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Author Topic: FFT vs RTA for live sound applications  (Read 6607 times)

walker rosewood

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Re: FFT vs RTA for live sound applications
« Reply #10 on: August 26, 2015, 10:03:00 pm »

Thanks for the input guys.  I just ordered the UMIK-1 to get me started.  I've been reading all the articles I can find on the topic, and looking for a class to take.  However, I'm not having any luck finding something near Western New York.   Can anybody recommend a decent book on the subject?
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Ivan Beaver

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Re: FFT vs RTA for live sound applications
« Reply #11 on: August 27, 2015, 07:31:15 am »

   Can anybody recommend a decent book on the subject?
Start by reading all the papers on Rational Acoustics website.

Read the Forums etc.

But REMEMBER-there are TWO parts to this.  ONE is the easy part-learning the software.


The SECOND is the hard part-understanding sound-how it propagates-cancels-adds etc-a bit about acoustics and how to interpret the lines on the screen.

Just because you get lines on a screen DOES NOT mean they are correct or accurate.  THAT is the hard part.
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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!

Justice C. Bigler

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Re: FFT vs RTA for live sound applications
« Reply #12 on: August 27, 2015, 10:01:36 am »

Thanks for the input guys.  I just ordered the UMIK-1 to get me started.  I've been reading all the articles I can find on the topic, and looking for a class to take.  However, I'm not having any luck finding something near Western New York.   Can anybody recommend a decent book on the subject?


This is the gold standard when it comes to measurement:


http://www.amazon.com/gp/product/0240521560/ref=s9_simh_gw_p14_d0_i2


And between the trials for Smaart DI and Smaart 7 you can get 60 days of free software to learn what you are doing:


http://www.rationalacoustics.com/smaart/about-smaart/
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Justice C. Bigler
www.justicebigler.com

Doug Fowler

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Re: FFT vs RTA for live sound applications
« Reply #13 on: August 27, 2015, 02:33:27 pm »


Different systems and how each system is set up (windowing-averaging etc) will determine how much "other" signals contribute to what you are seeing on the screen.


Windowing: each software has its own scheme, yielding different results.  You could argue which is "best", but that's a dead end.

Fun fact:  I wasn't there, but I got it first hand from a participant.  About four years ago, SMPTE hosted a measurement software comparison session.  Same mic, same inputs, etc.   Unwindowed responses matched perfectly, which is not surprising.  It's simple math to do the DFT and well defined.  Same sampling rate and same FFT should yield the same data.

Then, using windowing, they got five different magnitude responses from the five participants. 

SIM 48 PPO
Smaart MTW
Systune TFC
and two others

Think about that one for a while......

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Ivan Beaver

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Re: FFT vs RTA for live sound applications
« Reply #14 on: August 27, 2015, 08:04:41 pm »

Windowing: each software has its own scheme, yielding different results.  You could argue which is "best", but that's a dead end.

Fun fact:  I wasn't there, but I got it first hand from a participant.  About four years ago, SMPTE hosted a measurement software comparison session.  Same mic, same inputs, etc.   Unwindowed responses matched perfectly, which is not surprising.  It's simple math to do the DFT and well defined.  Same sampling rate and same FFT should yield the same data.

Then, using windowing, they got five different magnitude responses from the five participants. 

SIM 48 PPO
Smaart MTW
Systune TFC
and two others

Think about that one for a while......
Which just makes people ask "What IS correct"?

The correct answers are not always as they "appear"-especially on a 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!
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