Dayton Audio OmniMic V2 Precision Measurement System - Manual (Page 30)

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these peaks appear.
There is a set of example FRD files which can be loaded all at once by going to the Frequency
Response menu "Curves>LoadCurveList", then browsing
to C:\Users\Public\OmniMic\SEOS15 Examples and loading "All Curves". After loading
this, click on the Polar button to see the effect. Then try normalizing the files by going to
"Curves>Normalize", then browsing to the same directory and choosing one of the curves (the
22.5 degree curve is used for some of the illustrations on this Help page). Adjust the
frequency range of the Polar Display and note the effects -- if the lower frequencies below
700Hz (which are full of artifacts in the example), or the frequencies above 17kHz (also full of
normalization artifacts) are included, the artifacts will dominate the display's 0dB level. Adjust
the frequency ranges to exclude these. The result should be approximately the effects of
(hypothetically) equalizing the speaker's response to be flat at the normalization angle in that
frequency range.
Making Measurements for Polar Displays
For good quality Polar Displays, echoes should be minimized in the measurements. Set the
speaker out in a clear area so that reflected signals are delayed as much as possible. This will
allow them to be avoided at higher frequencies (see "Only To" and "Blended" in
Frequency
Response ). Either the microphone stand or the speaker can be moved to arrange for each
angle for measurement. Steps of approximately 7.5 degrees or less are preferred for good
detail. The program will interpolate between the steps, and if only positive (or only negative)
angles are given, will mirror the measurements to the opposite side (this will be accurate, of
course, only for symmetric speakers or drivers). Try to measure out to at least 75 degrees
from the baffle axis on each side -- unmeasured positions will not be represented in the plot.
Dipole or Bipole speakers should be measured a full 360 degrees.
Name each file so that you can identify the angle it was measured from -- if you include the
number in the file name, the OmniMic software will try to infer the angle from the file name
when you later bring in ("Add") the files to a frequency response page.
Tip:
If you save the files by right-clicking on the graph and then choosing "Save Curve to Text File
(auto-increment)" then the program will automatically name each file by incrementing a number
in the file name.