# T/S parameters

> Driver parameter symbols, units, derivation relationships and limits used by 00 Simulator.

Source: https://simulator.00aud.io/docs/reference/ts-parameters

The driver’s small-signal parameters define its electrical and mechanical behaviour. Xmax and the power rating add limits; they do not make the underlying model nonlinear.

## Box and motor parameters

| Symbol | Default input unit | Meaning | Can be derived from |
| --- | --- | --- | --- |
| Fs | Hz | Free-air resonance frequency | Mms, Cms |
| Qts | Unitless | Total quality factor | Qms, Qes |
| Qes | Unitless | Electrical quality factor | Qts, Qms |
| Qms | Unitless | Mechanical quality factor | Qts, Qes |
| Vas | L | Equivalent acoustic compliance volume | Cms, Sd |
| Re | Ω | Voice coil DC resistance | Enter from the data sheet or measurement |
| Le | mH | Voice coil inductance | Enter from the data sheet or measurement |
| Bl | T·m | Motor force factor (BL product) | Re, Qes, Mms, Fs |
| Znom | Ω | Nominal impedance | Enter from the data sheet or measurement |

Re is DC resistance. Znom is the nominal impedance class, not the resistance at every frequency. **Impedance** shows the changing load of the driver in the enclosure. Le describes coil inductance; the non-horn upper-response setting changes how it affects the acoustic estimate, as described in [Model and limits](https://simulator.00aud.io/docs/reference/model-and-limits#upper-response).

## Mechanics and radiating area

| Symbol | Default input unit | Meaning | Can be derived from |
| --- | --- | --- | --- |
| Mms | g | Moving mass including air load | Fs, Cms |
| Cms | mm/N | Mechanical compliance of suspension | Fs, Mms, Vas, Sd |
| Rms | kg/s | Mechanical resistance (damping) | Qms, Mms, Fs |
| Sd | cm² | Effective piston radiating area | Dd |
| Dd | mm | Effective piston diameter | Sd |

Sd is the effective radiating area and Dd is the diameter of that area. They describe the moving piston, not the outside basket diameter. Enter one and let the form derive the other.

Related parameters must agree: Qts = Qms × Qes / (Qms + Qes), and Fs depends on Mms and Cms. The form derives missing values where it has enough information. Do not mix measurements from different samples or coil configurations merely to fill every field.

## Travel and power limits

| Symbol | Default input unit | Meaning |
| --- | --- | --- |
| Xmax | mm | Maximum linear excursion (one-way) |
| Xmech | mm | Mechanical excursion limit (surround/spider bottoming) |
| Xdamage | mm | Excursion threshold for physical damage |
| Pe | W | Rated power handling (RMS) |

Xmax is one-way linear travel, not peak-to-peak travel. Xmech and Xdamage are optional further limits. The [Excursion tile](https://simulator.00aud.io/docs/reference/tiles/excursion) can show these reference lines, while [Max SPL](https://simulator.00aud.io/docs/reference/tiles/max-spl) uses Xmax and the selected thermal rule.

> **Read the manufacturer’s definitions** A mechanical clearance is not interchangeable with a linear excursion rating. Power ratings also depend on the test signal and conditions. Check the original data sheet before using either as a design limit.

## Check the inputs

1. **Match the exact driver.** Check the model suffix, impedance version and coil wiring against the data sheet.
2. **Check the units.** The form offers unit choices. Check whether a source gives litres or cubic feet, grams or kilograms, millihenries or henries, and one-way or peak-to-peak travel.
3. **Inspect derived values.** Open **T/S Parameters** and use **Edit params** to inspect the values. Missing information may be derived; derived information is not a separate measurement.
4. **Compare the resulting alignment.** Use the same driver in a known enclosure, or compare the predicted impedance with a measurement. Fix input mistakes before optimising the box.

**Ask your AI**

> Using 00 Simulator, read the driver data for my selected enclosure. Explain which parameters set its box alignment and which set its output limits. Flag missing or inconsistent values, and do not change the design.