Setup for Measuring Distance
Accurately knowing the effective in-air driver distance to a driver is important.  For a single driver this measurement is used to unwrap phase.  When two drivers are used in the Interactive Crossover Designer, distances and or phase become a measure of voice coil time alignment.  The tester finds distance using 'best fit' function of the measurement and reference signals.  The measurement runs continuously whenever a Real Time Analysis (RTA) mode is enabled.  Driver response variation and standing waves will cause the effective distances to differ slightly from the physical distance but the value should be somewhat stable for the best possible phase measurement.  Changing the RTA signal type may help since this changes the frequency domain energy density.

  • Open the Setup Control Window and select the Setup tab
  • Select the Step/Impulse test signal mode
  • Select MikeL or MikeR as the signal to measure
  • Select LineR or LineL (opposing channel) as the reference
  • Adjust the levels
  • Distance shows up in the real time window
  • Adding a tweeter (> 5Khz crossover) can help stabilize this kind of measurement

 Real-time Display Window
Amplitude and phase variation of the enture signal chain will effect the measured effective distance.  In the example show below the ruler measured distance was 434.3 mm while the tester measured distance was 458.2 mm.  When the distance between two microphones was measured the error was considerably less.  In that case, the speed of sound was the largest contributor factor.

                       Click Image to Enlarge

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