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power amp/cabinet question

Discussion in 'Amps and Cabs [BG]' started by adammazza, Feb 24, 2008.


  1. Hi,

    I will be replacing my GK 600 head with a Sansamp RBI and a QSC RMX 1450. Currently this will be feeding an Aguilar DB210 I hope to be adding a DB or GS112 soon. This cabinet handles 350 watts and can take either 4 or 8 ohm.

    The 1450 will do 280 watts per side at 8ohms and 450 watts per side at 4 ohms. It will also do 900w bridged at 8 ohms. It seems that my best bet would be to feed it 450 watts at 4 ohms so that I have some headroom. My question is can I get both to operate at 4 ohms? Is this a setting on each or will the Aguilar operate at 4 ohms only if I attach another cabinet?

    Thanks

    Adam
     
  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Unlike a tube amp, a SS amp doesn't have a setting for speaker impedance. The simplest way to put this is that the amp adapts to the impedance of the speakers. What's the impedance of your existing cab?
     
  3. It's an Aguilar DB210. The specs says 4 or 8 ohms.

    Thanks

    Adam
     
  4. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    The "4 or 8 Ohms" means the cab can be ordered with one or the other impedances. Is this a cab you already have, or one that you are thinking of buying?
     
  5. It's one I already have. It's the Aguilar DB210. All the specs on it say 4 or 8 ohms of impedance, including Agular's site. I thought it was a bit weird.

    Adam
     
  6. Whoops, sorry. I am dumb ;). I bought this at GC as they had it on close out at $449 (normally $679 I tihnk) I just looked on the back. It says 8 ohm on this one. So does that mean I am best off in the bridged mode for now, as long as I don't push it too much?

    thanks

    Adam
     
  7. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Cool. You could run the amp bridged, of course with the knowledge that the amp is capable of smoking the speaker. So be careful. I don't run with a lot of power, so I don't have personal experience with how much "overpower" one can get away with.

    It might be interesting to run it off just one side, and decide if it is loud enough for your use.
     
  8. Thanks. I've also read that it's better to push the speaker a bit then to push the amp. Is that true, or is it more of a 'depends' type situation? Also if I wanted to add a second speaker, say a DB112 which is 8 ohms, would that bring the entire load down to 4 ohms (if I ran everything from one channel?)

    Thanks

    Adam
     
  9. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    It's worth searching on the term "underpowering" for the breadth of opinions on this issue.

    Correct. However, running an 8-Ohm cab from each channel gets you 280 + 280 = 560 W, whereas running them in parallel from one side gets you only 480 W. Not a huge difference, though.
     
  10. The RMX 1450 will do 1400w at 4 ohms bridged. So if I have 2, 8 ohm cabinets at 350w each, that would put the load at 4 ohm (8/2) and I would have 1400w to feed 700w worth of speakers correct?

    I've read some of the FAQs on clipping and it seems that have 1.5x - 2x as much much amp power to speaker power is sort of the sweet spot.

    Am I understanding this correctly.

    Thanks for the help

    Adam
     

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