“WHAT DOES IT MEAN?”

The world is full of technical jargon, none more so than in the wonderful world of Pro Audio!

Here’s a list what the technical names mean in simple Music Gear Direct terms. If you think that we’ve got any of them wrong, or we have missed something you would like to know, or you would like to share any others with us that would be helpful to others, please drop us an email!  

Alternating Current (AC).
An electrical current that changes magnitude & direction 50 times per second (in Europe) and 60 times per second in many other parts of the world. (America)

AC Power Supply.
This normally refers to your local power supply coming out of the wall socket. In the UK this is typically 240Volts 50Hz. Always be cautious when handling mains power cables and connections.

A – B Test.
A test between two components, for example, a test between two loudspeakers. For a test to be meaningful, the signal levels should be the same to allow a proper comparison.

AES/EBU.
A balanced digital connection. The AES/EBU uses XLR connectors.

Amplifier.
A device which increases signal levels. Many types of amplifiers are used in audio systems but they all fulfil the objective of increasing voltage & current to match the requirements of the device to which they are connected. For example, an amplifier rated to deliver 300 watts will be used to ‘drive’ a loudspeaker whose rating is 300 watts or greater.

Attenuator.
A form of control to allow signal levels to be adjusted to allow controlled operation.

Analogue.
All transducers provide or require analogue signals in order to function. A microphone has a diaphragm that responds to variations in air pressure to create an electrical signal which is the electronic ‘analogue’ of the air pressure changes. A loudspeaker vibrates the air to create pressure variations in the air which you hear a ‘sounds’. Signals from microphones can be amplified by an ‘analogue’ amplifier which simply makes the electrical signal ‘bigger’ in order to ‘drive a loudspeaker directly. The signals processed in the amplifier chain remain in the same form throughout the process.

Balanced.
This is the preferred method for sending low level electrical signals along a cable to reduce the risk of interference or the effects of radiated magnetic fields introducing ‘hum’ effects into the signal. This is achieved by sending signals along two cables, usually contained within a ‘screening’ sheath. The signals in each cable are identical, but the second signal is inverted in phase with regard to the first. At the end of the cable, the input amplifier is configured to only be sensitive to the ‘differences’ between the signals in each cable.  As the second cable is ‘out of phase’, the amplifier ‘sees’ twice the input signal. Any other interference induced along the cable with be the same in each signal cable and will therefore be ‘ignored’ by the input amplifier. This is why all microphone signals are sent along ‘balanced’ cables to ensure that the tiny microphone signals arrive at the amplifier free of any interference effects.

Bandwidth.
This relates to the frequency range of signals that can be ‘handled’ typically by an amplifier. In the case of an audio power amplifier it is defined usually by the lowest & highest frequency that the amplifier can amplify when the frequency response is 3dB below the average throughout the performance range of the amplifier.  An audio power amplifier has a frequency response typically -3dB from 20Hz to 20kHz.

Bandpass Filter.
Typically, a circuit that allows audio frequencies to pass through between a defined ‘low’ frequency and a defined ‘high’ frequency. Frequencies below the selected ‘low’ frequency and those above the selected ‘high’ frequency are not allowed to pass through the filter.  

Bass.
This term defines the ‘low’ frequency components in an audio signal. Typically this covers the frequency range 20Hz to 500Hz.

Bridge/Bridged.
When an amplifier is switched to operate in ‘bridge’ mode, the second channel is driven ‘out of phase’ with the first channel. The loudspeaker load is connected between the ‘live’ output of the first amplifier channel and the ‘live’ output of the second channel which then presents the loudspeaker with ‘twice’ the drive voltage of a single channel. This arrangement is normally used to provide higher output power for ‘large’ high power bass loudspeakers without the need to purchase a much larger amplifier.

Cardioid.
This term is used to define the pick up pattern of a microphone to give a desired result. A microphone with a ‘Cardioid’ response has a pick up pattern of a ‘heart’ shape in the forward direction. The means that the ‘rear’ pick up sensitivity of the microphone is greatly reduced. This is greatly beneficial when performing ‘on stage’ as each microphone is considerably less sensitive to the sounds reflecting back on to the stage from the rest of the auditorium and this reduces the sensitivity to ‘microphone feedback’ effects.

Cold.
This term usually refers to the negative (or inverted) phase of the signal in a balanced wire connection. For an unbalanced signal, the screen connection is usually referred to as ‘cold’.

Crossover (Active).
An electronics processing unit used to ‘split’ audio frequencies into the component parts necessary to drive your loudspeaker system. A two way crossover will be used typically to split the audio frequencies into two bands, ‘low’ (20 Hz – 150Hz) for the ‘bass’ loudspeakers and ‘high’ (150Hz – 20kHz) for the mid/high frequency loudspeakers. A three way crossover is used to split the audio frequencies into three sections, typically ‘low’ (20 Hz – 150Hz), ‘mid (band pass) (150Hz – 3kHz) and ‘high’ (3kHz – 20kHz). An electronic crossover is desirable as it fulfils the function more precisely and usually at lower cost than passive components.

Crossover(Passive).
A passive crossover is usually located within a loudspeaker enclosure and consists of a selection of components to provide the necessary frequency range for each internal element of the loudspeaker. For example, a ‘low pass’ passive filter will be used to pass signal to the ‘bass’ loudspeaker and a ‘high pass’ passive filter will be used to pass signals to the high frequency loudspeaker (usually a horn).

Decibel dB.
This is a logarithmic method of defining levels in both acoustics and electronics. In order to help you understand this, an increase of voltage from 1 volt to 10 volts relates to a change of 20dB. A change of 1 volt to 3 volts, or from 3 volts to 10 volts equate to changes of 10dB.   In acoustic terms, a 1dB change is generally accepted as the smallest change that can be detected by the human ear.

dBA.
This is the unit of measurement usually used in acoustic tests. The ‘A’ weighting is designed to simulate the characteristics of the human ear in order to make measurements meaningful in relation to the sounds you actually hear.

dBV.
This defines a reference level of 1 volt for decibel measurements in amplifiers etc.

F.O.H.
Front of House. This usually refers to the audience area in front of the performance stage. The main loudspeakers in a pa system are usually referred to as ‘Front of House’ loudspeakers.  The main mixing desk is located out in the auditorium on larger performances and this again is usually referred to as the ‘Front of House’ desk.

Foldback.
Foldback or foldback loudspeakers are used to ensure that performers ‘on stage’ can hear a ‘balanced’ mixture of sounds in order to ensure that they can work together to provide a good balanced sound for the audience. On larger performances, it is normal for there to be a separate foldback (or monitor) mixing desk to ensure that each individual performer can hear the best ‘mix’ of sounds to assist their performance.

Frequencies.
Sound is made up of ‘vibrations’ in the air. This is defined as a number of ‘cycles per second’ and is currently defined in Hertz(Hz). 1 Hz is 1 cycle per second. 100Hz is 100 cycles per second, 1kHz is 1000 cycles per second and 10kHz is 10,000 cycles per second.

Ground.
This term is used to describe ‘signal ground’ and is a common point to which all signals a returned. It is usually connected to Earth.

Hertz.
A measurement of frequencies. (see ‘Frequencies’). Named after Heinrich Hertz.


High.
Generally refers to the high frequency content of an audio signal and is a term used on mixers & amplifiers in tone control circuits to adjust the high frequency sounds. (sometimes referred to as ‘treble’)

Hot.
The positive phase of a signal.

Impedance.
This is a term usually used to relate to the ‘load’ presented by a loudspeaker. As a loudspeakers has inductive and capacitive elements in its internal crossover network and also the speakers themselves have ‘inductive’ components the impedance is usually an average of the loudspeaker load measured over the audio frequency band.

Level.
The size of a signal at any given point in an audio system.

Line Level.
These are the signal levels at which most pieces of equipment are linked in a complete audio system.  Signal levels are usually in the range -10dBV to +4dBV and are usually ‘balanced’.  For example, most mixing desks & CD players will provide output signals in the range -10 to +4dBV and most power amplifiers have input sensitivities from -10dBV to +4dBV.

Mid.
Generally refers to the mid frequency content of an audio signal and is a term used on mixers & amplifiers in tone circuits to adjust the mid frequency sounds. Most vocal sounds fall into the mid frequency range.

Mono.
Single channel sound reproduction.

Monitor.
The speakers used by performers to hear themselves on stage or by a recording engineer in a studio.  Monitor speakers are also referred to a ‘Wedge’ monitors or ‘Foldback’ monitors.

Ohm.
A unit of electrical resistance.

Pink Noise.
Used in methods for testing the performance of a loudspeaker system. Pink Noise is ‘filtered’ in order to provide constant readings in the fixed percentage  bandwidth filter used for audio measurement.

RMS.
Root Mean Square – a standard term defining electrical measurement.

Screen.
Describes the outer braiding or electrical sheath of most signal cables used to suppress the ‘pick up’ of interference signals.

Send.
The connectors or controls used to change the level of signals sent to an external unit usually connected to a mixer.

Signal to Noise.
Usually expressed as a ratio but is defined as the signal range between the background noise of a unit and the maximum signal it can handle.  For example, in a power amplifier it is typical for the signal to noise ratio to be 100dB.

Speakon.
A high quality connector used to connect loudspeakers to power amplifiers. This connector uses a ‘twist’ action to connect and makes sure the high power outputs a safely shielded when connections are being made.

SPL.
Sound Pressure Level usually measured in decibels and frequently including some sort of frequency weighting (dBA, dBC, dBlin.).

Stereo.
Two channel sound reproduction comprising of ‘left’ & ‘right’ signals to give spatial information about the sound stage. Most ‘live’ music amplification is carried out in ‘stereo’ to allow sounds to be ‘positioned’ in the stereo mix to give a better, clearer result.

TRS.(Stereo Jack)
Tip, ring, sleeve refers to the connections for a 1/4inch three pole jack plug or socket. Normally used for balanced line signals.

TS.(Mono Jack)
Tip, sleeve, refers to the connections for a 1/4inch two pole jack plug or socket. Normally used for unbalanced line signals.

UHF.
Usually used for radio microphone systems in the 800 – 950 MHz frequency band.

Unbalanced.
A two wire connection usually involving a screened cable with the shielded cable used to carry the signal & the sheath used a ground shield.
VHF.
Used for older radio microphone systems in the 20 – 30 MHz frequency band.

Watts.
Unit of electrical power and is used to define the power handling capabilities of loudspeakers and also the power output capabilities of amplifiers.

Wavelength.
The distance a sound wave travels in order to complete one cycle.

White Noise.
A signal generated comprising of all signals in the audio frequency range and of equal power at all frequencies.

XLR. (Cannon Connector)
An industry standard connector used for balanced line signal connections for microphone level signal, line level signals & AES/EBU digital signals.