RTA in eq section?

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This topic contains 22 replies, has 10 voices, and was last updated by Profile photo of Bis-Repetita Bis-Repetita 2 years, 5 months ago.

Viewing 15 posts - 1 through 15 (of 23 total)
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  • #61440
    Profile photo of losted
    losted
    Participant

    Hello, I’m interested to purchase the qu sb mixer. I would like to know if there is rta function in the peq section of the input channels. I’m only aware of rta in geq in outputs. Thank you!

    #61443
    Profile photo of Dick Rees
    Dick Rees
    Participant

    No, the RTA is mated to the GEQ in that the display references the 1/3 octave divisions of the GEQ.

    For me, the ability to sweep a narrow PEQ filter, either boosted or cut, tells me what I want to know more quickly and accurately than RTA. I feel that making such decisions by ear is preferable than by eye.

    #61445
    Profile photo of Giga
    Giga
    Participant

    Partly Losted; you can see which eq-band is peaking by a little red dot on that band. The full blown RTA follows the PFL which you can than watch in the home -> meters sreen

    Giga

    #61594
    Profile photo of losted
    losted
    Participant

    Thank you for your answers!

    Dick Rees, for sure ear comes at first, but RTA is a helpful tool in some circumstances.

    Giga, you mean that if PFL is enabled i.e. only in ch.1, the RTA in meters screen should only show the ch.1 frequencies? And not all the other channels’?

    During a gig, how can be found which input(s) creates the feedback and at which certain frequency band?
    In my opinion this is the only flaw of this appealing mixer. And I think it can be changed with a software update.

    #61596
    Profile photo of Dick Rees
    Dick Rees
    Participant

    “During a gig, how can be found which input(s) creates the feedback and at which certain frequency band?
    In my opinion this is the only flaw of this appealing mixer. And I think it can be changed with a software update.”

    The correct answer to this is that a properly set up and configured system should not feed back in the first place. However…

    If you want a mixer which can give you an exact visual representation of an offending frequency, you need something which runs something like SMAART. Presonus has this, but you need to run the program on a laptop. If you want, you can do the same thing with a Qu or any other mixer by using a laptop with SMAART, Spectra-foo or the like.

    If you can’t tell which input (mic) is feeding back then you have a LOT to learn. Feedback is a SYSTEM phenomenon. The quickest way to identify the most likely offender is to mute/unmute your mic channels one at a time and see which one sets off the feedback. The quickest way to identify the offending frequency is to sweep a very narrow PEQ filter set to -12 dB across the channel spectrum. When the filter reaches the guilty frequency, the feedback should disappear.

    If ALL the mics feed back at the same point there is only one thing to do:

    Turn down the entire system and proceed at a workable level within the room/system limitations.

    #61597
    Profile photo of Giga
    Giga
    Participant

    Giga, you mean that if PFL is enabled i.e. only in ch.1, the RTA in meters screen should only show the ch.1 frequencies? And not all the other channels’?

    That’s correct

    Giga

    #61598
    Profile photo of GCumbee
    GCumbee
    Participant

    Use your ears. If you can’t identify problems by listening then maybe you need to be doing something else. I see this all the time. I have to setup systems and then the people run faders and mutes. That’s it. They have no concept of frequencies. Drives me crazy.

    #61602
    Profile photo of Dick Rees
    Dick Rees
    Participant

    George, you old codger…you probably remember Garnet Mimms (Cry, cry baby).
    Here’s another relating to lessons hard won:

    “The Truth Hurts”

    Keep telling it like it is.

    DR

    #61606
    Profile photo of GCumbee
    GCumbee
    Participant

    That’s cool Dick. Sometimes I get in trouble for telling it like it is. I would more but have to restrain myself.

    #61607
    Profile photo of Dick Rees
    Dick Rees
    Participant

    losted…

    Never mind us old folks. We’re so used to being independent of certain aspects of technology that such things seem cumbersome and time-consuming compared to a trained, experienced operator. So here’s something for you to try utilizing both available technology and training directed towards honing the skill set implicit in audio engineering.

    Since you’re considering an Sb you obviously have an iPad to run the control app…and I further presume you have a cell phone. Well, there are free apps you can get which can be found under the heading “pitch pipe”:

    https://play.google.com/store/apps/details?id=com.i2app.free.pitchpipe

    Or you can go to the music store and purchase an analog pitch pipe:

    http://www.musiciansfriend.com/accessories/becker-chromatic-pitch-pipe-key-of-c

    When feedback occurs it will have a specific pitch…unless something is DRASTICALLY wrong with your entire setup…this pitch being most easily found at the onset of the feedback loop before it gets totally out of control, so when you hear the sound, match it with your voice: sing the note.

    Now whip out your phone, open the pitch pipe app and find the pitch you’re singing by tone matching with the app or with an old-fashioned analog unit. All you have to know once you’ve identified the pitch is the basic frequency of that pitch. Look up a frequency chart for a chromatic octave of tones, A to A’ for example.

    A = 440/880/1760 etc doubling with each octave up.

    A bit of practice and you can easily learn how to identify the ringing frequency and apply corrective measures more accurately than a mere RTA. It doesn’t take long to learn/memorize enough of the basic frequencies and not have to refer to the small chart you’ve taped to the back of your iPad. It’s quite easy to quickly calculate the higher frequencies since they’re just two or three doublings of your basic pitch frequency.

    Middle C is 262, but I find it easier to remember and do the doubling by just using 250. So if the offending pitch should be C, I know it will be one of the higher multiples of 250: 500/1k/2k/4k

    You know, it takes longer to explain how to do it than it does to do it. I would say with practice that within a few months you should be able to identify and correct pitch anomalies in under a minute, better and faster than guesswork aided by RTA…which at the typical level of development and resolution is severely inadequate.

    So you see, our frustration in this area comes from the fact that even if integrated into an audio console, it is simply not a good tool to use…especially considering that a little time spent in training yourself will be much more accurate and useful and as I have learned can be applied without even having to be at the console or on the iPad. I hear the note, sing the note, compare it to the lowest note I’m comfortable singing (which happens to be a G one octave below middle C, approximate frequency 200), ascertain the pitch, do the doubling thing and BINGO…problem solved within 10 seconds.

    It can be done. YOU can do it.

    I’ll leave it to someone else to explain how to use PEQ sweep for feedback loop identification, yet another more precise and rapid method to address the problem.
    Right now I have to go teach someone how to catch fish…

    #61613
    Profile photo of [XAP]Bob
    [XAP]Bob
    Participant

    For those us who cant sing…

    A friend of mine is a walking rta. He spend a good while (years ago) with a signal generator- just learning the ‘sound to frequency’ conversions.

    Not only will he tell you what frequency feedback is at without batting an eyelid (single peak analysis) he will also identify broader issues by freq range rather than words like muddy…

    Really useful to have that kind of ear around. I’m nowhere near that, but am sufficiently practiced to know what I’m aiming for. Interestingly I can ‘see’ frequencies on the eq screen (rta is cool, but I have a feel for the shape I want to apply to an instrument/PA (somewhat excludes very specific problem freq cuts)

    #61620
    Profile photo of cantona
    cantona
    Participant

    Can I ask a stupid question about the fader flip please – When it shows eq-band’s peaking by a little red dot on that band do you normally just cut that frequency on the respective fader or is there more to it like going into the parametric eq and sweeping, cutting frequency’s?

    #61621
    Profile photo of [XAP]Bob
    [XAP]Bob
    Participant

    That’s the loudest, it might not be the offensive peak though…

    It depends is the normal answer here…

    #61622
    Profile photo of Dick Rees
    Dick Rees
    Participant

    “Can I ask a stupid question about the fader flip please – When it shows eq-band’s peaking by a little red dot on that band do you normally just cut that frequency on the respective fader or is there more to it like going into the parametric eq and sweeping, cutting frequency’s?”

    The question is…

    How does it sound???

    #61626
    Profile photo of Andreas
    Andreas
    Moderator

    As Bob said, the red leds in fader flip just marks the currently loudest band. Pulling that band down will let another one flash. Not necessarily related to the problem frequency and/or channel resp. mix.
    For me the GEQ is much too coarse to consider it for feedback handling, its like removing a splinter with an axe… 😉

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