Glossary
Definitions of common terms used in loudspeaker enclosure design and simulation.
A
Alignment
A specific combination of box volume and tuning frequency for vented enclosures that produces a particular response shape. Common alignments include QB3, BB4, and C4. Named after filter theory (Butterworth, Chebyshev, etc.).
Anechoic
Free from echoes or reflections. An anechoic chamber is a room with sound-absorbing walls used for measurements. The simulator shows anechoic response (no room effects).
B
Bandpass
An enclosure type where the driver fires into a sealed chamber, which then couples to the outside through a ported chamber. Produces a bandpass filter effect. Not currently supported by this simulator.
Bass Reflex
Another term for a vented or ported enclosure. Uses a tuned port to extend low-frequency response and increase efficiency.
Bl (Force Factor)
Product of magnetic flux density (B) and voice coil length (l). Measured in tesla-meters. Higher Bl means stronger motor and better control. See T/S Parameters.
C
Compliance
The inverse of stiffness. Mechanical compliance (Cms) describes how easily the driver's suspension moves. Acoustic compliance describes how easily air compresses.
Cutoff Frequency
The frequency at which a filter starts attenuating the signal. For high-pass filters, frequencies below this are reduced. For low-pass filters, frequencies above this are reduced.
D
dB (Decibel)
Logarithmic unit for measuring ratios. In SPL measurements, 0 dB SPL is the threshold of hearing. +3 dB is roughly twice the power, +10 dB is roughly twice the perceived loudness.
Driver
The loudspeaker component that converts electrical signals into sound. Consists of a cone, voice coil, magnet, and suspension. Sometimes called a "transducer" or "raw speaker."
E
Efficiency
How much acoustic power is produced for a given electrical input. Usually expressed as sensitivity (dB SPL at 1W/1m). Higher efficiency means less amplifier power needed.
Enclosure
The box or cabinet that holds the driver. The enclosure controls the driver's motion and shapes its frequency response. Also called "cabinet" or "box."
Excursion
How far the cone moves from its resting position. Peak excursion is one-way travel. Must stay within Xmax for linear operation.
F
F3 (-3dB Point)
The frequency where SPL drops by 3 dB from the reference level. Considered the lower limit of usable bass extension. Sometimes called the "half-power point."
F10 (-10dB Point)
The frequency where SPL drops by 10 dB. Indicates where response has rolled off significantly. Useful for comparing deep bass extension.
Fb (Box Tuning Frequency)
The resonant frequency of a vented enclosure. Determined by port dimensions and box volume. The port and box air resonate at this frequency.
Fs (Resonant Frequency)
The free-air resonance frequency of a driver. The frequency where the driver naturally vibrates when not in an enclosure. Lower Fs means potential for deeper bass. See T/S Parameters.
G
Group Delay
A measure of how different frequencies are delayed relative to each other. Related to phase response. Lower and flatter group delay means better transient response.
H
Half-Space
Radiation into a hemisphere (2π steradians). Occurs when a speaker is placed on the floor or against a wall. Provides +6 dB SPL compared to full-space.
Helmholtz Resonator
An acoustic resonator consisting of a volume of air connected to the outside by a neck or port. A vented enclosure is a Helmholtz resonator. The resonant frequency depends on the port and box volume.
I
Impedance
Electrical resistance that varies with frequency. A driver's impedance includes DC resistance, inductance, and mechanical effects. Measured in ohms. Important for amplifier matching.
L
Linkwitz-Riley
A filter type with specific phase characteristics. 4th-order Linkwitz-Riley filters sum to flat response, making them popular for crossovers.
Lumped-Parameter Model
A modeling approach that treats the driver and enclosure as discrete elements (masses, springs, resistances). Accurate at low frequencies. The basis for this simulator.
M
Mms (Moving Mass)
Total mass of the moving parts including cone, voice coil, and air load. Measured in grams or kilograms. Affects resonant frequency and efficiency. See T/S Parameters.
O
Octave
A doubling or halving of frequency. From 50 Hz to 100 Hz is one octave. From 100 Hz to 200 Hz is another octave. Roll-off is often expressed in dB per octave.
P
Passive Radiator
A cone without a motor (no magnet or voice coil) used in place of a port. Driven by pressure changes inside the box. Tuning is adjusted by adding mass to the radiator.
Pe (Power Rating)
Thermal power handling capacity. Maximum continuous power the voice coil can handle before overheating. Measured in watts. See T/S Parameters.
Phase
The time relationship between signals. Measured in degrees or radians. A 180° phase shift means the signals are opposite. Important for crossover design and port alignment.
Port
A tube or slot in a vented enclosure that allows air to move in and out. Creates a Helmholtz resonator with the box volume. Also called "vent."
Q
Q Factor
Quality factor that describes damping in a resonant system. Higher Q means less damping, sharper resonance. Lower Q means more damping, broader resonance.
Qes (Electrical Q)
Electrical damping from the motor. Related to how strongly the magnetic field controls cone motion. Lower Qes means stronger motor control. See T/S Parameters.
Qms (Mechanical Q)
Mechanical damping from suspension losses. Usually much higher than Qes. See T/S Parameters.
Qtc (Total System Q)
The Q factor of a driver in a sealed enclosure. Determines response shape. Qtc = 0.707 is the Butterworth (maximally flat) alignment. Target is typically 0.6-0.7.
Qts (Total Driver Q)
Combined electrical and mechanical Q. The most important Q factor for enclosure design. Low Qts (0.2-0.4) suits vented, high Qts (0.6-0.8) suits sealed. See T/S Parameters.
R
Radiation Space
The solid angle into which a speaker radiates. Full-space is 4π steradians (free-field), half-space is 2π (against one boundary), quarter-space is π (corner), eighth-space is π/2 (room corner).
Re (DC Resistance)
Voice coil DC resistance. Measured in ohms. Always lower than nominal impedance. Affects efficiency. Increases with temperature. See T/S Parameters.
Roll-off
The rate at which response decreases with frequency. Measured in dB per octave. Sealed boxes roll off at 12 dB/octave below F3. Vented boxes roll off at 24 dB/octave below Fb.
S
Sd (Effective Area)
The effective radiating area of the cone. Measured in square meters or square centimeters. Larger Sd means more air displacement. See T/S Parameters.
Sealed Enclosure
A closed box with no port or opening. The simplest enclosure type. Provides good transient response and predictable behavior. Also called "closed box" or "infinite baffle."
Sensitivity
SPL produced at 1 meter with 1 watt input. Measured in dB SPL. Higher sensitivity means louder for the same power. Typical values are 80-95 dB for woofers.
SPL (Sound Pressure Level)
A measure of sound intensity. Measured in decibels relative to the threshold of hearing (20 μPa). 0 dB SPL is barely audible, 85 dB is moderately loud, 120 dB is very loud.
T
Thiele-Small Parameters
A set of electrical and mechanical measurements that describe a driver's behavior. Essential for enclosure design. Named after A.N. Thiele and Richard Small who developed the theory. See T/S Parameters Reference.
Transducer
A device that converts one form of energy to another. A loudspeaker driver is an electro-mechanical-acoustic transducer (electrical → mechanical → acoustical).
Tuning Frequency
See Fb. The resonant frequency of a vented enclosure or passive radiator system.
V
Vas (Equivalent Volume)
The volume of air with the same acoustic compliance as the driver's suspension. Measured in liters or cubic meters. Indicates suspension stiffness and typical box size needed. See T/S Parameters.
Vd (Volume Displacement)
Maximum air volume displaced by the driver. Calculated as Sd × Xmax. Measured in cubic centimeters or liters. A useful indicator of potential output. See T/S Parameters.
Vented Enclosure
An enclosure with a port tuned to a specific frequency. Provides higher efficiency and extended bass compared to sealed. Also called "ported" or "bass reflex."
Voice Coil
A coil of wire attached to the cone that moves in the magnetic field. Current through the voice coil creates a force that moves the cone. The voice coil is where electrical energy converts to mechanical energy.
X
Xmax (Maximum Excursion)
Maximum one-way linear excursion before significant distortion. Measured in millimeters. Determined by voice coil overhang or suspension limits. Must stay within Xmax for clean output. See T/S Parameters.