Qms, Qes and Qts are Thiele-Small parameters used to describe how well a speaker or subwoofer is controlled around its resonant frequency. These values help installers and system designers understand how a speaker may behave in different enclosure types, including sealed boxes, ported boxes and free-air installations.
Qms, or Mechanical Q, refers to the mechanical control of the speaker. This includes the suspension components, such as the surround and spider, and how they control cone movement.
Qes, or Electrical Q, refers to the electrical control provided by the speaker’s motor system, including the voice coil and magnet. This value helps indicate how effectively the motor controls the speaker’s movement.
Qts, or Total Q, combines both mechanical and electrical control into one overall value. Qts is often used as a guide when determining what type of enclosure may suit a speaker or subwoofer.
As a general rule, lower Qts values are often associated with speakers suited to ported or vented enclosures, while higher Qts values may be more suitable for sealed or free-air applications. However, these are only guidelines. Real-world performance depends on the complete speaker design, enclosure volume, amplifier power, vehicle acoustics and tuning.
When choosing Focal speakers or subwoofers, Qms, Qes and Qts should be considered alongside other specifications such as Fs, Vas, Xmax, RMS power handling, sensitivity and impedance. Looking at one parameter alone will not tell the full story.
For the best result, Focal Australia recommends speaking with an authorised Focal Australia dealer. A professional installer can interpret the speaker data correctly and recommend the right enclosure, subwoofer or speaker setup for your vehicle, system design and listening preferences.
