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Selecting the Best Subwoofer

You’re looking for your first subwoofer, and trying to sort through all of the details. If this is your first look at subs, it can be a daunting task. In this article, I’ll sort through the language and try to put things in terms that make sense for the first-timer, and try to answer the most commonly asked question about subwoofers.

Let’s begin by answering the question: “What is a subwoofer?”

When you purchase a speaker system, it probably has a woofer, but not a subwoofer. The integrated woofer plays some low frequencies but will not deliver the full-range, power output, and high definition bass that today's audio sources offer. Only a quality amplified subwoofer will bring these sounds to you with full impact and clarity. A well engineered powered subwoofer very precisely matches a bass speaker (subwoofer), an amplifier (power), cabinet and crossovers (frequency dividing networks) all in a single efficient package that recreates bass you not only hear, but feel. The deep bass that you feel is important because it invokes an emotional reaction to the event or show and fully involves the audience in the event.

Let me go over the specific vocabulary again just to be sure that I haven’t lost anyone. A powered subwoofer consists of a set of basic components.

  1. The Speaker – a device that converts electrical energy waves into mechanical energy waves or audible sounds. The speaker is a collection of component technologies.
     
    1. The Cone or driver – the part of the speaker that moves air
    2. The Magnet – the part of the speaker that causes the movement
    3. The Coil – the part of the speaker that takes the input from the amplifier (link) and produces an electromagnetic field, causing the cone to move back and forth to produce sound
  2. The amplifier – a device that adds power to the signal coming from the audio source. The power of an amplifier is measured in watts. The amplifier is a critical component in the subwoofer as it provides the power to move the speaker to cause significant vibration by moving large volumes of air.
  3. The crossover – a piece of electronics that allows the user to isolate a frequency range to broadcast over the speaker. Crossovers allow the user to select the low or bass frequencies they wish to play over the subwoofer. Most subwoofers are set to reproduce the frequencies below 90 (+-10) Hz.

Do I need a subwoofer?

Unquestionably, every music and home theater system needs a subwoofer. Without a quality powered subwoofer you are missing the thrill of the lowest notes and exciting sound effects that modern digital technology has brought to today's music and movies. A subwoofer is a significant and efficient upgrade to any music or system. A subwoofer is an essential component of a home theater. Low and accurate bass has become such an important part of creating the mood in modern movies that there is a designated subwoofer output on almost all modern audio and video components. In the case of the new digital home theater formats and digital television, there is a specific, discrete channel dedicated just to a subwoofer. When you set up your Dolby Digital receiver, in the small speaker mode, you can be reproducing up to six channels of bass through your subwoofer.

What should I look for in a subwoofer?

The first issues to consider are the specifics or your room and your home. If you share walls with neighbors, expect a good subwoofer to cause some excitement. The feeling that the room is shaking will be shared by your neighbors. The size of your room also impacts the best choice for you. The issue of ample output is primarily a function of matching the sub size to the room size (the rooms volume). There are two primary factors to evaluate when looking at the size of a subwoofer:

  1. The size of the speaker – 8” is on the low end and 18” on the high end for a home subwoofer.
  2. The size of the amplifier – 100 watts on the low end and 1000 watts on the high end (of course you can go even bigger). Don’t be fooled by subwoofers that advertise high wattage in ‘peak power’. A good sub will provide you with a specification for ‘continuous power’ that is significantly below its peak power specification. Just be sure you are comparing apples to apples.

Bigger rooms need bigger subwoofers to energize all that air space. Twice the room volume requires twice the energy from your subwoofer to maintain the same loudness.

In general terms, you would use an 8” with a 100 watt amplifier in small rooms (200 square feet and smaller). Step up to a 10” with a 150 watt amplifier for medium sized rooms (up to 800 square feet) or for smaller rooms if you feel the need to crank it up. From there, step up to an 12” with a 250 watt amplifier for medium to larger sized rooms (up to 1000 square feet) or if you want your whole house to shake. For Subwoofers larger than 15” and 500 watts, you should check to be sure that your home is not located on an active fault.

Selecting a larger subwoofer than the minimum recommendation of the manufacturer or adding an additional subwoofer will increase low frequency extension, dynamics, output and the fun. Putting those issues aside for now, let’s look at what makes a good subwoofer.

A good subwoofer should have high definition (low distortion) to create realism, good low frequency extension for bass you can feel, and ample output (power) to ensure plenty of dynamic impact and excitement. The most elusive subwoofer quality is high definition. Unfortunately, most subwoofers have a distortion rate of 25% to 30% which translates into a severe lack of detail and clarity. These subwoofers sound muddy, boomy and lack realism in home theater and accuracy in music systems. Choose a subwoofer low in distortion. Less than 10% is good, less than 5% is great and 1% or less is the ultimate goal. Few subwoofer manufacturers discuss distortion figures, listening to a good recording with deep bass content and you can determine what sounds best to you. A high definition subwoofer will be able to unlock the ever increasing resolution of today's entertainment. Not all subwoofers have good low frequency extension (below 40 Hz). Low priced subwoofers lead you to believe that the will perform below these frequencies, but most come up short. Some manufacturers try to pass a powered woofer off as a subwoofer. These woofers do not perform at the low frequencies of a subwoofer. With today's recordings you do not want to be without the lowest frequencies, so listen to a film with some truly deep bass and experience the difference for yourself.

One last thing to consider is the experience and reputation of the manufacturer as it relates to subwoofer design and production. How long have they been making subwoofers? What have reviewers had to say about their subwoofers. A subwoofer is a very specialized product. Its performance is highly dependent on the very precise matching of all its components. As you might imagine, manufacturers who specialize in subwoofers hold an advantage over those who produce a very wide variety of products.

Which subwoofer is right for me?

A subwoofers ability to offer good low frequency extension with ample output (power) for the room (good impact), and yet still offer very good definition (low distortion), can make or break a home theater or music system. Choosing the proper subwoofer for your individual room size is critical to creating a truly enjoyable home theater and music experience.