RTA respons flat?

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This topic contains 6 replies, has 4 voices, and was last updated by Profile photo of volounteer volounteer 3 years, 6 months ago.

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    Profile photo of OlivierM

    What am I missing?
    Pink noise from the console to the main bus gives me a flat respons on my RTA on my laptop and iPad, but not on the build in RTA of the SQ.
    Picture in the annex.

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    Profile photo of SteffenR

    pink noise isn’t flat by definition

    Profile photo of volounteer

    Pink noise or ​1⁄f noise is a signal or process with a frequency spectrum such that the power spectral density (energy or power per frequency interval) is inversely proportional to the frequency of the signal.

    Pink noise is like white noise, but with reduced higher frequencies. It resembles the sounds of steady rainfall or wind and is often considered to be more soothing than white noise, which some people find unpleasant.



    Profile photo of OlivierM

    Ok, Pink Noise is not flat by definition.
    But all measurement software and RTA plugins I use give me a flat freq. respons with Pink Noise (unless I change settings), except this one (SQ7). Maybe it’s a decision of A&H to have a more musical result when mixing flat on the meters? Or when tuning a PA system?
    My aiming curve is mostly like this but in reverse. +3dB low-end and -1 or -2dB on the hi-end of the curve.

    Profile photo of volounteer


    No idea how AH did their pink noise or how their meters work.
    Dont recall their user manual saying either. But it does indicate there is sin pink white and bandpass options.
    Are you sure you chose pink not the others?

    It says this also:
    Pink Noise – Filtered white noise for equal energy per octave. This is a good source to use for testing loudspeaker drivers and phase. Its response matches the way we hear frequencies.

    Maybe it is not really pink by the standard definition. That last statement in the manual makes me wonder if it is truly pink.

    I thought the point of the PN was to let you ‘tune’ the room to EQ out freqs in the LR output that could cause feedback.
    What are you using the PN for ?

    Profile photo of KeithJ A&H
    KeithJ A&H

    Hi @OlivierM,

    In the photo, you are showing the channel RTA on the console, and the meters RTA on SQ-MixPad. These are different RTA’s with independent settings and measurements in the SQ, but all being equal they will work in exactly the same way (just before someone else spots that and thinks it might have something to do with what you’re seeing!).

    So the difference between these and the other RTA you have running will almost certainly be due to differences in averaging.

    If you ‘speed up’ the Average setting on the SQ for example, it is easy to see that there are fewer ‘bursts’ of noise being generated in the lower frequency bands which are then contributing to the average for that band (this is the same when measuring external pink noise sources btw). Even at the slowest setting for Average, there is still decay on the samples used for that Average ‘window’. Therefore the average for the band will be pulled down slightly and so the average level will be slightly lower for lower frequencies.
    Your other RTA however is set to ‘Average – Infinite’. You can achieve a similar measurement to this with the SQ, by using the Max/Peak indication rather than the Average bars/line and waiting for the ‘bursts’ at each centre frequency.
    Just set the Max/Peak fully ‘slow’, give it a minute (to allow for the ‘bursts’ at each band’s centre frequency to occur) and you should see a flat line.

    The other way would be if you were to set the averaging on your external RTA to something other than infinite, you should see that you can see it match the SQ behaviour.

    Hope this helps!

    (@volounteer – It sounds like you might be using ‘PN’ to refer generally to Pink Noise in your last post, so to avoid any confusion, Pink Noise ‘Periodic Noise’ is different to the standard/random Pink Noise used in our consoles.)

    Profile photo of volounteer

    @KeithJ A&H

    yes I used PN for pink noise in that post as we were discussing pink noise and already spelled it out earlier
    thanks for reminding us about periodic noise having the same abbrev

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