Sound is simply vibrating air. How fast, how much, and when the air is vibrated, determines what we will ultimately hear as sound. The science of this process is called acoustics. When a speaker cone (or anything else that has the ability to vibrate in the auditory range) moves forward, the air molecules in front of the cone are compressed, causing the molecules to form an accelerating wave forward. This continues to happen until the speaker cone moves in the opposite direction, which causes a rarefaction (or thinning) of the air mass between the speaker and the listener. This is the basic concept of how sound waves are produced.
A word prefacing certain circuits in which the processing is performed by use of transistor or tube juctions, rather than passive componenets such as resistors, capacitors, and coils. Such items as crossovers and equalizers may be constructed either way. Active processing usually affords more more options, and greater precision, albeit at greater cost.
In a speaker's motor section, the space between the top plate and the pole piece. This is where the magnetic flux field is concentrated and where the voice coil interacts with it.
Electricity which flows in opposite directions, alternating at a certain rate (Hz). As supplied by power companies, AC in the United States alternates 60 times per second and is deemed as 60 Hz power. However; some countries have a 50 Hz system, and ships and aircraft may use 400 Hz.
A siren-like whining that appears as the rotational speed of an engine increases. The noise is usually the result of a voltage differential created by more than one ground path or a poor ground path to the affected equipment.
Ampere is a unit measurement of current of electrical energy equal to one coulomb of charge per second. Most DC applications refer to positive current - current which flows from a positive potential to a more negative potential, with respect to a reference point which is designated as zero or neutral potential (usually ground).
The electrons in a circuit flow in the opposite direction as the current itself. Ampere is commonly abbreviated as "amp", not to be confused with amplifiers, of course, which are also commonly abbreviated "amp". In computation, the abbreviation for amperes is commonly, "I".
All sound is a sinosoidial waveform. It has alternating peaks and valleys. The center point of each wave is the zero, or switching point that separates the positive (top) from the negative (bottom) portion of each wave. When a tube or transistor amplifier operates in Class A, the output tubes or transistors amplify the entire waveform without splitting it into positive and negative halves. In Class AB, used in the overwhelming majority of amplifier designs, the signal is split into two halves, positive and negative, and each half is sent to a tube or transistor circuit for amplification. Both sides work in tandem, and the two halves are recombined at the output section to reconstruct the whole signal. This technique increases the amount of power that can be applied, but increases distortion. Class A amps usually provide lower, often imperceptable distortion, but at the expense of reduced power output.Class D or High Current operation is essentially rapid switching, hence the term switching power amplifier. Here the output devices are rapidly switched on and off at least twice for each cycle. Theoretically, since the output devices are either completely on or completely off they do not dissipate any power. If a device is on there is a large amount of current flowing through it, but all the voltage is across the load, so the power dissipated by the device is zero; and when the device is off, the voltage is large, but the current is zero. Consequently, class D operation (often, but not necessarrily digital) is theoretically 100% efficient, but this requires zero on-impedance switches with infinitely fast switching times -- a product yet to be made; meanwhile designs do exist with efficiencies approaching 90%. This is a design that is increasimgly popular for use in bass systems, where maximum power is necessary, and slightly elevated levels of distortion are easily tolerated.
The strength or intensity of an AC signal applied by the amplifiers output to a speaker's input. Also, a measure of the relative power of any variable recurring phenomenon. Typically, measurements are made in Decibels.
The act of reducing the Amplitude or intensity of a signal. In speaker systems, high frequency drivers are commonly more efficient than low frequency drivers. This creates a need to adjust the driver levels to create a uniform overall frequency response. L-pads are commonly used for many passive systems
A species of dedicated audio nut who actually reads definitions like this.
Acronym for American Wire Gauge, a standard for measuring the diameter of wire commonly used in electrical circuits. The higher the AWG number, the smaller the thickness of the conductor. For power carrying, choose lower numbers; for signal only wires, choose a higher number.
The part of the woofers metal Basket or frame on which the Magnet structure is mounted.
A flat panel that divides the front and rear sound waves produced by a woofer. Sometimes baffle is used to mean an enclosure or the front panel on which the speaker is mounted .
An enclosure that is specifically tuned to give maximum energy to a very limited range of frequencies, usually the lowest. In this arrangement, the woofers are fully enclosed in the box with the sound pressure being vented through one or more ports.
A filter that has a finite passband, neither of the cutoff frequencies being zero or infinite. The bandpass frequencies are normally associated with frequencies that define the half power points, i.e. the -3 dB points. In multi-driver speaker systems, the Midrange driver may be fed by a bandpass filter.
The increase (or decrease) in efficiency of loudspeakers, due to the enclosure size and tuning. This is measured by the midband sensitivity of the speaker as a whole.
Abbr. BW The numerical difference between the upper and lower -3 dB points of a band of audio frequencies. Used to figure the Q, or quality factor, for a filter.
The metal frame structure of a standard dynamic loudspeaker. In larger, heavier speakers, this may be made of cast metal for extra strength and rigidity. All the other elements of the speaker are mounted on this structure.
Bass Boost/Enhancer Circuit
An active low pass amplifier section added to some receivers, equalizers, and amplifiers that allows as much as an 18 decibel boost to be applied to an audio signal in the low frequency 35 to 90 Hertz range.
Bridging an amplifier, combines the power output of two channels into one channel. Bridging allows the amplifier to drive one speaker with more power than the amp could produce for two speakers. Because of this high power output, bridging is the best way to drive a single subwoofer. If the amp is bridgeable, the owner's manual will have directions that tell you how. Usually, an amp is bridged by connecting the speaker leads to the positive (+) terminal from one channel and the negative (-) terminal from the other channel. However, be sure to consult your owner's manual before attempting to bridge your amp!
Also, keep in mind that most amplifiers need to see a 4-ohm load when bridged to mono operation. When bridging an amplifier, use one 4-ohm speaker or, if you prefer multiple woofers, connect two 8-ohm speakers in parallel. Again, consult your manual before operating your amp in bridged mode.
Bullet Horn (tweeter)
A type of tweeter in which the radiator has a large passive, bullet-shaped device above its center that extends the nominal dispersion angle of the sound, thus allowing it to cover a greater area with high frequency radiation
Buss or Bus
A signal-carrying conductor or electrical pathway designed to carry multiple signals. A mixing console auxiliary bus may carry signals derived from several channels on that console. The term is sometimes used to refer to a power distribution circuit, or "mains".
A low frequency boost normally obtained inside a vehicle interior when woofers are optimally in phase, and with the proper enclosures.
The property of an electric device that permits the storage of energy as a result of electric displacement when opposite surfaces of conductive plates are maintained at a difference of potential. In a capacitor, capacitance is the measure of the property (the amount of charge that can be stored) equal to the ratio of the charge on either surface to the potential difference between the surfaces. Capacitance is measured in Farads, and micro, or pico-farads for smaller units..
Power stabilizing capacitors store the necessary power amplifiers need to punch larger bass notes while limitingclipping. They store energy during intervals when it is not required, which is most of the time, and release it when demand exceeds what is available from the car's power system. The amount of capacitance to be used is half (.5) farad per 500 watts of available RMS power. Capacitors are not used with amplifiers that supply less than 300 watts RMS in total.
A signal that results from an amplifier that is either overloaded or underpowered relative to the signal Amplitude it being asked to generate. A clipped waveform is one in which the gently rounded peaks and valleys of the AC audio wave are instead sliced off or clipped, to yield what looks a lot like a square or alternating DC wave. When DC is applied to a speaker, the voice coil has no means of propelling itself relative to a constant magnetic field. Instead, it can only convert the incoming current to heat, and ultimately burns up. The effect of alternating DC on speakers is remarkable, irritating, painful, and short. If you are able to hear evident Distortion at high volume levels, or smell smoke, reduce the volume. It may already be too late for your speakers, but at least you may be able to save the amplifier.
1. An increase in density and pressure in a medium, such as air, caused intermittently by the passage of a sound wave. 2. The region in either air or material in which this occurs.
The cone-shaped diaphragm of a speaker. This is directly attached to the voice coil motor which actions produces the pulsation's of air that the ear detects as sound. Also useful for holding ice cream.
The effective area of the diaphragm. The higher the cone area, the more air that will be displaced.
A device or passive 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. Most speakers have crossovers that consist of passive elements such as capacitors, coils, and resistors to separate the various frequencies. In a bi-amped or multi-amped system, the crossover is an active device that feeds the various frequency bands to the inputs of the amplifiers that operate the individual drivers.
The volume or quantum of the flow of electrons through a conductor, as opposed to voltage, which is the measure of the intensity or velocity of the electrical flow.
Acronym for Deutsche Industrie Norm (Deutsches Institut fuer Normung), the German standardization body. A world reference standard for the mounting parameters of many common receivers ( Head ends) as well as other types of cables and equipment. Single DIN is the standard face size for receivers, and measures 7-3/8"wide by 2-1/4" high. DIN+1/2 measures 7-3/8"wide by 3-3/8"high. Double DIN measures 7-3/8"wide by 4-1/2" high.
The measurement of cubic volume that an item (such as a speaker or port) takes away from the internal volume of an enclosure. When designing an enclosure, this figure must be added to the enclosure volume .
An alternate term for: speaker, transducer, or radiator. Properly speaking, the term speaker should refer to an entire sound producing system with whatever combination of woofer, midrange and tweeter; in whatever enclosure type it is housed.
The ability of an audio system to convert electrical energy (watts) into mechanical energy (Decibels of acoustical energy). This ratio is usually given as the amount of energy measured in Decibels at a distance of one meter from the input of one watt of electrical energy. In most speakers, the greater the efficiency rating, the louder the unit will play in response to the same setting of the volume control, in comparison to less efficient types. The overall efficiency for most speakers systems is under 20 percent. Typical speakers can be rated at anywhere from 85 to 110 dB. Keep in mind, of course, that efficiency is only one parameter of a speaker's overall quality.
Extended Pole Piece
Extended pole pieces on the magnet assembly allow for more voice coil travel, and thus lower Frequency Response, and less chance of "bottoming out"
The basic unit of capacitance. A capacitor has a capacitance of 1F when a charge of 1 Volt across the capacitor produces a current of 1 Ampere through it. Named after Michael Faraday.
An output signal in which fundamental frequencies and harmonics are in the same proportion as those of the input signal being amplified. A flat frequency response would exhibit relatively equal response to all fixed-point frequencies within a given spectrum.
Fletcher-Munson Curves (equal-loudness contours)
Fletcher and Munson were pioneering researchers who provided the basis of High Fidelity in the '30s. They accurately measured and published a set of plots showing the human's ear's sensitivity to loudness verses frequency. They conclusively demonstrated that human hearing acuity is essentially dependent upon loudness. The curves show the ear most sensitive to sounds in the 3 kHz to 4 kHz area. This means sounds above and below 3-4 kHz must be louder in order to be heard just as loud. For this reason, the Fletcher-Munson curves are referred to as "equal loudness contours." They represent a range of sensitivity from "barely heard," (0 dB SPL) all the way to "painfully loud" (120 dB SPL), usually plotted in 10 dB increments.
The cylindrical portion of a speaker's voice coil section. A wire is wound around this cylinder to form a coil such that when current interacts with the magnetic field it produces a pumping motion that alternatively compresses and rarifies air, and creates the velocity for such air masses to reach our ears as sound.
A type of Distortion in which resonance or sympathetic ringing vibrations are added to the original sound to produce second and third harmonics of a fundamental tone in a way that was not present in the original signal. Choosing good Drivers and a well-made enclosure design is essential in overcoming this tendency in speakers.
Parts of an amplifier, typically heavy metal "fins," and a section of the frame of the speaker used to conduct and radiate heat away from the ponit of electrical consumption, or motor assembly.
High Pass Filter (HPF)
An electronic filter of a type commonly incorporated in Crossover circuits that permits the passage of high frequencies while suppressing lower ones. The place in the frequency spectrum where this occurs is called the crossover point and is different for each set of Drivers being considered. The most basic form of such filter is a non-polarized capacitor. Typical values for such a unit would be in the range of 1 to 100 microfarads
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 Soundstagebelow). 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 to have equal and unobstructed path lengths between the tweeters and the listener's ears. That's one of the reasons why matched component speakers, with their versatile tweeter placement, sound as good as they do.
The totality measured in Ohms of all electrical opposition to current flow: resistance, reactance, capacitance, as well as all mechanical factors inhibiting the completion of energy transfer in a contained system. In practical terms, this means that most Drivers are assigned a certain nominal impedance based on their DC voice coil resistance and mechanical stiffness. For car audio this is usually 4 ohms; for home stereo, 8 ohms is the standard.
An infinite baffle speaker design is defined as an enclosure that contains a greater volume of air than the Vas requirement of the driver. An infinite baffle system can easily be applied to an automobile. This is accomplished by mounting the speakers on a board and using the trunk of the vehicle as the other walls of the enclosure. It is important that the enclosure be tightly sealed such that no air moves from the front to the back of the cone. Look for speakers where the Qts is greater than .6, and a Vas figure lower than the volume available, when selecting a woofer for an infinite baffle system.
Sometimes spelled Isobaric, this is an enclosure design in which two or more Drivers are coupled together by a sealed air mass to operate as a single driver. With proper sealing and design, very impressive results can be obtained from an unusually small box. A popular version of this simply consists of two woofers placed over each other in a 'clamshell' design. The downside consists of the fact that it does require at least twice the amplifier power as would be needed for a conventional speaker, in order to be operated successfully.
1. Referring to mechanical movement, the ability of the voice coil to move in and out in the air gap without moving side-to-side. Non-linear movement can damage the voice coil.
2. Referring to woofer response, the ability to maintain power or movement without loss of drive force.
3. Referring to enclosure port operation, the relationship bewteen the amount of air moving through the port vs. the amount of air moved by the cone. Non-linear response in a port can cause audible distortion
The resistance or impedance to which energy is being supplied. In amplifiers, the speaker or speakers connected to the output of the amplifier.
Low Pass Filter (LPF)
A network of components which attenuate all frequencies above a predetermined frequency selected by the designer. Frequencies below cut-off are passed without any effect.
A combination of magnetic material and connected field concentrators that creates the magnetic field within which the voice coil interacts to produce sound. Magnetic materials have changed greatly over the years to produce much higher concentrations of magnetic fields (rated in gauss) with lighter and smaller volumes of material.
In marketing speakers, a great deal of hype is often applied to the question of magnet weight. But many of these claims should be treated with skepticism. With greater and greater concentrations of gauss fields being developed from ever lighter and smaller mass metallurgical materials, the only good measure of adequate power handling is the manufacturer's RMS Wattage rating. Hefty magnets may look impressive, but while capable,they are no longer an essential index to a speaker's power capacity.
Those frequencies roughly between 100 and 300 Hertz. (CPS)
MOSFET (Metal Oxide Semiconductor Field Effect Transistor)
A type of large output transistor used in the final stages of many power amplifiers, and commonly found in most car and home amplifiers today. These field-effect transistors are controlled by voltage rather than current, like a bipolar transistor. MOSFETs have a significantly higher switching speed than bipolar transistors. They generate almost no loss (little heat generation), which lends the power supply fast response, excellent linearity, and high efficiency.
Mosfet transistors are most often discrete devices, used with smaller driver transistors and other devices, to convert a small signal to a large one. They are highly stable and efficient, compared to the bipolar types that preceded them.
In speakers, the complete sound generator or transducer that converts incoming electrical signals to mechanical/acoustic energy or sound. In a dynamic Driver, this includes the magnet, its directive field concentrators or Pole Pieces, and the voice coil that interacts with them.
The amount of physical space required to mount a Driver without having any of its parts touch objects below. This is particularly relevant to car speakers where such mounting spaces may be sharply limited as to their ability to accommodate deep speakers with large magnets. Door panels with movable windows are a typical example of where care must be taken in selecting speakers to be mounted. (see Mounting Ring, below)
A magnet material providing 7.5 times the magnetic strength of standard magnetic materials.
The amount of airspace that is enclosed within a speaker's enclosure. This does not include the airspace taken up by bracing, vents, or the speaker itself.
A special type of cut-only equalizer used to attenuate ( no boosting ) a narrow band of frequencies. Three controls: frequency, bandwidth and depth, determine the notch. Simplified units provide only a frequency control, with bandwidth and depth fixed internally.
In audio, the interval between any two frequencies having a ratio of 2 to 1. One octave up from 100 Hz is 200 Hz, where one octave down from 100 Hz is 50 Hz. A harmonic is a doubling (2nd harmonic), tripling (3rd harmonic), quadrupling (4th Harmonic... etc) of a fundamental frequency. Musical instruments (with the exception of electronic synthesizers) do not create pure tones. The fundamental (main frequency) is combined with its harmonics at various levels to create the sonic signature, or timbre of that instrument.
The measurement of electrical resistance and system impedance. It is a measure of the degree to which electrons are limited in both velocity and quantity in passing through a circuit. In Impedance measurements, this takes into account, the mechanical resistance inherent in the motion of transducers. The standard is usually 4 ohms for car audio and 8 ohms for home and commercial audio. Some specialty woofers may be rated at 16 ohms.
Sometimes known as a "drone cone," these passive devices respond to internal pressure within the speaker and react to it to produce reinforcing emissions to extend the output of the lower frequencies below the resonance point of the active woofer. They may look like Drivers but they lack an active motor assembly.
Peak Power Handling (MAX)
Peak power handling refers to the amount of power a speaker is estimated to handle during a brief high-intensity musical burst. Since this can vary with both frequency and amplitude, it is a much less accurate way to judge speaker durability and performance than RMS (see RMS).
The ends or "Poles" of a magnet from which the magnetic lines of force, measured in Gauss, are at the greatest strength. In a typical speaker, this will be at the gap within which the voice coil is located. (see Bumped & Vented
A rating of a Driver's ability in optimum conditions to handle a specified amount of audio power (electrical current power) on a constant basis, without damage. This is generally considered to be a conservative and reliable figure to use in judging what types of amplifier power will be most successful with a particular speaker design
In sound waves, the opposite of compression. An area of decreased air pressure caused by a sound wave. In a graphical depiction of a cyclical waveform rarefaction occurs when the wave is in the bottom segment. Sound is simply the alternating compression and rarefaction of air at varying and often overlapping frequencies, within a range to which humans are sensitive.
Most all conductors of electrons exhibit a property called resistance. Resistance impedes the flow of current. It is measured in units called Ohms. With a water hose, resistance could be regarded as friction between the water and the hose. A larger hose would create less friction and have a lower resistance than a smaller hose. In electrical circuits, small round cylinders with wires on either end are called resistors. These typically reduce the flow of electrons to serve the specific requirements of the circuit elements, such as amplification or switching functions
A graduated reduction in the strength of audio output above and below certain specified frequencies. (SeeCrossover)
Sound Pressure Level (SPL)
An acoustic measurement of sound energy. 1 dB SPL is the smallest increment in sound level to which the average human is sensitive. Theoretically, 0 dB SPL is the threshold of human hearing while approximately 120 dB is the threshold of pain.
A phenomenon where a sound is reflected between two parallel surfaces, such that certain sounds are made more intense and others diminished in given parts of a listening environment. Technically they are created by room modes, which are modes of vibration of air in the room. The sound waves interfere with one another to produce a series of places where the sound pressure level (SPL) at some frequencies is high, and another series of places where they are low. The places are sometimes called peaks and nodes. A standing wave exists in a room where a frequency is such that the distance between any two surfaces is equal to one half of its wavelength. For a given distance there will be many frequencies that will generate standing waves, each a multiple of the fundamental frequency whose wavelength is related to the dimension in question. Standing waves are always detrimental to the acoustics of a room, but can be avoided by careful room design, or minimized by absorbing certain frequencies where they build up, which is usually along walls or in corners.
The surround is the flexible ring around the edge of the speaker cone. In conjunction with the inner suspension element called a Spider, it determines the overall impedance of the speaker. Pleated, treated cloth surrounds are usually stiffer and less compliant than their foam and rubber rolled edge cousins. A flexible suspension system in the speaker usually indicates greater efficiency. For some units, it is desirable to have suspensions that are pliable enough to let the woofer cone travel freely in and out. A technical specification for this characteristic in more expensive speakers, is XMS. The further the cone can travel and the more compliant it is, the stronger the bass can be in enclosures that take advantage of it. However, certain types of very good enclosures require a more limited, stiffer cone movement to develop their more controlled and High Fidelity response. Surrounds are usually made of cloth, foam or rubber. Rubber tends to last longest.
Total harmonic distortion is a measure of the how much a given audio device may distort a signal through the introduction of added harmonics or overtones. These figures are usually given as percentages. THD figures below approximately 1% are inaudible to most people. However, distortion is a cumulative phenomenon, so that if a receiver, equalizer, signal processor, crossover, and amplifier are all rated at "no greater than 1%THD", together, they could produce 5%THD, which may well be noticeable in the perceived sound.
An electrical inductive device that can be used to provide circuitry isolation, signal coupling, impedance matching, or voltage step-up
The tendency of an enclosure to produce no spring or pressure on the woofer. Unloading produces an uncontrollable over-excursion of the woofer cone (it vibrates out of control); the speaker will exhibit inadequate power handling at lower frequencies.
The voice coil is the coil of wire fixed to a cylinder at the apex of the loudspeaker cone that interacts with a magnetic field. With the help of other speaker components, the voice coil is the active transducer that converts electrical signals from the amplifier or receiver into mechanical energy, which we hear as sound. The voice coil cylinder is the part of the speaker around which the voice coil is wound. More advanced speakers offer a heat-resistant voice coil to prolong speaker life.
Voltage is an electrical charge, or potential difference, between two points, one being of higher relative voltage than the other is. A 1.5-volt 'C' battery has 1.5 volts of difference between the positive and negative terminals, for example. The unit of voltage is called the "volt," named after Allesandro Volta. Voltage can be thought of metaphorically as a pressure, such as water pressure in plumbing, that is available to initiate action or work. It, however, cannot do any work until a circuit is complete so that current (measured in amperes) can flow.
A measurement of power. In speakers, wattage is a term that indicates power-handling characteristics in dealing with electrical voltage inputs from the amplifier. RMS or continuous power handling is the only accurate basis for comparing the capabilities of Drivers. In determining the proper power input for a speaker, use this measure only. So-called Peak Power handling is often only the manufacturers best guess at the power dissipation point, beyond which the unit will fail.
The waveform of a signal is a depiction of its instantaneous voltages versus time. In audio, for example, we are always dealing with periodic waveforms that make up what we hear. These periodic waveforms can be plotted on a graph and will show up as some type of squiggly line. The graph chart rom left to right represents time and from top to bottom is the amplitude of the sound or voltage at those points in time. The familiar sine wave is an example of this.
Edited by Neo_frog, 21 November 2010 - 07:45 PM.