In terms of features, the B&C Speakers DE360‑8 is designed for use with 1” throat horns, which means it has a 25 mm (1”) throat diameter and a field replaceable HT Polymer diaphragm, driven by a 38 mm (1.5”) diameter voice coil wound with CCAW on a Kapton-type non-conducting former. Other features include a neodymium ring magnet motor, nominal 35 W rated power handling (70 W continuous), a 1.8 kHz recommended crossover frequency (second-order or higher high-pass filter), and 2.83 V/1 m 110 dB sensitivity. B&C Speakers supplied the ME20 horn for use with the DE360-8. This exponential flare horn is a 1” exit bolt-on type made from cast aluminum. The ME20 has a 90° × 60° coverage pattern and a 1.5 kHz cut-off frequency, making it a good match for the DE360-8 compression driver.
To begin testing, I used the LinearX LMS analyzer to produce the 300-point stepped sine wave impedance plot shown in Figure 1. The solid black curve is with the B&C Speakers DE360-8 mounted on the ME20 horn and the dashed blue curve represents the compression driver without the horn. With a 5.65 Ω DCR (Re), the minimum impedance of the DE360/ME20 was 7.31 Ω and at 5.19 kHz.
Next, I free-air mounted the B&C Speakers DE360-8/ME20 combination without an enclosure and measured both the horizontal and vertical on and off axis at 2.83 V/1 m, again using the LOUDSOFT FINE R+D analyzer and the G.R.A.S. 46BE microphone to capture horizontal and vertical plane SPL data from 0° on-axis to 60° off-axis.
Figure 2 displays the on-axis frequency response of the compression driver/horn combination, which is smooth with no major anomalies with a declining response as frequency increases above 2.5 kHz, and extending to somewhat beyond 20 kHz. Figure 3 shows the on- and off-axis response in the horizontal plane. Figure 4 displays the normalized horizontal plane response. Figure 5 shows the CLIO Pocket analyzer-generated 180° horizontal polar plot (in 10° increments with 1/3 octave smoothing applied). Figure 6 gives the on and off axis to 60° response in the vertical plane. Figure 7 depicts the normalized vertical plane response. Figure 8 shows the CLIO Pocket generated vertical plane polar plot (in 10° increments with 1/3 octave smoothing applied). Last, Figure 9 illustrates the two-sample SPL comparison showing the two B&C Speakers DE360-8 compression driver samples to be closely matched within less than 1 dB throughout the operating range of the transducer.
For the remaining tests, I again set up the Listen AudioConnect analyze, SoundCheck 16 software, and the Listen 1/4” SCM microphone to measure distortion and generate time-frequency plots. For the distortion measurement, I mounted the DE360-8/ME20 combination in free-air in the same manner as was used for the frequency response measurements, and set the SPL to 104 dB at 1 m (1.49 V determined by using a pink noise stimulus generator and internal SLM in the SoundCheck 16 software). Then, I measured the distortion with the Listen microphone placed 10 cm from the mouth of the horn. This produced the distortion curves shown in Figure 10.
I set up SoundCheck 16 to generate a 2.83 V/1 m impulse response and imported the data into Listen’s SoundMap Time/Frequency software. Figure 11 shows the resulting CSD waterfall plot. Figure 12 shows the STFT plot.
From the measurements, the DE360-8 provides excellent performance in a small lightweight package, and is a nice addition to B&C Speakers’ extensive lineup of ferrite and neodymium motor compression drivers.
For more information, contact B&C Speakers N.A., National U.S. Sales Office, 220 W. Parkway, Unit 11, Pompton Plains, NJ 07444, by phone at 973-248-0955, by fax at 973-248-0956, e-mail Bennett Prescott, or visit the B&C Speakers website at www.bcspeakers.com. VC
This article was originally published in Voice Coil, May 2018.