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Author Topic: Differences between software...  (Read 842 times)

AllenDeneau

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Differences between software...
« on: December 18, 2013, 06:05:35 pm »

So I'm laid up for 2 month with a broken leg so there's no time like the present to take the time to learn more about the science of sound and system tuning etc...

I downloaded a version of TruRTA a while back to play with but quickly realized besides seeing the frequency response of material I have no clue how to really use this, or any, software for RTA etc...

My main question is what is the difference between TruRTA and SMAART?

Other questions will arise I'm sure once I begin learning but for now, what are the differences and what should I be able to do with TruRTA and then with SMAART...

I'd like to eventually go to the SMAART training classes but for now it's not in the budget so I was hoping I could learn some of the basics with TruRTA.

I can read an RTA as far as SPL and freq response but that's about as far as I go with that knowledge, I think...

Anyone care to help?

Thanks.
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Timo Beckman

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Re: Differences between software...
« Reply #1 on: December 18, 2013, 06:56:50 pm »

So as far as i can see TruRTA misses 1 rather important part : time or better yet time vs frequency .
I do not know the program so can't be sure but a phase display is essential when doing system tunings .

You might get the "green bible" by Bob mcCarthy
http://bobmccarthy.com/publications/

So hope the leg heals fast and the book by 606 is a "must read" so if you have got time to spent ..
« Last Edit: December 19, 2013, 03:09:33 am by Timo Beckman »
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Timo Beckman

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Re: Differences between software...
« Reply #2 on: December 18, 2013, 06:58:16 pm »

(Do not know where this came from sorry but edited.)

For the rest of it you might take a look at my blog there's a lot of things regarding measurements in there (http://timobeckmangeluid.wordpress.com).
Also i compared a few programs (SMAART 5 vs SIM3 vs SAT-live and just a couple of months ago SMAART7 vs SIM3).
In the end : there's not to much difference in the data so all programs mentioned give a bout the same result however the operating part somewhat divers between the programs .

« Last Edit: December 19, 2013, 03:17:54 am by Timo Beckman »
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David Sturzenbecher

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Re: Differences between software...
« Reply #3 on: December 18, 2013, 07:33:49 pm »

I will second the book by Bob.  You can read through it cover to cover 4 times, and you learn more every time. 

Systune also has a demo version as well for you to try for 30 days.
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Chris Tsanjoures

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Re: Differences between software...
« Reply #4 on: December 19, 2013, 01:37:03 pm »

+1 on the McCarthy book. It really is a must read. There is a reason why we in this industry refer to it as the bible - you will as well once you dive into it.

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Jay Barracato

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Re: Differences between software...
« Reply #5 on: December 19, 2013, 03:36:17 pm »

+1 on the McCarthy book. It really is a must read. There is a reason why we in this industry refer to it as the bible - you will as well once you dive into it.

One of the things McCarthy's book will help with is deciding how to use a measuring system to answer particular questions about a sound system. It will also help clarify the difference between one and two channel measurements which is fundamental to understanding measuring systems.
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Ivan Beaver

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Re: Differences between software...
« Reply #6 on: December 21, 2013, 10:05:15 am »

I don't know true RTA, but as Timo says-being able to see phase is a big deal.

SMAART also allows for multiple mics to be used at the same time-showing the results of all of them in real time.

To me that is a BIG deal.

Then you start getting into the little things like how the software operates-which gets into the "makes life easier" part. 

But you have to have the "big things" or all the "cool operations" really don't matter.
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AllenDeneau

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Re: Differences between software...
« Reply #7 on: January 02, 2014, 12:14:17 pm »

Thanks guys, that was helpful... As soon as I get a few extra bucks I'll be ordering the book. Gotta love doing corporate work that takes forever to pay :(

So maybe this question can be wasily answered here, maybe not but I'm going to ask anyway...

If you're "measuring" a system and using SMAART etc... How does the software determine the phase of an individual box or driver?

I'm looking forward to having that book in my hands to dig in, I do love learning...

Thanks again all. Happy New Year.
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Allen D.
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Tim McCulloch

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Re: Differences between software...
« Reply #8 on: January 02, 2014, 08:45:06 pm »

Thanks guys, that was helpful... As soon as I get a few extra bucks I'll be ordering the book. Gotta love doing corporate work that takes forever to pay :(

So maybe this question can be wasily answered here, maybe not but I'm going to ask anyway...

If you're "measuring" a system and using SMAART etc... How does the software determine the phase of an individual box or driver?

I'm looking forward to having that book in my hands to dig in, I do love learning...

Thanks again all. Happy New Year.

Phase is time.  Basically the software needs to know when the reference signal arrives (it becomes Time Zero) and when the measurement signal arrives from each source.  Phase alignment of pass bands is accomplished with various Tricks of Time to make the phase traces of the adjacent sources as overlaying as possible (flatter is better, too, but we'll start with overlaying).  For most speaker systems we'd like to have that overlay extend an octave on each side of the acoustic crossover.

Or do you mean "polarity"?


Chris or Adam from Rational?
« Last Edit: January 02, 2014, 09:24:20 pm by Tim McCulloch »
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Chris Tsanjoures

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Re: Differences between software...
« Reply #9 on: January 03, 2014, 03:58:16 pm »


If you're "measuring" a system and using SMAART etc... How does the software determine the phase of an individual box or driver?


When a dual channel Transfer Function measurement is generated, the reference signal is delayed to match with the measurement signal so that they can be compared. Because the measurement signal has a reference, we can tell timing information. When polarity is concerned, we match a systems polarity at a certain frequency, so two systems are in phase at that frequency but vary at others. This is why when you are matching the polarity of a subwoofer system to a main system you don't change the delay value in the analyzer - as the goal is to align the relative phase of the two systems, and match the polarity at your chosen frequency. Another example, if you are measuring two matched speakers, both of them will (ideally) be matched polarity at the frequency the 'delay tracker' has aligned to (we generally look to the 2-4khz range for emphasis on vocal intelligibility). The frequencies above the direct impulse will arrive sooner, and the frequencies below will arrive later - because the speaker elements are the same and have the same processing applied, also the phase traces will track each other well. That being said, if you have two speakers of different type, although they may be matched polarity at 2-4khz,  the phase will not be matched at the adjacent frequencies, especially as frequencies get lower. An extreme example of this would be matching the polarity of a speaker which utilizes advanced processing to achieve a flat phase response, and one that doesn't. What I mean is a speaker whose frequencies from as low as 200Hz (or so) arrive at basically the same time as frequencies at 4000Hz and up, with a speaker which does not. Matching these two systems polarity at 2-4K is easy, but once you reach the next pass band, the phase response of the two systems will not even be close.

Basically, Polarity reversals can be spotted in both the phase trace (via a 180 degree offset) or in the Live Impulse Response (via a negative impulse in Lin view when Live IR is on - as frequencies get lower and lower they get harder and harder to view this way). However unlike the phase trace, Live IR can only show you time arrival information; ie direct arrival, and reflections thereafter - especially at high frequencies. The thing to take away is - when measuring the polarity of systems, you must choose a frequency at which point the systems are to be in phase and match the polarity at that frequency.

If you have downloaded the demo version of v7, or v7Di - perform some Transfer Function Measurements - turn Live IR on and zoom into the impulse of your measurement (right click and highlight the area of interest). Flip the polarity on the the system and observe the change in the Phase trace and Live IR. Be sure to take a look at the Getting Started documents to save yourself from getting bogged down from not being familiar with the interface. Most answers to any questions you will have starting out will be found within the documentation.

***shameless plug***  If you haven't already - look into taking a Smaart Training Seminar.

-edited to attempt to make the first paragraph a bit less confusing, probably in vain.
« Last Edit: January 03, 2014, 04:14:56 pm by Chris Tsanjoures »
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