On paper, adding a subwoofer into your system seems to be a no brainer. A subwoofer has a dedicated amplifier and driver that is only targeted for one purpose - handle low frequencies. The problem is that most subwoofers are designed independently from the speakers and amplifiers and it is tough to get the balance just right, particularly in 2 channel music reproduction. Very often, tuning a subwoofer feels like a Goldilocks problem.. it is either too much or too little. Worse, it varies from track to track.

Using a subwoofer in a home theatre system is a fair bit simpler. This is in part because modern movie soundtracks will often have a dedicated subwoofer/low frequency channel which has been specifically mixed by the sound engineer for the movie. Most home theatre amplifiers also include a microphone - some more basic than others - that allow it to identify the capabilities of the speakers in your system and adjust the EQ and timing differences due to the room and distance from the listening position. It can also perform bass management to redirect bass information from the main speakers to the subwoofer. This helps offload the burden on the home theatre amplifier to drive the large bass drivers on a conventional speaker, and as a result, the system sounds better overall. Most home theatre amplifiers aren't designed to be as robust as a stereo speaker and their amplifier output ratings are measured in more relaxed and less demanding conditions than in a stereo amplifier. So this arrangement works out for home theatre applications.

Two channel music, on the other hand, are recorded as full range channels, without a separate low frequency track. When you use an amplifier to perform bass management, you are often required to convert analogue signals to digital first, and then apply a DSP filter to separate the bass from the mids and highs. The split digital signals are then reconverted back to analogue, and this potentially can introduce phase and timing changes, along with its own set of distortion.

One way, to get around this