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Beginner- very general- what is a mixing board FOR?

Discussion in 'Sound, Music, and Intercom' started by miriam, Aug 18, 2006.

  1. miriam

    miriam Active Member

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    Hi,

    I would appreciate a general view of what a mixing board is supposed to accomplish from anyone who can help.

    I am involved in a project and since I am the one interested, they would like to pass the technical operation to me. The one in charge now is swamped, so I am trying to get as much background info as I can on my own.

    It is a one-woman show. We have a Mackie cfx12, a cd player, a wireless mic, 2 unpowered speakers, and an amplifier. Plus one parcan.

    I'm reading the user manual for the Mackie board, but I have lots of gaps in my knowledge. Like what am I supposed to accomplish with this mixing board?

    The star has monologue, music with singing, music with speaking, and dancing (also with music).

    Thank you so much for anything you can tell me!

    miriam
     
  2. cutlunch

    cutlunch Active Member

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    Mackie has quite a bit of information on their website. If you go to the link below then open the introduction pdf it lists what is in all the other pdf's. You can open sections like mixer anatomy 101 for a start. This will be a good site to start as they refer to mackie gear.

    http://www.mackie.com/support/compactmixer/index.html

    The basic use of a mixer is to mix various sound sources (eg cd player, microphone etc) together and output them through loudspeakers in way that is pleasing to the audience. For example in your application you want the music from the CD player not to be louder then the singers wireless mike.

    If you can get your hands on the gear have a play with it this is the best way of learning. Start with something simple like getting a wired mike working. Then a CD player.

    A notebook could be handy so you can make notes as you go.

    Some of the other manufacturers such as Peavy, Yamha also have introductory articles on their websites. Your local library may have some books on the subject as well.

    Someone will probably put up a fuller explanation here soon. But I hope the link will give you enough to start with.
     
  3. soundman1024

    soundman1024 Active Member

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    I would say an audio mixer is to take multiple audio inputs and blend them in a fashion such that it is pleasing to the ear. Its pretty simple for you with just a CD player and a wireless mic. Just have the wireless mic at the right volume and the CD player at the right volume.

    The more complex one's setup the more things to blend at the right volume. With a band one needs to blend the instruments and the vocals to be the right volume. I would say two things determine how much needs to be miced, the budget and the venue. In some places all that is miced is a vocal. In some places multiple mics are used on one instrument. An example is that with large systems its a common practice to mic the top and the bottom of a snare drum. Some guitar rigs are so large that guitar amps are double-miced for a bigger sound, or there are wet (with effects) and dry (without effects) amps and they are miced separately. Even in the most complex setups the goal is the same, to take multiple audio imputs and blend them to be pleasing to the ear.

    A couple of the main tricks I would tell to someone new that have helped me, and in order that I would advise learning whats going on is first learn about feedback.

    Feedback happens when a microphone can hear what it picked up louder than it can hear the source basically. Imagine what happens when someone talks in a microphone and the microphone picks it up, it goes through the board, through the amp (which takes "line level" or low power audio signal and converts it into higher power audio signal for speakers), and through the speakers, interacts with the environment, and gets back to the microphone louder than the person that talked. It will just get louder and louder. It can be stopped by turning the microphone down or off. I'm sure people could pick that apart and tell me something that is wrong with it but its pretty accurate. If you start to hear a squeaking sound and its getting louder and louder turn the microphone off till it stops, then bring it back up quieter than it was, the microphone was too loud.

    The next thing I would look into is EQ. EQ is how audio people sculpt the tone of something. I'm going to get a bit deeper than you need here, but I think it will be good. I went into Wavelab and used a "parametric" style EQ to make a couple of illustrations. This first image is a "flat" EQ.
    [​IMG]
    I'm sorry that isn't embedded. I'm not exactly sure why it didn't embed, perhaps a moderator can help? Anyway what I want you to notice is the flat yellow line in the graph. What the graph is representing here is the shape of the "EQ." On the left side are the low sounds, the very left are the sounds humans hardly hear, and on the very right are the sounds that are extremely high pitched that once again humans hardly hear.
    [​IMG]
    This picture represents a change in the gain. Your mixer, the CFX 12 has three gain controls on it, and I'll explain those a bit more in the next section. Just take notice that when the gain nob was adjusted the yellow line made a spike. Just take notice that one of the boxes that was at 0.0 is now at 9.6. This is a measurement in dB, or deciBells. DeciBells are the standard in the audio world to measure the volume of sound. On your mixer you will see the top white knob (for the preamp) measures audio gain in deciBells, three of the EQ knobs measure cut or gain in deciBells, your fader shows cut or gain in deciBells (the U in the middle stands for "unity gain" or no gain change happens at the fader), and finally the output lights on your mixer show deciBells again. Even the volume out of speakers is measured in deciBells, and you can get a dB meter at RadioShack to tell you how many deciBells your speakers are putting out.
    [​IMG]
    Here you can see the spike in the yellow line has gone to the right, or higher pitch. The tone of audio is technically called its frequency and measured in Hz or Hertz which stand for cycles per second. On the low side is 20Hz, like a speaker vibrating 20 times a second, and on the high side is 20kHz or like 20,000 times a second. Also you can see that the box that was showing 200 is no at 863. 200Hz has become 863Hz, and the spike in the yellow graph has shifted accordingly. Your mixer has one of these controls on it.
    [​IMG]
    This last image is just something I put here to make you aware of. This last adjustment changed the "Q" factor of this or how wide the curve is. This knob is what makes it a "parametric" EQ. Without this but with the one knob above to change the frequency it would be a "shelving" EQ I believe. There is theory behind the number values but I'll spare you.
    Now for how these relate to your mixer..well you have 2 fixed frequency adjustments avalible, and one sweeping adjustment you can make. The furthest up blue knob changes the gain on the highs by the amount of dB you turn it, centered at 12kHz, the lowest blue knob changes the gain on the lows, centered at 80Hz. The knobs between these are for the mids though. The blue one changes the gain in dB, and the white one changes the frequency in Hz. On the last two sliders its different and I'm sure you can figure it out. Also in the upper right there are sliders that make up an EQ. They would change the graph so that it looked basically like the sliders are. This is a "graphic EQ."
    Take note though if you are having feedback issues at one frequency you can attempt to "EQ it out" or put a cut in dB at the troubled frequency. This allows all other frequencies to be louder because the feedback frequency is quieter. The trouble can be finding it, and thats where a frequency knob comes in handy.

    Anyway its about 3:30am local time and I'm wanting to get to bed. I hope this helps. Its probably far more than you need to know with just a CD player and a microphone but knowledge is power. A good idea would be to read up about the gain knob and solo mode, and clipping or distortion represented by the red lights on your board I'm guessing. I'm getting too tired to explain it though.
     

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