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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Audio Measurement and Testing => Topic started by: maximiliano estudies on April 20, 2019, 03:33:59 PM
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I wanted to try out different methods for main + sub alignment. Using Mappxt I started with an easy setup, one subwoofer on the floor and a point source speaker "hanging" 10 meters above. I also decided to do an overlap crossover at 100Hz.
Without doing any filtering or aligning, I get this as a result:
(http://i66.tinypic.com/24cwpc1.png)
(http://i67.tinypic.com/148q4d2.png)
which is not very good. I am using the third microphone (counting from the left) to do the measurements.
After setting the low and high pass filters and aligning the phase at the crossover frequency this is the result:
(http://i65.tinypic.com/34e7oub.png)
(http://i67.tinypic.com/j666o0.png)
which is better but I still get some cancellation in the front, between the first and second microphones. This makes sense, as the difference in distance between the loudspeakers changes as we move closer (left in the picture), so the relative arrival times between the speakers also changes and the phase is not aligned anymore.
I figured that I could solve the problem by bringing the speakers closer together, so that the relative distance from the audience to the speakers never allows the phase to go more than 120º apart.
First I tried bringing the top loudspeaker to 7 meters:
(http://i65.tinypic.com/nfnuvc.png)
(http://i64.tinypic.com/2hncruo.png)
and then at 5 meters:
(http://i68.tinypic.com/6z0v12.png)
(http://i64.tinypic.com/2nvyueh.png)
which looks quite ok but, is there another solution to this problem? One that doesn't require to physically move the speakers? In Mappxt is very easy to do, but in the real world is one of the most difficult parameters to change.
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I wanted to try out different methods for main + sub alignment.
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A more aggressive crossover, thats literally the only way. You cannot fix a physical problem with electronics. You will always have some sort of issue having two audio sources seperated.
Have a look at this resource (https://www.merlijnvanveen.nl/en/study-hall/119-sub-align-calculator-explained) from one of our forums members. Will be very useful. You can look at all his other stuff as well, there is a lot to learn there.