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Author Topic: Cheap and cheerful PA tuning without pink noise or test tones?  (Read 1049 times)

Lyle Williams

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Cheap and cheerful PA tuning without pink noise or test tones?
« on: December 07, 2013, 11:59:18 pm »

So, I probably should just bite the bullet and buy Smaart, but I like tinkering.

I have an idea and I'm wondering if it could be used for flattening a PA during playback of recorded material before the show.


Here is the idea:

Split the desk main outs and then sum one pair of these signals to mono.  Invert the polarity of this signal and then put it through an adjustable digital delay.  Sum this inverted/delayed signal with the amplified output of a measuring mic at the mix position.  Put the mic+delayed signal out on an iPad RTA app.

Set the delay for speaker-to-mic distance.  Tune for least spikes on the RTA.  Tune delayed signal level for least spikes on the RTA.  Repeat to get the unspikiest curve possible.

Adjust EQ to flatten the RTA trace.


Has anyone tried anything like this?
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Jay Barracato

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Re: Cheap and cheerful PA tuning without pink noise or test tones?
« Reply #1 on: December 08, 2013, 12:13:15 am »

So, I probably should just bite the bullet and buy Smaart, but I like tinkering.

I have an idea and I'm wondering if it could be used for flattening a PA during playback of recorded material before the show.


Here is the idea:

Split the desk main outs and then sum one pair of these signals to mono.  Invert the polarity of this signal and then put it through an adjustable digital delay.  Sum this inverted/delayed signal with the amplified output of a measuring mic at the mix position.  Put the mic+delayed signal out on an iPad RTA app.

Set the delay for speaker-to-mic distance.  Tune for least spikes on the RTA.  Tune delayed signal level for least spikes on the RTA.  Repeat to get the unspikiest curve possible.

Adjust EQ to flatten the RTA trace.


Has anyone tried anything like this?

A RTA simply does not account for the fact there are time domain issues that cannot be fixed by eq.

All getting a flat RTA trace gives you is a flat trace at that mic position. It actually has very little to do with how good a system sounds.

Sent from my DROID RAZR HD using Tapatalk
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Jay Barracato

dick rees

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Re: Cheap and cheerful PA tuning without pink noise or test tones?
« Reply #2 on: December 08, 2013, 09:51:44 am »

Lyle...

Old school:

Take an SM58 out into the middle of the room, raise it up about 8' in the air pointing straight up and do the old "boost until it rings, then cut" technique.  Lather, rinse, repeat.

That will be as good as anything for simply flattening a PA.
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Steve M Smith

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Re: Cheap and cheerful PA tuning without pink noise or test tones?
« Reply #3 on: December 08, 2013, 11:51:44 am »

The technique Dick suggests is all that is needed.

I initially took issue with the 'old school' comment until I realised that I first did this about thirty years ago!  Although we used to do it with the vocal mics on stage rather than out in the room.


Steve.
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Lyle Williams

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Re: Cheap and cheerful PA tuning without pink noise or test tones?
« Reply #4 on: December 08, 2013, 12:53:50 pm »

Thanks guys.  I do similar things now.  Some of my events are well underway at the time I set up and I was trying to find an audience friendly alternative.
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dick rees

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Re: Cheap and cheerful PA tuning without pink noise or test tones?
« Reply #5 on: December 08, 2013, 01:01:38 pm »

The technique Dick suggests is all that is needed.

I initially took issue with the 'old school' comment until I realised that I first did this about thirty years ago!  Although we used to do it with the vocal mics on stage rather than out in the room.


Steve.

Steve...

The mic out in the room is where I start.  That is meant to address room anomalies.  I find I seldom have to re-ring with the stage mics open, but if I have time, I'll run through it again.  Stage mic re-positioning can often obviate the need for EQ surgery, though.
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Jim McKeveny

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Re: Cheap and cheerful PA tuning without pink noise or test tones?
« Reply #6 on: December 09, 2013, 07:26:29 am »

I don't know about others, but tweaking during pre-show (1) is a bit late (2) invites disaster.
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Lyle Williams

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Re: Cheap and cheerful PA tuning without pink noise or test tones?
« Reply #7 on: December 09, 2013, 04:17:07 pm »

I do small shows.  Mainly outdoors.  When it is my own gear everything is set up pretty well OK to begin with.  When it is someone else's gear then it's not so simple.

There is an expectation that I can put on background music promptly on arrival.  There is a dislike of pink noise and feedback honks.  On the plus side I probably care more about the sound quality than anyone else.  At present all I really do is listen and tweak a GEQ to get rid of some shrillness and mud.

« Last Edit: December 09, 2013, 07:15:40 pm by Lyle Williams »
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Steve M Smith

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Re: Cheap and cheerful PA tuning without pink noise or test tones?
« Reply #8 on: December 10, 2013, 03:12:44 am »

If most of your shows are outside, what you are doing already is probably enough.  Ringing out a system compensates for resonances in the room. You will need a lot of power to get the whole of the planet to resonate - although Tesla almost got there once!

It also compensates for deficiencies in the system.  When I started in sound, systems didn't have a very flat response and a fair amount of EQ was required to flatten it out.  Systems today are much better and don't need so much EQ to get a flat response.


Steve.
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Lyle Williams

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Re: Cheap and cheerful PA tuning without pink noise or test tones?
« Reply #9 on: December 10, 2013, 07:24:25 am »

Thanks.  I'll stick to what I am doing.

(Until I get bored and buy some toys....)

:-)
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