Dayton Audio OmniMic V2 Precision Measurement System - Manual (Page 11)

11 | P a g e
Frequency Response - Advanced Functions
Index
Additional Advanced features are built-in and available in the OmniMic Frequency Response analyzer
for users who need to go into more depth in their measurements.
The advanced features are:
 a set of Math functions so that you can measure responses
-- as compared ("Normalized") to a saved file curve; This removes the effects of the curve
used. If you normalized a curve by itself, you'd get a flat line.
-- use file curves as a filter during measurement ("Filter"). If you Filtered a flat line with a
curve, you'd get the Filter curve.
-- sum (vector style, including phase) with a previously measured response from a FRD file
-- offset, that is, moved up or down by a specified amound (in dB)
-- with the response flipped (so that peaks are replaced with troughs and vice-versa)
-- or have the OmniMic evaluate whether the displayed portion of a measurement falls entirely
within the area between the first two specified file curves ("Evaluate within"). Offsets applied
to the curve files during display are utilized for the evaluation (so you can use the same file for
both limits, one offset upwards and the other offset downwards). You can also select whether
to allow the program some vertical shifting to get the measured curve to fit (good for when you
care about shape more than absolute sensitivity match).
Some of these functions utilize ".FRD" type text files as generated by OmniMic or other
programs. These files can also be easily created using any text editor such as Windows'
"Notepad", or a spreadsheet program.
 measured responses can be arranged to be inverted in shape or offset vertically in dB.
 averaging: Left-click the "New Average" button to freeze the current frequency response
curve on the graph (alternately, your keyboard's space bar can be used for this function). New
live measured curves will be shown along with the frozen one. If you left-click it repeatedly,
each current live curve will be averaged into the frozen curve (the button label will change to
"more average" and indicate the number of averages included so far). This function is very
useful for determining the average response curve over a range of listening positions in a
room. Click "Clear Averages" to erase a frozen or averaged curve and show only the live
curve. If you want to see only the frozen/ average curve, click on "Hide Main". You can save
an average curve for later recall using the "File" menu, or recall a previous saved FRD file to
replace the Average curve.
 To average in a response curve that has been previously saved to a file via the file menu,
first "Add" the curve to the display using the "Curves" menu. Then Right-click on the "New
Average" or "more Averages" button to include the last Added file to the average curve.
 An option to show the impulse response plot in "logarithmic" form rather than the usual
"linear" form. Logarithmic form hides polarity but makes it easier to look at the decay shape of
an impulse response curve. With logarithmic display it is often easier to identify discrete
reflections in the impulse response, which can be particularly helpful with Waterfall Displays.
 Two styles of color 3D Polar displays, for diplaying responses in sets of saved files in formats
that show how the frequency response of a speaker varies as it radiates into different