Systems List › DIY › B&C 21SW152-4 Sealed
This system exhibits the typical response shape of a very powerfully, motored driver with excellent inductance management in a small sealed box with a very high 70Hz F3 related to the rising sensitivity and a nice top end extension out past 200Hz. The anomaly at 200Hz is likely related to the baffle width of the enclosure used. The sensitivity is excellent for a sealed system of this size. The response is very well damped and shows no issues with ringing or energy storage.
The long term output compression testing shows this system to exhibit excellent behavior with negligible compression up through the 110dB nominal sweep. Compression remains below 1.5dB during the 115dB sweep and stays below 3dB even during the 118dB nominal sweep level. At this point the driver was clearly past its clean excursion level and was making a lot of excursion related distortion on top of the compression occurring so further testing was halted.
As seen in other tests using the 21SW152-4 B&C drivers distortion is exceptionally low even at very high power levels up until the point that the driver excursion is no longer linear at which point it jumps dramatically. Even during the 115dB sweep level the THD never breaks 13% THD even below 20Hz.
Above 20Hz it remains below 10% and above 40Hz is vanishingly low even during the 118dB nominal sweep staying well below 5%. During the 118dB sweep the low bass distortion rises dramatically which indicates that the driver is clearly being driven outside of its linear excursion range. The component make up of the distortion is 3rd harmonic dominated which is not unusual for large bass drivers.
CEA-2010 maximum distortion limited burst output testing shows this system to have prodigious output above 40Hz even breaking 130dB at 2 meters ground plane. Low bass output below 25Hz is still commendable thanks to the low distortion huge 21” cone and healthy excursion. If distortion is ignored completely the driver can produce another 3 to 3.5dB of output in the deep bass frequencies before mechanical limits of the driver start to become a concern. Clearly this is outside of the driver’s linear range of operation as distortion goes up dramatically.