SP395 SoundPro Audio Integrator Form7492 Operation Manual
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9. Graph Range – dB range of graphed levels. Adjust the dB range as needed so that the
display fits on the vertical axis, by selecting and changing the dB value at the bottom of
the vertical axis.
10. Average SPL – The digital SPL measurement that is displayed along the bottom of the
graph is calculated from an average of the RTA bands and is therefore slightly less
accurate than the standard SPL function. It is provided here for convenience while using
the RTA display. You can select dB SPL – the unweighted full-band SPL level; dBA -
the A-weighted SPL; or dBC - the C-weighted SPL. Turn the control knob until the
desired weighting value is displayed, then click to select the new value.
11. Measurement Cursor – Click the control knob on the cursor control field, then turn the
control knob to move the cursor to any measurement bar to read out the exact frequency
and dB level. Cursor measurements can be made in the Run or Pause mode, or on recalled
RTA graphs.
12. Cursor Level – Indicates the level SPL of the cursor position (octave or 1/3 octave band)
on the graph. The measurement Cursor allows you to analyze the RTA graph display in
detail. It is an inverse-highlighted vertical bar that you can position horizontally along the
graph. The center frequency of the selected band and the band's dB SPL level are
displayed in the lower right portion of the graph. Cursor measurements can be made in the
Run or Hold mode, or on recalled RTA graphs. To position the Measurement cursor along
the graph, highlight the frequency "Measurement Cursor" field and click on it
(underlined). Rotate the control knob to move the cursor.
RTA Operation
1. Position the microphone. A measurement microphone is normally placed at the desired
measurement location and pointed at the ceiling to be omni directional to all system
loudspeakers. Apply phantom power to the microphone and select the proper gain range.
2. (Optional) Connect a constant-level pink noise signal to the audio system. To use the
SP395 as a pink noise signal source, connect a cable from an SP395 output connector to
the desired input on the audio system. There will not be an output from the system until
the RTA and Signal generator are turned on from the RTA display. The output level of the
RTA pink noise is adjustable in the Signal Generator bottom toolbar menu section.
Caution: Preset the amplifier gain to minimum to prevent speaker damage when the
RTA test is turned on.
3. Select the octave band filter resolution. Use 1/3 octave for most RTA analysis, as this
resolution corresponds most closely to the resolution of the human auditory system.
4. Select the averaging time constant. Longer times provide a more stable display, while
slower times respond more quickly to changing sounds and noise. Use 6 second (or
longer) averaging when performing low frequency equalization.
5. Select the desired weighting. Use Flat (no weighting) for most applications.
6. Turn on the pink noise. If you are using the SP395 as the signal source, turn on both the
RTA function and the generator. ("Gen on" field).
7. Adjust the Graph Range and Graph Resolution. Adjust the range and resolution so that
the entire graph display fits on the vertical axis. Depending on the SPL difference between
the highest and lowest levels, you may need to use 35 dB resolution to see the entire
graph.
8. Use the measurement cursor to read the exact frequency and dB level of any
frequency band on the graph. Pause the RTA, if desired, to freeze the display.
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