Speaker Glossary
A speaker glossary of the terms that matter when you buy drivers, build cabs and run a sound system: definitions, the relevant numbers, and a link to the full guide where there is one. For common questions, see the FAQ.
A
AES power
A power rating from the AES2 standard: the driver plays pink noise with a 6 dB crest factor, filtered to its working range, for two hours and must survive unchanged. Power is calculated from the RMS voltage and the driver's minimum impedance in its working range. The WM1850/8 is rated 1800 W AES. See power ratings explained.
Acoustic centre
The point a sound appears to come from. Used when measuring spacing and setting delay between subs and tops, as covered in phase and polarity.
Anechoic
Without echoes. Anechoic measurements are taken in a special room or outdoors with reflections removed, so they show the speaker alone.
B
Baffle
The panel a driver is mounted on. It separates front and rear radiation of the cone, which would otherwise cancel at low frequencies.
Basket
The metal chassis that holds the cone, suspension and motor together. It must stay rigid under the forces of a high-power motor, or the coil goes off-centre in the gap.
Bass reflex
A cabinet with a tuned port or vent that reinforces the driver's output around the tuning frequency. Also called vented. See cabinet tuning.
BL
The force factor: magnetic flux density in the gap multiplied by the length of voice coil wire in the field. Higher BL means stronger control of the cone. See distortion explained.
Bolt circle
The diameter of the circle through a driver's mounting holes. It must match your cabinet's holes when replacing a driver.
Bridged mode
Running both channels of a stereo amplifier into one speaker, one in reversed polarity, to deliver more voltage. The minimum safe load usually doubles, so check the amp's bridged rating. See amp matching.
C
Cardioid array
A group of subs where a reversed, delayed box cancels bass behind the array. See sub arrays and cardioid.
Clipping
What happens when an amplifier runs out of voltage and flattens the waveform peaks. It sounds harsh and sends extra heat to voice coils.
Compression driver
A high-frequency driver with a light diaphragm that drives a horn through a phase plug and small throat. See compression drivers and horns.
Cone
The moving diaphragm of a driver, usually treated paper or a composite. It must be light, stiff and well damped.
Coverage angle
The horizontal and vertical angle over which a speaker or horn keeps an even response, often defined at the -6 dB points.
Crossover
A filter network that splits the signal into frequency bands for different drivers. Can be passive or active. See crossover basics.
Cutout
The hole cut in a baffle to fit a driver. Its diameter must suit the driver's frame, either front or rear mounted.
D
Damping factor
The ratio of the speaker's impedance to the amplifier's output impedance. A high figure helps the amp control the cone, though long thin cables reduce it.
dB SPL
Sound pressure level in decibels relative to 20 µPa, the nominal threshold of hearing. See sensitivity and decibels.
dBu
A voltage level in decibels referenced to 0.775 V RMS. Professional line level is commonly +4 dBu, about 1.23 V.
Delay
Holding back a signal in time, usually in DSP, to align speakers at different distances or build sub arrays.
Dispersion
How widely a speaker spreads sound. Dispersion narrows as frequency rises for any given driver or horn.
DSP
Digital signal processing. A DSP unit handles crossovers, EQ, delay and limiting for a whole system.
Dust cap
The dome at the centre of the cone that keeps dirt out of the magnetic gap. It can also add stiffness to the cone.
E
EBP
Efficiency bandwidth product, calculated as Fs divided by Qes. As a rough guide, low values suit sealed boxes and higher values, around 100, suit vented boxes.
End-fire
A sub array with boxes placed front to back and delayed so bass adds forward and partly cancels behind. See sub arrays.
Excursion
How far the cone moves from rest. See Xmax and excursion.
F
Ferrite
A ceramic magnet material, heavy but cost-effective and stable with heat. See ferrite vs neodymium.
Flare
The rate at which a horn's cross-section grows from throat to mouth. It sets the horn's lower cutoff. See horn loading explained.
Folded horn
A bass horn whose long path is folded inside the cabinet to save space. See scoop vs reflex vs horn.
Former
The tube the voice coil is wound on. Common materials include glass fibre, aluminium and polyimide films. It must survive the coil's operating temperature without deforming.
Fs
The free-air resonant frequency of a driver: where the moving mass and suspension stiffness resonate. See Thiele/Small parameters.
G
Gain structure
Setting levels through the chain from desk to amp so each stage has headroom and noise stays low.
Gasket
A seal, usually foam or rubber, between the driver frame and baffle. It stops air leaks and rattles.
H
Headroom
The margin between normal operating level and the point of clipping or limiting.
High-pass filter
A filter that lets frequencies above a set point through and cuts those below. It protects sub drivers from excursion below the cabinet's working band.
Horn
A flared duct that couples a driver to the air for higher efficiency and controlled dispersion. See horns.
Horn throat
The narrow end of a horn, next to the driver. Throat size relative to the driver affects loading and the upper limit of the horn.
I
Impedance
The total opposition a speaker presents to alternating current, measured in ohms and varying with frequency. See impedance and wiring.
Inductance
Le, the voice coil's inductance. It makes impedance rise with frequency and can vary with cone position.
Inverse square law
Sound from a point source falls by about 6 dB each time the distance doubles.
L
Limiter
A processor that stops the signal rising above a set level, used to protect amplifiers and drivers.
Line array
A tall column of closely spaced cabinets that behaves as a single line source. See line array vs point source.
Linkwitz-Riley
A crossover filter type whose high and low outputs are each 6 dB down at the crossover point, so they sum flat when aligned. The 24 dB per octave version is common in PA.
Low-pass filter
A filter that passes frequencies below a set point and cuts those above. Used to send only bass to the subs.
M
Mid-bass
The band between subs and mids, roughly the upper bass and low mids. See mid-bass drivers.
Mms
The moving mass of a driver, including the cone, coil, suspension parts and air load.
Mouth
The open end of a horn. For full loading it must be large compared with the wavelength at cutoff.
N
Neodymium
A rare-earth magnet material that is much stronger for its weight than ferrite, but more sensitive to heat.
O
Octave
A doubling or halving of frequency. 40 Hz to 80 Hz is one octave.
Ohm
The unit of electrical resistance and impedance. Common speaker loads are 4 Ω and 8 Ω. See 4 ohm vs 8 ohm.
P
Phase
The timing relationship between two waves at a given frequency, measured in degrees. See phase and polarity.
Phase plug
A shaped part in front of a diaphragm or cone that evens out path lengths to the throat, extending high-frequency response.
Point source
A speaker that radiates from one place, so level falls about 6 dB per doubling of distance.
Polarity
Whether the cone moves out or in for a positive signal. Reversed polarity between boxes cancels bass.
Port
The tube or slot in a reflex cabinet. Its size and length set the tuning frequency.
Power alley
A strip of extra-loud bass between two separated sub stacks, with weaker zones either side.
Power compression
Loss of output as the voice coil heats and its resistance rises. See voice coils and heat.
Program power
A rating for music signals, usually quoted as twice the continuous rating, because music has a much higher crest factor than test noise. B&C, for example, specifies continuous program power as double its nominal rating. Compare drivers on their continuous figure. See power ratings explained.
Q
Qes
Electrical Q: how much the motor's electrical damping controls the driver's resonance.
Qms
Mechanical Q: how much the suspension's mechanical losses control the driver's resonance.
Qts
Total Q, combining Qes and Qms. It guides which cabinet type suits a driver. The WM1850/8 has a Qts of 0.644.
R
Re
The DC resistance of the voice coil, measured with a meter. It is lower than the nominal impedance. See testing a driver with a multimeter.
Rear-loaded horn
A cabinet where the front of the cone radiates directly and the rear drives a horn.
Recone
Replacing a driver's moving parts (cone, coil, spider, surround) while keeping the frame and motor. See reconing explained.
RMS power
Commonly used to mean continuous power handling. See power ratings explained.
S
Scoop bin
A short front-loaded horn cabinet with a sealed rear chamber, a classic UK sound system bass box. See how to build a scoop bin.
Sd
The effective radiating area of the cone. With Xmax it sets how much air a driver can move. The WM1850/8 has an Sd of 1244 cm².
Sealed box
A closed cabinet with no port. It rolls off gently at about 12 dB per octave below resonance.
Selector
In sound system culture, the person who chooses and plays the records. See selector, operator and MC.
Sensitivity
The sound level a speaker produces at 1 m for a set input, such as 1 W or 2.83 V. See sensitivity and decibels.
Speakon
A locking loudspeaker connector widely used in pro audio. See Speakon wiring.
Spider
The corrugated fabric suspension behind the cone that centres the voice coil. A double spider adds stability under heavy drive, as on the WM18X451.
Sub
Short for subwoofer: a driver or cabinet for the lowest frequencies. See sub-bass drivers.
Surround
The flexible outer edge joining the cone to the basket. It forms part of the suspension and seals the cone edge.
T
T/S parameters
Thiele/Small parameters: small-signal figures such as Fs, Qts and Vas used to design cabinets. See Thiele/Small parameters.
THD
Total harmonic distortion, the sum of added harmonics as a percentage of the original signal.
Tops
The mid and high-frequency cabinets in a system, placed above the bass.
Tuning frequency
The frequency a reflex port resonates at with the cabinet volume, often written Fb. See cabinet tuning.
Tweeter
A small driver for high frequencies. See tweeters vs horns.
V
Vas
The volume of air with the same compliance (springiness) as the driver's suspension. The WM1850/8 has a Vas of 120.9 L.
Vd
Displacement volume: Sd × Xmax. It sets excursion-limited output, and 20·log₁₀ of the ratio between two drivers gives the difference in dB. The WM1850/8: 1244 cm² × 1.2 cm = 1493 cm³. See 15 vs 18 inch subs.
Vented motor
A motor with vents through the pole piece or plates to move air across the voice coil and help cooling, as on the WM1850/8.
Voice coil
The coil of wire attached to the cone that sits in the magnetic gap and drives the cone. A larger diameter gives more surface to shed heat: the WM1850/8 uses a 125 mm coil, the WM18X451 a 115 mm copper coil. See voice coils and heat.
W
Wavelength
The physical length of one cycle of sound: about 343 m divided by the frequency in hertz. At 50 Hz it is nearly 7 m.
Woofer
A driver for low frequencies. In PA, woofers often cover bass and mid-bass above the subs.
X
Xmax
The maximum one-way excursion a driver can manage while staying within its linear range. The WM1850/8 is rated at 12 mm. See Xmax and excursion.
Xmech
The mechanical excursion limit, beyond which parts can collide or be damaged.
Sources: B&C Speakers, power handling (AES2 test method and program power), checked October 2026; Wavemark WM1850/8 spec sheet and WM18X451 product data.