Your Guide to Audio Speakers
Parts and Specs
Shopping for audio speakers is an important step in the development of an awesome home theater setup. Depending on your preferences for, you may end up purchasing horned speakers, indoor/outdoor, or satellite speakers. There are several other choices as well, and the type you buy has a lot to do with what you will be using the speakers for, such as using sturdy indoor/outdoor speakers for connections to weak audio sources like a standard personal computer.
Whatever you use your audio speakers for, however, the way that all speakers are put together is much the same, and has a lot to do with the parts used to construct them. So what exactly are those parts, and how do they work? We are so glad you asked...
How They Work
The first component of a speaker that you should be aware of, and perhaps you have already heard of it before, is the tweeter. This is a dome-shaped driver which reproduces high frequencies like cymbals and soprano vocals. The very best tweeters are light and rigid, but they can be made from a whole variety of different substances. This includes construction materials like paper, plastic, beryllium, even diamond.
Next, we have the woofer, as well as the midrange drivers, easily identified on most speakers as the circles found on the face of the speaker. The woofer, the tweeter, and the midrange driver are all drivers, and every single driver on a speaker's face moves in and out as signals from a receiver tell them to, so that air pressure is changes and sound is created. Woofers, specifically, handle the lower frequencies, like drums, and midrange drivers handle most human vocals (but probably not Barry White). If you purchased a more expensive high-end speaker, chances are that the cones in the middle of your speaker's driver circles are constructed from metal.
So what tells the drivers which signal is what? That would be the crossover, a circuit that sorts all incoming audio signals for the speaker. Obviously, the designer of the crossover has a lot of control over what frequencies end up at which driver, so this is part of why sound may vary from speaker to speaker with the same sound source.
The voice coil, situated behind the cone, is a system of electromagnets that accepts power provided by the amp, then converts it to magnetic fields that move the drivers. Magnets, how do they work? Just kidding, there is simply no time to cover that right now. And the voice coil is placed in the basket, a round piece of metal which also holds the driver. If someone offers you the choice take die-cast metal over pressed metal.
Now that we have a better idea of what is inside a typical speaker, including the general components of the tweeter, woofer, midrange driver, crossover, voice coil, and basket; let's take a look at general specifications for a standard speaker, and translate just what those specs are telling you as a consumer.
What Specs on the Box Promise
The next time you are shopping for audio speakers, take a look at the box or the tag that lists that unit's sound specs. This is information that will probably tell you four important things about how those speakers will sound: sensitivity, impedance, frequency-response tolerance, and sub-bass response.
First of all, we have sensitivity, which is a measurement of loudness. Now we're talking, that's what we're here for, right? LOUDNESS! Any speaker system that pumps out more than 90 decibels is good for this category, because if you go much louder than that, you risk permanent hearing loss or degradation. But if a speaker only pumps out less than 80 or even 85 decibels at its maximum volume, well, that is simply not too hot. But at least you won't upset the neighbors.
Impedance measures the power demands that your speakers will place on the amplifier, and most home speakers have a nominal impedance rating of 8 ohms. Be careful, because speakers with lower impedance ratings, such as 4 ohms may cause problems with 8-ohm receivers by asking them to deliver more current than they are capable of producing. This can also result in greater distortion of sound, which may be what some listeners are trying to achieve, but this is hazardous and should be avoided in most scenarios.
The frequency-response tolerance the fidelity of the sound, or how accurately a speaker reproduces the desired frequency or musical tone. This is measured in Hertz, and the range of human hearing is about 20Hz, which are very low bass tones, up to 20kHz (20,000Hz), a treble sound. But just being able to reproduce that spectrum does not guarantee that a speaker has great frequency-response tolerance. Instead, this is judged on whether a speaker is capable of reproducing all audio frequencies at the same volume at which they were recorded. Within 1 decibel is excellent, and anything outside of 4 decibel range is less than stellar.
Finally, we have the sub-bass response, which measures the lowest possible bass a speaker can provide. Remember, you can only hear down to 20Hz, so any speaker capable of getting there is awesome. 42Hz is the bottom note of a bass guitar, so if the speaker cannot hit that frequency, it is understood to have a lousy sub-bass response.
Ready To Build Your Own Speakers
Or At Least Buy Them With More Confidence
So that is all it takes to have a cursory understanding of exactly what certain audio specifications mean, as well as the components that are used to build pretty much any standard audio unit. And while this information may not have you constructing your own speakers at home anytime soon (or fitting components into a gourd), it may help you to refrain from assuming that there are magic elves inside your home theater system, tirelessly working to make sure you have sound for your James Bond movie marathon or Phish jam session.