Why is speaker wire so thin?

Discussion in 'Amps and Cabs [BG]' started by wolfkeller, Nov 21, 2017.

  1. wolfkeller

    wolfkeller Supporting Member

    Aug 11, 2013
    The other day I was installing a speakon Jack on my ampeg 810. Doing this, I of course has to cut and strip the wires which are around 18g or so. I've worked on many cabs, Ampeg, gallien Krueger, Mesa boogie, peavy, ect. They ALL have the thin, weak looking wire.

    After I was done, I had to test it so I plugged in my huge 12g speaker cable and it occurred to me, "why do I need this huge cable to run the voltage when the wires inside are so tiny?" Those wires handle all that power, so why can't small speaker cables?

    Before anyone says it's because amps are higher powered now, let us remember that a 70s SVT put out the same power as the new ones. Further, high power handling cabs means high power handling speaker.

    I'm curious.
    Michael Schreiber likes this.
  2. Manufacturers use 18 ga wire inside speaker cabinets because it is an ideal size considering cost, current carrying capacity, and resistance, and the low physical strain of the weight it places on the lugs at the speaker.

    Speaker cables are heavier because the design considerations include current carrying capacity and resistance required for longer lengths of the cable compared to the wiring inside a cabinet.

    The handling characteristics, and crush resistance of a larger cable is more suited to how the cable is used.

    The pricing of a separate item like a cable can be easily scaled up, as the material costs of larger diameter wire increases with increasing wire gage and length.
    Last edited: Nov 22, 2017
  3. basscooker

    basscooker Commercial User

    Apr 11, 2010
    Northern KY
    Cab fan, hobbyist
    Pretty much anything we (the bass player) do can be handled just fine with 18 or 16 ga wire. No need to go bigger for 99% of our needs. The 1% of players that might want more robust wiring could do fine at 14ga....12ga or heavier is basically unnecessary for pretty much anything on a stage backline, like ever. There are no seriously long runs, and the current just doesn't necessitate heavier gauges.

    That damn Tim Taylor and his Binford tools....

    Knowing TB, a chart (or three) will pop up soon, explaining it all. I see a looooooong thread possible here. But this has been covered before... Maybe a link will do. I'll look.
    Last edited: Nov 21, 2017
    pacojas, Ductapeman and wolfkeller like this.
  4. ddnidd1

    ddnidd1 Supporting Member

    I have a 1000 watt amp. I asked the amp designer what gauge is adequate and the answer was 16 ga. between amp and cabinet.
  5. If you think 18AWG is small, you should see what the voice coil of the speaker is wound with.
  6. basscooker

    basscooker Commercial User

    Apr 11, 2010
    Northern KY
    Cab fan, hobbyist
  7. basscooker

    basscooker Commercial User

    Apr 11, 2010
    Northern KY
    Cab fan, hobbyist
    Does that link work? Anyway, if not, just use the TB search for "gauge".... Titles only.
  8. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    1,000 Watts into 4 Ohms is almost 16 Amps of current, and 14 AWG wire is rated for 15 Amps.
    16 AWG would be fine if you never went past 40% (10 Amps)

    add: My mistake, forgot this is not continuous current, so duty cycle applies.
    Last edited: Nov 23, 2017
    gumtown and Technicality like this.
  9. If you referred to NFPA 70, also commonly called the "National Electrical Code" in the USA to state that "14 AWG wire is rated for 15 Amps", you are using a standard that does not apply to speaker cables.
    Last edited: Nov 22, 2017
  10. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    So speaker wires are allowed to get warmer?

    (Oops, forgot it's not continuous current, re: duty cycle)
    Last edited: Nov 22, 2017
  11. It's not a matter of being allowed to "get warmer". It is a matter of classification for the use. I could be wrong about this, but I think the "classification" is determined by the equipment supplying power to the speaker cables are connected to. That being the amplifier. While the class might be referenced in the NEC, other standards, and engineering factors apply. You may have seen labels on equipment that states "Class 2 wiring". That would be one part of the regulatory aspect of acceptable wiring. UL, NRTL, CSA, TUV, and other regulatory agencies may be involved, depending on what approvals the manufacturer of the equipment sought for the design.
    Last edited: Nov 23, 2017
    petey293 and Geri O like this.
  12. mmbongo

    mmbongo I have too many basses. Supporting Member

    You're connecting to these wires, so huge cable is overkill and can actually cause issues.

  13. monsterthompson

    monsterthompson The Eighth Note Wonder Of The World Supporting Member

    Nov 25, 2008
    Electrons are pretty small.
  14. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    You can certainly use the smaller cable. In fact, for wiring the insides of cabinets, if the wire becomes to thick and heavy it can break the terminals on the speaker.

    Totally does not apply. The NEC heating argument only applies to the steady state application of current. Audio is different in that the signal in the real world always has duty cycle associated with it. Duty cycle is analogous to dynamics. All music has dynamics, so for example the average power of a clean signal reproduced by a 1000 watt amp with 6dB of dynamics is only 250 watts. The wire heating ONLY looks at the average.

    Of course voltage drop is responsible for SPL loss from the wire, this does use the actual current but the wire is so short that the voltage drop is generally very small (unlike flown PA systems with the amps on the deck, which may have 75-100' of cable attached).

    Speaker wire heating is based on average power, which is derated based on duty cycle. Rarely do you see duty cycle greater than 25-30%, so now you know why what you see in your cabinets works so well.
  15. So are Ooompa-loompas :woot:
  16. Raf Seibert

    Raf Seibert

    Dec 16, 2013
    Yes, but there are soooo many of them.

  17. sawzalot

    sawzalot Supporting Member

    Oct 18, 2007
    The distance between amplifier and speaker is a huge factor in the equation. Too long a speaker wire and you lose almost all the amp's damping factor, and you also lose quite a bit of sheer power as well. A nice 12 ga speaker wire is mostly good for about 50 feet or so and 18 ga will work for the short run inside the cabinet.

    Coolhandjjl likes this.
  18. tubedude


    Jan 19, 2015
    I think they prefer the term " fun size".
  19. biguglyman


    Jul 27, 2017
    Pownal, ME
    The cable from amp to speaker carries the whole load. It gets split up after entering the cab and less goes to each speaker. Sounded good when I thought of it...
    two fingers likes this.
  20. Jeff Scott

    Jeff Scott Rickenbacker guru..........

    Apr 11, 2006
    Out there!
    Sounds like you've just had one of those "Ah ha!" moments.
    Michael Schreiber and wolfkeller like this.