The following equipment was used:
1. A 31-band real-time spectrum analyzer with a built-in omni-directional microphone, 0.5dB resolution, PAA2 Personal Audio Assistant("PAA2"), Phonic Corporation of America
2. Laptop computer (Apple G4 17-inch, 1GHz CPU, 1GB RAM, System OS 10.3.7)
3. Spectrum analyzer computer interface software, Windows-based, Phonic Corporation of America
4. RS-232 interface cable for PAA2
5. Microsoft Office 2004 for the Mac (with Virtual PC 7.0.1 running Windows XP Professional operating system)
6. Music playback software Apple iTunes 4.7.1
7. USB-to-serial adapter Keyspan PN USA-19HS
8. Keyspan software driver for Macintosh OS 10.3.X
9. Digital Multimeter, Micronta model number 22-185A, Radio Shack
10. Audio amplifier, Adcom, model number GFA-545II
11. Audio loudspeaker, Vandersteen Audio, model number 2Ce
12. Audio preamplifier, Conrad-Johnson, model number PV10A
13. Audio interconnects, Kimber Kable, model PBJ, 1-meter pair, 2 pair required.
14. Mini audio microphone jack to RCA stereo adapter, Radio Shack
15. Loudspeaker cable, Kimber Kable, model 4TC, approximately 70ft (21m)
16. Audio software, "Pink Noise (20Hz to 20KHz) Right Channel Only," Autosound 2000, Test CD#102
17. Ladder
18. Measuring tape
In order to determine the free-field loudspeaker response, I set up the audio playback equipment in a garage according to each of the manufacturer's instructions. Since only one loudspeaker was used, only the right channel was configured for playback. According to Vandersteen's recommendations, I biwired the loudspeaker. The length of each speaker cable was about 35 feet (11m), which is a sufficient length to extend from the workbench, where the audio equipment was positioned, to the loudspeaker positioned in my driveway.
The loudspeaker was oriented in such a way that the nearest object to the front or side was in excess of 100 feet. A small ladder was used to position and support the PAA2 so that the microphone was a meter (3.28 feet) in front of the loudspeaker and on axis with the tweeter. The PAA2 was programmed to record sound using A-weighting, the 30 to 90dB measurement range, and a 250 milliseconds response time. The digital multimeter was configured to measure the RMS voltage across the positive and negative amplifier speaker binding posts for the right channel. The "pink noise" audio track was played and the volume of the preamplifier was adjusted to achieve an RMS voltage of 2.83 volts across the speaker binding posts. The preamplifier volume setting remained unchanged for the remainder of the experiments. The "pink noise" audio track was played while three measurements were taken and stored to memory. The data stored in memory was imported into the PAA2's Windows-based software and saved as a comma-delimited text file. The comma-delimited text file was imported in Microsoft Excel 2004 for the Mac. The mean SPL was calculated for each of the 31 frequency bands.