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Smaart Queries

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Dave Gould:
Hey guys,

Over the past fews days I have been trying to get to grips with Smaart v6 by testing various aspects of sound systems and rooms. Although I do a lot of work around my local area I am yet to bump into any individual who is totally confident with the program to give me help.

Today I managed to do tests on a 300 cap. venue kitted out with a 4-way TurboSound Floodlight system. To test the system I used the following equipment:
Berhinger ECM8000 measurement microphone (all I could get my hands but I did manage to get my hands on a pro calibrator!)

Sony Vaio Laptop
Smaart v6
Lexicon Omega
Yamaha M7 (I know it would have been better to bypass the desk but using the M7 was only the way I could possibly patch everything correctly with the audio interface I was using)

For me the confusion begins when I then begin to analyse the results that I have captured. I have attached some screen shots and if there is any advice you guys can offer on how to best read the results it would be much appreciated.

Example 1
The first screen shot is of the sub and low mid crossovers and the phase between the two. Am I right in saying that the crossover happens at 190Hz and that they are about 120 degrees out of phase with one another? I know from reading about phase - which I am slowly getting my head around - that when two signals are 120 degrees out of phase either acoustically or electronically then this is part of the phase cycle known as cancelation.
The second jpg shows the magnitude results with all drivers on at once with a null in the response where the x-over point appears to be. Am I correct in saying this?

Example 2
Impulse responses are also another aspect of Smaart that is confusing. To do the IR test I am using the signal generator sweep within Smaart. I have great difficulty getting the IR to look anything like the ones that I have thus far in books, instead it looks like a massive block of noise and it is hard to see the RT60 of anything useful from the figure. I have attached a screen shot of the IR where you can see the setting I used.

I have read both the manual and several chapters of the brilliant Bob McCarthy book still I feel very confused.

Any help or advice would be much appreciated and I am sorry for the purely written post it has been a long day being exposed to pink noise and computer screens and it sure does make one tired!

Dave Gould:
And here are the IR screen shots!!! 8)

Arthur Skudra:
I'd remeasure the system with averaging turned on, set it to 32 averages for starters.  This will give us coherence data from which we can better evaluate what you have on the screen.  With the screenshots you captured an instantaneous moment in time, noise, reflections, anomalies included, so we really can't do much to evaluate things accurately based on what we see here.  Make sure your time delay is set correctly for each measurement.

Also, decrease the smoothing to 3 points or less, anything higher smooths out narrow band cancellations and/or peaks, giving you a false sense of how narrow or wide your problems are.  Increased smoothing is only good for spotting overall trends in response, and does little to help you evaluate smaller problems that will bite you.

The Impulse response you captured looks "normal", and in Smaart v6 you won't be able to easily figure out RT60 without using a ruler overlaid on top of your screen and a calculator. Maybe you could improve the signal to noise ratio of the impulse response measurement by measuring the system louder (or eliminating any background noise in the venue)?  Really you're best off saving the impulse response to a file and using another acoustical analysis program to figure out whatever acoustical measures you're looking for.  Without knowing more about the venue and how you conducted your tests, it's hard to make any conclusions that would be helpful!  Yes, you seem to have a clear direct field of the loudspeaker, and yes, you have reflections, and yes there is background noise, and apart from changing things in the physical realm, what can you do about the information you gather from the impulse response?  Move the mic?  Move the speaker?  Acoustically treat a wall?  Tell the custodians to turn off their vacuum cleaners?

Dave Gould:
The screen shots you are seeing are reloads of .ref files that were all done using averaging between 32 and 64 and even 128 just so I could make sense of the readings. The Cohearance of readings were always at 100% which I thought was very bizarre. Is there something I'm failing to do here? I enabled the coherence but still it never changed.

The smoothing i used was a little much and will keep it down next time.

The room is very lively, of quite large volume, with the ceiling almost being the same dimensions as the width.

Yes each of the screen shots are a moment in time, though I did take 5 readings of each measurement. Would you suggest combining these as one single average reading?


Arthur Skudra:
Ah ok, the screenshots you posted show "Inst" averaging, so that threw me off on an assumption on my part.  Make sure that you have coherence enabled in Options:Freq Resp.  Then make sure you click on the trace in the legend to show the coherence associated with the trace when it was captured and post a screenshot of each trace, with both magnitude a phase in a dual screen view.

So you're saying that coherence is 100% all the way across?  Very odd, sounds like something is awry!  Typically in very live rooms, the coherence trace should be all over the place depending on conditions (reverberance, noise, etc), but you should see very good coherence in the upper frequencies if your time delay is set correctly.  Check your setup, make sure the right inputs are selected.


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