how do i make my amp put out 4 ohms

Discussion in 'Amps and Cabs [BG]' started by a e i o u, Nov 6, 2003.

  1. i forgot how to hook up the two 8ohm cabs... do you plug them both in to the amp seperatly, or hook up the two cabs together, then plug one into the amp
  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    First of all, an amp does not "put out ohms".
    You just measure the impedance (resistance in an ac circuit) of a cab (for example) in ohm.

    Both ways connect the cabs in parallel, making the total load 4 ohm.
  3. sorry, i dont know much about the technical stuff. So as long as i have my two 8ohm cabs in use, no matter how i plug them, i will get what i want, and if i just use one, ill have 8ohms
  4. Yeah, pretty much. The calculations for connecting cabinets in parallel is:

    (Cab1 x Cab2) / (Cab1 + Cab2) = Total resistance

    With two 8 ohm cabs, you get:

    (8 x 8) / (8 + 8) = (64/16) = 4 ohms

    Edit: Bassmantele is right. If you want to calculate for series:

    (Cab1 + Cab2) = Total resistance
    (8 + 8) = 16 ohms.

    I didn't mention this because I've never seen an amp connected in series. All of this calculation stuff is just FYI, by the way.
  5. bassmantele


    Jul 22, 2003
    Boston MA USA

    No. Two 8 ohm speakers wired in parallel gives you 4 ohms. Two 8 ohm speakers wired in series gives you 16 ohms. There are many sites on the web that explain speaker wiring.
  6. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    a e i o u, most of the time if your speaker cab has more than one jack on it, the jacks will be wired "in parallel" (in other words, it won't matter which one you plug into).

    There are some exceptions though, like if you have a stereo cab where one jack is stereo and the other is mono (I have a Line 6 cab like that, and some Marshall cabs are that way too).

    The same would be true for amps. Most of the time, if your amp has multiple speaker jacks they'll be wired "in parallel", but there are exceptions (for instance, sometimes one of the jacks will say "8 ohms" and the other will say "4 ohms", so in that case you should make sure to use the right one).

    I think, that if you have "normal" equipment, it won't matter which of the two methods you mentioned you choose to use. They'll both end up with the same result, which is that the two cabs will be wired "in parallel", and then all the math that people discussed will apply, and so two 8 ohm cabs in parallel will result in a final impedance of 4 ohms.

    If you're in doubt about how your amp or cabs are wired, consult the manual or the manufacturer's spec sheet. You can even get schematics and layouts for many amps on, so if the manual doesn't have the information you're looking for you can go straight to the schematic.

    If you tell us what specific amp and cabs you're using, we can probably tell you how they're wired and how they should be hooked up.
  7. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Very true, but he's not talking about wiring up two 8 ohm drivers, he's talking about using two 8 ohm cabinets. And his question was about daisychaining them versus plugging them into separate amp outputs. In that setting, either way is going to give him a 4 ohm load, and using one cab by itself would give him an 8 ohm load.

    I mention this not to give you a hard time, because what you said was right--but you might be confusing the lad just when he's figured out what to do with his two cabs!;)
  8. pbd

    pbd Commercial User

    Jul 17, 2003
    Metro Detroit
    owner Procables N Sound
    Here's the next twist, not to throw anyone off, If your using a stereo head and you plug an 8 ohm cab into left and right separately then you will only be driving 8ohms each side.