No home or car audio system is complete without a good subwoofer setup. Subwoofers produce a low-frequency sound that fills in for the bass notes that most normal speakers tend to leave out, resulting in a listening experience truer to the original recording. All subwoofers require an amplifier to operate, and the two must match precisely to ensure the best sound quality and to prevent blowouts. This guide will help educate consumers on the basics of subwoofers and amplifiers, proper matching, and additional considerations when searching for equipment from online retailers.
The Basics of Subwoofers, Amplifiers, and Matching
At their most basic level, subwoofers are hollow boxes that produce a low-frequency sound by moving air around with a mechanism known as a subwoofer driver. Subwoofer drivers are cones that use magnets to "press" air inside the box, resulting in the pulsating motions synonymous with most audio systems. Since subwoofers and their drivers are completely non-electric by default, they require a source of power--in the form of an amplifier--to move air and produce sound.
However, not every amplifier is capable of powering every type of subwoofer. Since subwoofers vary greatly in size and capability, each requires a specific amplifier whose power output matches the power needs of the subwoofer driver. As a result, matching subwoofers to the right amplifier can be a difficult and confusing process. Thankfully, there are a number of resources and standards in place that can make this process a breeze.
How to Match Power Ratings
Power ratings for subwoofers and amplifiers are measured in "watts root-mean-squared," usually known as watts RMS. Ideally, the watts RMS requirement of a subwoofer will match - or come close to - the watts RMS output of the amplifier. This helps ensure proper performance and power handling. While they may not always match, sticking to a range within 25 per cent below or above the subwoofer RMS rating is usually acceptable. For example, an amplifier with a 200-watt RMS output would work best with a subwoofer with a 200-watt RMS power requirement. However, it could also work with subwoofers within a range of 150 (25 per cent below) and 250 watts RMS (25 per cent above).
An easier way to match subwoofers and amplifiers is to follow standards established by the Consumer Electronics Association (CEA). These standards, CEA-2031 and CEA 2006-B, provide ratings for subwoofer power requirements and amplifier power output, respectively. This makes matching as easy as finding CEA-approved amplifiers and subwoofers and matching their watts RMS rating.
Additional Amplifier Considerations
There are several different additional considerations one should take into account when choosing an amplifier.
Choosing Between Channels
Amplifiers can have anywhere from one to multiple audio outputs known as "channels." Each channel consists of a positive and negative speaker terminal, and they can appear in the following configurations:
- Mono Amplifiers: As their name suggests, mono amplifiers only have a single channel and are specifically built for subwoofers, since most low-frequency sound comes out as a mono signal in cars and other small spaces. Most mono amplifiers are exceptionally power efficient and offer bass-boosting capabilities.
- Dual-Channel Amplifiers: With two channels, dual-channel amplifiers offer the greatest level of flexibility. Depending on individual preferences, these amplifiers are capable of powering one or two subwoofers, as well as additional audio equipment. Combining the two channels can also power a subwoofer with a higher power rating, a technique known as "bridging."
- Multi-Channel Amplifiers: Sometimes boasting up to six channels, multi-channel amplifiers make it possible to power an entire audio system with only a single amplifier. On most models, each channel has a unique power output, allowing them to power everything from small car speakers to large subwoofers.
Powering Multiple Subwoofers
When installing multiple subwoofer drivers into the same box, all of them should share a single amplifier - preferably mono or dual-channel - so that they all move at the same time. This ensures that they produce a consistent and even sound. If using a multi-channel amplifier or multiple amplifiers, separating subwoofer drivers by space dividers is usually the best way to ensure an even sound. Regardless of the setup, subwoofer systems should work within the car's electrical and power capabilities.