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Biamp Inquery: Help!

Discussion in 'Amps and Cabs [BG]' started by steriogenesis, Nov 2, 2003.

  1. (Using the Ampeg B4R as an example [it has two seperate amps])

    With two 8 Ohm Cabinets

    If the stereo ratings are :
    (2x420 Watts @ 4 Ohms)
    (2x255 Watts @ 8 Ohms)

    With Biamp and Stereo On:
    Does that mean that I am only going to get 255 watts to either cabinet (from each amplifier) because the cabs are 8 Ohm, or is the load still considered 4 Ohm even with the amps working independently (making it 420 watts per cabinet)?

    In other words, is it only going to make it a 4ohm load if I am using Bridged Mono and Daisy Chaining the cabinets?
  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    1. That's not really biamping. Biamping is splitting the signal in high and low, running it thru separate amp channels and cabs.
    What you do is running the amp in dual mono (or stereo in some cases).
    2. With 2 8 ohm cabs each one will see 255 W nominally. The rating is per side at the respective impedance.

    3. Daisy-chaining is the same as running in parallel. This will make the total load 4 ohm, which you can drive with one(!) side of the amp. You can't use this setup in bridged mode because the minimum load in bridged is 8 ohms.
  3. Thank you.

    I understand that biamping is separating low and high. With the B4R there is a switch to turn biamp on/off. (The amp must be set to stereo though.) When biamp is off, it is just in full range stereo. If you turn stereo off, it is in mono.

    Are you sure? In the owners manual it says that it is 1350 Watts Mono Bridged @ 4ohms. So doing so (and daisy chaining) would create a 4ohm load that pushes 675 Watts to each cabinet. Am I right?

    So in order to get the most out of the cabinets, should I use Bridged Mono from the A/B Speakon output and daisy chain the cabs... rather than running stereo (or Biamp if prefered) from channel A to one cab and B to the other (because they will run with the 8ohm rating, which distributes less wattage than a 4ohm)?


    I apologize for being full of so many questions...
  4. BillyB_from_LZ


    Sep 7, 2000
    I didn't look at the Ampeg's manual but what you wrote looks right. Run Bridged, connect the amp to cabinet one and then cabinet one to cabinet two (assuming that cabinet one has multiple input jacks).

    Most bridged amps require a specially wired Speakon using 1+ and 2+ rather than 1+ and 1-. I don't know if the Ampeg is that way too, but you need to check the manual for instructions.
  5. Cool. Its too bad that I can only run bridged though...My cabinets are rated too high to run at such a low wattage in 8ohm stereo...

    The manual says that I need to use Speakon 1+ 2+ (whatever that means...) or the binding posts (bananas) for Bridged Mono.

    Would using Speakon allow for better transmition (sound,power) that the binding posts?
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