Thiele et Small parameters


Technical parameters

Named after their inventors, Thiele and Small parameters are used to characterise individual speaker specifications. This technical data is used to calculate necessary loudspeaker volume. Therefore, it can be used to compare the capabilities of several different speakers and perform simulations for the type of housing appropriate for a subwoofer for example.

BLSpeaker motor force factor.
Cas (m5 per N)Acoustic compliance - speaker surrounds.
Cms (m per N)Mechanical compliance of driver surrounds.
Diam. (m)Speaker emissive diameter.
Fs (Hz)Speaker resonance frequency in the open air.
Voice-coil H. (mm)Voice-coil height - speaker moving voice-coil.
Air gap H. (mm)Speaker air gap height.
Les (mH)Equivalent electric inductance - speaker surround compliance.
Mas (Kg per m4)Equivalent acoustic mass - speaker moving equipment.
 Mms (Kg)Mechanical weight - speaker moving parts
 N (%)Speaker efficiency expressed as a percentage.
 N0 or SPL (dB per W per m)Speaker efficiency expressed as an acoustic level.
QesElectrical Q-factor: speaker electrical surge coefficient at resonance frequency.
QmsMechanical Q-factor: speaker surge coefficient at resonance frequency.
QtsTotal Q-factor: speaker mechanical surge coefficient at resonance frequency.
Ras (Ohms ac.)Equivalent acoustic resistance - speaker internal surround damping.
Rcc (Ohms)Speaker resistance to direct current.
Res (Ohms)Equivalent electrical resistance - speaker surround internal damping.
Rms (Kg per s)Equivalent mechanical resistance - speaker surround internal damping.
Sd (m2)Speaker emissive surface area.
Vas (l)Equivalent volume of air - speaker surround elasticity.
X. max. (mm)Maximum linear peak-to-peak excursion.