Subwoofer speakers are very misunderstood aspect of live sound systems. Some of that misunderstanding comes from the use of subwoofers for consumer stereo gear, and gets carried onto the musician side. Most all of us have seen “subwoofers” for personal computers, 5.1 home theater systems, and many other home uses. But in reality they are miniature cruel jokes being foisted on an unsuspecting public consumer.

Subwoofer speakers are very misunderstood aspect of live sound systems. Some of that misunderstanding comes from the use of subwoofers for consumer stereo gear, and gets carried onto the musician side. Most all of us have seen “subwoofers” for personal computers, 5.1 home theater systems, and many other home uses. But in reality they are miniature cruel jokes being foisted on an unsuspecting public consumer.

True sub-woofer speakers are cabinets optimized to reproduce frequencies from 20Hz up to about 120Hz by using proper acoustic methods. The wavelengths of these frequencies are 10 feet and much larger, which means only large speakers do a decent job of creating these sound waves. In fact, small rooms like most households have can not really couple these large sound waves from subwoofers very well. But in bars, nightclubs, music halls, and outdoor festivals; sub-woofers work very nicely and can really add a seismic dimension to your show.

 

 

Entry-Level Subwoofers

When looking for subwoofers for your sound-system, it is implied that you have sound sources in the 20Hz to 120Hz range to reinforce. If you are not miking up the Bass Guitar Amp or Kick Drum, then you are throwing away money on the image of large speakers and not getting any of the benefit. So at least make sure you are miking subwoofer frequency sources or using direct-injection (DI) boxes for the bass rig.

When looking at subwoofer cabinets, note the types available. You have choices like single-15” woofer cabinets in ported or direct radiating cabinets, dual-15” direct radiating cabinets, old fashioned scoops and earthquake folded horns, single-18” direct radiating cabinets, and my favorites the dual-18” direct radiating cabinets and single-21” cabinets. My advice to entry level subwoofer buyers will not sit kindly with the manufacturers, but ignore all the smaller cabinet choices and just limit the candidates to dual-15” and larger subwoofers. I say this because those smaller boxes are not efficient enough to reproduce the modern low frequencies like the 41Hz low E-string on a bass guitar. These lower frequencies need “air”, both inside the speaker cabinet and outside on the front of stage area. Also, the larger cabinets will provide sensitivities in the region of 99dB SPL at 1-watt, 1-meter rating that will not waste the precious amplifier power that you paid dearly to drive the subwoofers.

To sum up entry level subwoofers, it is all in the frequency range of the cabinets, and the dB-SPL efficiency in that frequency range. Read the subwoofer cabinet rating real closely and look at the frequency response plots with equal scrutiny. Many frequency response ratings will imply -10dB corners if not labeled, and not the desired -3dB frequency corner points that are usable for comparison. Even many good dual-18” subwoofers will struggle to reproduce below 55Hz frequencies if they do not have enough air inside the cabinet. While the goal of the 41Hz low E-string on the bass guitar is desired, you may have to settle for good 50Hz to 55Hz subwoofers in the interim. Of course if your band’s bass player plays a 5-string bass; that low B-string has a 31Hz fundamental frequency that should be enjoyed with good subwoofers.

In the next installment, we will get down to the numbers game.

Originally posted 2009-02-01 23:09:50.