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How to run speaker cables from amp to speaker cabinets?

Discussion in 'Amps and Cabs [BG]' started by gfab333, Oct 29, 2002.

  1. gfab333


    Mar 22, 2000
    Honolulu, Hawaii
    Although I have a good understanding about matching speaker cab impedances to amp ratings (two 8 ohm cabs = 4 ohms, etc.), I'm a little rusty on the nuances of running speaker cables in parallel vs in series.

    Assuming you have two 8 ohm cabs rated at 350 watts each, and one amp, when would it be appropriate to run the cabs:

    scenario #1: in series, with what would seem to be a custom wire job, as shown in some speaker manufacturers' electronics diagrams?

    scenario #2 by connecting one cab with a cable running from the one of the amp's output jacks, and connnecting another cab with a cable from the other amp output jack?

    scenario #3 by connecting the first cab to one of the amp's output jacks, and connecting the second cab by running a cable from the first cab to the second cab?

    Thanks in advance for the details.
  2. Assuming the amp can run ar 4 ohms, scenario #1 is definitely suboptimal - You'll be running an impedance of 16 Ohms, which will give you about half the wattage you'll get with the other two scenarios.

    I like the scenario #2 method. That way if one speaker wire fails or gets accidentally unplugged, I'll still get sound.

    Good Luck
  3. gfab333


    Mar 22, 2000
    Honolulu, Hawaii
    I figured as much about scenario #1, but what's the difference between #2 and #3, as far as power?
  4. Hugh Jazz

    Hugh Jazz

    Sep 13, 2001
    Atlanta, GA
  5. there is always one who says that! and you got in before me dammit!

    I have my rig wired up as scenario #3, but can have each cab wired up to the outputs of my amp, but they are parallelled anyway so its the same thing.


  6. Matthias


    May 30, 2000
    Vienna, Austria
    Regarding power output of the amp there's no difference between #2 and #3. But longer cables reduce the damping factor, so if you want to keep cable length as short as possible go for #2.
    If your amp only has one output (e.g. poweramp in bridged mode) you will have to chose #3 anyway.
    But I don't think that there will be any audible difference unless the speaker cables are very long and/or thin.

    PS: Please don't ask me to explain the damping factor. I just know that higher damping factor means better control over cone movement resulting in faster response = tighter/better tone.
  7. Hugh Jazz

    Hugh Jazz

    Sep 13, 2001
    Atlanta, GA
    I am ze vinner! :D

    I normally run my cabs in the #2 formation (they're usually stacked). However, when I can't stack them and have to put them both on the ground and the cables won't reach all the way to cab (shortest cables = best), then I go with #3 which gives me a foot or so of "extra" cabling.
  8. Matthias


    May 30, 2000
    Vienna, Austria
    The question is: what is short, what is long?
    When I look at speaker cables of PA's which are several meters long, I guess it doesn't make much of a difference if the cables of a bass rig are 2ft. or 6ft.

  9. Hugh Jazz

    Hugh Jazz

    Sep 13, 2001
    Atlanta, GA
    I read somewhere that as a guideline, you should try to keep them under 10 feet if you have 16 guage cables (the smaller the guage, the longer you can go). However, the sonic differences would probably be very minute.

    The other advantage to short cables (at least for me) is that there's less cable to get tangled up with everything else. I like to keep the rig as neat and clean as possible. Not to mention that they're cheaper too! However, should the need arise for a longer cable and you only have short ones, you could be f***ed.

    Anyway, If I remember correctly, my cables are 1 ft. and 3 ft. long (both 16 guage).
  10. Basso Gruvitas

    Basso Gruvitas Supporting Member

    Jun 7, 2000
    Dallas/Ft. Worth TX
    Guys, please correct me if I'm wrong.

    Scenario #2 is stereo, scenario #3 is bridge/mono. If that's the case, would the wattage going to each individual cab change depending on the scenario? How would each affect loudness?Wouldn't the load from the cabs be 4ohms either way?

    I'm so confuuuuuuuused....
    :confused: :(
  11. You're wrong.:D Or at least not completely right. #1 is only stereo if the two outputs are connected to two discrete sides of a stereo amp. But most mono amps of a certain size have two outputs (or more) that are simply wired in parallel to each other. This is not stereo, it's still mono.

    #2 indeed has to be mono, but it doesn't have to be bridged.

    Stereo is a different ball game. You have to treat a stereo amp as two amps for the purposes of figuring impedance on the two channels, unless you're bridging the two channels (in which case you've turned the stereo amp into a mono one).

    But we're talking about mono here, I think. In which case the power delivered and the impedance seen by the amp are the same in scenarios #1 and #2.

    EDIT: Ouch! My error: for my #1 and #2, read #2 and #3! Sorry.
  12. gfab333


    Mar 22, 2000
    Honolulu, Hawaii
    Thanks for all the replies.

    Yep, I'm talking mono. Just your run of the mill GK, Eden, SWR, or Hartke head.
  13. I like #2 for a couple of reasons. First of all when you run 2 cabs from 1 amp output you are push/pulling all that power through 1 wire say 16 GA. and when you push/pull it this way you are having to do so for the entire length of both wires combined. When you run 2 wires from the amp directly to each speaker you are only push/pulling the current the length of the longest wire ( you should make them both the same length) and you are using 2 16 GA wires to move the current instead of only one. I doubt if you can hear any difference this way but in most cases It doesn't take anymore work.
  14. DCman


    Apr 7, 2002
    #2 is good for the reason that if one cab/lead gives up, then the other is still there and will still make some noise....

    DC :)

    edit: think someone else said that earlier.... :oops:
  15. That's not a bad idea, but it hardly matters as long as your speaker cables can carry the current produced by the amp. I like it because you can lose the connection to one cab and still have the other.

    About Damping Factor: Any halfway decent power amp will have a DF in the thousands but speakers only need to see a DF in the tens for good response. The reason amp manufacturers put in high damping factors is so the amps can drive long cable runs and still show the speaker enough DF. I often do speaker cable runs of 75 or 100 feet and haven't had any problems. The bigger issue with long cable runs is line loss.

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