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Our Speakers'eth

Discussion in 'Sound, Music, and Intercom' started by Schniapereli, Jan 23, 2007.

  1. Schniapereli

    Schniapereli Active Member

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    Location:
    Provo, Utah, United States
    We currently have some EV Xi-1122/85 and some other speakers that are a larger version but I have not gotten to read what is on them. (I think they are the Xi-1152/64 or something like that)

    We have 4 of the larger ones at the front of the audience. (1 left, 2 middle, 1 right) and 3 smaller ones(left, center, right) on the back half where the seating makes a __/. There are also some of the smaller ones used as stage monitors that are hanging with the cluster of 2 big speakers in the front center.

    We use Crown's Com-Tech 410's for Hi freq, and Com-Tech 810 for Lo's.
    We have had a problem getting bass out of our front right speakers. I Put the attenuation from 5 to 0 which helped a little. (the other was at 5 also) I also checked the inputs on the speakers, which seemed weird to me. Here is a kind-of map/table.

    Left Front----Center Left--Center Right----Right Front
    Lo-Z-----------Hi-Z---------Lo-Z------------Hi-Z

    Left Back-----------Center Back-----------Right Back
    Lo-Z (?)-----------------?-------------------Both

    (could not tell Center Back. (I was looking from the floor.))
    (The stage monitors also ahev 1 that is Lo-Z, and one that is Hi-Z)

    Is there any reason why these would be plugged in this way?
    Should I switch the Right Front to Lo-Z?

    There has been issues before where they wanted more sound out of the speakers, but I don't want to blow them by adjusting them without absolutely knowing exactly what I'm doing.
     
  2. kovacika

    kovacika Active Member

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    I dont know to much about this series of amps, but they are comercial use, and were designed for 70v operation. This would normally be used with a sound system found in a department store for ambient music. It may be that the amps werent designed produce very good low end because that would make the store seem much louder. By giving more juice to the high frequencies it allows the music to be heard without increasing the apperent volume. (funny thing is, it might actually be harder to talk over since our voice resides in the middle to high frequency range, also what our ears are tuned to her better)

    As for the impedance issue, I like all my connections the same impedance, that way everything is based off the same reference point. If your using transformers to change impedance, some transformers do degrade signal quality, but normally not much.
     
  3. Schniapereli

    Schniapereli Active Member

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    Location:
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    So, should these all be on low impedance?
     
  4. kovacika

    kovacika Active Member

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    It depends, if all your outputs from the mixer going to the amps are low impedence (such as XLR outputs) then you should maintain a low impedance signal unless you use a transformer. If your mixer outputs are high impedance (1/4", RCA ) you should again maintain a high impedance signal. I believe the Comtechs have the ability to run balanced and unbalanced, so presumably at high and low impedances with the same gain-- I think, but im not sure.

    A possible reason your system is wired the way it is might be that when looking for more volume someone found that running a high impedance signal to an input meant for low impedance made the speakers louder. This volume increase would be caused because most low impedance lines run at a typical -12db and high impedance at +4db. This can work for a little, but will end up in a higher risk of distortion. (due to loss of gain structure).

    As for being able to blow the speakers, just stay away from a switch on the back. There will be a switch to change the amp from 70v to 8ohm operation. You want to stay on 8ohm/4ohm operation. Other than that just be careful with the volume control and turn things off or down when you hear distortion.
     
    Last edited: Jan 25, 2007
  5. Schniapereli

    Schniapereli Active Member

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    Location:
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    We use the XLR mains from our mixer.

    I'm going to ask a sound guy who graduated from our school a while ago, but is still into sound locally. Maybe he knows if there was some reason for it when it was set up. I don't think we have any transformers.

    Also, random question, why are all of the amps connected with ethernet cables? Also, what happens when one is turned off out of the set. (does it mess up whatever the ethernet is for?)

    We were also taught that when you turn on all the amps, you wait till you hear a clik before you turn on the next one. Why is that, and is it connected to the ethernet cables? Does this rule also apply when turning them off? What happens when you do not do that.
     
  6. cutlunch

    cutlunch Active Member

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    Just a quick one about waiting for the click. I haven't had a chance to study these amps but I think this has to do with inrush current at turn on. Equipment connected to the mains draws more current at switch-on then in later use. This is basically the power supply has to store energy so it can pass it on to the circuit.

    Think of it like taking a car from standing start to cruising along the road at a constant speed. To get the car going you will have the aclerator held down more which lets the engine have more fuel. But once the car has overcome inertia and is cruising less acclerator thus less gas is needed. The basic principle applies with amplifiers.

    Now back to the click. Until the power supply has stabilised sometimes this will cause a pulse of current through the loudspeaker. This can be heard as a loud bass thump which can damage the speaker. To prevent this some manufacturers use relays that disconnect the loud speakers from the amplifier until the power supply has stabilised. This may be the click of a relay operating you hear.

    So as you can see when you switch on the amplifer it takes more current at startup then during normal operation. So if you turned all the amps on at the same time the total in-rush current may actually be greater then the circuit breaker is rated for. If the amps are all connected to the same circuit. But the total of the normal operating currents is less less then the CB load.

    So I would follow the wait for the click rule still. Also a good rule to apply to sound systems is: Amps on last, Amps off first. That way as your turn on equipment in the signal path eg mixer, eq etc it won't cause a damaging thump in the speakers. The same applies when turning off, if the amps are off first then they can't let any thumps through as other equipment is turned off.

    Just as an aside lights have inrush current too but this is due to them cold when turned on.

    Hope this helps.
     
  7. silvrwolf

    silvrwolf Member

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    Location:
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    It sounds like your amps have cobranet cards installed or somthing, If you know, what are the ethernet cables connect the amps too, each other or are they on a network to control the parameters of the amplifer ?? This could be some type of variable in you signal strength between the mixer and the amps. What I mean by this is that your amps may have been set by software to cut the signal down coming from the board.
     
  8. Schniapereli

    Schniapereli Active Member

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    Location:
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    They are only connected by ethernet to eachother. Just daisy chained along like the inputs.

    Small side question that is not as important: Our inputs to the amps have the special cables with 1 TRS end leading to multiple XLR ends. Like /UUUU where each of the XLR ends has 2 cables coming out of it. (all 1 cable) How is this different as opposed to just lots of short cables going from input to output to input to output. / U U U U U (daisy chained.) And what is this type of cable called. (the /UUUUU)

    Thanks :mrgreen:
     
  9. kovacika

    kovacika Active Member

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    THe ethernet cables are for using the dsp capabilities. This is normally done via a computer.

    Cutlunch is correct about the reason for the click. But Ive never heard anything about having to wait for it before turning the next amp on. (I never do) It may be that each amp is assigned a number/adress for ethernet upon start up and if all the amps go on at once, they end up with the same adress, but i wouldnt think so.

    There is no difference between /UUUUUU and / U U U U
     
  10. Schniapereli

    Schniapereli Active Member

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    Location:
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    I've been thinking of running our next show from the computer. (They sing along to the CD, and our CD player is kind-of crappy.)

    Is a digital connection to the amps better than just using an adaptor, and hooking it up to the sound board? I could just use the computer volume controls, etc. (which would be a little better than the board's just because the board is a little broken)

    If it is better, how much better would it be? (Would it be worth it? Just an ethernet cord right to the amps. Our board does not take ethernet.)

    Do you need a special program to be able to use the ethernet for sound? What other things do you need for it to work?

    Any other important step I'm missing?
     
  11. kovacika

    kovacika Active Member

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    I dont htink you can use the ethernet as an input. As for using a computer through the board, you will need a pair of direct boxes with ground lifts (one for left, one for right). Otherwise you will get lots of harddrive noise.
     
  12. avkid

    avkid Not a New User Fight Leukemia

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    Occupation:
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    Or one of these babies:
    [​IMG]
     
  13. Schniapereli

    Schniapereli Active Member

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    Location:
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    Where has this whirlwind site been all my life?!?

    Finally! Things explained in layman's terms!

    15.6 Brownie points for avkid!

    Anyways, we don't have a fancy shmantsy direct box like that, or the money to buy one, so, I'm so far going with the 1/8'' to RCA Y adaptor.
     

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