First set up your mic at the listening position, aimed towards the speaker you want to measure. It's best to have a stand for it, but if not hold it at arm's length during the measurement tone. For full range, it’s best to measure one speaker at a time.
1. Prepare to run the Check Levels routine (Settings icon, Soundcard tab) selecting Check/Set Levels with Subwoofer in the Levels pull down box.
2. Change Input Device Input and Output Device Output from Default to USB Audio, or the name of the soundcard, if that option is available, and Speaker for output, and Line In for input.
3. Begin the Check Levels routine. Ensure the REW output VU meter is at -12db and the Sweep Level at -12dB. If those fields are blank, check the two Control Mixer Volume boxes.
4. Set the Wave Volume at 1.000 and the Output Volume about ~0.500. (If those fields are blank,).
5. Adjust your receivers volume control so the actual standalone Radio Shack SPL meter reads ~75db at the listening position. Then adjust REW Input Volume to end up with -18dB on the REW input VU meter.
6. Still in the Settings section, run the Calibrate SPL routine (in the Mic/Meter Tab) to match REW's SPL meter to the real SPL meter to ~75dBSPL. Make sure the “C Weighted” SPL meter is checked (if you’re going to use the meter to make the measurements).
7. Close Settings window. Run the Set Target Level routine (Target Settings icon to left of screen), which will set the target to ~75dB. Make the Speaker Type selection for what you want to measure – subwoofer, full range, etc. For subwoofers and bass-limited full range measurements, also, set the Cutoff, which is the crossover frequency you’re using
8. Run the Measure routine.
9. Using the Graph Axis Limits icon, set the vertical scale to 45dB to 105dB and the horizontal scale for subs to 15Hz to 200Hz.
10. To save the graph, select Graph from Menu Bar, then Save Graph as JPG. Use 600 size setting.
Regards,
Wayne