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Bridge Mono - Wanting to Avoid Mistakes

Discussion in 'Amps and Cabs [BG]' started by Sanctum, Mar 29, 2003.


  1. Having recently acquired an Eden 410XLT, I have put my QSC 1850HD in bridged mono, as I found running it off one side of the poweramp wasnt giving me enough headroom. Cab is 700 watts (8 ohm) - so I'm talking 360 watts off one side vs 1200 bridged into the 8 ohm load.

    Question 1 - I also have an Eden 210XLT (350 watts, 8 Ohm). I won't be using the cabs together too often, but when I do, and daisy chain them, I will then be running 1800 watts bridged into the 4 Ohm load. Thus each side of the QSC will be running @ 2 Ohms, which should be fine according to the specs, but was just wondering if this is inherently bad :)

    Question 2 - With the above configuration, how is the power distributed to the cabs? I lose individual volume control in bridged mono, so I dont wanna trash the 210 with too much power.

    Question 3 - The 210 will be in another practice area, and used alone. Can I keep the amp in bridged mono and just keep my eye on the volume levels, or should I reset the dip switches on the QSC just to be safe and run it off one side of the amp? Seems like a lot of power into a 350 watt cab - again I don't want to blow the thing.

    Sorry for the long post, and many thanks in advance.
     
  2. rockindoc

    rockindoc Daily Lama

    Jan 26, 2002
    Bonham, Tx
    1) No problem bridging the QSC into a 4ohm load.

    2) Two cabs of the same ohmage will share the power equally. Each gets 900 W. I'd feel "safer" with 700W into a 350W cab, but another way of looking at it is, with 900W you've got miles of headroom :D . Just be careful.

    3) Are you talking about bridging the QSC into only the 210? 1200W into a 350W cab would make me a little uneasy. One side of the amp should be enough with 360W into a 350W cab.
     
  3. 3) yea, my thoughts too I"m just so lazy and was trying to avoid changing dip switches :D
     
  4. A 4-ohm bridged load is seen by the amp as a 2-ohm load in each channel. Bridged mode is the hardest on the amp, especially at lower impedances, because the voltage swing is much higher.

    Lethal (read: this can kill you) voltages are present in bridged mode.

    My personal opinion is to only use Bridged mode when there is a pressing need that cannot be satisifed by normal stereo operation of the amp.
     
  5. Well the 410XLT sounds killer with the amp bridged, and geez, what headroom ... plenty o' power all around. I wonder if I'll ever need to pair it with the 210XLT :D
     
  6. Schwinn

    Schwinn

    Dec 4, 2002
    Sarasota, FL
    I want to pick your brains, guys...

    I'm about to make a speakon to 1/4" cable for bridging. (I had to order 4 pole speakons cuz mine are 2 pole...)

    Is this how the wiring goes?

    Pin 1+-------1/4" tip
    Pin 2+-------1/4" sleeve

    Thanks...figured I'd ask and do it right the first time :)
     
  7. Schwinn

    Schwinn

    Dec 4, 2002
    Sarasota, FL

    BUMP.

    Can anyone verify this? Thanks.
     
  8. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
  9. Schwinn

    Schwinn

    Dec 4, 2002
    Sarasota, FL
    Thanks Bob. I tried the cable out and it works fine. My cabs seemed to sound even a little better with the extra power from bridging. (Could be my imagination though).
     
  10. Na man, mine sounds better too :) Thanks for stealing the thread :p
     
  11. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Bridging an amp gives you twice the voltage swing of a single channel, or a 6 dB boost, for the same gain setting. That in itself will tend to make your bass rig sound better. ;)