# Power and limits

> Set the input power for each design in 00 Simulator, then use Max SPL and Headroom to see how loud it can play and which limit stops it first.

Source: https://simulator.00aud.io/docs/guides/power-and-limits

Set how hard each design is driven, then find how loud it can go and what stops it: cone travel, voice coil heat or port air. Power is set per enclosure, so two designs on the same tiles can be at different levels.

## Set the power

1. **Select the enclosure.** Power belongs to each enclosure, not to the workspace. Click its row in the enclosure list.
2. **Open Power.** In the Driver panel, open **Power**. Its header shows the current watts, so you can read it with the section closed.
3. **Set the input power.** Type a value in **Input power**, drag the slider, or click one of the numbers under it. The slider is logarithmic, from 0.01 W to 100 kW, so each tenfold step in watts is the same distance.

- **Load voltage**, at the foot of the section, is the drive voltage that power works out to.
- **Series resistance** stands for the cable and the amplifier’s output, from 0 to 10 Ω; it starts at 0.1 Ω.
- **Series capacitor** puts a capacitor between the amplifier and the drivers, with its **Capacitance** (0.1 µF to 100,000 µF) and **ESR** (0 to 10 Ω). It starts at a stock value sized for the load: 1000 µF for the Ciare 12.00SW’s 3.3 Ω coil.
- With several drivers in one box, the input power is the total for all of them, shared equally. A multiple-entry horn has a power row for each driver, with a button that mutes it, and the header shows the total.
- On a phone, tap the watts in the dock to open the same control.
- Someone viewing your share link can change the power to hear your design at their level. The box itself stays as you made it.

## What power changes

More power raises the SPL curve without changing its shape. In the [vented example](https://simulator.00aud.io/app?template=vented), doubling the power from 100 W to 200 W adds 3.0 dB of level, and ten times the power adds 10.0 dB. The cone’s travel and the port’s air speed grow with the square root of power: both are 1.41 times as much for the same doubling.

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

The app’s own SPL, Excursion and Port Velocity tiles running the vented example in your browser as the power goes from 1 W to 200 W. Nothing here is saved.

> **Compare designs at the same power** Each enclosure keeps its own power. Before you compare two designs on the same tiles, set both to the same **Input power**, or to the power each will really get.

## How loud can it go: Max SPL

1. **Add the tile.** Add **Max SPL (dB)** with **Add tile**. Its curve is the loudest each design can play at each frequency, one frequency at a time, before the cone passes Xmax or the voice coil passes its thermal limit.
2. **Turn on Limits.** Click **Limits** in the tile’s header to draw the two ceilings, heat dashed and Xmax dotted. The Max SPL line follows whichever is lower, so you can see which one stops the design at each frequency.
3. **Check the thermal rule.** Open the tile’s **Settings**. **Thermal limit** chooses how the driver’s power rating becomes a heat ceiling, and **Voice coil temperature** (20–300 °C) models a hot coil. Xmax applies in every rule.

How the rules differ, and why the coil heat budget is lower than the rating: [Limits: travel, heat and air](https://simulator.00aud.io/docs/start/limits).

| Thermal rule | Matches | Its ceiling for the Ciare 12.00SW |
| --- | --- | --- |
| Real input power (default) | Hornresp | 2,000 W into the driver, its rating |
| Constant voltage | WinISD | 81.2 V at every frequency |
| Coil heating | Estimate | 1,029 W of heat in the coil |

_Figure: The vented example’s SPL at 10, 100, 1000 W against its Max SPL line. Each tenfold step in power lifts the SPL curve by 10 dB; the Max SPL line stays put._

Ciare 12.00SW in the 55 L vented example tuned to 32 Hz, half space, 1 m. Simulated when this page was built.

| Frequency | Max SPL | SPL at 10 W | SPL at 100 W | SPL at 1000 W |
| --- | --- | --- | --- | --- |
| 20.0 Hz | 93.7 dB | 80.1 dB | 90.1 dB | 100.1 dB |
| 32.0 Hz | 120.7 dB | 96.1 dB | 106.1 dB | 116.1 dB |
| 50.0 Hz | 117.9 dB | 96.3 dB | 106.3 dB | 116.3 dB |
| 100 Hz | 122.4 dB | 96.9 dB | 106.9 dB | 116.9 dB |

Where an SPL curve rises above the Max SPL line, that power asks for more than the design can give. Here that first happens at 100 W, below 11.8 Hz; at 1000 W it is below 27.4 Hz. Low down the line is set by Xmax, so it is the cone that runs out first. The Max SPL line itself does not move with **Input power** or EQ: at 50 Hz it reads 117.9 dB at 10 W and at 1000 W.

> **Max SPL leaves out the port** Port air speed is not part of Max SPL. At 200 W the vented example is well under its Max SPL line from 32 Hz up, but its port is already past 17 m/s. Check **Port Velocity** too, or use Headroom, which counts it. [Fix a noisy port](https://simulator.00aud.io/docs/guides/noisy-port) brings it back under.

## Check a listening level: Headroom

Max SPL answers “how loud at most”. **Headroom** answers “can it play this level cleanly”, for music with peaks above its average, and it counts every limit, port air speed included.

1. **Add the tile.** Add **Headroom** with **Add tile**.
2. **Set the target.** Open its **Settings**. Under **Target level**, **Average** starts at the level the design already plays, at its loudest point. **Crest** is how far the peaks rise above the average, 12 dB unless you change it, and **Distance** is where you listen, 1 m to start with.
3. **Read the bands.** The coloured bands are what the design can play at each frequency: **Clean**, then **Threshold**, then **Over max**. Its average level is the solid line and its peaks the dashed one, drawn red where they are over the limit; **Tgt avg** and **Tgt peak** mark your target. Wherever the dashed line leaves the clean band, a limit is in the way.

> **The target and the power move together** Type a new **Average** and the enclosure’s **Input power** changes so its loudest point reaches it. Change the power and the target follows. Each enclosure keeps its own target.

The Headroom tile’s default limits, under **Limits** in its settings. Between the two columns is **Threshold**.

| Limit | Clean up to | Over max above |
| --- | --- | --- |
| Thermal power | 0.5 × Pe | 1 × Pe |
| Driver excursion | 1 × Xmax | 1.125 × Xmax |
| Port velocity | 17 m/s | 30 m/s |
| PR excursion | 1 × PR Xmax | 1.25 × PR Xmax |

## What limits what

| Limit | Where you see it | As power goes up | What helps |
| --- | --- | --- | --- |
| Cone travel past Xmax | **Excursion**; the Xmax line on **Max SPL (dB)**; **Headroom** | Grows with the square root of power | A high-pass below the tuning ([EQ and filters](https://simulator.00aud.io/docs/guides/eq-and-filters)); less power |
| Voice coil heat | The thermal line on **Max SPL (dB)**; **Thermal power** in **Headroom** | Grows in step with power | Less power; more drivers to share it (**Number of drivers**); a driver with a higher rating |
| Port air speed | **Port Velocity**; **Headroom**. Not in Max SPL | Grows with the square root of power | More port area, less power ([Fix a noisy port](https://simulator.00aud.io/docs/guides/noisy-port)) |
| Passive radiator travel | **PR Excursion**; **Max SPL (dB)**; **Headroom** | Grows with the square root of power | Less power; see [Passive radiator](https://simulator.00aud.io/docs/boxes/passive-radiator) |

Which limit comes first depends on the design and the frequency. The vented example runs out of cone travel below its 32 Hz tuning and of port air speed at it, long before its voice coil gets hot. Read the limits at the power you mean to use.

> **The limits are warnings, not ratings** The model is linear: a real driver softens as it nears Xmax, a hot coil compresses the output, and a port compresses before it chuffs. Design to stay clear of the lines rather than to sit on them.

## Ask your AI

**Ask your AI**

Your assistant runs the same solver at other powers through the 00 Simulator connector, without changing your design.

> Using 00 Simulator, run each enclosure in my open workspace at 50 W, 100 W and 200 W without saving, and tell me for each power the peak cone excursion against Xmax, the peak port air speed against 17 m/s, and the Max SPL at 50 Hz.