Dayton Audio OmniMic V2 Precision Measurement System - Manual (Page 29)

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these patterns -- dipoles, omnidirectional, bipole, arrays, or waveguides.
To see the response magnitude (dB) varying with both frequency and radiation angle, a 3-
dimensional graph is required. OmniMic provides two versions:
 A "flat" format, as shown above. In this format the horizontal axis is frequency, the vertical is
radiation angle, and the color represents corresponding dB level. An index relating color to dB
levels is shown to the right of each plot.
 A "cylindrical" format, in which frequency is the vertical axis, the angle around the projected
cylinder is radiation angle, and both color and distance from the cylinder axis represent dB
level. The colored region of the graph can be rotated using provided buttons to give a more
intuitive view of the response shape than is obtainable by colors alone. This format can be
time consuming to process, so the "density" can be selected to trade-off graphic quality versus
time. Smaller form sizes for the plot also take less time to calculate, so you may wish to drag
the Polar form to a small size.
The graphs assume that the highest level in the included frequency range (of all included
curves) is displayed as "0dB" (red). If you are investigating a driver (or horn, or waveguide)
that hasn't been equalized (or voiced in a crossover), it is best to select the
"Curves>Normalize" menu and choose one of the curve angles to reference the others from.
The result would then be the pattern you could get were you to perfectly equalize the response
as seen from that angle. Typical normalization angles are for 0 degrees or 22.5 degrees (for
toed-in waveguides).
Normalizing the responses, however, can result in some apparently large peaks at frequencies
where the reference curve has low output. Such peaks would dominate the "0dB" value, so
you may want or need to adjust the frequency range of the polar plot to avoid ranges where