Three High-Frequency Drivers ... tested by Voice Coil, the periodical of the loudspeaker industry, December 2012by Vance Dickason
This month, I will review three different drivers. (...) I also received the new HF105 compression driver and the STH100 horn from Faital Pro, an Italian pro-sound OEM.
The HF105 and the STH100 The last driver I examined this month was the Faital Pro HF105 compression driver coupled with Faital's 5TH 100 horn (see Photo 3). I reviewed the Faital Pro HF104 coupled to the same STH100 horn in Voice Coil March 2012.
The HF105 is essentially a ferrite-motor version (the HF104 uses neodymium), which in today's market means lower cost, but with only a modest increase in weight of 0.58 lb. Like the HF104, the HF105 is an interesting compression driver and has several unique features.
This includes a Ketone polymer annular-shaped diaphragm and a radial-shaped phase plug. The throat diameter is 25.4 mm (1") and it is coupled to a 28-mm (1.5") diameter voice coil wound on a Kapton former with CCAW.
Other features include an aluminum body, 40-W AES-rated power handling (80-W maximum), and solderable terminals.
The horn supplied with the HF105 driver, as in the HF104 review, is Faital's 1" throat, 80-H x 70-V short elliptical tractrix flare STH100.
Testing commenced using the LinearX LMS analyzer to produce the 300-point stepped sine wave impedance plot shown in Figure 17.
Note the solid black curve shows the HF105 mounted on the STH100 horn and the dashed blue curve represents the compression driver without the horn. With a 5.5-Ohm DCR, the HF105/STH100's minimum impedance was 5.9 Ohm and at 5.9 kHz.
For the next test sequence, I recess mounted the Faital HF105/5TH100 in an enclosure with a 9" x 12" baffle and used a 100-point gated sine wave sweep to measure the horizontal and vertical on- and off-axis at 2.83 V/1 m.
Figure 18 shows the on-axis of the compression driver/horn combination with the sensitivity at about 108 dB, somewhat higher than the specified 107 dB from Faital's published data. (The Faital Pro's sensitivity spec is 1 W/1 m.)
The SPL profile measures ±4 dB from 1 to 8.8 kHz. (The recommended cross-over frequency for the HF105 is a minimum of 1.7 kHz with a second-order network.)
Since the coverage of this horn is 80 H x 70 V, you wouldn't expect much of a difference in the horizontal and vertical off-axis plots (see Figure 19 for the horizontal orientation and Figure 20 for the vertical orientation).
Figure 21 provides the two-sample SPL comparison, showing both samples to be closely matched.
For the remaining tests, I used the SoundCheck analyzer and 0.25" SCM microphone and power supply to measure distor-tion and generate time frequency plots.
For the distortion measurement, the HF105/STH100 combination was mounted with the same baffle used for the frequency-response measurements.
I used a noise stimulus to set the SPL to 104 dB at 1 m (0.65 V) and measured the distortion with the microphone placed 10 cm from the horn's mouth. This produced the distortion curves shown in Figure 22. I then used SoundCheck to get a 2.83-V/1-m impulse response for this driver and imported the data into the SoundMap time/frequency software. The resulting CSD waterfall plot is shown in Figure 23 and the STFT plot is shown in Figure 24.
Comparing the HF104/STH100 data to the above data, the HF105/STH100's performance is similar to the neodymium version but at lower cost with not a lot more weight.
Visit www.faitalpro.com for more information, or in the U.S., contact Faital USA, Inc., Keith Gronsbell, 220 West Parkway, Unit 13, Pompton Plains, NJ, 07444; (516) 779-0649; Fax (973) 835-5055; or e-mail
FaitalPRO officially thanks Mr Vance Dickason for the kind permission to re-public his tests.
