Room Tuning. Noise Generator + RTA.

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This topic contains 32 replies, has 12 voices, and was last updated by Profile photo of volounteer volounteer 1 year, 3 months ago.

Viewing 15 posts - 1 through 15 (of 33 total)
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  • #43622
    Profile photo of drumlyell
    drumlyell
    Participant

    Has anyone been using the QU to “ring out a room”, “Ping a room”, “tune a room”…
    Should be relatively straight forward, just wondering if anyone has done it and learned any tricks.

    I don’t have my QU yet, hopefully next week!

    Im planing to play white noise through a speaker direct into a condenser mic and use the RTA on the mic channel to determine the response of the particular mic I am using. Then I should be able to place the mic in the center of the room, studio, venue, whatever, and determine if there are nodes and standing frequencies that should be taken out on the master EQ.

    Thoughts?

    lyell

    #43641
    Profile photo of BLKGHOST
    BLKGHOST
    Participant

    Works well for me but I use pink noise instead of white.

    #43642
    Profile photo of GCumbee
    GCumbee
    Participant

    Use pink. But, consider that broadband noise exciting a room can be deceiving. I have seen many situations where the RTA looked fine but there were still lots of problems. I use a custom CD with 31 individual pink noise frequencies. Works much better. I use an spl meter. Set reference level then write down db reading of each compared to ref. Adjust GEQ accordingly. Works much better.

    #43647
    Profile photo of Andreas
    Andreas
    Moderator

    hmm, wouldn’t this be a nice feature request: adding an (optional) steep bandpass filter to the noise generator with the frequencies of the GEQ along with next/prev selection when active in GEQ mode. …no need for the CD… 😉
    Anyway: Clever idea GCumbee, thanks!

    #43648
    Profile photo of GCumbee
    GCumbee
    Participant

    Thanks. I can’t claim original credit. It was developed by a couple of Nashville engineer friends of mine. Dbx actually has a similar thing on a test disc they put out years ago. I like mine better. Longer recordings. Seems to be filtered better. I have ran both and had better luck with the custom one. I can tell you. It generates a much better sounding system result than full broadband pink noise.

    Back in the 70’s UREI had a product called Sonopulse. It was basically the same idea but used pulsed tones. Idea was the tone was pulsed and then with a calibrated microphone feeding an spl meter the signal peaked and held. Pulsing tones is better especially in the LF range so as not to create standing waves. It was a great room tuning tool.

    #43649
    Profile photo of drumlyell
    drumlyell
    Participant

    Nice, thanks guys. Makes sense about the pulses for getting really detailed.

    Would definitely be a nice upgrade to the noise generator. Can you not send the Noise generator through an EQ or is it somewhere in the signal path that doesn’t have that capability? (Sorry, mine is in the mail so I cant try it out yet)

    Have you guys found it crucial to use an omni pattern? I only have cardioid mics at the moment. Was hoping to not have to buy another mic, but gear shopping sure is fun…

    #43650
    Profile photo of mervaka
    mervaka
    Participant

    Isn’t there a bandpass noise option in siggen for this purpose?

    #43663
    Profile photo of knga
    knga
    Participant

    Hello!

    I don’t exactly understand how I would do it. Yes, I would play pink noise through speakers, sound would go through microphone, I would hit PFL, because RTA follows PFL. But than I don’t understand quite clearly how things would work. Which frequencies would you cut/boost on GEQ? You would cut frequencies that appear most (have highest values) on RTA? Am I correct? Which frequencies would you boost, if for example one type of room ‘eats/absorbs’ some frequencies a lot. I also find RTA a bit hard to work with, those frequencies, and red colour change so fast, you must really look carefully to see those frequencies.

    Thanks!

    #43669
    Profile photo of BLKGHOST
    BLKGHOST
    Participant

    For best results, you want to use a measurement microphone (also called reference or RTA microphone). Your goal is to get a curve as flat as possible (a straight line) on the RTA when using pink noise. As you raise the volume, it will feed and it will show on the RTA which frequency it is (It will stay red on one band). Cut that frequency. I like to start with a 10db cut and 5db on the previous and following frequency band to get a smoother curve. General rule for the EQ is to cut and avoid boosting. It will most likely feed at more than on frequency band so rinse and repeat.

    #43671
    Profile photo of [XAP]Bob
    [XAP]Bob
    Participant

    After reading this last week I rang out the venue using the RTA for the Silent Night carols at Rugby Town FC yesterday.

    Makes it nice and easy to duck a few of the problem frequencies – mostly harmonics of 400Hz in this case…

    #43684
    Profile photo of knga
    knga
    Participant

    Thanks! Now all I have to do is buy RTA mic 😉

    Isn’t a term ‘room tuning’ a bit incorrect? When you are making this whole proccess, you are not actually tuning a room, you are tuning a sound system in that room. Is that correct? So can I for example tune my system at home, and then use my GEQ setting in all types of room. I know system behaves differently in different rooms, but I don’t always have time to make ‘room or system tuning’ proccess. I never done tuning before, but I somehow managed to find some frequencies that are tending to cause feedback (frequencies in middle section, 1kHz, and some highest frequencies). And I almost never have problem with feedback.

    Greetings!

    #43686
    Profile photo of BLKGHOST
    BLKGHOST
    Participant

    You are correct. Tuning a room would actually be treating the room acoustically (bass traps, acoustic panels, etc…). Just avoiding feedback is ok when you don’t have time. But you also want the room to sound as flat as possible to help you shape your sound the way you really want it when mixing. This is where the pink noise is useful.

    #43688
    Profile photo of drumlyell
    drumlyell
    Participant

    You can essentially do both. Tune your system to achieve as flat an output as possible, then in different rooms and venues tweak output further more to account for any frequencies that ring out louder than others.

    I agree: “General rule for the EQ is to cut and avoid boosting”

    #43689
    Profile photo of Dick Rees
    Dick Rees
    Participant

    If you’re dealing with your own system, best practice is to start with it tuned using DSP to get the response you want right out of the gate, then deal with system/room interaction with the mains L/R PEQ. With your speaker system optimized prior to setup and effective speaker positioning the PEQ should offer enough filters to deal with room modes.

    I find the concept of using RTA and pink noise interesting, but prefer to do my tuning after ring-out by ear using a well-recorded ensemble representative of the music that will be on stage…making allowance for the typical changes once the audience arrives.

    If for some reason the four PEQ filters on the main bus should not be enough I place a Sabine GraphiQ between the mixer and the amps or in a pinch route signal to the mains via Mix 9/10 and hard-patching back via ST1 or 2 so as to be able to use four or eight more PEQ filters.

    I seldom find I need more than the four filters available on the mains bus, though.

    #43690
    Profile photo of [XAP]Bob
    [XAP]Bob
    Participant

    why not use the graphic?

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