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Glossary: Speakers

Hi-Fi Audio Glossary: Loudspeakers

Over recent years, our online guides have created an extensive encyclopedia of audio terminology. We decided to bring these disparate dictionaries of audio terms together for the first time. This exhaustive guide is the result.

While the days of trying to baffle people with terms only the cognoscenti know are (hopefully) behind us – many readers might recall the patronizing salesman in the ‘Grammo-phone’ sketch from Not The Nine O’clock News in the early 1980s – this is still a terminology-led industry, and knowing the terms is a good idea if we are to be able to recognize how components might conceivably be different, and why.

While it’s important not to get too hung up on the terminology – we are in an industry where observed performance should always remain more important than specifications – knowing the difference between a ported loudspeaker and a sealed-box loudspeaker is important and knowing that a sealed-box loudspeaker and an infinite baffle design are basically one and the same is important, too.

 

LOUDSPEAKER TERMS

The world of high-performance loudspeakers has cultivated a language all its own to describe not only the various configurations and types of speaker and drive units, but also their performance characteristics.

 

Active

Loudspeaker systems that contain or partner dedicated electronics – power amplification plus electronic crossovers and equalizers, some of which can be entirely in the digital domain.

Bandwidth

The range of frequencies with defined upper and lower limits over which a system operates.

Bass

Lower part of the audible frequency range. Can be subdivided into deep bass (below 40Hz), midbass (40Hz–100Hz), and upper bass (100Hz–250Hz).

Baffle

The front face of a loudspeaker. Its role is to hold the loudspeaker drivers securely, while preventing the sound emanating from the front of the loudspeaker interacting with any emanating from the rear.

Bracing

The inside of a loudspeaker cabinet can flex and resonate, adding its own colorations. Judicious and careful use of cabinet bracing can help stiffen the cabinet and reduce unwanted distortions.

Brilliance

Alternative terminology for the highest audible frequencies from 6kHz–12kHz.

Co-Axial

Literally ‘symmetrical about a common core’, as in shielded aerial cable or loudspeaker drive units (such as those made by KEF or Tannoy).

Coloration

A general term used to describe the audible effects of a whole range of different distortions in different hi-fi components, but especially record decks and loudspeakers.

Crossover

More precisely described as a dividing network, the electrical circuitry inside a loudspeaker, which apportions the drive signal to the individual drive units.

Decibel (dB)

A logarithmic unit used to express relative loudness.

Distortion

Literally any deviation from the original, though often specified to particular mechanisms. Also known as ‘nonlinearities’.

Drive Unit or Driver

The sources of acoustic output in a loudspeaker; includes woofers, tweeters, and so on.

Dynamic Drivers

Loudspeaker drivers that create compressions and rarefactions in air by means of a pistonic drive unit operating at audio frequencies. These are typically cone-shaped for drivers operating in the bass and lower midrange, and dome-shaped for upper midrange and high frequency drivers.

Dynamic Range

The ratio (dBs) between the loudest and softest sounds a system or component can handle.

Electrostatic

A principle employed in some exotic loudspeaker and headphone transducers, whereby a large sheet of thin material (typically Mylar) is induced to vibrate (at audio frequencies) across its whole area by an electrostatic charge.

Enclosure (a.k.a. Cabinet)

The rigid mounting for the loudspeaker drive units, often also containing the crossover network, and – in some active loudspeaker systems – even the amplifiers. In most cases, the term is self-explanatory (the enclosure encloses the drivers, crossover, etc.), but can also notionally be applied to the frame housing planar magnetic or electrostatic panels.

Filter

An electrical circuit used to limit the bandwidth of a signal, and one of the principle properties required of a crossover.

Frequency Range/Spectrum

Can refer to any spread of frequencies, but most commonly the Audio Band of human hearing, from 20 cycles per second (20Hz) in the extreme bass to 20,000 cycles per second (20kHz) in the highest treble.

Frequency Response

The variation in output across a specified range of different frequencies.

 

Harmonic

Harmonics are the whole number multiples of a base frequency called a fundamental.

Harmonic Distortion (Thd)

The addition of unwanted harmonics to a signal.

 

HF

High frequency (i.e., treble). Often used in terms of describing loudspeaker drive units (‘HF’ directly equating to ‘tweeter’).

Horn

As the name suggests, a design using an acoustic horn – often with a specialized compression drive unit – to increase the efficiency of the loudspeaker system. This is one of the earliest examples of loudspeaker technology, as the basic concept predates electrical loudspeaker driver design.

Hz (Hertz)

Unit of frequency of vibration, 1Hz = 1 cycle per second.

Impedance

Measure of the electrical resistance (and reactance) of a component’s inputs and outputs.

Infinite Baffle (a.k.a Sealed Box)

In theory, the sides and rear of a loudspeaker cabinet act as extensions of the front baffle in trying to keep rear-radiation from the loudspeaker drivers at bay. When the cabinet is fully sealed, preventing any rear-radiating sound in the process, it is considered an infinite baffle.

kHz

1000Hz or vibrations per second (1kHz actually corresponds to a tone nearly two octaves above middle C).

LF

Low frequency (i.e., bass). Often used in terms of describing loudspeaker drive units (‘LF’ directly equating to ‘woofer’).

Materials

Materials science has caught up with the world of loudspeakers in all three places, but especially in enclosure material (which can often be aluminum, carbon-fiber, or one of a wealth of mineral-filled resins) and drive unit materials (which can be also be made from aluminum or carbon-fiber, but also ceramic, industrial diamond, beryllium, a number of different plastics, as well as composites conjoined by lightweight foam.

Midband or Midrange

The middle range of audio frequencies, where the ear is most sensitive. Can be subdivided into lower midrange (250Hz–500Hz), midranges (500Hz–1kHz), and upper midranges (1kHz– 2kHz).

Monitor

High quality (usually standmount) loudspeaker.

Moving Coil

A transducer system that changes mechanical energy into electrical energy or vice versa, used in high quality pickup cartridges and in conventional loudspeaker drive units.

Noise

Random unwanted low-level signals.

Octave

Span of frequency or pitch that represents a doubling or halving of frequency.

Ohm

Unit of electrical impedance or resistance.

Port

In reflex loaded loudspeakers, the opening which is ‘tuned’ to the box size and main driver characteristics to improve output at low frequencies.

Presence

Alternative terminology for the high frequencies between 4kHz–6kHz.

Reflection

Higher frequencies can be very directional, and their output can easily ‘bounce’ off reflective walls and ceilings, interfering with the sound directly from the tweeter itself. Room acoustics experts recommend placing absorption at the ‘first reflection points’ either side of the loudspeaker to limit this interference.

Resonance

A physical property where one vibrating system causes another system to ‘sympathetically’ vibrate at specific frequencies. These resonances can happen inside the loudspeaker cabinet, along the walls of the cabinet.

Sensitivity

The amount of output (loudness, expressed in decibels) for a given electrical input (usually 1 watt).

Separation

The separateness of the left and right channels of a stereo audio system.

Signal-To-Noise, S/N

The difference between maximum level of a signal and the background noise left when the signal is removed.

Snake Oil

A term used by consumers to describe products that involve technological principles that are not well understood by the consumer. Examples of such technologies include EMI, decimation mathematics, image creation in the brain, bandwidth of the ear, phase effects, pre-ringing and reference measurement parameters. Snake Oil is a term of approbation which strongly implies that what is not understood is not valuable, rather than focusing value judgements on results achieved.

Stereo

Literally ‘solid’ – a system which uses two loudspeakers (or a pair of headphones) to create solid spatial sonic images.

Subsonic

Below the audible frequency range, commonly considered to be anything below 20Hz.

Top Octave

Very high frequencies in the 10kHz–20kHz region.

Treble

Upper part of the audible frequency range. Can be subdivided into lower treble (2kHz–3.5kHz), treble (3.5kHz–6kHz), and upper treble (6kHz– 10kHz). Also see Presence and Brilliance.

Transmission Line

Instead of a conventional sealed or ported enclosure, a transmission line takes the sound generated from the back of the bass speaker through a long and labyrinthine damped pathway within the speaker enclosure itself.

Tweeter

Small loudspeaker drive unit used for higher frequency (treble) sounds. Commonly a pistonic dome design but can be anything from a planar magnetic or folded ribbon of metal foil to the corona discharge of high-energy electrical plasma. As this last can produce hazardous levels of nitrogen oxides and ozone in a living room, plasma tweeters are relatively rare!

Ultrasonic

Frequencies above the notional limits of audibility, but still considered important in high-resolution audio systems. Typically, in the region from 20kHz–100kHz.

Watt

Unit of electrical power (the product of voltage and current).

Woofer

Loudspeaker drive unit that handles lower frequency (bass) sounds.

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