Audio & Physics TerminologyActive Crossovers
An active crossover is an electronic crossover having well-defined and precise frequency responses unchanged by the signal level or power loading of the loudspeaker, unlike the frequency responses in a traditional passive crossover. They operate at signal levels suited to power amplifier inputs and can have analog or digital signal processing.
A-weighting is related to measuring the sound pressure level. Because the human hearing system is more sensitive to some frequencies (500 Hz…8 kHz) than others (very low or very high frequencies), A-weighting defines a frequency-dependent method to scale the sound level measurement to calculate a value representing the subjective impression created by sound at various frequencies.
Bass management is a method to reproduce the lowest frequency content in audio channels using one or more subwoofers instead of loudspeakers. This audio can be the low frequency content in the full-bandwidth audio channels. Parts of the entire LFE audio channel can also be bass managed. Bass management provides several benefits including higher sound output capability and better control of the acoustical environment to improve the quality of reproduction.
The decibel (dB) is a representation of magnitude relative to a reference level on a logarithmic scale. Since it expresses a ratio of two (same unit) quantities, it is a dimensionless unit.
Flush-mounting / Half-space
When a straight plane such as a wall or floor limits the spherical radiation of a loudspeaker by splitting the space (sphere) to two halves, the radiation will occur into a half space. A special case of the half space is flush-mounting which has several benefits such as improved low frequency efficiency, elimination of rear wall cancellation and avoidance of cabinet edge diffraction. Once a loudspeaker is flush mounted the acoustical radiation load on the loudspeaker changes and acoustical adjustment of the loudspeaker’s frequency response is required to maintain a flat response at low frequencies.
Free-standing / Free-field
When a loudspeaker can radiate sound without limiting obstacles or surfaces (radiating in the free field) around it it is said to be free standing. The radiation space is a sphere if loudspeaker directivity does not limit the directions the loudspeaker radiates into (at a given frequency).
Magnetic shielding limits the magnetic fields. Low frequency drivers are magnetically shielded to minimize stray magnetic fields from emanating out from the loudspeaker. The magnetic stray fields can disturb computer screens and other video displays.
Radiation space refers to the surroundings of a loudspeaker. In simple cases the radiation space can be described by a solid angle (space angle). The radiation angle is an essential factor when investigating the interaction between the loudspeaker and the surrounding air. The radiation space of a loudspeaker can be limited by its radiation characteristics. The radiation characteristics describe the complex, three-dimensional and frequency dependent property of a loudspeaker.
The reflex port is an acoustically optimized opening in a ‘bass reflex’ loudspeaker enclosure which enhances the reproduction of the lowest frequencies generated by the woofer in a loudspeaker. The bass reflex port generally consists of one or more shaped tubes mounted in the front or rear wall of the loudspeaker enclosure.
Room Response Controls
A collection of controls built in the Genelec loudspeakers used to compensate and eliminate listening room generated acoustical problems in the loudspeaker or subwoofer frequency responses to improve the in-room sound at the listening position.
Sound Pressure Level (SPL)
Sound pressure level is a measurement of the pressure produced by the sound wave, expressed in decibels (dB) relative to 20 microPascals (2 x 10-5 N/m2). 0 dB SPL is the average threshold of human hearing at 1 kHz frequency for young adults.
-3 dB cutoff frequency
The term cutoff frequency (also called the corner frequency or the break frequency) represents the frequency where the energy radiated by the loudspeaker system has been attenuated to one half. At the -3 dB cut-off frequency the sound level has decreased by 3 dB.