Woofers, mid-range speakers, and tweeters are all types of loudspeakers. Most often, all three types of speakers are mounted in a single enclosure, but you can also find each in discrete enclosures. Let’s take a closer look at how they work.
Loudspeakers are a type of electrical transducer that converts an electrical audio signal into sound. The most widely used type of speaker today—the dynamic loudspeaker—was first built in the 1920’s. It uses a magnetic field to move a flexible diaphragm back and forth very quickly to produce sound waves that carry those sweet tunes right to our ears. That diaphragm is usually fabric, plastic, or paper, and is most often conical in shape, though some speaker makers use different designs.
We categorize speakers by the range of sound they put out, as measured in Hz. Some speakers are considered full-range, since they attempt to put out all the frequencies they are sent. The trouble with that is that the size of these full range speakers typically limit how good they sound. Small full range speakers just can’t get enough of that bass, and larger ones tend to not do well with the higher frequencies.
Other speakers are more specialized to different ranges. Woofers handle the lower range, mid-range speakers handle the middle range, and tweeters handle the highest range. Put these discrete speakers together, and you get a much fuller, more accurate sound reproduction than you get with a single full-range speaker.
Woofers
Woofers are made to handle the lower range of frequencies (sound waves) for a speaker system, and there are a few different types, depending on your needs. Although they are all built very similarly, there are some distinct differences between each type:
Standard Woofer: A standard woofer produces frequencies from 20 Hz up to 2,000 Hz (2 kilohertz, or 2 kHz). The woofer is often characterized by its bassy sound which comes from the lower frequency sine wave. You’ll typically see standard woofers as part of higher-end speakers that contain either a woofer and tweeter (a setup known as a 2-way speaker) or a woofer, tweeter, and mid-range speaker (a setup known as a 3-way speaker). Subwoofer: Subwoofers are only capable of producing tones lower than 200 Hz in consumer systems. They are made up of one or more woofers, often mounted inside a wooden enclosure. Although the human ear is only able to pick up a frequency as low as 12 Hz, subwoofers working at lower frequencies can only be felt, if not heard. Subwoofers are the most common add-on to a consumer speaker setup. They are typically placed in their own, isolated enclosure and provide the low-level thump that you just can’t get with standard woofers. Midwoofer: Midwoofers land right in the middle of the ‘woofer’ range, coming in from 200 Hz -5 kHz. Having such a wide range of frequencies, this speaker will produce the best quality sound from 500 Hz-2kHz and start to deteriorate at either end of the spectrum. Rotary Woofer: A rotary woofer is a woofer-style loudspeaker that uses a coil’s motion to change the pitch of a set of fan blades, instead of using the cone shape. Since the pitch of the blades is changed by the audio amplifier, the power required is much less than that of a conventional subwoofer. They are also far superior at creating sounds well below 20 Hz, below the normal level of human hearing, able to produce frequencies down to 0 Hz by compressing the air in a sealed room.
In most consumer speaker setups, you’re likely to find a standard woofer as part of your main speakers and possibly an additional, but separate, subwoofer.
Mid-Range Speakers
Mid-range speakers are targeted to handle the ‘middle’ range of the spectrum, coming in between 500 Hz-4 kHz. This is probably the most important range of frequencies due to most audible sounds, such as musical instruments and the human voice, being produced here.
Since the human ear is most sensitive to the mid-range frequency, the driver can remain at a lower power, while still providing good sound in terms of quality and volume. Because mid range speakers are unable to produce the extreme low or high spectrum, they often sound dull, or flat, and need the support of a woofer or tweeter to get the full level of sound.
You’ll find mid-range speakers used as part of a speaker that also includes a woofer and tweeter, and they’re also used in the center speakers often used with surround sound systems.
Tweeters
On the high end of the sound spectrum, we have tweeters, which get their name from the high tweet of birds. Tweeters typically cover the range of 2 kHz-20kHz, though some specialty tweeters can go as high as 100 kHz.
Traditionally, tweeters were designed pretty much the same way as other speakers—just smaller. The trouble is that sound at that frequency is pretty directional, meaning that the highs in your music sound best when the tweeters are pointed right at you. Modern tweeters are starting to adapt a dome version that uses a soft dome diaphragm made from polyester film, silk, or polyester fabric that has been impregnated with a polymer resin. Dome tweeters are capable of a wider area of sound distribution.
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