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Author Topic: Use of RTA  (Read 14412 times)

Brad Weber

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Re: Use of RTA
« Reply #20 on: September 13, 2010, 07:43:03 am »

Don Sneed wrote on Sun, 12 September 2010 20:06

I am a sound contractor/installer for churches & movie theaters, I use a 2 or 4 microphone setup using a USL microphone 4-plexer, & an Ivie IE-35 RTA/Scope, I use averaging Equalization.
Don Sneed wrote on Sun, 12 September 2010 20:06

I can get in the ball park with an GEQ, but perfer to use a RTA to do it correctly....

As noted back at the beginning of the thread, an RTA can be very useful but does have several limitations.

Having multiple measurement points is a great idea, but direct averaging may not always be desirable.  For example, say your goal is a value of 90 and you have four measurements of 90, 90, 90 and 80.  The average is 87.5, but do you really want to add 2.5 to all of them when three of the measurements are right on and that still leaves the fourth 7.5 away from the target goal?  That may depend on where the individual measurements were taken or any of a number of subjective considerations.  Many people find, and research supports, that determining how to address variations between multiple measurements is often a much more complex issue with both objective and subjective components and is not best addressed by than simple averaging.

This also touches on the differences between a typical cinema application and a typical church application.  A cinema tends to be a much more controlled acoustical environment and the room is usually not as much of a factor in terms of reflections, echoes, etc.  Cinemas also typically have a single speaker per channel for the main channels and you are typically not dealing with speaker arrays, delay speakers, fills and so on.  And perhaps most importantly, cinemas do not usually have open microphones in the main space, much less multiple open microphones, along with stage monitors, amps on stage and so on to address.  A good example of where the application can strongly impact the most effective approach and tools to apply.
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Brad Weber
muse Audio Video
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Dick Rees

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Re: Use of RTA
« Reply #21 on: September 13, 2010, 12:46:59 pm »

Brad Weber wrote on Mon, 13 September 2010 07:43

Don Sneed wrote on Sun, 12 September 2010 20:06

I am a sound contractor/installer for churches & movie theaters, I use a 2 or 4 microphone setup using a USL microphone 4-plexer, & an Ivie IE-35 RTA/Scope, I use averaging Equalization.
Don Sneed wrote on Sun, 12 September 2010 20:06

I can get in the ball park with an GEQ, but perfer to use a RTA to do it correctly....

As noted back at the beginning of the thread, an RTA can be very useful but does have several limitations.

Having multiple measurement points is a great idea, but direct averaging may not always be desirable.  For example, say your goal is a value of 90 and you have four measurements of 90, 90, 90 and 80.  The average is 87.5, but do you really want to add 2.5 to all of them when three of the measurements are right on and that still leaves the fourth 7.5 away from the target goal?  That may depend on where the individual measurements were taken or any of a number of subjective considerations.  Many people find, and research supports, that determining how to address variations between multiple measurements is often a much more complex issue with both objective and subjective components and is not best addressed by than simple averaging.

This also touches on the differences between a typical cinema application and a typical church application.  A cinema tends to be a much more controlled acoustical environment and the room is usually not as much of a factor in terms of reflections, echoes, etc.  Cinemas also typically have a single speaker per channel for the main channels and you are typically not dealing with speaker arrays, delay speakers, fills and so on.  And perhaps most importantly, cinemas do not usually have open microphones in the main space, much less multiple open microphones, along with stage monitors, amps on stage and so on to address.  A good example of where the application can strongly impact the most effective approach and tools to apply.


Excellent, Brad.  Getting right to the heart of it, the difference between live sound and playback is apples/oranges, night/day.  What may work for one does not mean it will work for the other.
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Richard Carter

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Re: Use of RTA
« Reply #22 on: November 17, 2010, 09:32:18 am »

I agree RTAs and AutoEQ are generally not good for what you are doing.  I would suggest a program called ARTA (http://www.fesb.hr/~mateljan/arta/) which has a lot of the functionality of SMAART but can be used for free with some limitations.

With something like the Driverack, I would try to use the parametric EQ first for overall sound and then use the 1/3 octave for specific areas.  You can get an idea of where these are by hooking up a mic and then turning it up until you get feedback.  Then either measure it with a frequency meter or adjust the board EQ until you find it and transfer to the Driverack.
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Brad Weber

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Re: Use of RTA
« Reply #23 on: November 17, 2010, 12:36:01 pm »

Richard Carter wrote on Wed, 17 November 2010 09:32

I agree RTAs and AutoEQ are generally not good for what you are doing.  I would suggest a program called ARTA (http://www.fesb.hr/~mateljan/arta/) which has a lot of the functionality of SMAART but can be used for free with some limitations.

Smaart, SysTune, Praxis, WinMLS, etc. also have free working demo downloads with some restrictions but that may be fine for some limited use.  I found ARTA not as user friendly or well supported as some of the other options but a pretty amazing program for just over $100 for a personal use license and just over $200 for a commercial/multi-user license.
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Brad Weber
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Tom Young

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Re: Use of RTA
« Reply #24 on: November 17, 2010, 06:05:27 pm »

Quote:

With something like the Driverack, I would try to use the parametric EQ first for overall sound and then use the 1/3 octave for specific areas. You can get an idea of where these are by hooking up a mic and then turning it up until you get feedback. Then either measure it with a frequency meter or adjust the board EQ until you find it and transfer to the Driverack.


This is NOT how you should equalize a speaker system.

What you describe may be OK for finding feedback frequencies and addressing them with channel EQ for the specific mic. But if you grab a mic and adjust the speaker system (with its DSP) based on where this mic feeds back this will result in a speaker system that is sort of "tuned" for that microphone and where it is placed. This is not good for all of the other mic's and their response (individually and collectively).
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Tom Young, Church Sound section moderator
Electroacoustic Design Services
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Re: Use of RTA
« Reply #24 on: November 17, 2010, 06:05:27 pm »


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