The SB Acoustics Satori TW29BN Beryllium Dome Tweeter

October 11 2017, 09:00
For this Test Bench, SB Acoustics sent its new high-end Satori line neodymium 29 mm beryllium dome tweeter, the TW29BN (see Photo 1). I reviewed the Satori ring dome version of this SB Acoustics neodymium tweeter, the Satori TW29RN in 2016, and the motor structure of the TW29BN is very similar. Features include a 29 mm wide surround beryllium diaphragm sourced from Materion, a non-reflective cast-aluminum rear cavity, a two-part aluminum faceplate with integrated mechanical decoupling, dual balanced compression chambers, a high-saturation neodymium ring type motor magnet with a T-shaped pole and dual copper cap shorting rings (Faraday shields), a shallow flow optimized magnet structure for optimum coupling to the rear chamber, a CCAW voice coil with silver lead wires, a foam mounting gasket, and gold-plated terminals.
 
Photo 1: SB Acoustics TW29BN beryllium dome tweeter.
Figure 1: SB Acoustics TW29BN impedance plot.
Figure 2: SB Acoustics TW29BN on-axis response.
Figure 3: SB Acoustics TW29BN horizontal on- and off-axis frequency response (0° = solid; 15° = dot; 30° = dash; 45° = dash/dot).
Figure 4: SB Acoustics TW29BN normalized on- and off-axis
frequency response (0° = solid; 15° = dot; 30° = dash; 45° = dash/dot).

Testing commenced using the LinearX LMS analyzer to produce the 300-point impedance sweep shown in Figure 1. The impedance resonance occurred at a moderately low 656 Hz (factory spec is 725 Hz). With a 2.94 Ω DCR, the minimum impedance for this tweeter was 3.20 Ω at 3.2 kHz.

Following the impedance testing, I recess-mounted the TW29BN in an enclosure that had a baffle area of 17” × 8” and measured the on- and off-axis frequency response with a 100-point gated sine wave sweep at 2.83 V/1 m. Figure 2 shows the on-axis response to be a flat ±1.98 dB from 1 to 36.2 kHz, with the SPL extending out to 40 kHz. Figure 3 depicts the on- and off-axis response. Figure 4 shows the off-axis curves normalized to the on-axis response. Figure 5 shows the CLIO 180° polar plot (measured in 10° increments). The two-sample SPL comparison is shown in Figure 6, indicating the two samples were closely matched, with a small 0.5 to 1 dB variation between 6.75 to 10 kHz.

For the next test protocol, I fired up the Listen SoundConnect analyzer along with the Listen SCM 0.25” microphone to measure the impulse response with the tweeter recess-mounted on the test baffle. Importing this data into the Listen SoundMap software produced the CSD waterfall plot shown in Figure 7. Figure 8 shows a Short Time Fourier Transform (STFT) displayed as a surface plot.

For the final test procedure, I set the 1 m SPL to 94 dB (2.05 V) using a noise stimulus, and measured the second and third harmonic distortion at 10 cm, depicted in Figure 9. All things taken together — and since I know that Ulrik Schmidt and Frank Nielsen, co-owners of Danesian Audio (www.danesian.dk), spend a lot of time listening to various iterations of a driver as they go through the development process — I’m guessing this is a fine sounding product. For more information, visit www.sbacoustics.com. VC
 
Figure 5: SB Acoustics TW29BN 90° horizontal plane CLIO polar plot (in 10° increments).
Figure 6: SB Acoustics TW29BN two-sample SPL comparison.
Figure 7: SB Acoustics TW29BN SoundCheck CSD waterfall plot.
Figure 8: SB Acoustics TW29BN SoundCheck STFT surface intensity plot.
Figure 9: SB Acoustics TW29BN SoundCheck distortion plots.

This article was originally published in Voice Coil, February 2017.
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