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VS21 “Rum Punch” Subwoofer

May 11, 2016

VS21 Single 21″ Subwoofer

VS21 “Rum Punch” Profundo Powered Subwoofer mid-May 2016.

BASSBOSS Designer David Lee gave us a look at the technical needs and design philosophy behind the VS21 Subwoofer. We’ll be posting full specs, information and response graph shortly. Stay boomed. 🙂

“This VS21 Subwoofer box has an authoritative sound. It sounds big. If you live for bass, you’re always looking for more of something. More impact or more depth tend to be the two competing ideals. More SPL is the common big wish. What do each of these require and what do they cost?

At this point it’s fair to say that one’s preferred musical style will likely influence where one’s priorities lie. For the high-impact folks, it’s likely there will be more live music fans and fans of musical styles that make use of acoustical instruments for the low-frequency content, so bass guitars, upright bass, drum sets and other percussion instruments provide most of the low frequency content. For the deeper-is-better folks, the low-frequency content of their music tends to include more electronically generated or electronically enhanced sounds. Sometimes pipe-organs and movie special effects also fit into this preference.

These preferences aren’t mutually exclusive, but when someone is forced to choose between one or the other, they will usually express a preference for the sound that suits their tastes best. What’s the point of all this? Everyone looking for a subwoofer has to face that choice. I’d like to clarify not only what drives those initial sub design choices but also what compromises have to be made, with the limits of current technology, in order to achieve one ideal or the other, and what this new VS21 Subwoofer does to bridge the divide.

More impact is largely synonymous with more SPL. The greatest impact and the highest SPL can be achieved more easily at the expense of smooth frequency response. If one were to build a system that took advantage of multiple resonances and targeted the enclosure and driver to accentuate a narrow range of frequencies it would be possible to build a loudspeaker that would get very loud and provide massive impact in that narrow range. When one’s subs are focused on delivering a massive kick-drum hit, that hit can be very impressive. Tune the subs to the drum or the drum to the subs and the subs will hit hard when the drum hits.

VS21 'Rum Punch' Sub

The VS21 with LA88 at SXSW 2016

Higher SPL numbers are easier to achieve at higher frequencies and over narrower ranges. The typical kick-drum’s power lies in the 60Hz range. Mid 50s to mid 60s is where that kick-drum impact lives. Subwoofers that peak in that range will be perceived to “hit” hard. Unfortunately subwoofers that peak in that range rarely offer good performance an octave lower, where it takes FOUR TIMES the displacement to achieve the same SPL.

On the other side of the divide are those who want depth as the priority. As noted above, it takes four times more displacement to achieve the same SPL one octave lower. To put that in perspective, a subwoofer that is delivering 130dB at 30Hz is moving 4 times more air than a sub that is delivering 130dB at 60Hz. Same SPL, one octave lower, four times the output required! To achieve this kind of performance, some accommodations need to be made.

In practical terms, the driver in use has to be able to displace sufficient volume of air, meaning it will need to make longer excursions and probably also handle greater drive voltages. An enclosure could be made more efficient at the lower frequencies, but that does two things to the system: first, it will likely get less efficient at higher frequencies, where the “hit” lives, requiring more voltage to deliver the desired impact; second, it will have to pass more current to make the required excursions, leading to increased voice coil temperatures.

The bottom line is that a driver that’s going to be effective at producing those very low frequencies is very likely to be both more expensive and less efficient. To an extent, the enclosure design can compensate for the loss of efficiency but there is always a price to pay: in the case of subs it’s usually in the size and complexity of the enclosure. The other cost of reduced efficiency is an increased demand for power. The cost of power can be seen in the high price of good amplification but it’s also a concern in terms of how much of it you have available at the wall.

The VS21 Subwoofer uses a very expensive, very long excursion, very high power handling, very large displacement 21″ driver in order to deliver extended low frequency performance from a relatively uncomplicated and reasonably sized enclosure. The enclosure is tuned to provide excellent efficiency at very low frequencies, allowing the big 21″ cone to push the air necessary to deliver the big, low notes. In order to not compromise in the “hit” range of frequencies, the other side of the driver is loaded into a short horn that provides increased efficiency at the upper end of the subwoofer range. These increases in efficiency allow the amplifier to take greater advantage of its dynamic headroom when delivering the big hit of a kick drum, the rolling notes of a synth bass line, the attack of a plucked bass string and the tone of a floor tom.

The second but no less important advantage of these efficiencies is seen in the cost of the included amplification and in the sound level that can be achieved using them on just your average, 120 V wall outlet. The third advantage realized from the combination of the vented and horn-loaded sections working together is that they each damp the others’ resonances, making the system sound neutral and transparent, which is the ideal in terms of versatility, no matter the preferred genre or style. This new VS21 Subwoofer is extraordinarily versatile. It’s ideal for customers who play or provide sound for a wide variety of musical styles and need a subwoofer that can do it all.” – David Lee