Test Bench: SB Audience 44CDN-PK 1" PEEK Diaphragm Compression Driver

Over the last several years, Indonesian-based Sinar Baja Electric in partnership with Danesian Audio of Denmark, have generated an excellent reputation for the high-end home and car audio drivers that have been marketed under the SB Acoustics name. Pretty much the same thing has been happening with its Pro Sound Division, SB Audience, as it has been gradually expanding and improving the product line. The company recently released six new compression drivers — four with Polyether Ether Ketone (PEEK) diaphragms and two with titanium diaphragms. SB Audience has three product lines: Rosso is the “high performance at an attractive price” line, the Nero line is the “highest performance” line, and the Bianco line is the “good performance at the lowest cost” product line.
   SB Audience sent me one of the new compression drivers from the Rosso model line, the Rosso 44CDN-PK combined with the H250 90°×60° exponential horn (Photo 1). Features for the SB Audience 44CDN-PK include a 1” throat exit designed for use with 1” horns, a 44.3mm (1.75”) diameter voice coil wound with flat copper-clad aluminum wire (CCAW) on a high temperature Kapton non-conducting former driving a single piece PEEK diaphragm and surround (Photo 2). Other features include a FEA-optimized neodymium (neo) ring magnet motor structure, a cast-aluminum damped rear chamber, a 60W AES power handling rating (120W maximum power handling defined 3dB over nominal), a 1.8kHz recommended crossover frequency (with a minimum 12dB/octave high-pass network), an annular phase plug design, and a 1W/1m 109dB sensitivity. The 90°×90° H250 horn that accompanied the 44CDN-PK is a constant directivity category device (directivity factor Q=6.3, DI=8dB) made from injection-molded ABS with a 1” throat diameter and a 600Hz cut-off frequency.
 
Testing the SB Audience 44CDN-PK/H250 combination commenced using the LinearX LMS analyzer to produce the 300-point stepped sine wave impedance plot shown in Figure 1, with the solid black curve made with the neo motor 44CDN-PK mounted on the H250 horn and the dashed blue curve representing the compression driver without the horn. With a 5.87Ω DCR (Re), the minimum impedance of the 44CDN-PK/H250 was 7.09Ω and at 5kHz.
 
For the next set of SPL measurements, I free-air mounted the SB Audience Rosso 44CDN-PK/H250 combination without an enclosure and measured both the horizontal and vertical on- and off-axis at 2.0V/0.5m, normalized to 2.83V/1m, with the Loudsoft FINE R+D FFT analyzer and the GRAS 46BE ¼” measurement microphone to produce both horizontal and vertical plane SPL data from 0° on-axis to 60° off-axis. The Audiomatica CLIO Pocket analyzer and the MIC-02 measurement microphone were utilized to generate the 180° polar plots.
 
Figure 2 illustrates the on-axis frequency response of the compression driver/horn combination, which is flat and a relatively smooth ±2.1dB from the 1.8 kHz recommended minimum crossover point to 18kHz with no major anomalies followed by a steep low-pass roll-off above 20kHz. Figure 3 depicts the on- and off-axis (0° to 60°) response in the horizontal plane. Figure 4 displays the normalized horizontal plane response, and 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 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 Audience compression drivers to ≤1dB throughout the operating range of the transducer from 1.8kHz to 20kHz.
 
For the remaining series of tests, I again set up the Listen AudioConnect analyzer, SoundCheck 20 software, and the Listen ¼” SCM microphone to measure distortion and generate time-frequency plots (courtesy of Listen, Inc.). For the distortion measurement, I again mounted the 44CDN-PK/H250 combination in free-air in the same manner that was used for the frequency response measurements, and set the SPL to 104dB at 1m (2.17V determined by using a pink noise stimulus generator and internal SLM in the SoundCheck 20 software). I then measured the distortion with the Listen ¼” measurement microphone located 10cm from the mouth of the horn. This produced the distortion curves shown in Figure 10 (red curve=second harmonic, blue curve=third harmonic. Note the very low third harmonic distortion for this driver.
 
Following this test sequence, I set up SoundCheck 20 to generate a 2.83V/1m impulse response for this driver/horn combination and imported the data into Listen’s SoundMap Time/Frequency software. The resulting cumulative spectral decay (CSD) waterfall plot is given in Figure 11 and the Short Time Fourier Transform (STFT) plot is shown in Figure 12.
 
From the above measurements, the SB Audience 44CDN-PK 1” neo ring magnet compression driver displays excellent performance for a relatively cost-effective moderately high-power handling package, and very good overall build quality typical of all the SB products with which I have worked. For more information about this and other pro sound products from SB Audience, contact Mark Thomsen. VC

This article was originally published in Voice Coil, May 2023