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fun with speakers!

Discussion in 'Safety' started by EPAC_Matt, Nov 7, 2004.

  1. EPAC_Matt

    EPAC_Matt Member

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    .. not really. I'm the sound designer and board op for our schools production of MacBeth. Our theatre has two mid/high speakers and a subwoofer infront of the proscenium but I also wanted to place some loudspeakers in the upper balcony.

    Now, the way we have our main audio system set up, our Mackie's main outs directly go to our two main amps that power the main speakers. Four of our mackie's six aux sends are plugged into two more amps, whos outputs go to a little switchpanel that lets us assign certain amplified aux sends to one or two of any 12 speaker jacks located throughout our theatre.

    The thing is though, there are no speaker jacks in our balcony, so we had someone come in who wired our switchpanel so we could assign aux sends to bare wires comming out of the back of the main rack isntead of to speaker jacks. We wired these up to two quarter-inch cables, threw them out the soundbooth window, and pulled them around into the upper balcony.

    Because one of the cables didn't reach all the way from the soundbooth to the oposite end of the upper balcony, we used a 1/4" barrel connector to attach another cable to it and lengthen it so it'd reach the far speaker.

    When I assigned Aux1 to Balcony-house-right and sent a signal, the balcony-house-right spekeaker worked fine.

    However, when I unassigned that and assigned Aux 1 to balcony-house-left and sent a signal, nothing came out of the left speaker, but audio DID come out of the right speaker. This lead us to belive there was a wiring problem.

    Another student tech and I spent seven hours troublehooting this.. we replaced cable, we re-wired some stuff in the back of our main amp rack, tried different aux assignments, and still nothing.

    As sort of a little test at 7:00 PM, we werent really expecting anything, but we moved the left monitor to the middle of the balcony where the barrel connector was used to extend our cable. we took off the barrel connector and extra cable and plugged the shorter cable directly into the monitor. Having aux-1 assigned to the left speakerk and aux2 assigned to the right, it all worked perfectly.

    Here's the kicker -- I unplugged the left monitors cable, then plugged JUST the bare barrel connector onto it... and audio would start playing out of the RIGHT speaker!

    so anyways... I learned something yesterday.. Don't use cheap radioshack 1/4" barrel connectors, use nice beefy metal ones.
     
  2. zac850

    zac850 Well-Known Member

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    Haha, yea, I had the same thing at my school. I bought the 1/4 barrel connectors and 15 foot jumper cables. From time to time I would have to unplug and re-plug in the barrel adaptor, because the sound would randomly die. I have no idea why, but now that it works, just as long as I don't touch it, it works fine.

    As they say, you get what you pay for.
     
  3. ccfan213

    ccfan213 Active Member

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    ouch... i know the feeling
    i spent at least 2hrs a couple of weeks ago trying to figure out why our 1 year old amp wasnt working when it had shown no signs of damage before. after checking every input and output and eventually giving up because someone told me i didnt need it for that show and we are getting new equipment installed, i discovered that in the process of installing the new equipment one of the electricians had unplugged it. because of the way the wires are tied with cable ties it wasnt obvious at first, but i felt stupid anyway.
     
  4. RedEyeProd

    RedEyeProd Member

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    I would firstly say, dont extend on 1/4" jack use XLR they clip together nicely and all you have to do is the have somekind of adaptor at the end.
    a collegue of mine learnt this the hard way when i nearly shot him for extending jack for a monitor using none other than an expencive DI box. two XLR lines and adaptor later and DI box was unharmed, ( he had desk wired to output side and monitor into input ).
     
  5. EPAC_Matt

    EPAC_Matt Member

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    I'm not sure I'd want to use XLR cable for speakers... It would be rather unfortunate if someone besides me had decided to plug a microphone into the other end of an amplified current carrying XLR cable. Are the conductors inside of them even rated for carrying that much current?
     
  6. RedEyeProd

    RedEyeProd Member

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    Thats easy enough to fix just make sure the sockets end is nearest the speaker then if someone unplugs they can only plug into the speaker side.
    Problem solved, no fried mics.
     
  7. koncept

    koncept Active Member

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    If I remember correctly, the xlr cables can carry the current without a problem. Also when using speakers most xlr speaker systems have the male end at the speaker and the female end at the amp/mixer. I have used xlr with a speaker system and it ran excelent until the music director said i wanna be heard louder than the actors....thats for another place though
     
  8. BNBSound

    BNBSound Active Member

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    Lousy thing about 1/4" connectors, they work fine for ten years sometimes, then overnight, kaput! And about using XLRs on speaker cables... that's so 80s man. Why even bother when for about the same money you can use Speakon.
     
  9. fosstech

    fosstech Active Member

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    Well, using XLR's for powered/active speakers is OK, in fact that's what you need to do (use 'em on my Mackie 450's), but for carrying speaker level signals, it's not a very wise thing to do. I've never seen an XLR cable being used as a speaker [level] cable. If XLR cables are used, you're setting up a recipe for dissaster. What happens if someone thinks it's a line output from FOH? Plug that hot signal into your board's input and the mysterious blue smoke will be released 8O . Also, XLR cables don't use low gauge wire, either. You'll most likely find somewhere in the neighborhood of 20AWG wire in there, which is too small for carrying speaker level signals. I generally don't use speaker cables smaller than 14AWG; I usually use 12.

    I have used 1/4" for speakers before, and I'd have to say that Speakons are your best bet. If a 1/4" cable gets a hefty yank perpendicular to the jack, something is going to break. It's happened to me before (I had to replace a 1/4" connector on a speaker because of that once :wink: ). The design of the 1/4" jack isn't really beefy enough to handle the abuse that speaker cables get. Speakons, on the other hand, are tough enough to get yanked. I've yet to have one break on me. And, they give a much more secure connection than 1/4".
     
  10. RedEyeProd

    RedEyeProd Member

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    i would agree with fosstech on that one.
     
  11. sound_nerd

    sound_nerd Active Member

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    Yah, but I think they are talking about using XLR connectors on standard 12 or 14 AWG speaker cable. It was done, and sometimes standard equipment at one point in time.
     
  12. Thranduil

    Thranduil Member

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    Dont run 1/4in over long distances, more things go wrong. Wer use XLR for everything at our theater. We have 2 going to out MTS-4s which are self powered, so we dont need to carry the amp signal, and we just have an adapter on the back of the board because for some reason 16 channel mackies only have 1/4th in out. Our wireless recievers are all in the booth, so we use 1/4 in for those and for the cd/ md player, but evrything else is xlr. We also dont get a balanced and unbalanced system hum.
     
  13. The_Guest

    The_Guest Senior Team Emeritus Premium Member

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  14. Andy_Leviss

    Andy_Leviss Active Member Premium Member

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    Two-pin XLR used to be a standard speaker connector; as recently as three years ago I worked overhire for a company in Cambridge, MA who still has a lot of gear running on these (I seem to recall the females being three pins with plugs in the third pin).
     

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