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Thread: Check Words

  1. #1

    Check Words

    I was learning the finer points of my sound mixer from an experienced friend of mine the other day, and one the I picked up from him was that there is a technique to setting your eq levels.

    Does anyone know that those tricks are, or maybe other ones?

    He was saying that you can tell what frequency is feeding back by the sound of the screech you hear.
    And he said that some works like "check", "one", "two", and "four" were good for checking eq levels.

    Can anyone verify that stuff and maybe offer other advice as well?

    Thanks, Caillte

  2. #2
    You will always want to check pops and hisses (Peter piper picked a peck of pickled peppers is a good one, as is She sells sea shells by the sea shore). Don't worry about saying them perfectly, it's the pops and hisses that you listen for and work to make sound normal!
    Eric Adler (tonsofpcs) Chat at:
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  3. #3 Eric said: normal.

    Can't be emphasized enough. I've seen systems EQ'd with the bass boosted for the sake of "warmth" and the treble boosted for the sake of "crispness" until speech sounds like someone spitting through a tuba.

    You may know that in their buildings, the Greeks made their columns just a tad convex, because otherwise the columns looked concave. I've seen imitations where the columns are so convex they look almost like footballs. It wasn't enough that the architect knew the principle; he had to show everybody he knew it.

    Just so with EQ: people tend to exaggerate the extremes so everyone will know they have a real "hi-fi" system.

    Well, "fi" means fidelity, with means accuracy, correctness, truth. If the sound is so boomy and spitty you couldn't possibly mistake it for a person's actual unamplified voice, it's probably wrong.

    Re: specific feedback frequencies, search my posts, somewhere I did one on which notes correspond to which frequencies.

  4. #4
    Thanks to both of you for the help! I appreciate the input.

    To Karl:
    Hey man, I searched your posts and I couldn't find the post with the frequency list you were talking about. The posts only go back to May though. Do you know if the post was older than that?

  5. #5
    dunno what happened, and for some reason I can't get into my email either. when I get time I'll re-post.

    If your friend really has the technique nailed, sounds like you should persuade him to get on this forum and teach us all. Or maybe Eric has it too?

  6. #6
    Senior Member SC358's Avatar
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    Quote: karl eilers
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    Re: specific feedback frequencies, search my posts, somewhere I did one on which notes correspond to which frequencies.
    I read that post. I never got a chance to comment on it but since we're discussing it - I found it to be a very basic, under used and much needed for those of this forum who look for some answers and techniques with live audio. I feel that it is so important, that I hope you'll be able to re-write it and submit it to Dave to be part of the Audio Tutorials under Sound Quality. I'll even, "go to bat" for it, also.

    In truth, I'm sorry that I was so busy at that time that I just didn't copy it for my own references.
    Relationships are based on compromises - behavior accepted is behavior repeated.

  7. #7
    I went back to May, when I first joined this forum, and I didn't find it. It's buried in a reply on some other topic. I'll rewrite it, but offline... has a certain amount of calculation to it and I don't want to post something I'll have to correct later.

  8. #8
    Okay. This is a way to nail feedback frequencies in the lower and mid frequency range. It assumes 1) we're dealing with a 31-band equalizer with standard center frequencies and 2) the user has enough musical training to understand a discussion of pitches and intervals.

    You need a way to pick out musical notes. Ideally, you have perfect pitch, but that's rare. I had something close to perfect pitch when I was younger, but in late middle age the reference often begins to shift, and my built-in reference is unreliable now. When mixing a group, you can often ask the keyboard player to find the note that corresponds to a feedback frequency. Or, you can pick up a tuning fork; a cheap one isn't a strain on anybody's budget. If all else fails, a 60Hz hum is near B-flat. For European readers, 50Hz is about a G.

    Most musically-inclined people can train their ears to pick out at least one note reliably, and use their knowledge of musical intervals to go from there.

    A musical octave represents a frequency ratio of 2:1. Thus, A above middle C is 440 Hz, which means A an octave higher is 880 Hz and A below middle C is 220 Hz.

    Audio engineers have found that the ear can hear deviations from flat response to a resolution of about 1/3 octave - I don't want to go too deeply into that, it'll get really complicated - which is why 1/3-octave equalizers have become popular. In a graphic equalizer, each slider gives you a peak or dip centered on some frequency; in a 1/3-octave equalizer these frequencies are spaced so as to divide each octave evenly in three. Standard frequencies have been settled on, which span the audio spectrum conveniently and which can be labeled with sensible numbers. In each octave, they happen to approximately correspond to the musical notes D#, G and B.

    Musically, a 1/3-octave interval is a major third. If you were to start at the bottom "B" of a piano keyboard and go up in major thirds, playing B, D#, G, B, D#, G, B etc, you would be hitting notes that are very close to the standardized slider frequencies of a 1/3-octave equalizer. We're going to use that fact to correlate feedback pitches to the frequencies they represent.

    In the middle octave of a piano, D# is very close to the standard EQ frequency of 315 Hz. G is close to 400 Hz, B is close to 500 Hz. If you can identify a feedback frequency as one of these notes, you know which slider to push down.

    Notes in between need two sliders to be pushed down. For example, middle F is halfway between the 315 Hz slider and the 400 Hz slider.

    Each octave above or below the middle C octave involves doubling or halving the frequency. For example, G in the octave above the middle C octave represents the 800 Hz slider. G two octaves up is about 1600 Hz. Going the other way, G below middle C is about 200 Hz. You may be able to train your ears to pick out pitches in the 3rd octve above middle C; higher than that, it's difficult for most people to identify notes.

    If you regularly run a live sound system, it's worth coming in between shows and doing some practice. The ability to grab exactly the right slider and quickly kill a howl is something few people can do, but almost anybody can learn.

    80 D# 2 octaves below middle C
    100 G "
    125 B "
    160 D# 1 octave below middle C
    200 G "
    250 B "
    315 D# above middle C
    400 G "
    500 B "
    630 D# 1 octave above middle C
    800 G "
    1k B "
    1.25k D# 2 octaves above middle C
    1.6k G "
    2k B "


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