ARTICLE: WHAT MAKES UP A SUBWOOFER

23 November 2021

SUBWOOFER FUNDAMENTALS

The first thing to understand is the basic concept of a subwoofer system. What it is trying to do, and how does it work? Obviously, the fundamental idea is to reproduce low frequencies. In most cases, this is roughly the bottom two octaves, from 20Hz to 80Hz. However, here lies the first major issue we need to take onboard: having a special box that generates low frequencies doesn't guarantee good bass in the listening room — in fact, far from it!

The room's own acoustic properties are of paramount importance. If you put the world's best subwoofer in an acoustically poor room, you'll get very poor bass performance! I have frequently come across monitoring systems where the owner has added a subwoofer in the hope of curing a weak or lumpy bass response, only to discover the situation either doesn't improve or actually gets worse!

If the room has nasty standing-wave problems — and almost all home studios do — it's vital that these acoustical problems are sorted out first, before you spend money or time on a subwoofer.

Bass trapping to control and reduce room standing-waves is a subject that we've covered many times, and is also a popular topic for ongoing discussion and guidance on the Studio Design & Acoustics forum on the SOS web site. You can often improve a room's acoustics dramatically for minimal cost with some basic DIY. And with a treated room you may well find that your existing speakers actually deliver much more and better bass than you thought!

Another useful benefit of a subwoofer is the additional power handling accorded to the system as a whole. The acoustic energy in music is highest at low frequencies and tails off with increasing frequency. So employing a dedicated box to handle much of the power-hungry bass takes that burden from the satellites, with useful benefits in overall power handling and clarity.

 

 

  

 

BASS MANAGEMENT

Bass management is the process of removing the bass element of the signal fed to each satellite speaker, and routing it instead to one or more subwoofers. In essence this is no different to a normal crossover — it's just that the bass driver happens to be housed in a separate enclosure, and there needs to be some sort of mixing facility included to combine the low-frequency contributions from at least two channels.

In the case of a simple 2.1 stereo system, this bass management or crossover filtering is usually built into the subwoofer, and may be active or passive (most systems are active these days). There are various approaches to wiring, but most route line-level signals from the controller or preamp to the subwoofer first, which filters the signals and outputs them for the satellites. Some systems work the other way around, connecting the signal to the satellite first, and then down to the subwoofer. Systems intended for domestic use often work with speaker-level signals.

 

     

 

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