Long ago, when audio systems consisted of 2 speakers, bass management was nothing a home user needed to be concerned about. The 2 speakers in the system were usually large tower or bookshelf sized speakers, and capable of producing bass frequencies on their own. With the widespread adoption of digital surround sound, combined with tiny speakers and powered subwoofers, properly configuring bass management is imperative for getting the most from your audio experience.

What is Bass Management?

Since many of today's speakers are no bigger than a coffee mug, they are often incapable of reproducing low frequency sounds. That, or there is a different speaker more suited to better produce bass effects than another.

Bass management is a process in the receiver that redirects bass frequencies from speakers that can't handle it to another speaker that can.

Audio engineers have no idea what your system consists of. Some people still use two large front channel speakers, others have two large fronts and small surrounds, and many use five small speakers and a subwoofer. Either way, an audio engineer mixes sound assuming that all speakers are capable of producing bass effects. This means that without bass management, all of your speakers would need to be large enough to produce the sound in your living room.

Most home users don't want five very large speakers in one room. Instead, many opt for smaller sized (known as satellite) speakers, with one larger box to produce bass (known as a subwoofer). It's these variations in size and capability that make bass management important.

If bass management is not properly configured, you may be relying on your tiny speakers to produce the majority of bass effects. This is like forcing a Honda Civic to pull a 2-ton trailer. The Civic may be able to budge it, but certainly not cross country. Forcing your tiny speakers to produce bass would result in sub-par bass performance (in some cases no bass at all) that could easily be corrected just by changing some settings in the receiver. If you don't feel the T-Rex's footsteps in Jurassic Park, you definitely need to read on.

[[ad]]

Look to the Receiver For Guidance

If you think the world of audio hasn't changed much in the last 20 years, think again. The heart of the audio system is the receiver, which not long ago consisted of a pre-amplifier, two power amplifiers, and volume control. Today, a receiver adds video switching, 5 or more amplifiers, and 1000 times more processing power than the first space shuttle.

Bass management happens in the receiver. Audio signals are processed in a digital domain, where the receiver can determine, in real-time, what audio frequencies make up the input signal, and what speaker they should be sent to. Those in the know would ask how signals can be processed in the digital domain when they are input via an analog connection. Simple. The receiver uses an analog to digital converter to convert the incoming analog signal into a digital one. This means that bass management can be applied to every audio source you own, including an 8-track player if you have one.

As brilliant as receivers are these days, they still have no idea what your speaker configuration looks like. So until they are given cameras as eyes, plus adaptive intelligence to automatically figure it out for you, they still rely on you, the mighty home user, to tell the receiver what your speaker configuration is like.

Small or Large? Simple, Right?

If you decided to step into your home theater receiver's menu when you first set it up, you probably found a section that gave you a choice to set your speakers as small or large. Perhaps you were confused why size matters to the receiver, but no matter. Soon you'll know what it's all about.

The size question your receiver poses instructs it on what to do with bass frequencies. Unfortunately, the simplistic design of this interface has some pitfalls that cause many users to set it improperly, and hinder their ability to get the best performance from the system.

First off, the receiver really doesn't care what the physical size of the speaker is. It only cares whether or not it is capable of producing bass. Thus, it makes an assumption; small sized speakers are not capable (or less capable) of producing bass, so I should route bass to somewhere else. It seems logical enough, but it's limiting in some cases. When set to small, the receiver cuts all of the bass frequencies from that speaker and sends it to another.

After all of the size questions, another question is asked. Do you have a subwoofer? In most cases, subwoofers are the most capable bass speaker in your setup, so you normally want all bass to wind up there. However, there are some cases when this is not true (see example system #2). Continued on page 2 >>

[[page]]

The Logic Behind Bass Management

Any speaker set to "large" is capable of producing all bass, therefore no bass is redirected.

With the subwoofer set to "yes", bass will be directed from any speaker set to "small" to the sub-out jack on the back of the receiver.

With the subwoofer set to no, bass will be directed from any speaker set to "small" to the front channel speakers.

Set It Once, Set It Right

Set aside the assumptions based on size, and view this as a question of efficiency and capability. Here's the types of speakers you'll be dealing with.

Satellite Speakers - Very small size. Incapable of producing bass.
Bookshelf Speakers - Medium size. Capable of producing some bass.
Tower Speakers - Large size. Usually capable of producing most or all bass.
Subwoofer - Size varies. Designed only to produce bass.

Example System #1

Speakers in system: 5 small satellite/bookshelf speakers, 1 powered subwoofer.

This is a very common home theater setup these days. Since small satellite speakers are usually incapable of producing low frequencies, you want to set all speakers to "small", and subwoofer to "yes".

While bookshelf speakers are usually capable of outputting some bass, the subwoofer is still much more capable than the speakers (therefore the most efficient), so you will want to follow the same logic as you would for satellites.

[[ad]]

Example System #2

Speakers in system: 2 tower sized speakers, 1 bookshelf sized center channel, 2 satellite surrounds, 1 powered subwoofer.

This is a great example where routing by examining the speakers size can hurt performance. How great is a tower speaker at reproducing bass? There are many floor-standing tower speakers that don't do a good job with bass, but most would consider the size to be large. What happens is that all the bass for those speakers (heavily dominant in both music and movies) will not be routed to the subwoofer, and performance will suffer. In this case, all should be set to "small", with the subwoofer set to "yes".

However, the reverse does not hold true. Say your front tower speakers are big and burly, but your subwoofer is a bargain bin cheap-o model. This would mean that your fronts should handle their own bass, while the sub takes care of the bass for the center and surround speakers. You can do this by setting the fronts to "large", the center and surrounds to "small", and the subwoofer to "yes". If your sub is truly awful, using it at all may still hurt your system's performance, so disconnect it and set the sub to "no". The bass for the center and surrounds will be routed to the more capable front channel speakers. Continued on page 3>>

[[page]]

Trouble systems

While the size approach works well in most situations, there are some problematic setups that make it difficult to set up bass management properly.

Trouble system #1

Speakers in system: 2 satellite front speakers, 1 satellite center channel speaker, 2 large tower surround speakers, no subwoofer.

The trouble here is that when the subwoofer is set to "no", the receiver assumes that your front left and right speakers are the largest speakers in the system. Therefore, it locks the front speakers to the "large" setting. Following basic logic for bass management, it would be ideal to set the surrounds as "large" and redirect all bass to the surround speakers. Unfortunately, this is not possible. The only way to overcome this limitation is to use your largest speakers in front, or purchase a small subwoofer.

Trouble system #2

Speakers in system: 5 small satellite speakers, 1 passive subwoofer.

Any subwoofer connected with speaker wire in-line with your other speakers (and not driven by an external amplifier) should be treated as a passive subwoofer. Passive Subwoofers make configuring bass management tricky, since size logic isn't applicable in this kind of system. For more on this kind of system read Configuring Your Receiver for a Passive Subwoofer.

[[ad]]

Crossover Settings

If you just stop at getting the basic management stuff correct, you'll enjoy a rewarding audio experience. Depending on the receiver you use, there can be many other controls available to fine-tune the sound to your speakers. One of the more common advanced controls deals with the low-pass (or crossover) point for bass management.

With the shrinking size of speakers in recent years, satellite speakers are having a harder time producing low frequencies. While most small speakers will be able to produce sound frequencies down to 80hz, many of the really tiny ones can barely hit 160hz with success. The crossover setting in the bass management section of your receiver tells the receiver what frequency and lower should go to the sub.

80hz is the typical, ideal setting if your speakers can do it, which is where bass is omni-directional in nature. This means that you should not be able to pinpoint the sub's location in the room based on sound alone. If your sub is incapable of producing effects that low, increase the point in which bass is removed. If you have large tower speakers, you can lower the crossover point to allow your big speakers to handle some of the bass on their own.

There is no rule of thumb for this setting. Experiment and see what sounds best to you.

Summary

The logic behind bass management is befuddling to many, but now you should have a clear understanding of how bass management works, and how to set it for your system. Examine each speaker in the system to determine how bass should be handled, as well as how each speaker is connected to the receiver to make sure it gets there.

In audio, there are many tweaky things you can do to squeeze a little better sound out of the gear you own. However, proper bass management must be properly set to realize even half the performance of your gear. It's that important.