Test Bench: Russo 44CD-K Compression Driver from SB Audience, a New Brand from SB Acoustics

August 20 2019, 10:10
For this Test Bench, I had the opportunity to characterize the Russo 44CD-K from SB Audience, a new brand from SB Acoustics. Over the last several years, Indonesian-based Sinar Baja Electric in partnership with Danesian Audio of Denmark, has generated an excellent reputation for the high-end home and car audio drivers that have been marketed under the SB Acoustics name. However, the company has also been producing a rather extensive line-up of pro sound OEM products including 6.5” to 18” PA woofers, midranges, and compression drivers. This month, Sinar Baja has announced a new product category organization for its various brands
 
Photo 1: SB Audience 44CD-K compression driver.
Figure 1: SB Audience 44CD-K free-air impedance plot.
Figure 2: SB Audience 44CD-K on-axis frequency response.
Figure 3: SB Audience 44CD-K horizontal on- and off-axis frequency response (0° = black; 15° = blue; 30° = green; 45° = purple; 60° = blue).
Figure 4: SB Audience 44CD-K normalized horizontal on- and off-axis frequency response (0° = black; 15° = blue; 30° = green; 45° = purple; 60° = blue).

SB Acoustics will continue to be its hi-fi driver product range, including Satori, SB Audience is now its pro sound product line, and SB Automotive is now its car audio product line. That said, SB Audience sent me the 44CD-K, a new compression driver from the Russo model line (Russo being the “high performance at an attractive price” line), along with its ABS-250 90° × 90° exponential horn (see Photo 1). SB Audience also has two other product lines that include Nero, the “highest performance” line, and Bianco, the “good performance at the lowest cost” product line.

Features for the SB Audience 44CD-K include a 1” throat exit designed for use with 1” horns, and includes a 44 mm (1.75”) diameter voice coil wound with round copper wire on a high-temperature Kapton non-conducting former, driving a single piece polyimide diaphragm and surround. Other features include a FEA-optimized ferrite magnet motor structure, a continuous power handling of 100 W with a nominal 80 W power handling rating, a 2 kHz recommended crossover frequency (with a minimum 12 dB/octave high-pass network), and 2.83 V/1 m 101 dB sensitivity.

I commenced testing the SB Audience 44CD-K/ABS-250 combination using the LinearX LMS analyzer to produce the 300-point stepped sine wave impedance plot shown in Figure 1. The solid black curve was obtained with the 44CD-K mounted on the ABS-250 horn and the dashed blue curve represents the compression driver without the horn. With a 6.01 Ω DCR (Re), the minimum impedance of the 44CD-K/ABS-250 was 7.07 Ω and at 5.14 kHz.

For the next set of SPL measurements, I free-air mounted the SB Audience 44CD-K/ABS-250 combination without an enclosure and measured both the horizontal and vertical on and off-axis at 2 V/0.5 m normalized to 2.83 V/1 m, again the Loudsoft FINE R+D FFT analyzer to produce both horizontal and vertical plane SPL data from 0° on-axis to 60° off-axis. The Audiomatica CLIO Pocket analyzer and measurement microphone were utilized to generate the 180° polar plots.
 
Figure 5: SB Audience 44CD-K 0°-180° horizontal plane polar plot (10° increments).
Figure 6: SB Audience 44CD-K vertical on- and off-axis frequency (0° = black; 15° = blue; 30° = green; 45° = purple; 60° = blue).
Figure 7: SB Audience 44CD-K normalized vertical on- and off-axis frequency response (0° = black; 15° = blue; 30° = green; 45° = purple; 60° = blue).
Figure 8: SB Audience 44CD-K 0° to 180° vertical plane polar plot (in 10° increments).

Figure 2 shows the on-axis frequency response of the compression driver/horn combination, which is flat and a relatively smooth ±2.6 dB from 2 kHz to 14.8 kHz with no major anomalies followed by a steep low-pass roll-off above 15 kHz. Figure 3 depicts the on- and off-axis (0° to 60°) response in the horizontal plane.

Figure 4 displays the normalized horizontal plane response. Figure 5 shows the CLIO Pocket analyzer-generated the 180° horizontal polar plot (in 10° increments with 1/3 octave smoothing applied). Figure 6 gives the on- and off-axis 0° 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 SB compression drivers less than 1 dB throughout the operating range of the transducer from 2 kHz to 15 kHz.

Next, I again set up the Listen AudioConnect analyzer, the 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 44CD-K/ABS-250 combination in free-air and set the SPL to 104 dB at 1 m (3.1 V determined by using a pink noise stimulus generator and the internal SLM in the SoundCheck 16 software). Then, I measured the distortion with the Listen 1/4” measurement microphone located 10 cm from the mouth of the horn. This produced the distortion curves shown in Figure 10 (red curve = second harmonic, blue curve = third harmonic).
 
Figure 9: SB Audience 44CD-K two-sample SPL comparison.
Figure 10: SB Audience 44CD-K SoundCheck distortion plots.
Figure 11: SB Audience 44CD-K SoundCheck CSD waterfall plot.
Figure 12: SB Audience 44CD-K SoundCheck STFT plot.

I then 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 above measurements, the SB Audience 44CD-K 1” ferrite compression driver displays excellent performance for a cost-effective moderately high power handling package, and very good ferrite motor compression driver build quality. For more information, contact Mark Thomsen. VC

This article was originally published in Voice Coil, May 2019.
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