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We’re still updating and improving these pages, they are intended as general guidelines to help with the understanding of T&S Parameters and their relevance to speaker design. In some cases, a simplified explanation or example is used to illustrate a point, and may not be 100% accurate in all circumstances., BL – Motor Strength or […]

What Is Sd? Sd (Effective Diaphragm Area) is the active surface area of a speaker cone that moves air to produce sound. It’s usually measured in square meters (m²), but sometimes also specified in square centimeters (cm²). Sd is most often used for calculating other TS parameters, and its fairly common for all woofers with […]

Qms represents the mechanical damping of a speaker driver, determined by the losses in the suspension system (spider & surround). It indicates how well the driver’s mechanical components control cone movement at resonant frequency (Fs). What Qms Tells Us About a Driver How Qms Affects Speaker Design Qms works alongside Qes (electrical damping) to determine […]

Cms is a measure of the suspension compliance. Compliance is the opposite of stiffness. A driver with a stiff cone suspension will have a low Cms, and a driver with a ‘loose’ cone suspension will have a higher Cms. Vas is known as the compliance equivalent volume, and is specified in litres. Cms is proportional […]

Xlim (also called Xmech or Xdamage) represents the absolute maximum excursion a driver can reach before mechanical failure occurs. It accounts for physical limits such as: Unlike Xmax, which defines the linear range of motion before distortion increases, Xlim marks the point of no return—exceeding it risks permanent damage to the driver. For subwoofers and […]

Vd represents the maximum volume of air a driver can move within its linear operating range, calculated as: Where: A higher Vd means the driver can displace more air, which is essential for deep bass reproduction. This makes Vd particularly useful for comparing subwoofers, as it directly correlates with low-frequency output capability. Since this formula […]

The resonant frequency (Fs) is the frequency at which a speaker cone and voice coil naturally oscillate with minimal resistance. At this frequency, the driver moves more easily, requiring less energy to reach high excursion. Ever seen that famous footage of a bridge wobbling like jelly before collapsing? That’s a classic example of resonance in […]

Pe – Power Handling Capacity Pe represents the thermal power handling capacity of a speaker driver, measured in watts (W). It indicates how much continuous power the voice coil can handle without overheating or suffering permanent damage. The test is done in a controlled environment with specific cabinet volume and controlled room temperature. The test […]

Qes – Electrical Quality Factor Qes represents the electrical damping of a driver at its resonant frequency (Fs). It describes how efficiently the voice coil and magnet system control cone movement, with lower values indicating stronger motor control and higher values indicating weaker electrical damping. How Qes Affects Speaker Performance Qes and Its Relationship to […]

Efficiency Bandwidth Product (EBP) is a useful guideline to determine whether a speaker driver is better suited for a sealed, ported (bass reflex), or even horn-loaded enclosure. It provides a quick way to assess how the balance between resonant frequency (Fs) and electrical damping (Qes) influences enclosure suitability. How to Calculate EBP Where: A higher […]