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Speaker Wire Extension and How to Plug in a Sound Rack?

Discussion in 'Sound, Music, and Intercom' started by BenjaminD, Sep 4, 2006.

  1. BenjaminD

    BenjaminD Member

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    I want to move the sound rack in my booth, but the speaker wires running to the FOH speakers have no slack whatsoever. I was wondering if it would be safe to cut off the banana terminator (I think that it is banana, I'm not sure) and extend them with some cheap unshielded speaker wire from wal-mart. I believe the current wires are shielded.

    In other situations, I have found speaker wire to be very tolerant to being extended by having the bare wires twisted together, but I have no experience with shielded wire.

    What would be the best way to extend these wires? FYI, there is no "adult" in the school system that I could ask, and the fire marshal has a tendency not to like to see bare wires, yet allows such things as doors that you cannot get out of when locked and the sound rack to be plugged in with a single 15-amp surge protector (the mains amplifiers are fused at 15 amps (2 of them), and the stage and booth monitor amplifiers are fused at 10 amps (3 of them) as well as one fx processor, mackie 24 chan mixer, tape deck, cd player, DAT tape machine, and eq)!

    This leads to my other question, what would be the best way to power this rack? And what is the likelihood that I can convince the school electrician to buy and install it?
     
  2. mbenonis

    mbenonis Wireless Guy Administrator Premium Member

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    I'd be surprised if the speaker wire is shielded - while I suppose it's possible, it's really unnecessary considering the high amounts of voltage and power in them - any induced EMF is unlikely to cause problems. To that end, I see no problem extending the wires with unshielded cable. Just make sure it is the proper gauge - this is written on the jacket of the installed wire. My guess is that it is 12 or 14 gauge, but whatever you buy to extend it should be at the minimum the same gauge, if not thicker (thicker wire = smaller gauge number. That is, #12 is thicker than #14). While you may not have immediate problems with thinner wire, it's just not good practice.

    As far as terminating the speaker wire goes, I would personally recommend getting some Neutrik Speakon connectors. They're a couple of bucks apiece, but they're easy to install and very high quality. You'll need four connectors and two female-female barrels (I don't have the part numbers handy) for the splice. Depending on the amplifier you have, you may be able to put Speakon connectors on the other end of the extension too, or you may need to terminate that with banana plugs. I couldn't tell you without knowing what model amp you have.

    If you don't want to go with Speakon connectors, you can just splice the new wire to the old wire using wire nuts and a bit of electrical tape to secure them together. If the built-in wire does have a shield, leave it unconnected (this applies to the Speakon too).

    As far as powering the rack goes - you should be using 20A circuits. My guess is that you are using one from the wall, just with a 15A power strip. If you want to upgrade this, you'll need an electrician to come in and wire another 20A circuit (or two) in. DO NOT DO THIS YOURSELF! That said, if things are working now and you never blow any fuses or breakers, and all of the wires are in good shape, you probably don't need to worry about it unless you're doing a really really loud show.
     
  3. cutlunch

    cutlunch Active Member

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    Just to keep things tidy I would probably buy a small plastic box of the type that can screw on the wall. Then you just bring the two sets of wires together inside the box and use terminal blocks to join them. It is slightly more work but the result will be neater and the join is less likely to be kicked or stood on then if you just join part way along the cable.

    As for the power as it has been said it seems to be working so that's the main thing. If you are worried you could get another surge protector and just split the load.

    Just note there is difference between the fused current rating and the power consumption of a piece of gear. The fuse ratings are often standardised to save money. For example if the maximum load on piece of equipment needed to be 7.25 Amps they won't get a special fuse made at 7.5 amp. They would use an off the shelf 10 Amp fuse it's cheaper. I am just making those figures up as a guide, there normally is a bigger difference between constant current in use and fault current.

    I have a behringer amplifier and from the manual it says when drawing the most current @ 120V consumption is 9.7 amps but it is fitted with a 15 amp circuit breaker.

    So if you are concerned then just get the manuals for your pieces of equipment and add up the power consumption figures.
     
  4. SHARYNF

    SHARYNF Well-Known Member

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    As with anything you ask 3 people you will get three different answers ;-)

    It is possible that they used shielded wire to prevent any interference from the speaker lines to other wires near by, if you look at the banana connectors you will see that the shield is not connected, so it is overkill and probably done more because that was the wire they had. It is also possible that when the system was installed they wanted the option to run a balanced line level signal down to the stage, and as such they simply used standard shielded audio cable. Problem with that approach, and in cases where I have seen what your are talking about, they used much thinner wirer (high awg number) n stead of the 12 or 14 awg you really should be using . BUT at this stage there is little you can do on the total length. Another thing is that are you sure it is actually shielded or is it just three conductor wire white black green? if so they were just using the more common power type cable and just not using the green wire.

    SO extending it, I would suggest that you get a good quality extention cable, you might need to get three conductor since it is more common, and just not use the green wire.

    I do not recommend using wire nuts for low voltage low amperage connections, they tend to come loose, corrode, and are fine for standard wall power but not the best for speaker lines.

    Using a box with connectors/terminal strip is ok, but again you have the connections, you need some kind of straing relief/protection on the wire going in and out of the box.

    The speakon suggestion is a good one but a trick that is used is to get the panel mount connector, and a small section of heat shrink tubing and after connect it up, heat shrink the connection. There actually are cable female speakon connectors but do to limited use, they are quite expensive. I usually don't like to use the speakon to speakon barrels as again you have just added two more additional connections.

    the common speakons are nl4 which have 4 connections, but you usually only use 1+ and 1- and leave the 2+ 2- unconnected, if you want to have a standard connection. Advantages are that you can now disconnect and also you can extend them further, but there is some cost

    The cheapest way to go is to get your new wire, and splice it to the existing cable, solder the connection and use heat shrink tubing (remembering to place it over the wires BEFORE you connect them, and have a larger heat shrink tubing over the entire connectioin. You can cut the cables so that your splices are not next to one another. This works fine for speaker cable but you would NOT do this for power lines.

    Anyway some options

    Sharyn
     
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  5. mbenonis

    mbenonis Wireless Guy Administrator Premium Member

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    That seems like a really bad idea to me...isn't the point of a fuse to protect the equipment? Unless the equipment can really handle an overcurrent big enough to blow the fuse, shouldn't the fuse be properly sized?

    (my criticism isn't directed at you, cutlunch - it's directed at the manufacturers :) )
     
  6. SHARYNF

    SHARYNF Well-Known Member

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    It is the difference between the load that the equipment requires to operate, and the protection level it needs. So if the equipment only draws 7.5 amps but you want to protect it from an overload situation at 10 using a 10 amp fuse makes sense.

    sharyn
     
  7. Chris15

    Chris15 CBMod CB Mods Premium Member

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    I would think a slight overrating of a fuse to be a smart idea, so that on a very loud peak, fuses don't blow, but gross overrating of protection devices sound like a stupid idea to me. As mbenonis said, it does little to actually protect the device.

    When the first post referred to "shielded" cable, could it a misinterpretation of a double insulated cable? No to offend anyone, but to install speakers using a mic type gauge of cable, unless they are say a couple of watts, is sheer stupidity.

    As far as extending it, I know that the use of mains cable is common practice at least in flexible leads, I would tend to think that there would be better alternatives for a permanent install. Now I'm not up on the rules about these hings, but I believe that you may need special cable if the runs go through a relief air plenum.
     
  8. cutlunch

    cutlunch Active Member

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    There has to be a difference in the current consumption and the fault current so that fuses don't keep blowing when you turn the equipment on.

    When a piece of gear especially amplifiers are first turned on they draw more current then when they are drawing their normal operating currernt.

    If the fuse rating was too close to this surge current it would be tripped before the equipment started operating normaly .

    In an amplifier if you have a normal laminated transformer as opposed to a torriodal transformer you will find the toroidal takes more surge current at startup. This is when both transformers are rated for the same voltage and current output.

    I agree with Chris that to have too big a difference between operarting and fault current is not good. The electronic components chosen for a design should be rated that they can handle some fault current before the fuses below. This is because not all fuses of the same ratings will blow at the exact same current point.

    To protect some components from having to high a fault current flow through them some circuits include a crowbar circuit. A crowbar circuit is when a fault current is detected a nearly dead short is put across the power supply lines. This forces the fuses to blow before the componets can go into run away mode where the current through them is no longer controlled.
     
  9. SHARYNF

    SHARYNF Well-Known Member

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    Another great discussion

    I think that there is a lot of misunderstanding re fusing in devices, how much the device actually draws and the protection on the circuit it is attached to.

    Lighting is totally different from audio, when you plug in a 1000 watt light to an outlet it takes 1000 watts, and infact even if it is dimmed, it takes more than the dimmed percentage, so for instance in a large concert it is easy for the lighting to take up a full 400 amp or higher three phase connection and it is a resistive load

    Audio is totally different, and it is interesting to see just how little actually is drawn. First of all you typically don't run the amps flat out, but more important the draw in not continuous, it is inductive, and takes far far less in typical running mode. Where you get in to problems and blow speakers, and fuses is not from running a super powerful amp but rather a lower powered amp that is being over driven to the point of clipping. This is why for instance most audio folks will typically say that you should have an amp that is twice the rating of the speakers. Most people don't understand it but for instance if you take a speaker rated at for sake of argument 100 watts, and you feed it from a 100 watt amp, and you drive the amp to the full 100 watts and it clips, you will blow the speaker. IF on the other hand you take a 200 watt amp, drive it to 100 watts and it does not clip you will not. To give you an example in a large Metallica concert we were involved with, they had a 80,000 watt pa system, it all ran off a 200 amp three phase connection, measuring the current showed using less than 30 percent of the rating (about 70 amps a leg). Rarely do you need more than 200 amps three phase for audio. If you have access to a clamp on meter and you look at the current draw on the audio side of things you will be amazed at just how little it is drawing. In addition on large setups to avoid the inrush current draw you have power on sequencing as a side issue.
    So for instance if you look at audio stuff and read the amp requirements on each item and add them up, you typically are way off. Again totally different for lighting.

    So being able to run all the audio from a single 15 amp strip is probably not a s crazy as it seems. If you really crank up the subs and the amp starts to distort then you will pop the breaker but other wise it is probably going to blow the breaker. More of an issue especially in schools which typically have poor electrical systems from an audio standpoint, you wind up where all the outlets in the room are on the same breaker so it really does not matter if you plug them into different outlets, OR they are on differnet breakers but on different phases and therefore have different ground connections back to the panel. It is at this point especially with unbalanced connections that you start to get hum problems. For instance are the inputs to the amps trs/xlr connectors or rca or 1/4 inch ts connectors. If it is all balanced in all the connections then probably no problem but say you add a cd player or something that does not have a balanced connection to the mixer, then your problems start if all the equipment is not on the same phase and the same ground.


    There are all sorts of plenum rated cables etc etc, but in general audio is put into the low voltage side of things and has different requirements and they are more concerned with fire hazard from burning insulation that the gauge of the wire. Ironically no one says for a 1000 watt amp you need to run 14 awg wire.

    I noticed the other guy was from florida, and it is amazing the stupid things contracters will do when they install for audio. There are all sorts of NEC
    regulations for electricity and all the electricians are up to speed on that stuff, but on low voltage audio stuff they are on their own based on how well things were speced out.

    A lot of times what happens is that the designer originally is thinking of having the speakers and the amps together down on the stage. So they are going to run a line level connection from the mixer. Then someone decided to put the amps back at the mixer, and they then want to run the speakers. You saw this in the other post re a new setup for a pa at a school. So someone decides to spec a snake running the speaker lines, or they should run special cable. I guess it really comes down to if the cable is actually shielded, then it probably is mic cable which I AGREE is stupid. It could be double insulated or what ever, but I was assuming the poster was familar with shielded cable.

    anyway all good stuff

    Sharyn
     
    Last edited: Sep 5, 2006
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  10. BenjaminD

    BenjaminD Member

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    Thank you all very much for your responses, I'm sorry I was unable to respond until today, but my laptop's power brick fried itself.

    Anyway, I now that I think about it, the speaker cable was probably three-wire cable that just didn't have the shield connected. I can't get anywhere near the speaker end of the cable, as the speakers are dead... um... sitting on the ceiling of the auditorium about 30 feet from the floor and 12 feet from the structural steel in the ceiling, so I’m nut sure what the connections look like at that end. I cannot be sure of the gauge as I haven't cut it open yet, and there is not enough of the cable in the booth for me to read the specs on it.

    I like the suggestion about soldering/heat-shrinking the cable, but we don't have any heat shrinks, a torch, solder, or a budget. I know that wire nuts would not be the best for this, but I think it may be the only feasible method...

    I should have thought more carefully about the power consumption of the equipment... I am still slightly nervous about putting it all through a 15 amp surge strip, but it hasn’t blown up or tripped any breakers yet, so I guess it’s fine.

    Again, thanks everyone!

    Ben
     
  11. SHARYNF

    SHARYNF Well-Known Member

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    Hey Ben

    well at least it was not an exploding li ion battery!

    Can you look at the banana plug side of things and see if there is actually shielding? you probably can see the size of the wire going into the plug also. A lot of low voltage wire is not market on the outside as to awg

    If it is infact shielded then I am guessing the wires are 20-22 gauge?? which of course is way to small for a speaker run. If the wires look like the size that you have in electrical cords then it can be 16 or 14 or 12, but it would be very rare to have that with shielding.

    Shrink tubing can be used with a hair dryer. you might be able to borrow a soldering iron/ etc but if you have to just twist the wires together, then I wouls still look at shrink tubing as a good option, looks professional vs just some electrical tape.
    Don;t know if you have a "TRUE VALUE" but the for instance tend to have the shrink tubing for a few dollars in little packets.

    Most pro audio folks recommend against using the typical surge protection compter type of strip, and usually go with a simple quad box plugged into the outlet. You may have seen some but the have setups for stages where you have a 12/3 cable with a plug, goes to a quad box (two duplex outlets in a metal box) and then another 12/3 cable goes to the next box. etc Typically this is what is used to connect multiple audio gear together. Not a big deal but just something to think of.

    No budget is always fun

    Sharyn
     

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