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Cabs and ohms....

Discussion in 'Amps and Cabs [BG]' started by andreas_bass, Feb 18, 2003.


  1. Hi!
    Here's my problem:
    I've got an Ampeg 410hlf (4ohm) that I really love. Sometimes on bigger stages I want to run with an extra cab. I'm thinking of buying another 410hlf used. Unfortunately here in Sweden, there are no hlf's used on the market. So my plan is to buy a 410HE (8ohm) instead.

    Here's my question:
    Can I occasionally change the ohm on my hlf to 8 ohm by adding a resistance before the cab so I can run with my poweramp (Mackie 1400) bridged for maximum power? Any other suggestions?

    Thankful for every thoughts about this!

    Andreas
     
  2. Thanks Meekster, for your thought.
    The problem is that that way I only get 300 W instead of 700 W (1400/2) into the HE. Maybe I'm crazy but I think I want more headroom. But thanks anyway.
     
  3. You could add a 4 ohms resistor to the 4 ohms cab to get 8 ohms, put the two cabs in parallel and get a 4 ohms total load. But the added resistor would burn up as much power as the 8 ohms cab will get itself. So there really no point in doing that. You're stuck with it :(
     
  4. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    You'll be wasting amplifier power if you try to correct the impedance with resistors. Think of the resistor as another cabinet...if you put two in series to double the impedance, each one gets half the power.

    I'd second (or third) the separate channel approach. That way, you'll be able to control the relative level of each cabinet and set the filters as appropriate. Besides, 700 watts into a cab won't be much louder than 300 watts...and if 8 10s and all that power isn't enough, tell the guitarists to turn down a bit...

    Good luck!!!!
     
  5. Thanks everyone for your advice.
    I will try with one cab/ ch. Thank you for your invaluable help.

    Andreas
     
  6. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    OK I'm trying to think outside the square here.... If you ran a parallel link from the 8 ohm cab to a third cab (say a single 10) which is also 8 ohms, you'd effectively turn that cab into a 9x10 at 4 ohms.

    Guru's please jump in here. I'm sure this is wrong but I can't put my finger on why?
     
  7. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I know why I'm wrong. The amp won't send equal power to the 9 speakers. The single 10 to will steal half of it........ Sorry.

    Here's another suggestion. Instead of a 4x10, get 2 cabs with 2x10's at 8 ohms each and link them in parallel.
     
  8. You can do it, but you have to re-wire you cabs. It's late and I've been plowing snow all day, so bare with me, and if i'm wrong now, i'll correct myself later. The speakers in the HLF i have are 4 ohms speakers, wired in series/parallel to give the whole cabinet a 4 ohms impedance, same as one speaker. So, take 2 of those 4 ohms speakers, wire them in series to create 8 ohms, then take the other 2 and do the same thing. Then take these 2 8 ohms sets and wire them in series for a total of 16 ohms. Then, when you parallel that 16 ohm cabinet with the 8 ohm cabinet, you get 5.33 ohms. And if you think i am being sacastic, i'm very serious, as i comtemplated doing this very thing.
     
  9. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    That makes sense...

    Although the 16 ohm 410HLF would only receive 1/3 of the power and you couldn't control the relative level of the two cabinets.

    I assumed that Ampeg used 16 ohm drivers in the 410HLF wiring them all in parallel (since they use 8 32 ohm drivers in the SVT 810 cabinets).

    Would work though...