Test Bench B&C DE980TN-8 Compression Driver

May 24 2016, 05:05
In this Test Bench I examined the DE980TN-8 from B&C Speakers, an Italian pro sound OEM. The DE980TN-8 is a new titanium-diaphragm neodymium-motor compression driver coupled with B&C Speakers’s ME90 horn. The DE980TN-8 joins B&C Speaker’s 1.4” neodymium-motor titanium-diaphragm compression driver series that includes the DE620TN, the DE820TN, the new DE880TN, and the DE920TN. This series has several unique features, including titanium diaphragms, neodymium ring magnet motor assemblies with cast-aluminum heatsink caps, and copper shorting rings.
Photo 1: B&C Speakers’s DE980TN-8 is a compression driver coupled with the ME90 horn.

The B&C Speakers DE980TN-8’s throat diameter is 36 mm (1.4”) coupled to a 75-mm (3”) diameter voice coil wound with copper-clad aluminum DE980TN-8 has a 1.4” throat diameter, 80° horizontal × 60° vertical, constant-directivity cast-aluminum horn with a solid 900-Hz cut-off frequency.

I used the LinearX LMS analyzer to produce the 200-point sine wave impedance plot shown in Figure 1. The solid black curve in Figure 1 shows the DE980TN-8 mounted on the ME90 horn and dashed blue curve represents the compression driver without the horn. With a 6.0-Ω DCR, the DE980TN-8/ME90’s minimum impedance was 7.8 Ω at 5.9 kHz.

For the next frequency-response tests, I recess mounted the B&C Speakers DE980TN-8/ME90 in an enclosure with a 10” × 15” 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 2 displays the compression driver/horn combination’s on-axis, which is smooth with no major anomalies out to 18 kHz. There is a small mode at 15.6 kHz, and a declining response as the frequency increases, which is typical of constant directivity horns. B&C Speakers’s recommended crossover frequency for the DE980TN-8 is 1.2 kHz with a second order or higher slope.
Figure 1: B&C Speakers DE980TN-8 free-air impedance plot.
Figure 2: B&C Speakers DE980TN-8 on-axis frequency response.
Figure 3: B&C Speakers DE980TN-8 horizontal on- and off-axis frequency response (0° = solid; 15° = dot; 30° = dash; 45° = dash/dot; 60° = dash).
Figure 4: B&C Speakers DE980TN-8 normalized horizontal on- and off-axis frequency response (0° = solid; 15° = dot; 30° = dash; 45° = dash/dot; 60° = dash).
Figure 5: B&C Speakers DE980TN-8 vertical on- and off axis frequency response (0° = solid; 15° = dot; 30° = dash; 45° = dash/dot; 60° = dash).
Figure 6: B&C Speakers DE980TN-8 normalized vertical on- and off-axis frequency response (0° = solid; 15° = dot; 30° = dash; 45° = dash/dot; 60° = dash).
Figure 7: B&C Speakers DE980TN-8 SPL comparison.

Figure 3 shows the on- and off-axis response in the horizontal plane. Figure 4 gives the DE980TN-8’s normalized horizontal plane response. Figure 5 provides the on- and off-axis response in the vertical plane. Figure 6 shows its normalized vertical plane response. Figure 7 displays the two DE980TN-8 compression driver samples to be closely matched in a two-sample comparison. 

I used the Listen AmpConnect ISC analyzer and 0.25” SCM microphone to measure distortion and generate time-frequency plots. For the distortion measurement, I mounted the B&C Speakers DE980TN-8/ME90 combination with the same baffle used for the frequency-response measurements. I used pink noise stimulus to set the SPL to 104 dB at 1 m (1.88 V) and placed the Listen microphone 10 cm from the horn’s mouth. This produced the distortion curves shown in Figure 8. I then used SoundCheck to get a 2.83 V/1 m impulse response and imported the data into Listen’s SoundMap time-frequency software. Figure 9 provides the resulting CSD waterfall plot. Figure 10 shows the short-time Fourier transform (STFT) plot. The DE980TN-8’s build quality and performance is excellent. 
For more information, visit www.bcspeakers.com
Figure 8: B&C Speakers DE980TN-8 distortion plots.
Figure 9: B&C Speakers DE980TN-8 CSD waterfall plot.
Figure 10: B&C Speakers DE980TN-8 STFT plot.

This article was originally published in Voice Coil, September 2013
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