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Author Topic: Smaart Phase traces  (Read 10505 times)

Johnny Diaz

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Smaart Phase traces
« on: July 13, 2011, 12:49:05 pm »

Im new to Smaart and learning how to use it.   From what I gather the phase traces show us if the speakers are firing at the same time and the impulse response shows us the direct sounds and reflected sounds. Is this correct?  Can someone upload some phase traces which are good and bad so I can visually see the difference.  Same with the impulse response.

Thanks
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Tim McCulloch

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Re: Smaart Phase traces
« Reply #1 on: July 13, 2011, 01:26:43 pm »

Im new to Smaart and learning how to use it.   From what I gather the phase traces show us if the speakers are firing at the same time and the impulse response shows us the direct sounds and reflected sounds. Is this correct?  Can someone upload some phase traces which are good and bad so I can visually see the difference.  Same with the impulse response.

Thanks

Have you gone through the case studies and other material available on Rational's website?

The "impulse response" is actually a simple display of when various signals arrive and their amplitude.  Many speaker system alignments have been done this way... just line up (in time) the peak arrivals of each pass band.  Systems aligned this way tend to be loud and will sound better than unaligned or arbitrarily (unmeasured) aligned systems.

Phase alignment refers to the time relationship between 2 transducers where the acoustic levels are roughly equal at a given frequency (this is called "acoustic crossover").  Phase alignment results in systems that have much more detail without sacrificing output level.

On the various forums (including PSW's "FUD Forum"), Bennett Prescott, Ivan Beaver, Phil Graham, Evan Kirkendal and others have posted screen captures of phase alignment.  I suggest a search.

Have fun, good luck.

Tim Mc
« Last Edit: July 13, 2011, 01:28:24 pm by Tim McCulloch »
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Johnny Diaz

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Re: Smaart Phase traces
« Reply #2 on: July 17, 2011, 02:39:29 pm »

Have you gone through the case studies and other material available on Rational's website?

The "impulse response" is actually a simple display of when various signals arrive and their amplitude.  Many speaker system alignments have been done this way... just line up (in time) the peak arrivals of each pass band.  Systems aligned this way tend to be loud and will sound better than unaligned or arbitrarily (unmeasured) aligned systems.

Phase alignment refers to the time relationship between 2 transducers where the acoustic levels are roughly equal at a given frequency (this is called "acoustic crossover").  Phase alignment results in systems that have much more detail without sacrificing output level.

On the various forums (including PSW's "FUD Forum"), Bennett Prescott, Ivan Beaver, Phil Graham, Evan Kirkendal and others have posted screen captures of phase alignment.  I suggest a search.

Have fun, good luck.

Tim Mc

How would you interpret my phase / magnitude trace?
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Dennis Awrey

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Re: Smaart Phase traces
« Reply #3 on: July 17, 2011, 02:43:25 pm »

How would you interpret my phase / magnitude trace?

As traces with no offset delay
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Mac Kerr

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Re: Smaart Phase traces
« Reply #4 on: July 17, 2011, 02:52:20 pm »

How would you interpret my phase / magnitude trace?

As Dennis said, you have not inserted the offset delay. Before you measure, hit "Auto Small" and when it finds the offset delay hit "Insert Delay". Then post your new phase trace.

Before doing any measurements, read the manual and the online tutorial.

Mac
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Dennis Awrey

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Re: Smaart Phase traces
« Reply #5 on: July 17, 2011, 02:52:57 pm »

How would you interpret my phase / magnitude trace?

Also, engage the coherency trace. (Set the button labeled "Coh Th" to 15%)
« Last Edit: July 17, 2011, 03:03:21 pm by Dennis Awrey »
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Johnny Diaz

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Re: Smaart Phase traces
« Reply #6 on: July 20, 2011, 01:25:00 pm »

As Dennis said, you have not inserted the offset delay. Before you measure, hit "Auto Small" and when it finds the offset delay hit "Insert Delay". Then post your new phase trace.

Before doing any measurements, read the manual and the online tutorial.

Mac

I did the auto small and inserted the delay and engaged the coherency trace.  Here are the results.

What do the results now show?
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Johnny Diaz

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Re: Smaart Phase traces
« Reply #7 on: July 31, 2011, 01:50:27 pm »

???
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Douglas R. Allen

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Re: Smaart Phase traces
« Reply #8 on: July 31, 2011, 08:37:12 pm »

???

It would be better if we knew what it is your trying to measure.
It looks like a full range speaker system. Maybe muliti way but not sure.
From about 800hz up to 14k or is within 360 degrees of the reference. Below 800hz it is more than 360 degrees.
Most likely when you did auto small smaart picked 1k , 2.5k or aprox 6k as the first loudest arrival.
The closer the phase trace is to 0 degrees (not within wraps) the closer it is to being in phase with the reference.

Below 500hz or so you can see where the signal is behind the reference area more than 360 degrees. When the angle between the straight up and down lines are leaning to the left then this area is behind reference.
Think  "You don't want to be left behind"
Should they have been leaning to the right then you would have been ahead of the reference signal area. Not enough delay would have been added to the reference.

Coh is not turned on.

Is the crossover to the horn around 2.5k or so?

If this is a full range stack then its about normal for some systems. Again its what your looking for and wanting to do.

I did this for fun and its Very Basic. Don't know if it has anything for you but it may be worth the read.

http://acapella.harmony-central.com/showthread.php?2264387-Sub-Mid-DEMO&highlight=dookietwo

This link as well. It may not work in the early morning hours.

http://srforums.prosoundweb.com/index.php/mv/msg/42761/0/0/51/

If you look at the first phase and freq. response picture of the QSC sub you will see how below the area that is in phase with the reference signal the angle leans to the left. Above the area it leans to the right or ahead of the referenced area.

Measure,measure,and measure again. Keep asking questions. You'll get it.

Douglas R. Allen

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Curtis H List (Too Tall)

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Re: Smaart Phase traces
« Reply #9 on: August 01, 2011, 01:11:03 pm »



Im new to Smaart and learning how to use it.   From what I gather the phase traces show us if the speakers are firing at the same time

One type of delay is called “Flat Delay” where the same amount of delay is applied to each frequency.

Phase is the delay at any one frequency or as we often say “Frequency dependent delay”.
First thing we need to know is the wavelength of the frequency.
It is easiest with a calculator.
Enter the frequency and then touch the “1/X” button.
2000Hz = 0.0005seconds is the time it takes to complete one wavelength.
Since milliseconds will be easier to work with multiple time 1000.
0.5ms  (millisecond)
If we start with the speed of sound is 1130 feet per second.
1130 * 0.5ms =  0.565 feet.
Note the “ms” moves the decimal point three places to the left.

For phase divide the wavelength by 360 degrees.
Again to make it easier lets change it from feet to inches.
0.565ft * 12in =  6.78 inches /360 = 0.0188 inches for each degree of phase.

Look at a lower frequency for comparison.
300Hz = 2.5ms
1130 * 2.5ms = 2.825feet or 33.9inches
33.9inches /360 degrees = 0.094 inches for each degree of phase.


So you can see if we add flat delay the higher the frequency the more degrees of phase it will move.

One of the tricky things that can happen is a frequency, usually a higher frequency can go beyond 360 degrees of delay.
So if we move 300Hz with flat delay one wavelength, or about 34” then we move  2000Hz about five times past 360degrees.


The impulse response shows us the direct sounds and reflected sounds. Is this correct?

That is one thing it can show you, but again it is better to understand it on a basic level.

IR (Impulse response) shows how much energy (voltage for instance) is happening at a specific time. It does not tell you what  frequency may be causing that energy, though when you see a low wide peak next to a very narrow and high peak we can guess which is the woofer and which is the high frequency horn.

Note when looking at the high narrow peak at full scale you may not see the low wide peak even though you know it is there.
You have to set the scale so you only see only the bottom of the narrow peak and then the wide low peak can be seen on the display.

If I get time I will post some pictures from Praxis.







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Re: Smaart Phase traces
« Reply #9 on: August 01, 2011, 01:11:03 pm »


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