Reference · Terms
Glossary
Short definitions of the terms you meet when designing an enclosure. Follow the links for the controls, graphs and worked examples behind them.
Response and level#
- SPLalso sound pressure level
- Sound pressure expressed in decibels at the chosen listening distance and radiation space. The SPL tile shows the response at the input power you set.
- F3also −3 dB point
- A frequency where the response is below its reference level by 3 dB. Read it with the response shape: a peak can make a single cutoff figure misleading. Reading a response.
- F6 and F10
- Cutoff markers like F3, but at drops of 6 dB and 10 dB. They show how the low-frequency roll-off continues beyond F3.
- Phase
- The angle of an oscillating response relative to the drive. Outputs add with their phase, so similar levels can reinforce or cancel. Phase.
- Group delay
- How quickly phase changes with frequency, expressed as a time. It describes the modelled response and filters, not a separate echo from the room. Group Delay.
- Impedance
- The frequency-dependent electrical load, with both magnitude and phase. It includes resistance, coil inductance and the driver’s movement against its acoustic load. Impedance.
- Baffle step
- The broad level change as wavelengths become large compared with the baffle. The app’s optional model is a smooth correction, not a full diffraction simulation. Baffle Layout.
Driver and limits#
- T/S parametersalso Thiele/Small parameters
- Small-signal measurements that describe a driver’s motor, moving mass, suspension and damping. See the parameter reference for the symbols and units.
- Fs
- The driver’s free-air resonance frequency, before the enclosure adds its acoustic load.
- Qts
- The total quality factor of the driver’s free-air resonance, combining electrical and mechanical damping. It is not the Q of the finished box.
- Vas
- The volume of air with the same compliance as the driver’s suspension. It is a property of the driver, not a recommended box size.
- Sd
- The effective area of the moving piston. Cone velocity multiplied by Sd gives volume velocity.
- Excursion
- The cone’s displacement from its resting position. The Excursion tile reports peak, one-way movement.
- Xmax
- The manufacturer’s maximum linear one-way excursion. Passing it warns that the small-signal model no longer describes the driver reliably; it is not itself a prediction of damage.
- Max SPL
- The modelled sound level at which excursion or the chosen thermal ceiling is reached, one frequency at a time. Port air speed is checked separately. Max SPL.
- Headroom
- The margin between the demanded level and a limit. The Headroom tile compares average and peak demand with clean and maximum thresholds.
- Crest factor
- The difference between average and peak level. It lets the headroom calculation separate sustained thermal demand from brief peaks.
Boxes and ports#
- Alignment
- The response produced by a particular driver, box volume, tuning and losses together. A box size alone is not an alignment.
- Net volume
- The air volume available to the acoustic chamber, excluding the space occupied by the port, driver and other objects. From simulation to a build.
- Gross volume
- The internal cabinet volume needed to contain the net air volume plus the port and entered displacements. It does not include wall thickness.
- Qtc
- The total Q of a driver in a sealed box. It describes the damping and shape around the system resonance. Sealed.
- Fbalso tuning frequency
- The resonance of the air in a port against the chamber air, or the corresponding tuning of a passive radiator system.
- End correction
- The allowance for air moving just beyond the ends of a duct. It makes the acoustic length greater than the physical length. Ports and end correction.
- Port velocity
- Peak air speed through the port opening. It is a useful warning for noise and compression, which the linear model does not calculate directly. Port Velocity.
- Volume velocity
- Volume flow per unit time, equal to particle velocity multiplied by cross-sectional area. The same flow moves faster in a narrower passage.
- Passive radiator
- An undriven diaphragm that replaces the moving air mass of a port. Its mass tunes the system and its travel needs checking. Passive radiator.
Horns#
- Throat
- The start of a horn path, normally its smallest cross-section.
- Mouth
- An opening where the path radiates into the surrounding space. Mouth area and radiation space affect the load seen by the path.
- Flare
- The change of cross-sectional area along a segment. The horn editor can join segments with different profiles. Horn Editor.
- Tapped horn
- A horn with both faces of the driver coupled into one path at different positions. Their outputs combine with a frequency-dependent phase relationship. Tapped horn.
- Particle velocity
- The local speed of air in a horn section. It differs from volume velocity because it also depends on the section area. Horn diagnostics.