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Author Topic: Testing PA?  (Read 814 times)

Daniel Mock

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Testing PA?
« on: December 21, 2012, 02:34:22 am »

I use my mobile sound system in many types of venues which I'm sure each need special room EQing etc. I can hear when the system doesn't sound great but often am not sure what the offending  frequencies are.

I want to purchase a mic that can accurately read the system response from the dance floor and then also be able to read the direct output on the mixer and compare them to assist in EQing the system.

It doesn't need to be in real time, I just want to get an idea of where there are abnormal peaks or dips in response that the mic is receiving and adjust the system EQ accordingly. 

What are my options if I'm on a budget but still want accuracy?

I've also read that a way to check that different drivers are in phase is by playing a tone that is about directly between their crossover points, then invert one of the drivers and adjust delay until they are silent. Does that sound about right? What's a good way to find or produce different tones?

Many thanks for your advice
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Patrick Tracy

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Re: Testing PA?
« Reply #1 on: December 21, 2012, 02:48:35 am »

There's a whole forum here just for system measurement:

http://forums.prosoundweb.com/index.php/board,78.0.html

But you should realize there's a high threshold of competence you need to reach before you can reliably translate measurement into better sound.

Ivan Beaver

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Re: Testing PA?
« Reply #2 on: December 21, 2012, 09:05:14 am »

DO NOT get sucked into the RTA path.  It is full of thorns and rocks.  Sure it is simple and cheap-and the results you get are simple and wrong (in most cases).  But it does have its uses-and I still use it from time to time-but you have to understand the limitation and what you can and cannot get from it.

There are a lot of dual FFT systems out there-which is your best bet.  The mic is the least expensive part.

Smaart is one of the more popular. 

But as Patrick said-there is a learning curve-that does not come from a day or 2.

Making the measurement is one thing- UNDERSTANDING if it is a GOOD/ACCURATE measurement is the second part.

The Third (and hardest part) is understanding what the measurement means and what to do about it.

Is the dip in the response a part of the loudspeaker-or a reflection-or an interaction of the loudspeakers?

The hardest thing for most people is understanding what they can and CANNOT eq.  Even though it "appears" as fi they have done some good on the computer screen.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Jordan Wolf

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Re: Testing PA?
« Reply #3 on: December 21, 2012, 09:12:41 am »

I use my mobile sound system in many types of venues which I'm sure each need special room EQing etc. I can hear when the system doesn't sound great but often am not sure what the offending  frequencies are.
If you are trying to figure out what frequencies are more excitable than others in a certain space, Bink's Audio CD has sine waves that you can play back to find out what "problem" frequencies do not need reinforcement - and heck, that might only be for one or a couple of spots in the venue.  It's a starting point...

Quote
I want to purchase a mic that can accurately read the system response from the dance floor and then also be able to read the direct output on the mixer and compare them to assist in EQing the system.
The Marketplace has some good deals on used mics.  I haven't had the chance to get into system (component) measurement just yet, but I have a decent microphone that will suffice for when I get started.  I bought it from the Marketplace from a reputable poster, along with some other items I use currently.

Quote
It doesn't need to be in real time, I just want to get an idea of where there are abnormal peaks or dips in response that the mic is receiving and adjust the system EQ accordingly. 

What are my options if I'm on a budget but still want accuracy?
Although the real-time aspect of measurement may not be as feasible during the show, BEFORE the show, it can be invaluable to show how microphone placement (in distance from boundaries as well as the source) affects your reading(s).

Quote
I've also read that a way to check that different drivers are in phase is by playing a tone that is about directly between their crossover points, then invert one of the drivers and adjust delay until they are silent. Does that sound about right? What's a good way to find or produce different tones?
The Bink Audio CD is a great one for those tones.  Void Speakers also has a sine wave tone CD, as well as one with various tracks of band-limited pink noise.

It looks like Bink's website lease has run out - if anyone has a copy of the CD they can post for the OP, it would be helpful.
« Last Edit: December 21, 2012, 09:15:16 am by Jordan Wolf »
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Jordan Wolf
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"We want our sound to go into the soul of the audience, and see if it can awaken some little thing in their minds... Cause there are so many sleeping people." - Jimi Hendrix
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