Subwoofer Guide: Exploring Different Types of Active Subwoofers

Is your audio system lacking oomph or pizzazz? Are you trying to add extra bass to your full-range speakers with EQ, but not achieving acceptable results? Are you in awe of large-scale club systems and festival shows? If you are looking to increase the low-end of any PA or sound system, read on!
A subwoofer is a loudspeaker designed to reproduce low-pitched audio frequencies known as bass and sub-bass. These frequencies are often much lower than those that can be (optimally) generated by a woofer in a full-range speaker. Even full-range speakers that generate frequencies from 45 Hz to 20 kHz can benefit from a dedicated sub cabinet. By adding a matched subwoofer with a properly calibrated crossover to your system, your full-range speaker will run more efficiently and without additional intermodulation distortion and resonance. In fact, you may find that your full-range speaker can output more SPL before distorting, making the high-mids and highs clearer and more precise, while the low-mids and lows have a tighter bass response.

Deciding on whether you need a subwoofer or what type of subwoofer will inevitably come down to its intended purpose—how low does it need to play and how loud does it need to be at a given distance? Much of this is dependent on the source material. In general, you wouldn’t need as much low end for a rock show as you would for an EDM event. Even jazz and classical are highly dynamic and will often require a wide frequency response, but with a balanced / flat frequency response.
Be aware, there are significant tradeoffs to size, output, and extension. If you are looking for extreme output with low-frequency extension, you won’t find it in a compact box. If you need something compact, then be prepared to settle for less output and/or less bass response. Also, take into consideration the type of drivers used (12, 18, 21") and their power requirements and, remember, you can always scale up for additional output. Meaning if you add more subwoofers, you will increase the overall output and, in some cases, extend the lower-frequency response.
By doubling the power (or boxes), you will achieve an additional 3 dB of output.