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[Mac Kerr]

Adam Schaible wrote on Tue, 27 April 2010 15:41

Is this equivelent to the "delay finder" in smaart 7? When running pink noise through the subs, the results of the find delay feature vary extremely (like 300ms).  When I do it with the tops it is pretty accurate, but comes up with over 16ms which seems way higher than I expect.  I anticipate 1-2 for the desk, and maybe up to 5ms for the ux8800.

The delay finder, and inserting that delay into Smaart (or any FFT) is to compensate primarily for the time of flight from the speaker to the microphone. With digital gear that also adds latency you will compensate for that as well.

It is important in this measurement to not move the mic between measurements. It must be in the same place for the subs and the mains. As I said before, do not reset the delay after you have captured the phase trace of the subs.

Often when Smaart returns an obviously wrong delay time it is because the ref and measurement signals are reversed.

Mac

[Art Welter]

Adam Schaible wrote on Tue, 27 April 2010 13:50

I just checked this PDF:  http://www.rationalacoustics.com/files/v7GS_Ch4_Transfer_Fun ction.pdf and read the v6 manual.. That's what i was doing, but perhaps the issue was that the pink noise was coming from my iPod and not the console.  I don't really think that's the problem but it's something I will try?

To eliminate as many variables as possible, I'd suggest using the noise generated from Smaart.

Test outside if possible, you only need enough level to get good coherency.  

As you progress, you will find corrective EQ adjustments will smooth the phase response, but you won't eliminate the "drooping" phase response with conventional filters.

More than 720 degrees of phase rotation from 40 Hz to 18kHz would be common.

[Adam Schaible]

I was attempting to do this in my basement, and then once I had learned the technique well enough, get the gear outside and do a better job.  Could/would the boundaries create that much of an issue?  I don't mind lugging it all outside, but I'd rather learn how to measure inside, and maximize my time outside.

[Adam Schaible]

Art Welter wrote on Tue, 27 April 2010 15:12

Adam Schaible wrote on Tue, 27 April 2010 13:50 I just checked this PDF:   http://www.rationalacoustics.com/files/v7GS_Ch4_Transfer_Fun ction.pdf and read the v6 manual.. That's what i was doing, but perhaps the issue was that the pink noise was coming from my iPod and not the console.  I don't really think that's the problem but it's something I will try? To eliminate as many variables as possible, I'd suggest using the noise generated from Smaart. Test outside if possible, you only need enough level to get good coherency.   As you progress, you will find corrective EQ adjustments will smooth the phase response, but you won't eliminate the "drooping" phase response with conventional filters. More than 720 degrees of phase rotation from 40 Hz to 18kHz would be common.

I will try this .. I tried before but for some reason it wasn't making any noise!

Thanks again Art.

[Mac Kerr]

Adam Schaible wrote on Tue, 27 April 2010 16:14

I was attempting to do this in my basement, and then once I had learned the technique well enough, get the gear outside and do a better job.  Could/would the boundaries create that much of an issue?  I don't mind lugging it all outside, but I'd rather learn how to measure inside, and maximize my time outside.

The close reflections will lower the coherence, but you should still be able to get measurements that work. As Art said, you don't need a lot of level. When you are doing more precise work with system eq you will probably want to be outdoors, or in a large room, like a real venue.

How far away from your system is the measurement mic?

Mac

[Mac Kerr]

Adam Schaible wrote on Tue, 27 April 2010 16:18

Art Welter wrote on Tue, 27 April 2010 15:12 Adam Schaible wrote on Tue, 27 April 2010 13:50 I just checked this PDF:    http://www.rationalacoustics.com/files/v7GS_Ch4_Transfer_Fun ction.pdf and read the v6 manual.. That's what i was doing, but perhaps the issue was that the pink noise was coming from my iPod and not the console.  I don't really think that's the problem but it's something I will try? To eliminate as many variables as possible, I'd suggest using the noise generated from Smaart. Test outside if possible, you only need enough level to get good coherency.   As you progress, you will find corrective EQ adjustments will smooth the phase response, but you won't eliminate the "drooping" phase response with conventional filters. More than 720 degrees of phase rotation from 40 Hz to 18kHz would be common. I will try this .. I tried before but for some reason it wasn't making any noise! Thanks again Art.

Either noise source should be fine, but I disagree here with Art on which eliminates the most variables. I find running the noise from the console and being able to route it to both the ref in of Smaart and the system under test from one point easier. YMMV.

Mac

[Adam Schaible]

Mac Kerr wrote on Tue, 27 April 2010 15:19

Adam Schaible wrote on Tue, 27 April 2010 16:14 I was attempting to do this in my basement, and then once I had learned the technique well enough, get the gear outside and do a better job.  Could/would the boundaries create that much of an issue?  I don't mind lugging it all outside, but I'd rather learn how to measure inside, and maximize my time outside. The close reflections will lower the coherence, but you should still be able to get measurements that work. As Art said, you don't need a lot of level. When you are doing more precise work with system eq you will probably want to be outdoors, or in a large room, like a real venue. How far away from your system is the measurement mic? Mac

I had it about 5 ft from the cabs, about 2 feet off of the ground.  I didn't have it cranked, but probably like 95dbish at that distance.  Would it be better to turn down some?

[Mac Kerr]

Adam Schaible wrote on Tue, 27 April 2010 16:24

Mac Kerr wrote on Tue, 27 April 2010 15:19 Adam Schaible wrote on Tue, 27 April 2010 16:14 I was attempting to do this in my basement, and then once I had learned the technique well enough, get the gear outside and do a better job.  Could/would the boundaries create that much of an issue?  I don't mind lugging it all outside, but I'd rather learn how to measure inside, and maximize my time outside. The close reflections will lower the coherence, but you should still be able to get measurements that work. As Art said, you don't need a lot of level. When you are doing more precise work with system eq you will probably want to be outdoors, or in a large room, like a real venue. How far away from your system is the measurement mic? Mac I had it about 5 ft from the cabs, about 2 feet off of the ground.  I didn't have it cranked, but probably like 95dbish at that distance.  Would it be better to turn down some?

The easy answer is try it. Turning down and shooting another delay time shouldn't take long. I rarely touch the number of averages, maybe someone with more experience with different averages will chime in with help getting a good delay time on a sub in your conditions.

Mac

[Art Welter]

Lay the cabinets down and put the microphone head on the ground to avoid floor bounce.

I would really suggest going outside, all the LF room reflections in a small room make it harder to understand what is going on.

[Evan Kirkendall]

You want your phase trace to look similar to the pink trace in this shot:



Measurements were made 10' away from the cab in the ground plane. The pink trace is the combined sub and low of the system once they've been aligned.



Evan