What Bass Management Is and How It Works

The home theater experience isn't complete without the thundering bass that shakes a room. However, after connecting the components and speakers, you can't turn everything on, raise the volume, and think you'll hear great home theater sound. It takes more than that.

The high-range and mid-range (vocals, dialogue, wind, and most musical instruments) and bass frequencies (electric and acoustic bass, explosions, and earthquakes) need to be sent to the correct speakers and is referred to as bass management.

Surround Sound and Bass

Music (especially rock, pop, and rap) may contain low-frequency information that a subwoofer can take advantage of. When movies (and some TV shows) are mixed for DVD and Blu-ray Disc, sounds are assigned to each channel.

In surround formats, the dialogue is assigned to the center channel, main effect sounds and music are assigned primarily to the left and right front channels, and additional sound effects are assigned to the surround channels.

Some surround sound formats assign sounds to height or overhead channels. They often assign extremely low frequencies to their own channel, referred to as the .1, subwoofer, or LFE channel.

Implementing Bass Management

A home theater system (usually anchored by a home theater receiver) needs to distribute sound frequencies to the correct channels and speakers to replicate a cinema-like experience. Bass management provides this tool.

You can perform bass management automatically or manually. Before starting, place the speakers in the proper locations, connect them to your home theater receiver, and then designate where the sound frequencies need to go.

Set Your Speaker Configuration

For a basic 5.1 channel configuration, connect the left/right front speakers, center speaker, and left/right surround speakers. If you have a subwoofer, connect it to the receiver's subwoofer preamp output.

After you connect the speakers with (or without) a subwoofer, go into the home theater receiver's on-screen setup menu and find the speaker setup or configuration menu. There should be an option to tell the receiver which speakers and subwoofer are connected.

Set Speaker/Subwoofer Signal Routing and Speaker Size

After confirming the speaker setup, designate how to route sound frequencies between the speakers and subwoofer.

• If you have floor-standing speakers but not a subwoofer, designate that you don't have a subwoofer. The receiver will route low frequencies to the woofers in your floor-standing speakers. Also, if prompted, set the floor-standing speakers to large.
•  If you have floor-standing speakers and a subwoofer, designate that you have a mixed (or both) speaker/subwoofer setup. The receiver will route low frequencies to the woofers in your floor-standing speakers and the subwoofer. If prompted, set the floor-standing speakers to large.
• If you have floor-standing speakers and a subwoofer, send the low frequencies to the subwoofer by designating the floor-standing speakers, if prompted, as small. Even if the floor-standing speakers can pump out bass frequencies, chances are, they can't reproduce the extremely low frequencies that a good subwoofer can.
• By moving lower frequencies to the subwoofer-only, you are extending low-frequency response further even if you have floor-standing speakers. However, since the subwoofer typically has a built-in amplifier, you are taking a load off the receiver that it can use to provide power for mid and high frequencies.
• Experiment with both floor-standing speaker options (mixed or subwoofer only) for low frequencies and hear what works best for you. You can always redo the settings.
• If you have bookshelf-type speakers for the rest of the channels combined with a subwoofer, route all low frequencies to the subwoofer only. This takes the low-frequency load off the smaller speakers since they can't reproduce lower bass frequencies. If prompted, set all the speakers to small.

Subwoofer vs. LFE

When deciding which of the above options to use, most movie soundtracks on DVD, Blu-ray Disc, and some streaming sources contain a specific LFE (Low-Frequency Effects) channel (Dolby and DTS surround formats).

The LFE channel contains specific, extremely low-frequency information that can only be passed through the receiver's subwoofer preamp output. If you tell the receiver you don't have a subwoofer, you won't have access to the specific low-frequency information encoded on that channel. However, other low-frequency information not encoded specifically to the LFE channel can be routed to other speakers.

Automated Bass Management

After designating speaker/subwoofer signal routing options, one way to finish the rest of the process is to use built-in automatic speaker setup programs that many home theater receivers provide.

Although there are variations in how each of these systems works, here is what they have in common:

• A special microphone is provided that you place at the primary listening position that also plugs into your home theater receiver.
• After you plug in the microphone, press a start button or select a start option from an on-screen menu. Sometimes the start menu comes on automatically when you plug in the microphone.
• The receiver then emits self-generated test tones from each speaker that the microphone picks up and sends back to the receiver.
• The receiver analyzes the information and determines the speaker distance, balances the output levels between the speakers, and finds the best points where the frequencies are divided between the speakers and the subwoofer.

Setting Bass Management Manually

If you are more adventurous and have the time, you can implement bass management manually. To do this, besides setting the speaker configuration, signal routing, and size, you also need to set the crossover frequency.

What Crossover Frequency Is and How to Set It

The crossover is the frequency point in bass management, where mid/high and low frequencies (stated in Hz) are divided between the speakers and subwoofer.

Frequencies above the crossover point are assigned to the speakers. Frequencies below that point are assigned to the subwoofer.

Although specific speaker frequency ranges vary between specific brands and models (thus the need to make adjustments), some general crossover settings guidelines are included.

• If you use bookshelf/satellite speakers, the crossover point between the speakers and the subwoofer usually lies between 80 Hz and 120 Hz.
• If you use floor-standing speakers, you can set the crossover point between the speakers and the subwoofer lower, such as around 60 Hz.

One way to find a good crossover point is to check the speaker and subwoofer specifications to determine what the manufacturer designates as the speakers' bottom-end response and the subwoofer's top-end response listed in Hz. You can then go into the home theater receiver's speaker settings and use those points as a guideline.

The Bottom Line

There's more to getting that knock your socks off bass experience than connecting your speakers and subwoofer, turning on your system, and raising the volume.

By purchasing the best matching speaker and subwoofer options for your needs and budget, taking extra time to position the speakers and subwoofer in the best locations, and implementing bass management, you'll discover a more satisfying home theater listening experience.

For bass management to be effective, there must be a smooth, continuous transition, both in frequency and volume output, as sounds move from the speakers to the subwoofer. If not, you'll sense an un-evenness in your listening experience—like something is missing.

Whether you use the automated or manual path to bass management is up to you. Don't get bogged down with the techie stuff to the point where you spend most of your time making adjustments rather than enjoying your favorite music and movies.

The important thing is that your home theater setup sounds good to you.