Crossover A device or circuit used in systems with separate tweeter and/or midrange drivers. It "rolls off" frequencies above and below certain points in the range, to allow the sound to be tailored for the specific driver to which it is sent.

Driver An alternate term for "speaker."

Dual-Cone Many factory installed auto speakers are of the dual cone type. Sometimes also referred to as a "full-range" speaker, it uses an inexpensive, efficient design. The small "whizzer" cone in the center of the woofer reproduces high frequencies, but not with the dispersion or intensity of a separate tweeter.

Dual Voice coils Some woofers have two voice coils. This permits both variations in the impedance characteristics and power handling, and the possibility of connecting the outputs of two channels to the same driver. This must be done very carefully, particularly with regard to the issue of polarity matching.

Efficiency or Sensitivity The efficiency or sensitivity rating indicates how effectively a speaker converts electrical power from the amplifier into sound. This is frequently related to larger magnet sizes, larger voice coil diameters, and more compliant suspensions. The higher the decibel number, the more efficient the speaker and the louder it will play with the same input power. While usually more expensive, an efficient speaker helps maximize the potential of the available power.

Enclosure, or box A cabinet in which the various drivers are housed. This arrangement is absolutely essential if you want to get any bass response from your woofer, which by itself in the open air will produce very little low frequency response. This is so because of an effect called phase cancellation. This means that the sound wave coming from the back of the speaker at low frequencies is identical in form and intensity to the one coming from the front of the cone. When they meet, as in the open air, they are exactly 180 degrees out of phase and thus cancel each other out. An enclosure either prevents this from occurring or modifies the interaction so that the backwave actually reinforces the front wave. Tweeters and midranges are less directly effected by the presence of enclosures.

Frequency Response The range of frequencies the speaker will reproduce (lowest frequency to the highest). The wider the range, the better. While the optimal normal is 20 - 20,000 Hz (Hertz), the range of human hearing for individuals is often much more restricted. A good speaker system however, will reproduce as much of this range as possible, to cover all variations.

Imaging Imaging describes the extent to which an audio system reproduces the directional cues that enable the listener to locate the instruments and vocalists as they were positioned during recording and mixing (See also soundstage below). Good imaging creates a listening experience that seems natural and lifelike. Since directional cues in sound come mainly in the higher frequencies, the key to attaining the best possible imaging is equal and unobstructed path lengths between the tweeters and the listeners ears. That's one of the reasons why matched component speakers, with their versatile tweeter placement, sound as good as they do.

Maximum RMS Power Handling Maximum RMS Power Handling or often just RMS watts, refers to the amount of power a speaker can handle on a continuous basis. This is the best, most accurate, figure to use in matching speakers and amplifiers for basic compatibility.

Midrange A driver that is usually much smaller than a woofer, but with a surface area greater than the typical tweeter. It reproduces the mid frequency range from approximately 500 to 5000 Hertz. This optimum range can vary considerably from one driver to the next, thus giving the system designer more flexibility in choosing crossover points for the other drivers.

Peak Power Handling Peak power handling refers to the amount of power a speaker can handle during a brief musical burst. Since this can vary with both frequency and amplitude, it is a much less accurate way to judge speaker durability and performance

Separates or Matched Components . A typical separates system includes a separate woofer, tweeter, and external crossover, all of which are designed to work smoothly with one another. Generally, these components are made of better materials than their two-and three-way single drivers. Separate woofers may be easier to mount in tight places because tweeter protrusion is not a factor. Separate tweeters allow positioning for optimum imaging. Given adequate power, separates can deliver excellent dynamics and detail. Separates are often a superior speaker design choice for the best possible sound.

Soundstage Individual vocal and instrumental "images" make up your stereo system's soundstage. The better the soundstage, the greater the sense of its definite width, depth and height. See also imaging above.

Surround The surround is the flexible ring around the edge of the woofer cone. A highly flexible suspension system in the woofer usually indicates greater efficiency. For most units, it is desirable to have suspensions that are pliable enough to let the woofer cone travel freely in and out (excursion). A technical specification for this characteristic in more expensive speakers, is XMS. The further the cone can travel, the more compliant it is, the stronger the bass. Surrounds are usually made of cloth, foam or rubber. Rubber provides excellant excusion and has higher longevity.

Three-way Three-way, or triaxial speakers take the separate woofer and tweeter from a two-way design and add a dedicated midrange driver for enhanced warmth and texture. The extra high-frequency energy also boosts overall sensitivity.

Tweeter Highs are reproduced by the tweeter, a small speaker mounted inside the woofer cones of multidriver 2 and 3 way car speakers and separately in other systems. Cone tweeters are efficient and the most economical. Dome tweeters, the type found in most home speakers, sound smoother and more accurate. Some domes are made of metals like neodymium or titanium, that yield extended high frequency response. Others are made of Mylar, or a fine cloth like silk for a smoother sound. Some are made from a combination of materials.

Two-way A music's high frequencies are reproduced accurately by two-way, or coaxial, designs. These speakers use a separate tweeter to deliver high frequency reproduction that surpasses that of dual-cone "extended range" models with whizzer cones. This tweeter, usually a cone or a dome, is either on a post or bridge over the woofer.

Voice coil The voice coil is the coil of wire at the apex of the loudspeaker cone that interacts with a magnetic field. With the help of other speaker components, the voice coil converts electrical signals from the amplifier or receiver into mechanical energy which we hear as sound. The voice coil former is the part of the speaker around which the voice coil is wound. More advanced speakers offer a heat-resistant (Kapton) voice coil to prolong speaker life.

Woofer The bass and lower midrange sounds are reproduced by the woofer, the speaker's big cone. To operate efficiently, a cone should be made of material that is stiff, yet lightweight. Cones made of polymers, polypropylene, or poly mixed with other materials, provide excellent sound, and stand up to the heat, cold and moisture. Paper cones treated for moisture resistance also do a good job, and are usually efficient.

See also our discussion on How Speakers Work.