In a previous article we talked about Tweeters, this time let’s get into woofers.
When you’re buying a new home theater system, sound bar, or even when looking for a new car It’s very likely you have heard the words: tweeter, woofer, subwoofer, and midranges without really knowing what that means.
Every sound you hear has a given frequency, typically the human hearing range is from 20 Hz to 20,000 Hz which you may think is a very wide range, indeed it is. That’s the reason there are several types of speakers, a Woofer is designed to reproduce low-frequency sounds, typically from around 50 Hz to 1,000 Hz (50Hz to 1KHz).
How a speaker works?
Traditional speakers produce sound by using an electromagnet to move a flexible cone back and forth. They use drivers to help translate electrical signals into physical vibrations so that you can hear recorded sounds. A woofer is one of the three main speaker types.
Why woofers are important?
Woofers and subwoofers are important because the low frequencies are also the ones that help produce the full, rich, three-dimensional effect we love in movie soundtracks and in music. Without a woofer/subwoofer, you’ll be missing out on some of the explosions and gunshots for movies and videogames. Music-wise, you will partially miss some instruments like the bass, tuba, and trombone.
Wait! What is a woofer and is it different from a subwoofer?
Woofer and subwoofer both reproduce low frequencies, but the main difference lays in the frequency range they work. A woofer has frequency ranges of between 20Hz to 2KHz while a subwoofer is only capable of covering a much narrower frequency range of 20Hz to 200Hz.
In resume, a woofer is a specialized speaker; and a subwoofer is a specialized woofer that covers a more narrow frequency range. Some examples where a subwoofer is useful are reproducing specific low-frequency effects (LFE), such as earthquakes and explosions in movies, and for music, pipe organ pedal notes, acoustic double bass, and tympani.
How can I tell apart a woofer?
Pretty easy, the key is the size:
- Tweeter: The smallest of all.
- Midrange: They are….well, mid-size.
- Woofer: They are noticeable bigger.
- Subwoofer: Even bigger and likely to find multiple woofers within a large speaker enclosure.
Why woofers are bigger than tweeters?
The lower the frequency, the longer the sound wave, this means drivers need to work that much harder to produce low frequencies in volumes you can actually hear, which is why woofer drivers tend to be so much bigger than midrange or tweeters (high-frequency drivers): the bigger the driver, the easier it is to produce the long-wave frequencies.
The larger size allows the driver to move a lot of air while at the same time maintaining the required low frequency.
Which is the typicall size of a woofer?
A woofer can be as small as 4 inches in diameter or as large as 15 inches. Woofers with 6.5-inch to 8-inch diameters are common in floor-standing speakers. Woofers with diameters in the 4-inch and 5-inch range are common in bookshelf speakers.
What happens if a woofer reproduces high frequencies?
To tell the truth not much happens, most modern sound systems include filters (also called crossovers) that will block any sound that is out of the frequency range of your woofer.
Materials used in woofers
It is usually the cone material that is used in most speaker marketing material to get you to buy speakers. The three chief properties designers look for in cones are lightweight, stiffness, and lack of coloration (unwanted resonances).
Below are some of the most common materials used for woofers:
- Paper: Mistakenly believed that paper is an old fashion way to build a speaker. Sensitive to temperature and humidity.
- Doped paper: A layer of plastic or other material to protect paper from the environment. Also, makes paper cones more “stable” and rigid.
- Polypropylene: By far the most common material used in today’s speaker manufacture.
- Kevlar: It’s light and stiff, but can have coloration problems. Needs to be carefully constructed and built.
- Metals (Magnesium): Similar to kevlar, metals can produce great low-end sound but also bring coloration issues if not well-designed
Other materials could include injection-molded graphite (IMG) and glass fiber. There are hundreds of subcategories under each of these as speaker manufacturers try to differentiate their speakers and make them special from the competition.
Then, which is the best material for woofers?
¡All of them! and none at the same time. There are so many factors that contribute to a great woofer, not just the material. A well-designed paper woofer could outperform a poorly designed kevlar woofer which looks nicer and costs twice.
Some of the factors that matter for overall woofer performance are:
- The cabinet
- The crossover (filter)
- Ported or not ported (a hole in the front/back of the speaker cabinet)
- Your listening environment (room layout)
Anything else to know about woofers?
Remember that any speaker will sound completely different in your home than in the store. A good piece of advice is to listen to music you know very well to get your first impressions.