange and low midrange. This is independent of any gains in amp power due to lower impedence. Perhaps I should have said that you get a couple dB of amp headroom. At any rate, the 6dB quoted in the SWR thing is pushing it. There aren't that many situations where you'll get that much. But I assure you the phenomenon is due to acoustic coupling.

    I just read "more than double the volume." Boy is that ever wrong....
     
  8. It would be a better comparison if we knew exactly how much power was going into the cabinets. For example, what is differance in volume betwene one cabinet driven at X watts and two of those cabinets each driven at X watts?
     
  9. Andrew Jones

    Andrew Jones Banned

    Feb 28, 2001
    Northampton Mass
    Thanks Guys

    This is getting to be much more thorough than I expected,I appreciate the effort though.Im driving these with a walter woods ultra 1200watts 4ohm.Each cab is 8 ohm.

    AJ