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Speaker parameters

The driver datasheet values used to predict fit, box behavior, output, and limits.

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Why it matters

Parameters turn a driver from a guess into a design input.

They help an author decide whether a driver fits a sealed box, a ported box, a subwoofer, a midrange, or a small portable build. They also show where the driver may run out of excursion, power handling, or clean working range.

How it works

The most common driver parameter set is called Thiele/Small, often written as T/S.

Useful basics:

  • Fs: free-air resonance of the driver.
  • Qts: overall damping. It hints at sealed or ported fit.
  • Vas: equivalent air compliance. It affects box size.
  • Re: DC resistance of the voice coil, not the same as nominal impedance.
  • Sd: cone area.
  • Xmax: linear excursion limit.
  • Pe or RMS power: thermal power rating, not a clean output guarantee.
  • SPL or sensitivity: output from a known input.

Common mistakes

Simple example

Speaker driver A speaker driver is the moving part that turns amplifier power into air movement. Woofers, midranges, tweeters, and full-range drivers are all speaker drivers. Impedance Impedance is the electrical load the amplifier sees. It changes with frequency, so a speaker marked 8 ohms is not 8 ohms everywhere. Sensitivity Sensitivity tells you how loud a speaker gets from a known input. It helps estimate output, amplifier needs, and how well drivers will match. Sealed vs ported A sealed box traps the rear wave in an airtight cabinet. A ported box uses a tuned vent to add bass output around tuning.

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