Help with speaker wiring

Discussion in 'Amps and Cabs [BG]' started by chipmolter, Sep 17, 2001.

  1. chipmolter

    chipmolter Guest

    Aug 27, 2001
    Baltimore, MD
    Good afternoon, TBers.

    I'd like to build a 4x10 extension cab, but I'm having some trouble figuring out impedance.

    Let's say I've got 4 8 Ohm speakers with an RMS of 100. If I hook them up all in parallel, I end up with a 2 Ohm circuit, right? What's the RMS for the entire group, 400?

    What happens if I put the speakers in series 2 apiece on parallel lines? Does that give me 8 Ohms?

    Is there anyway to get a set of 4 speakers to be be either 4 or 8 Ohms based on the design of the circuit?

    Your help will be greatly appreciated.
  2. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Saint Louis, MO USA
    This is how many 8 ohm boxes are wired. It is fine to run it this way.

    There is no way to configure four 8 ohm speakers to get a 4 ohm load.
  3. Hmm, sounds like you've got a pretty good handle on it actually. Hooking up in parallel adds the RMS handling capability. Just think about the loads (speakers) and the wiring as an electric circut (suprise!). If you have 4 speakers in parallel, then you have 1/4 of the current reaching each speaker. Which means you can use 4 times the current with 4 speakers, etc. In series, it gets theoretically divided. But for practical applications, I've seen some opinions that you can just make the RMS value for speakers in series the RMS value for one of the speakers in the series circut. But I'm a little shaky on this, so I'm not stating it as fact.

    So in theory, four 8ohm speakers in Parallel/Series config would have a RMS handling equal to the RMS rating for an individual speaker. But as for reality, I've yet to test enough to see (blow stuff up).

    I personally made two 2x10's. I used 8 ohm drivers, and I wired them as 16ohms with parallel jacks on them. Comes together as a system of 8ohms. I need to get out my fluke and measure the resistance so I can make sure of the wiring..but I haven't done it yet. To busy playing the suckers!

    Good luck, hopefully someone more knowledgable will stop by.
  4. chipmolter

    chipmolter Guest

    Aug 27, 2001
    Baltimore, MD
    What if I set up the 2 parallel series with 2 8 Ohm drivers on each, then added a 3rd circuit path in parallel with an 8 Ohm resistor and a switch? When the switch was active, the circuit would have a 4 Ohm load, when the switch was inactive, the circuit would have an 8 Ohm load. Is this feasible? Would it accomplish anything?
  5. Sounds like you're talking about a "Dummy Load". This would just eat up power. It'd probably over heat or destroy itself with high current loads. It'd take current away from the drivers, and actually half the amount of current. Making them somewhat less effective. You could always just add a tweeter to the system and a crossover. Design the crossover correctly (WinISD comes to mind) and you can alter the impedance of the system. Check out
  6. Chipmolter, if you build your cab make sure you get the phasing of the speakers correct. And, not often said, make sure the phase of your new cab matches the phase of the existing cab. Don't want one set of spkrs going one way whilst the other set do the reverse. No problem electrically but not good for the sound.

    Speaker phasing is easily done with a battery and a couple of wires.

    I can see little point to your idea of the 'dummy load'. You'd need a resistor of hellish big wattage (=big$$) and a switch of equally suitable rating. And it would add nothing to your sound.