Dayton Audio OmniMic V2 Precision Measurement System User Manual
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Optimally position speakers within a room
Speaker and listener positioning within a room is probably the most significant factor determining how a system will
sound. This can usually be best adjusted using the Frequency Response display and either the Pseudo-Noise or the Sine
Sweep signal. Set the control near the top to "All" for a display in which all echoes, reflections, and room effects are
included and apply 1/3rd octave smoothing. Start with one speaker playing at a time. The response will normally be
irregular, but try moving the speaker position or listening position for the most uniform response, particularly at lower
frequencies below 200Hz. For stereo, you will need to find two locations which can give a good stereo image together
while optimizing the low frequency response. Very often such factors are not mutually attainable. Low frequency
positions may also be optimized to minimize standing waves by use of the
A strong advantage of using separate subwoofers (rather than only full range speakers) is that they allow you to optimize
the mostly non-directional subwoofers for smoothest bass response and the upper frequency speakers for best stereo
imaging. While bass tends to be nondirectional, the in-room response of the bass speakers is extremely sensitive to
placement. You will almost always be able to get the smoothest overall low frequency response by using two or three
subwoofers optimally placed in different parts of the room, rather than a single subwoofer - even if the single subwoofer
were of much higher quality. The room position and diversity of placements will have significantly more effect on bass
frequency response than could subwoofer response flatness.
Adjust an Equalizer
Omnimic now has a very sophisticated feature for manually or automatically
nd downloading
settings to
through its Biquad Parameters.
When adjusting equalizers:
adjustment at lower frequencies should use a measurement setup similar to the one for positioning speakers (but
the placement should be determined first). Strong boosts with the equalizer should be avoided at any frequency,
but response peaks can be effectively removed to any degree necessary.
Equalization at higher frequencies are usually best done only in moderation, and generally adjusted with echoes
removed by setting the Frequency Response analyzer to "blended" and clicking the mouse within the Impulse
Response display on a point just before the first strong reflection. Avoid sharp narrow-band adjustments on the
equalizer at higher frequencies because they can cause significantly worse sound at slightly different listening
positions.
Adjusting for more than one listening position
For theaters or other situations with multiple listeners, compromise settings must be made to provide the best
sound overall for all listeners. Begin by optimally positioning the low frequency speakers (or main, if full range) to
avoid major problems at various seats, particularly those furthest from the center. Again, use of several well-
placed low frequency speakers will be most effective for giving good results for all listeners.
Then, with the Frequency Response analyzer set to "All" and with 1/6th octave smoothing use
the
features. Make a series of measurements at all (or at least a good representative number) seats,
starting with "Clear Averages" then "New Average" for the first, and clicking "More Averages" (or pressing the
spacebar) once with the OmniMic placed at each position. This will result in an overall average room frequency
response, which you should save to disk or print for future reference. You can then adjust your equalizer to
provide approximately the opposite of the resulting response; the new
makes this
easy. That is, if there were an 8dB peak (relative to response at most frequencies) in the 4kHz range, then if a
flat response is desired, then the equalizer should be set for -8dB at 4kHz. Avoid applying large increases (more
than about 6dB) with the equalizer and use only moderate and broad (not sharp in frequency) settngs at
frequencies above about 500Hz.