Test Bench: B&C Speakers DE1090TN Compression Driver

May 31 2017, 02:00
The transducer I examined this month came from Italian Pro Sound OEM manufacturer B&C Speakers, who sent the DE1090TN, a 1.4” neodymium motor compression driver with a titanium diaphragm. The DE1090TN compression driver is coupled with B&C Speakers’ ME90 80° × 60° constant directivity horn (see Photo 1 and Photo 2). The DE1090TN joins B&C Speakers’ series of 1.4” throat compression drivers, at this time numbering 14 models (seven ferrite motor compression drivers and seven neodymium motor compression drivers).
 
Photo 1: B&C Speakers DE1090TN-8 1.4” neodymium motor compression driver.
Photo 2: At 120 W, the new DE1090TN is the highest power handling model in the series.
Figure 1: B&C Speakers DE1090TN-8 free-air impedance plot.
Figure 2: B&C Speakers DE1090TN-8 on-axis frequency response.

However, the new DE1090TN is the highest power handling model (120 W) in the line. The DE1090TN has a 36 mm (1.4”) throat diameter. It is driven by a titanium diaphragm with a 100 mm (4”) diameter voice coil wound with copper-clad aluminum wire (CCAW). Other features include a neodymium ring magnet motor structure, nominal 120 W rated power handling (240 W continuous), an injection-molded aluminum black heatsink, and color-coded chrome push terminals. The horn supplied with the DE1090TN is B&C Speakers’ 1.4” throat 80° H × 60° V constant directivity cast-aluminum ME90 horn with a 0.9 kHz cutoff frequency.

I used the LinearX LMS analyzer to produce the 300-point stepped sine wave impedance plot shown in Figure 1. The solid black curve was taken with the DE1090TN mounted on the ME90 horn. The dashed blue curve represents the compression driver without the horn. With a 6.2 Ω DCR, the minimum impedance of the DE1090TN/ME90 was 7.9 Ω at 4.2 kHz.

For the next set of frequency response test, I free-air mounted the DE1090TN/ME90 without an enclosure and measured both the horizontal and vertical on- and off-axis at 2.83 V/1 m using a 100-point gated sine wave sweep 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, ±3.5 dB from 1 kHz to 8 kHz with a declining response as frequency increases above 2 kHz. B&C Speakers’ recommended crossover frequency for the D1090TN is 800 Hz with a second-order or higher high-pass filter.
 
Figure 3: B&C Speakers DE1090TN-8 horizontal on- and off-axis frequency response (0° = solid; 15° = dot; 30° = dash; 45° = dash/dot; 60°=dash).
Figure 4: B&C Speakers DE1090TN-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 DE1090TN 0° to 90° horizontal plane polar plot (in 10° increments).
Figure 6: B&C Speakers DE1090TN-8 vertical on- and off-axis frequency response (0° = solid; 15° = dot; 30° = dash; 45° = dash/dot; 60° = dash).
Figure 7: B&C Speakers DE1090TN-8 normalized vertical on- and off-axis frequency response (0° = solid; 15° = dot; 30° = dash; 45° = dash/dot; 60° = dash).

Figure 3 gives the on- and off-axis response in the horizontal plane. Figure 4 shows the normalized horizontal plane response. Figure 5 shows the CLIO Pocket-generated horizontal polar plot (1/3 octave smoothing applied). Figure 6 gives the on- and off-axis response in the vertical plane. Figure 7 depicts the normalized vertical plane response. Figure 8 shows the CLIO Pocket-generated polar plot (1/3 octave smoothing applied). Last, Figure 9 has the two-sample sound pressure level (SPL) comparison showing the two DE1090TN compression driver samples to be very closely matched within less than 1 dB.

I set up the Listen, Inc. AmpConnect ISC analyzer and 0.25” SCM microphone and power supply to measure distortion and generate time-frequency plots. For the distortion measurement, I mounted the DE1090TN/ ME90 combination in free air and set the SPL to 104 dB at 1 m (1.76 V, determined by using a pink noise stimulus generator and internal SLM in the SC14 software). Then, I measured the distortion with the Listen microphone placed 10 cm from the horn’s mouth. Figure 10 shows the distortion curves. Then, I set up SoundCheck 14 to generate a 2.83 V/1 m impulse response curve and imported the data into Listen’s SoundMap Time/Frequency software.

Figure 11 shows the resulting cummulative spectral decay (CSD) waterfall plot. Figure 12 shows the Short-Time Fourier Transform (STFT) plot. Italian pro sound OEM B&C Speakers is a very consistent manufacturer, with excellent build quality, performance, and engineering, and the new DE1090TN certainly falls into that category.

For more information, visit www.bcspeakers.com.
In the US, contact Bennett Prescott by email here
 
Figure 8: B&C Speakers DE1090TN 0°-90° vertical plane polar plot (in 10° increments).
Figure 9: B&C Speakers DE1090TN-8 two-sample SPL comparison.
Figure 10: B&C Speakers DE1090TN-8 SoundCheck distortion plots.
Figure 11: B&C Speakers DE1090TN-8 SoundCheck CSD waterfall plot.
Figure 12: B&C Speakers DE1090TN-8 SoundCheck Short Time Fourier Transform (STFT) plot.

This article was originally published in Voice Coil, August 2016.
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