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Thread: ..linking FOH speakers and monitors

  1. #1
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    ..linking FOH speakers and monitors

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    hi there,
    got a little question here,
    i'm the PA man of a small pop band, they got their own (junk) equipment and my job is to make them sound better,
    the incredible BAD mixing desc only has speakon outs,
    those two cables go the the FOH speakers,
    then we got two monitors onstage, they are connected to the FOH speakers (with jack or xlr)
    now , i'm not 200% sure but i think the stage monitors are just passive,
    so they take the 'power' from the FOH speakers,

    can i put a graphic EQ between the FOH speakers and those monitors?
    or is there any current going from FOH to monitors? i guess not...
    just want to make sure i don't blow anything up ...
    ...listen...

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    Its a bad thing to do

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    nothing goes betwwen an amp and the speakers. NOTHING....EVER!!

    You need another amp to run monitors. There should be a monitor output on the board (or you can use an aux send) Use that to feed an amp. Connect that amp to the monitors. You would put the EQ between the monitor send and the amplifier.
    Jay Walsh
    Farview Recording. I am also the forum spokesmodel for Terasyne Amplification

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    Quote Originally Posted by earworm
    now , i'm not 200% sure but i think the stage monitors are just passive, so they take the 'power' from the FOH speakers,

    can i put a graphic EQ between the FOH speakers and those monitors?
    or is there any current going from FOH to monitors? i guess not...
    just want to make sure i don't blow anything up ...
    farview is right. However I thought I'd address a couple of points.

    The monitors don't 'take' power from the FOH speakers. It's kind of like plugging in another light bulb in a wall socket that already has one lamp in the other jack. It's a parallel connection, so the overall setup will draw more current from the board. The question is can the board handle that? It probably can, but you need to learn how to calculate ohms to be sure.

    For example, the speakers & monitors are probably 8 ohms, so each side with a main & monitor will be 4 ohms. If you board outs are labeled 4 ohms or less minimum, you won't break anything.

    Not breaking things is not the only issue. With the mains and monitors wired together, you can't control EQ and volume independently. Thus farview's advice to get another amp for the monitors.

    If you are on a very tight budget, you can run the mains off the left channel and monitors off the right. I did that in the bad old days but it's a pain in the butt to mix, and not intuitive at all if somebody else needs to take over the mix. And you would still not have monitor EQ.

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    ok thanks for the input,
    i know that the best thing to do is use an AUX for the monitors, togethjer with another amp,
    but we don't have that budget yet, thats my plan, to buy an amp and eq so i can control the monitors
    but i'll have to wait untill newyear cause now we're saving up money to buy 20 meter speakon cables, i already got my stagebox, but i can't stand in the back of the club yet since the speaker cables aren't long enough

    we're upgrading step by step, next year we'll sound good i hope

    now of course the question:
    what amp would you suggest?
    when i rent PA equipment i work with nexo, crest, i've had crown in my setup, but thats over our budget,
    i just mean, what brands should i avoid? like behringer and stuff,
    i see there are lots of cheap PA amps on ebay, what are the "dangerous" things i should look out for?
    i guess the cheap ones have a low signal to noise value?
    we got FOH speakers of about 400watt each (only for vox,bass,keys,gut)
    ...listen...

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    I don't know what is available where you are, but if you can find a peavey cs800, you will be in good shape. For the money, these things are indestructable. They have made them for almost 30 years, if I were putting a PA together now, I would have several.
    Jay Walsh
    Farview Recording. I am also the forum spokesmodel for Terasyne Amplification

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    thanks,
    well seems like peavy does make some nice PA stuff then,
    i remember that a while ago i was looking up info about small PA speakers and the peavy ps15 (or something similar) received some decent comments

    and when i check out ebay.de (germany) i see ALOT of
    "Hollywood" amps, they seem to be the new hype of cheap pa-amps,
    anyone heard those machines work?
    ...listen...

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    I would highly recomend either QSC PLX, or RMX series amps. these amps are very fairly priced, and are rock solid. I've worked with the peavey CS series often, they are extremely heavy, and their transient response is lacking.

    i don't think anyone's made this point yet, but with 20m speaker cables, you'll be losing probably about 20-30% of the amplifier's output in the wires! it's very common practice to place the amplifiers at the stage, where your speaker cable runs will be as short as possible. line and mic level signals are much more efficient when it comes to traveling long distances.

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    Quote Originally Posted by Cave Dweller

    i don't think anyone's made this point yet, but with 20m speaker cables, you'll be losing probably about 20-30% of the amplifier's output in the wires! it's very common practice to place the amplifiers at the stage, where your speaker cable runs will be as short as possible. line and mic level signals are much more efficient when it comes to traveling long distances.
    Excellent point. Shorter is better. More resistance eats up headroom, and makes you push your amps harder.

    A couple things about this, the gauge of the wire makes a difference, and so does the load impedance. Lower gauge wire loses less power, and higher impedance loads cause less power loss into the cable as well. So 12 gauge loses less than 16 gauge, and you will lose more power into the cable if you have a 2ohm load than if you have an 8ohm load.

    80 feet of 12 gauge loses 3% into an 8ohm load, but 12% into a 2ohm load.

    80 feet of 16 gauge loses 8% and 26% into the same loads.

    Here is a table from Tracertek that lays it out pretty well.

    cable loss chart


    The other thing to note is that the losses for the most part are pretty insignificant in terms of volume. If you lose 50% of your power into the cable, that really only translates to 3db less volume from your system. Any loss under 25% knocks less than 1 db off your volume.

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    interesting replies,
    but i know that cable wires should be as short as possible,
    BUT, here's the BUT,
    we work with a mixing desk with a built in amp,
    there are only speakon outputs,
    so i can't run 2 XLRs to the stage, to an amp... the mixer is the amp :'(

    now, another question about those impedances, i'm not good in that...

    i thought that:
    to our mixer i can connect a pair of 8 ohm speakers and it will work fine...
    but now we link our 2 monitors directly to the FOH speakers,
    does that mean that all 4 speakers should be 4 ohm, so in total they're 8 ohm?

    today i took another look at the FOH speakers and saw that they're 8 ohm,
    what happens if i connect 4 ohm speakers to that? can the amp handle this?

    i think its easy to see that i'm confused, am i right to say that
    "the more speakers you connect to an amp, the lower the impedance has to be", and all speakers must have the same impedance?

    when you take a look at specs of amps you read things like:
    400watt at 4 ohm
    200watt at 8 ohm (you get 8 ohm when u use 4-4ohm speakers,no?)
    and are 8 ohm speakers louder than 4 ohm speakers?

    ...listen...

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