A subwoofer amp, or amplifier, boosts an audio signal until it is loud enough to be produced by the subwoofer. These are used with passive subwoofers, since they do not have built-in amps. By choosing the right subwoofer amp for your sound system, you can ensure that the subwoofer is able to play audio clearly and loudly without damaging either the subwoofer or amp. To select the right type, you need to match the amp's technical specifications to the subwoofer, consider its features, and select one that is appropriate for the installation location.
Two of the most important specifications to consider when selecting a subwoofer amp is the root means squared (RMS) wattage and the impedance of the subwoofer. The RMS wattage represents the amount of power, or loudness — in watts — that the subwoofer requires for operation. To get the most volume out of your subwoofer, select an amp with a matching amount of RMS wattage, or choose one that's rated within the upper third of the subwoofer's recommended RMS wattage. The impedance, which is defined in ohms, represents the amount of resistance in the system. When the impedance of the amp matches the impedance of the subwoofer, you'll be able to maximize the amount of loudness in your sound system.
While some subwoofer amps are designed specifically for subwoofers, others are designed for full speaker systems. Mono or stereo subwoofer amps can be used with up to two subwoofers, while multichannel amps with a designated subwoofer output are used with at least one subwoofer and other speaker components, such as mids and tweeters or surround sound speakers. Before selecting an amp, determine how many speakers you need to connect, so you can choose one with an appropriate number of outputs.
By selecting an amp with connectors that match those on the subwoofer, you can easily install the subwoofer and amp without having to purchase adapters or special cables. This decreases the number of components in the sound system. Some of the connectors used by subwoofers and amps include banana; tip, ring, sleeve (TRS); and speaker cables. If you can't find an amp with matching connectors, use adapters or adapter cables to connect the subwoofer to the amp.
Some subwoofer amps provide special features, such as built-in crossovers and equalization (EQ) or bass boost. A crossover splits the audio signal into separate frequency bands — such as high and low, or high, middle, and low — and allows you to send those signals to the appropriate speakers. You might want to opt for a subwoofer amp with a built-in crossover if your subwoofer or receiver doesn't contain crossovers. Sending only low frequencies to a subwoofer via a crossover ensures that it only reproduces the low frequencies it was designed to handle. If you want to condition the audio signal to make it sound better or more bass-heavy, select a subwoofer amp with onboard EQ or bass boost.
Different types of subwoofer amps exist for the home, professional, and car audio markets. Some of the major differences between these amps include size, cost, and accuracy. Amps for car audio are usually smaller than other types, since they must fit in smaller spaces, while amps for home audio and professional use are usually sized to fit in home theater stands or standard musical equipment racks, respectively. Typically, professional amps cost more than other types, since they're designed to reproduce audio with greater accuracy and minimal distortion. In general, you can use any type of subwoofer amp with a subwoofer, if its technical specifications match the subwoofer's specifications.