Test Bench by Vance Dickason. A New Bullet Tweeter from FaitalPRO (...) by Vance Dickason
(…) This month's driver samples are both pro sound products. I received a Faital Pro FD371, which is a new bullet-phase plug tweeter, and (...).
The Faital Pro FD371
The first driver I examined this month was FaitalPRO's FD371 bullet-type, high-SPL tweeter (seek Photo1). Faital Pro's FD371 is built around a CNC'd aluminum horn and phase plug. Other features include a Ketone Polymer annular-shaped diaphragm, a 37-mm (1.4") diameter voice coil using a Kapton former wound with aluminum wire, and a ferrite motor structure with polished front and back plates.
Testing commenced using the LinearX LMS analyzer to produce the 300-point sine wave impedance plot (...). With a 5.6-a DCR, the FD371's minimum impedance above resonance was 7 Q at 7.79 kHz. The FD371's primary resonance occurs at 1.79 kHz with an 11.2-Q magnitude.
Next, I mounted FaitalPRO's FD371 in an enclosure with a 15" x 6" baffle and measuring the on- and off-axis frequency response at 2.83 V/1 m with a 100-point gated sine wave sweep. Figure 2 shows the bullet tweeter on-axis and shows the sensitivity varies between 102 and 109 dB. The company-specified sensitivity of 107 dB falls between those measurements. This SPL profile measures ±3 dB from 2 to 9 kHz. The FD371 pro sound tweeter's recommended minimum crossover frequency is 2.5 kHz, which is low for this type of device. The response is ±3.75 dB from 2 to 20 kHz. Figure 3 shows the on- and off-axis SPL out to 60° off-axis, with the normalized view shown in Figure 4. You can get a graphic look at the device's directivity in the factory beamwidth plot shown in Figure 5. Figure 6 shows the two-sample SPL comparison, indicating both samples are well matched. For the remaining tests, I used the Listen SoundCheck analyzer, 0.25" SCM microphone and power supply to measure distortion and generate time-frequency plots. For the distortion measurement, the FD371 tweeter was mounted on the same baffle used for the frequency-response measurements, and a pink noise stimulus was used to set the SPL to 104 dB at 1 m (0.64 V). I measured the distortion with the Listen microphone placed 10 cm from the horn's mouth. This produced the distortion curves shown in Figure 7. I then used SoundCheck to measure the driver's 2.83-V/1-m impulse response and imported the data into Listen's SoundMap time/frequency software. The resulting CSD waterfall plot is shown in Figure 8.
The short-time Fourier transform (STFT) plot is shown in Figure 9. I haven't had a chance to verify this, but Keith Gronsbell, FaitalPRO's U.S. representative, said the Ketone polymer diaphragm yields a smooth subjective performance, considerably more musical than bullet tweeters from the pro sound past. For more about this and other Faital Pro pro sound products, visit the company's website at 
www.faital-pro.com, or in the U.S., contact Faital USA, Inc., Keith Gronsbell (
