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Stereo or parallel mode when running two cabs?

Discussion in 'Amps and Cabs [BG]' started by mrpackerguy, Aug 1, 2005.

  1. mrpackerguy

    mrpackerguy Supporting Member

    Jul 3, 2004
    Madison, Wisconsin
    I run two Acme 2x10 Low B2 II's. How would you run your power amp into these - stereo or parallel and wondering if there is an advantage to either?

    Parallel seems to make the most sense as I run an out from my RBI into the power amp then out to the cabs. I'm not even sure how to run out of the RBI in stereo in the most efficient manner?
  2. KJung

    KJung Supporting Member

    All depends on the ohms of the two Acme's and what your power amp cababilities are. If you have two 8ohm cabs, that usually is the 'worst case' scenario if you have a typical stereo power amp. Running in stereo would result in very low power coming from each side of your stereo power amp, since to get full power out of the amp, most are looking for a 4ohm load. However, you probably can't run bridged, since most stereo power amps bridged require an 8ohm load minimum.

    If you have 4ohm cabs... no problem... run in stereo and you will be wumpin' it.

    If your stereo power amp allows a 4ohm load bridged and your cabs are each 8ohm... you are then in good shape... run bridged and your amp will be putting out big watts.

    If you do have two 8ohm cabs, and your stereo amp is not capable of running at 4ohms bridged... sell the amp and buy a good mono amp head that puts out 500-1000 watts into a 4ohm load and you should be good.

    There are efficiency issues with the Acme's... but that's another story.
  3. mrpackerguy

    mrpackerguy Supporting Member

    Jul 3, 2004
    Madison, Wisconsin
    Should have clarified. I'm running two 4-ohm Acme 2x10 cabs with a Yamaha amp with the following specs

    1kHz, THD+N=1% 8 Ohms Stereo: 525W + 525W
    1kHz, THD+N=1% 4 Ohms Stereo: 750W + 750W
    1kHz, THD+N=1% 8 Ohms Bridge: 1500W
    20Hz-20kHz, THD+N=1% 8 Ohms Stereo: 500W + 500W
    20Hz-20kHz, THD+N=1% 4 Ohms Stereo: 700W + 700W
    20Hz-20kHz, THD+N=1% 8 Ohms Bridge: 1400W
    1kHz, 20mS nonclip 2 Ohms Stereo: 1300W + 1300W
    1kHz, 20mS nonclip 4 Ohms Bridge: 2600W

    So isn't parallel going to give me 750w + 750W just like stereo? What's the difference? Finally, how would you run one output from a Sansamp RBI in stereo without getting a second RBI?
  4. You've got your terminology a little sideways. Stereo is each side of the amp operating independently with a different audio source to each side. Parallel is each side of the amp operating independently with a common audio source feeding both channels. Bridge mode is both channels coupled together operating as one big amp with a common audio source. In your case I'd go with bridged mode. In the case where you're running two dissimilar cabs, say a 1x15 and a 2x10 I'd go with parallel mode.
  5. KJung

    KJung Supporting Member

    Seems to me since he has two 4ohm Acme's that parallel would be the way to go... that would result in more than double the suggested wattage for the B2's and still not be running that amp at an extremely low ohmage like bridging into a 2ohm load.
  6. Ahh! You're right! I missed the part about the cabs being 4ohms each. You don't want to bridge that Yamahopper into 2ohms so parallel mode would the choice.
  7. mrpackerguy

    mrpackerguy Supporting Member

    Jul 3, 2004
    Madison, Wisconsin
    That's what I thought. Thanks guys