# Model and limits

> What 00 Simulator calculates, how the linear model treats boxes and horns, and which results still need measurements.

Source: https://simulator.00aud.io/docs/reference/model-and-limits

00 Simulator predicts the response of the driver and acoustic system you describe. Use it to compare designs and find likely limits, then measure the finished cabinet and system.

## What is modelled

| Part | Model | Practical limit |
| --- | --- | --- |
| Driver | An electrical and mechanical network built from the T/S parameters, coupled to the enclosure. | It depends on the quality and consistency of the driver data. |
| Box chambers | Lumped air compliance, with the configured losses and connected ports or passive radiators. | A chamber is not a three-dimensional cabinet with panel vibration and internal standing waves. |
| Ports | A lumped port model, or a distributed duct when selected. | Neither predicts audible turbulence, chuffing or large-signal flow compression. |
| Horns | A one-dimensional plane-wave solution along each path and its changing cross-section. | Bends, higher-order modes and three-dimensional mouth directivity are outside this model. |
| Electrical drive | Driver count and wiring, series resistance and capacitor, and the configured filters. | The amplifier is not a full clipping, current-protection or power-supply simulation. |
| Listening conditions | Radiation space, distance, and optional baffle-step correction. | Room modes, reflections and listening-seat cancellations need measurement. |

Horns carry an **Alpha** label in the enclosure selector. Check the relevant topology and diagnostic pages before using a design for a build.

## What linear means here

At fixed settings, increasing drive raises SPL and motion without changing the shape of the response. The model does not suddenly compress or distort when the cone crosses Xmax. That is why the output curves and limit checks must be read together.

_Interactive walkthrough in the page: the simulator's own tiles running a short demo._

The same vented design at changing drive: SPL rises, while excursion and port air speed reveal the cost. This demonstration does not save changes to your workspace.

> **A warning line is not a nonlinear simulation** Xmax and port-speed thresholds mark conditions to investigate. They do not predict a distortion percentage, the sound of a port, or the exact point of mechanical damage.

## The upper response

For box designs, **Settings › Simulation… › Non-horn upper response** offers two readings of the upper acoustic response.

| Setting | What it means |
| --- | --- |
| **Estimated · BITS frequency limit** | Estimates an ideal driver response without the acoustic roll-off from coil inductance, then applies the published upper-frequency limit when the driver data provides one. The chamber response and EQ still apply. |
| **Physical model** | Uses the driver’s physical electrical and mechanical model, including its coil inductance. Horns always use this mode. |

The estimate changes acoustic magnitude and SPL limits; electrical impedance, cone motion and phase remain physical results. Neither mode replaces a measured midrange or treble response. Changing **Upper frequency** under **Settings › Display…** extends the calculation range, not its accuracy.

## Output limits

| Check | What it tells you | What it does not tell you |
| --- | --- | --- |
| [Excursion](https://simulator.00aud.io/docs/reference/tiles/excursion) | Travel compared with the entered Xmax, and optional further mechanical limits. | How distortion changes with displacement in the actual driver. |
| [Max SPL](https://simulator.00aud.io/docs/reference/tiles/max-spl) | The lower of excursion and the selected thermal ceiling, one frequency at a time. | A broadband music rating or a port-noise limit. |
| [Headroom](https://simulator.00aud.io/docs/reference/tiles/headroom) | Average and peak demand compared with its configured clean and maximum thresholds. | A guarantee that the system sounds clean under every signal. |
| [Port Velocity](https://simulator.00aud.io/docs/reference/tiles/port-velocity) | Peak air speed compared with a warning threshold. | The effect of the exact flare, surface finish or obstructions on audible noise. |

**Voice coil temperature** in the Max SPL settings changes the resistance used for the capacity calculation. It is a specified thermal condition, not a time simulation of a coil warming during a track. The normal SPL response stays at its regular model condition.

## Validation and measurement

The [validation pages](https://simulator.00aud.io/validation) show comparison cases and their scope. Agreement with another simulator checks a particular model, driver and configuration; it does not prove every enclosure or a finished physical build.

1. **Match the inputs.** Use the same driver data, net volume, port ends, losses, electrical drive, radiation space and distance before comparing tools or measurements.
2. **Check the physical build.** Measure impedance to check resonance and tuning. Verify internal volume and port dimensions, and investigate leaks or unexpected peaks.
3. **Compare acoustic response.** Import a measured trace with its distance and space recorded. Compare shape as well as level, and account for the room and microphone position.
4. **Increase level gradually.** Check amplifier clipping, driver noise and port noise as level rises. The small-signal curve alone cannot approve the final operating limit.