Using spectrum/RTA for live feedback tuning

[Ram]

What are the best procedures for using spectrum/RTA to fix the feedback issues in a live sound situations? Appreciate any youtube or other references.
Thanks.
-Ram

[dpdan]

Hi Ram,
The RTA and Spectrograph that Mackie has included in Master Fader 4.5 is a nice set of tools to assist us with various frequencies, but during a live song virtually all of the bands on the RTA and Spectrograph are going to be dancing in time with the music, but neither one of these tools will magically tap you on the shoulder and show you the likely offending frequency unless it is used during a soundcheck where the feedback can purposely be repeated. To me, the Spectropgraph is more useful if you are already familiar with frequencies and have enough experience and ears to call out the frequency. If you don't, then that's why I suggest this very fast and simple app to determine the frequency (pitch of feedback or ringing)
It is called "feedback detector" and it's free. 

You need to be able to sing the pitch of the feedback that you just heard with your voice and use your iphone or iPad and sing the pitch right into the iPhone or iPad's mic.
If the feedback is a pitch that is out of your vocal range, then all you have to do is sing the pitch at an octave that you can sing for instance,... if the feedback is too high for you to sing but you can sing it and octave lower then just do that, but double the pitch displayed on the app, if the pitch is too low for you to sing, simply sing it an octave above, then devide the displayed frequency in half and there's your feedback frequency,.... easy peasy Sometimes I sing it an octave or two lower so I can do it quietly, if I don't want anyone in the room to hear me.
like this...

<a href="http://www.youtube.com/watch?v=GVxVPNQL0Zw" target="_blank">http://www.youtube.com/watch?v=GVxVPNQL0Zw</a>

[robbocurry]

Good app tip Dan👍🏼😃
Btw, when is your album of "Gregorian Chants" coming out?😝😝😝

[Rdmitch]

Could you just put the iPhone mike by the speaker and let its mike pick up the feedback frequency?

I'm a terrible singer and would rather hear the feedback😀

[dpdan]

Rdmitch, you certainly could do that, but usually that is not possible during a song 

And, the app won't scream at you for having terrible pitch accuracy, or excessive vibrato 

Gregorian chants,,, hmmm  as long as I can use bagpipes and banjos,,,
hey, that sounds like a great name for my new album...

Bagpipes and Banjos

[Topsøe]

If you use the spectrum display you have a few seconds of memory , so if a feedback occurs it is easy to spot it and change the eq accordingly , you can change the threshold between colors by sliding the red and blue squares up and down

Martin

[Rdmitch]

I will have to try that

[Ram]

Thanks everyone!
>>>you can change the threshold between colors by sliding the red and blue squares up and down
Can you explain little more?
Did you mean:
When you see the feedback , you look at the spectrum and
increase the frequencies (in the eq) for the frequencies of red squares in spectrum? , and
reduce the frequencies (in the eq) for the frequencies blue  squares in spectrum?

Thanks.
-Ram

[dpdan]

the red and blue squares to the left of the Spectrograph can be moved up and down to raise or lower the threshold (point at which red color takes over) and blue can also be moved to raise or lower the threshold... moving these red and blue squares has no effect whatsoever on the sound. These are movable so that really soft and really loud signals can be viewed with a sensitivity that pleases you.
in other words, if you are dealing with a very quiet signal, the blue square will need to be raised considerably, then adjust the red accordingly. All I can say is experiment with it,, that's what I did.
the brighter the color shows the root pitch over time. Obviously, you do NOT want to raise and lower a bunch of bands in the EQ just because some are red.

This is just a visual tool that is now incorporated into Master Fader, never let volume meters, spectrographs or EQs tell you what sounds correct. ONLY use your ears for that, then use one of these tools to verify what your ears are hearing and make adjustments only when necessary, when all else fails turn everything down a little.