Thiele-Small Parameters Explained

Introduction

Thiele-Small (TS) parameters are a set of electromechanical characteristics that define the performance of a loudspeaker. These parameters help audio engineers design and optimize speaker enclosures to achieve desired performance outcomes.

Key Parameters and Their Functions

• Fs (Resonant Frequency):

  The frequency at which the speaker's mechanical and electrical systems naturally resonate. It is crucial for determining the low-frequency performance of a driver.

• Qts (Total Q Factor):

  A measure of the speaker's damping characteristics, combining electrical (Qes) and mechanical (Qms) damping. Lower values indicate tight, well-controlled movement, while higher values suggest looser, less controlled movement.

• Vas (Equivalent Volume):

  The volume of air that exhibits the same compliance as the speaker's suspension. This parameter impacts the size of the enclosure needed for optimal performance.

• Sd (Effective Surface Area):

  The radiating area of the speaker cone. A larger Sd results in higher output at a given power level, particularly in the low-frequency range.

• Re (DC Resistance):

  The electrical resistance of the voice coil, influencing amplifier load and system compatibility.

• Bl (Force Factor):

  The strength of the magnetic field in the voice coil, determining the efficiency of converting electrical energy into mechanical movement.

• Xmax (Maximum Linear Excursion):

  The maximum distance the cone can move linearly. A higher Xmax enables greater low-frequency output without distortion.

Interactions Between Parameters

TS parameters are interdependent. For example, a high Qts paired with a low Vas results in a smaller, sealed enclosure, while a high Vas and low Qts are better suited for large, ported designs. Understanding these interactions is key to achieving optimal performance.

Practical Applications

By using TS parameters, you can predict how a speaker will perform in different enclosures:

• Determine the best enclosure type (sealed, ported, or bandpass).
• Optimize frequency response and efficiency.
• Prevent mechanical or thermal failure through proper design.

Conclusion

Mastering TS parameters allows you to design speaker systems that meet specific performance criteria. For detailed calculators and tools, explore our Audio Tools section.