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In this episode of the Sound Design Live podcast, I chat with Dale West and Brian Mohr about the most important things we learned at Meyer Sound’s SIM3 seminar with Bob McCarthy. We talk about calculating phase offset for a frequency range, using lateral aspect ratio to space your front fills correctly, aligning off-axis points of your speakers for even coverage, and debunking line array myths.

Download Dale’s Phase Alignment Calculator

The biggest thing I’ve found in system teching is that if things aren’t behaving in a way that you predicted, you really need to find out why. -Dale West

People have been perfecting and teaching cello playing for hundreds of years. Whereas the science of sound system engineering is only 50 years old. -Brian Mohr

SIM3 is easy. It just delivers data. The hard thing is figuring out what to do with that data. -Bob McCarthy

Show notes:

1. All music in this episode by Graham Spice.
2. Software: Smaart, SATlive, Room EQ Wizard, Daniel Lundberg’s Uncoupled Array Calculator
3. Hardware: SIM3
4. Other Training: Smaart, Merlijn Van Veen
5. Math
   1. To convert phase offset to time offset for a frequency range: T = (∆Phase / 360) / ∆Frequency
      1. ((60-0) / 360) / (1000 – 250) = .2ms
      2. ((60-0) / 360) / (125 – 90) = 4.76ms
   2. Linear to LOG
      1. 20xLOG10(Linear)
         1. 20xLOG10(2) = 6dB
         2. 20xLOG10(0.5) = -6dB
      2. Memorize
         1. 20dB = x 10
         2. 6dB = x 2
         3. 5dB = x 1.8
         4. 4dB = x 1.6
         5. 3dB = x 1.4
         6. 2dB = x 1.25
         7. 1dB = x 1.1
         8. 0dB = x 1.0
         9. -1dB = x 0.9
         10. -2dB = x 0.8
         11. -3dB = x 0.7
         12. -4dB = x 0.6
         13. -5dB = x 0.55
         14. -6dB = x 0.5
      3. When calculating summation, subtract if polarity reversed
   3. LAR (Lateral Aspect Ratio): the usable lateral width perpendicular to the speaker from 0dB on-axis to -6dB at the edges. Ideal for e.g. front-fill spacing.
      1. 60º speaker
         1. FAR (Forward Aspect Ratio) = 1 / sin(60/2) = 2
         2. LAR = 2 / FAR = 1
         3. At 10ft we know the coverage width is 10ft because 10 x 1 = 10
      2. 90º speaker
         1. FAR = 1/sin(90/2) = 1.42
         2. LAR = 2 / 1.42 = 1.4
         3. At 10ft we know the coverage width is 14ft because 10 x 1.4 = 14.
6. Quotes
   1. The biggest thing I’ve found in system teching is that if things aren’t behaving in a way that you predicted, you really need to find out why.
   2. SIM3 is easy. It just delivers data. The hard thing is figuring out what to do with that data.
   3. Anyone who has ever tried to do their system tuning with a graphic EQ and RTA has either not done so again or gone into video.
   4. You can’t solve acoustic problems with electronic solutions.
   5. People have been perfecting and teaching cello playing for hundreds of years. Whereas the science of sound system engineering is only 50 years old.
   6. There is this idea out there that line arrays focus low end energy, but that’s not what they do. They focus the cancel.