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series/parallel speaker cable/splitter/box

Discussion in 'Live Sound [BG]' started by Chris Breese, Jan 23, 2012.

  1. I have two 8 ohm speaker cabinets and want to wire them so that my amp sees an 8 ohm load using a splitter cable or by using several speaker cables and a box of some kind.

    Does anyone know how to make such a cable/box/splitter? Is this even possible?

  2. Zooberwerx

    Zooberwerx Gold Supporting Member

    Dec 21, 2002
    Virginia Beach, VA
    JOOC....why? I know of no such device.

  3. There is no way to wire two 8 ohm cabs to get an 8 ohm total load.
    s0c9 likes this.
  4. James Judson

    James Judson

    Jul 16, 2009

    Two 8ohm cabinets in series = 16 ohms

    Two 8 ohm cabinets in parallel = 4 ohms

    Now if you can open up those cabinets and rearrange internal wiring so that each cabinet is 4 ohms or 16 ohms we could get you there.
  5. Jazz Ad

    Jazz Ad Mi la ré sol Supporting Member

    None of these examples have two 8 ohm speakers showing 8 ohms of total impedance. It can not be done.
    s0c9 likes this.
  6. Hi.

    Not according to those diagrams. And as a result, it's not possible to make a cable or box to do that.

    8Ohm + 8Ohm = 8Ohm is not possible without a passive resistance or a transformer component in the wiring.

  7. Believe what you want, but you can only get 4 or 16 ohms from two 8 ohm cabs.

  8. You could accomplish the dual 8-ohm cabinets @ 8-ohms total load with a high-powered resistor of the correct impedance value. However, the amp’s power output would be divided between the two cabinets and the resistor, and any power going to the resistor would merely be dissipated as heat, which is a total waste. So for instance, with a 200 watt @ 8-ohms amp, you’d end up with a mere 67 watts per cabinet. Assuming one of your 8-ohm cabinets is good for at least a couple hundred watts, you’re worse off rigging all this up for two cabinets than you would be if you just used one cabinet that would/could utilize the amp’s full power output.

    All in all, an inefficient way to accomplish whatever it is you’re trying to accomplish. Which exactly is what, by the way?

    Wayne A. Pflughaupt

    Administrator, Pedulla Club #45
    Administrator, Tobias Club
    Big Cabs Club #23
    My Rig: Stage and FOH Friendly

  9. Ric5

    Ric5 Supporting Member Commercial User

    Jan 29, 2008
    I convert 4 string Rickenbackers to 5 string basses.
    Yes that is the way resistance works. It is basic math.

    Most amps can handle a 4 ohm load.

    I have 6 speaker cabs. All are 8 ohms. I can mix and use any 2 and get a 4 ohm load. The cabs with single speakers have a single 8 ohm driver. The 2x10 cabs have 2 16 ohm drivers wired parallel for an 8 ohm load.
  10. Ok, so it's not possible. Thanks alot, everyone.

    I was just trying to get my amp to see a 8 ohm load with two 8 ohm speakers. The amp seems to have trouble with 4 ohms.

    The reason for the question was that I thought I saw one of these 'series/parallel' cable in an issue of bass player years ago. I was mistaken!
  11. OnederTone

    OnederTone Aguilar Everywhere Gold Supporting Member

    Aug 15, 2002
    Thornton, CO
    I remember the article you're talking about. Terry Buddingh wrote about the basics of ohms and speaker wiring, but essentially he was talking about wiring up 2 4ohm cabs to see 8ohms instead of 2.

    So... you're not crazy, just confused by the passage of time.

  12. That's the one! Must have been a series cable. Thanks again!
  13. ggunn


    Aug 30, 2006
    Austin, TX
    What are the symptoms of this trouble?
  14. It's an Ampeg PF500. It had issues with cutting out at 4 ohms. It's under warranty and a replacement is on its way.
  15. xnewyorka

    xnewyorka Supporting Member

    Jun 26, 2006
    NYC Area
    I know this is an old thread, but I just wanted to comment that it IS possible to get your amp to see an 8 ohm load with two 8 ohm speakers. In fact, there are two ways to do it:
    The easier way is to simply disconnect one of the speakers, and use it just for show. :)
    The other way, assuming you want both speakers to be active, is to use an Adcom GFS-4 speaker selector. With one of those, you can use any combination of one, two, three or even four 8 ohm speakers and have your amp still see 8 ohms. They come up on ebay periodically. I'm not sure of the power handling rating - I'm sure it should be at least a few hundred watts. I have been using one with a 300 Watt amp for many years with no issues. It works fantastic. It uses impedance transformers to keep the load at a constant 8 ohms regardless of which combination of speakers are selected, as long as they are all also 8 ohms.

    Note: There are other speaker selector switches out there from Adcom and other manufacturers. I have not tried them all, but I would not recommend any other model other than the GFS-4.

  16. As I mentioned above in my previous post, it seems to me to be a pointless exercise. There’s no free lunch. With a speaker selector in place to maintain the correct load, the amplifier power is merely divided out between all the speakers connected. Are you going to get more output (meaning SPL) from a single speaker cabinet getting a full 200 watts from the amp, or with two cabinets getting only 100 watts from the same amp? Or three cabinets, with each only getting 66 watts from the amp?

    So I’m wondering, what are you getting from multiple cabinets that you aren’t getting if you only used one rated at the impedance that the amplifier wanted?

    Wayne A. Pflughaupt

    Administrator, Pedulla Club #45
    Administrator, Tobias Club #133
    Fretless Club #943
    Big Cabs Club #23
    My Rig: Stage and FOH Friendly
    My Basses

    s0c9 likes this.
  17. CharlieMac

    CharlieMac Supporting Member

    Aug 27, 2017
    Of course you can do it.
    Inside of a single cabinet you connect two pairs of speakers in parallel (Each pair would be 2x8 Ohms parallel = 4 Ohms) and then you connect these two pairs in series (2x4 Ohms in series = 8 Ohms) for your output. It's called series parallel and would only work in sets of 4 speakers. The wattage is quadrupled. See this simple diagram in the link the OP originally posted.
    Thank you for the applause.. . .

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