It drives me crazy when I read articles that use technical terms as though the whole world knows what they mean. Just what does a car do when it understeers? Beats the heck out of me, but you won’t find a road test that doesn’t mention it. And as it turns out, we’re hardly blameless in this regard.
In hindsight it should have been obvious that GoodSound! attracts both budget-minded audiophiles and people who are new to the hobby or who just want to assemble a decent audio system. And it’s the latter group we’ve been letting down.
As educators, we have a responsibility to make sure our readers understand what we’re talking about. So starting now and over the coming months, this column will be dedicated to explaining commonly used audio terms that appear in our reviews. We’ll also go into the weeds and talk about what we think are important considerations in assembling an audio system. While not meant to be exhaustive, this series of columns will arm you with enough information to see through salesperson bafflegab and make informed buying decisions.
Loudspeakers
The single most important parts of any audio system are its speakers. Choosing the right speaker can ratchet up the enjoyment factor, while a poor choice can ruin a system’s sound. The good news is that if you stick with speaker makers that are both engineering- and listening-driven, you’ll be hard pressed to find a real dud. But before we discuss how to match speakers to electronics and your room, let’s get some basic terminology on the books.
The drivers
The number of ways (two-way, three-way, 3.5-way, etc.) refers to the number of frequency segments -- divided by crossover points -- found in a given speaker. A two-way will feature a woofer(s) and a tweeter, and a three-way will add a midrange. A 3.5-way will probably have a tweeter, a midrange, and two woofers, one to handle the full bass spectrum and the other for the very lowest frequencies.
Driver (aka transducer): the dynamic component of a loudspeaker that vibrates in sympathy to an incoming electrical signal. There are three main types of driver: woofer, midrange, and tweeter. These are usually in the form of a cone (woofer, midrange) or a dome (tweeter).
Woofer: the largest single driver found in any speaker. A woofer is designed to produce bass frequencies, and its diameter is usually indicative of the bass energy and depth of frequency it can reproduce. This means that the bigger the woofer, the lower and louder the bass, all other things being equal. A subwoofer reproduces frequencies at the bottom of the bass range, usually down to the 20Hz level, where bass is felt rather than heard.
Midrange: the middle-sized speaker that’s most often associated with reproducing tones in the midband frequencies, such as those making up the human voice. A typical midrange might be 2" to 6.5" in diameter and cover from 300Hz to 3000Hz.
Woofer and midrange drivers can be made from a variety of materials that must be both light and stiff. Light materials are easier to start and stop, and stiffness is necessary to reproduce frequencies with low distortion. Common woofer and midrange cone materials are polypropylene, treated paper, and even carbon fiber. Many speaker makers use a polypropylene composite cone with other materials, such as ceramics or glass fiber, added to improve performance.
Tweeter: the smallest driver, designed to reproduce the highest frequencies, from perhaps 2000Hz to 40,000Hz, beyond the limit of human hearing. Tweeters may be hard domed (made of metal), soft domed (made of fabric), or ribbons (a folded metal ribbon).
Tweeters may be made of materials like aluminum, titanium, silk, beryllium, or diamond. The latter two are generally considered to be the best materials for tweeters, but they are expensive and hard to work with. Many speaker makers coat metal-dome tweeters with another metal, such as gold over aluminum, in order to tweak performance.
The cabinet
Acoustic suspension (aka sealed box): an air-tight speaker enclosure. Generally, proponents of a sealed-box design tout the speaker’s ability to respond quickly to inputs, resulting in what might be described as a "fast" speaker or one that "transitions" between frequencies or energy levels quickly. On average, an acoustic-suspension speaker will achieve its speed at the expense of low-bass reproduction.
Bass reflex (aka ported enclosure): a box that, through an open port, allows the driver’s back wave to reinforce bass response. Ports may be mounted on the front, back, or bottom of an enclosure. Where there are two or more ports there’s usually more than one woofer in use, and each woofer may be housed in its own sub-enclosure inside the speaker.
As with woofers, size matters when it comes to speaker cabinets. Generally speaking, the larger the cabinet, the deeper the bass the speaker can reproduce. Floorstanding speakers therefore tend to be better with bass than stand-mounted speakers.
Another term often seen in speaker reviews is baffle. The baffle is the front face of the speaker cabinet, on (or through) which the drivers are mounted. A baffle should be stiff and sturdy, as its goal is to allow the drivers to vibrate without losing their energy to the cabinet.
The crossover
Think of a speaker’s crossover as the acoustic equivalent of a railroad junction. As its name implies, a crossover is designed to shunt certain frequencies to the type of driver designed to reproduce them. Crossovers are necessary in multi-driver speakers because sending the wrong frequencies to a certain driver type, such as heavy bass to a tweeter, will tend to damage that driver. Crossovers use three primary components: resistors, capacitors, and inductors. Through various electrical principles, these components filter out certain frequencies and allow others to pass through.
Binding posts
Many people have asked me what "five-way binding posts" are. Well, they are the terminals that speaker cable is attached to at the back of a speaker. Binding posts have a central stem, and over that stem is a nut that can be tightened to hold cable in place. As for the "five ways," the cable can be attached as bare wire through a hole in the post, accessible from the top (first way) or bottom (second way). A spade connector can also be used between the nut and the stem from the top (third way) or bottom (fourth way). Finally, a banana connector can be inserted into a hole in the nut (fifth way). Posts are usually made of gold-plated brass, which is used for its good electrical connectivity and its strength. Some manufacturers use pure copper, but it’s softer than brass and can break under strain. The same goes for silver.
Next month I’ll talk about shopping for speakers and matching speakers to components.
. . . Colin Smith
colins@soundstagenetwork.com