# Reading a response

> How to read an SPL curve in 00 Simulator: how F3 and F10 are measured, what radiation space and distance do, and what bumps and dips mean.

Source: https://simulator.00aud.io/docs/start/reading-a-response

A response is the level a design plays at each frequency. The **SPL (dB)** tile draws one for every visible enclosure, at its input power, the listening distance and the radiation space you set. This page reads one curve from end to end.

_Figure: The SPL tile for the vented example at 1 W, with its reference level and the −3 dB and −10 dB lines that set F3 and F10._

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

| Point | Level | Frequency |
| --- | --- | --- |
| Reference: loudest octave average | 88.1 dB | 249–499 Hz |
| F3 | 85.1 dB | 30.3 Hz |
| F10 | 78.1 dB | 24.9 Hz |

## The curve

- Frequency runs left to right on a log scale, so every octave is the same width: 20 to 40 Hz takes as much room as 200 to 400 Hz.
- Level is sound pressure in dB at the listening distance. The [vented example](https://simulator.00aud.io/app?template=vented&power=1) at 1 W is flat at about 88 dB and rolls off below 32 Hz, its tuning.
- Level follows power: ten times the power adds 10 dB and twice the power about 3 dB. The shape does not change, because the model is linear.
- Hover the tile to read the level at a frequency. Each visible enclosure draws its own curve in its colour.

## F3 and F10

F3 and F10 are where the curve has fallen 3 dB and 10 dB below its reference level. 00 Simulator takes the reference from the loudest one-octave stretch of the curve, averaged: for the vented example that is 88.1 dB between 249 and 499 Hz. With the default Auto reference, it uses the outer crossings across the simulated range. An internal dip does not set an edge, but a separate lobe above the threshold can move one.

- Turn on **F3** in the SPL tile’s header to mark F3 and F10 on every visible enclosure. The **F-point settings** cog beside it adds F6 or a custom level.
- Bandpass boxes and horns pass a band, so they get two marks for each level: a low edge (F3L) and a high edge (F3H).
- Under **Advanced** in the same settings, **Auto · loudest octave average** is the default reference. **Selected band average** averages a band you choose, and **Response peak** measures down from the highest point. Summary tiles always use Auto.
- The **Metrics** tile compares visible designs by one measure at a time; choose F3 or F10 to compare their extension.

Each example at its own power, half space, 1 m, with the default Auto reference. Bandpass and horn rows show both edges where both fall between 10 Hz and 500 Hz.

| Example | Power | F3 | F10 | Reference level |
| --- | --- | --- | --- | --- |
| [Sealed](https://simulator.00aud.io/app?template=sealed) | 1 W | 62.2 Hz | 33.8 Hz | 85.4 dB |
| [Vented](https://simulator.00aud.io/app?template=vented) | 1 W | 30.3 Hz | 24.9 Hz | 88.1 dB |
| [Passive Radiator](https://simulator.00aud.io/app?template=passive-radiator) | 1 W | 63.8 Hz | 34.9 Hz | 83.1 dB |
| [Bandpass](https://simulator.00aud.io/app?template=bandpass) | 100 W | 38.9 and 92.2 Hz | 27.2 and 134 Hz | 111.9 dB |
| [Tapped Horn](https://simulator.00aud.io/app?template=tapped-horn) | 100 W | 37.2 and 249 Hz | 32.8 Hz | 121.4 dB |
| [Multiple-Entry Horn](https://simulator.00aud.io/app?template=multi-entry-horn) | 50 W | 70.4 and 366 Hz | 59.3 Hz | 127.3 dB |

> **When the high edge jumps** The tapped horn’s F3H lands at 249 Hz because a second lobe above its band comes back within 3 dB. With **Selected band average** set to 40–110 Hz, F3 reads 37.3–117 Hz. For horns and narrow bandpass boxes, pick the band you mean to use.

## Radiation space and distance

The **Radiation space** setting represents how much space the speaker radiates into. For boxes it applies the level offsets below; for horns it also changes the mouth loading, so the response can change shape. It is in the **Environment** section of the Driver panel and applies to every enclosure in the workspace; the default is half space.

Box-model level offsets relative to full space. These are idealised boundary conditions; the model does not include room modes, reflections or the speaker’s directivity.

| Radiation space | Box-model gain | Where the speaker is |
| --- | --- | --- |
| **Full space** | +0 dB | Away from every surface, such as a speaker flown outdoors. |
| **Half space** | +6 dB | On the floor, or flush in one large surface. |
| **Quarter space** | +12 dB | On the floor against one wall. |
| **Eighth space** | +18 dB | In a corner: the floor and two walls. |

**Listening distance** in the same section sets where the level is read, from 0.1 to 50 m. Level falls 6 dB each time the distance doubles, so 2 m reads 6 dB below 1 m. Distance moves the SPL and Max SPL curves up and down without changing how hard the driver or the port works.

> **Compare like with like** The example curves on this page use half space at 1 m; other figures state their own settings. When comparing a datasheet or measurement, match space and distance first. In the box model, full space reads 6 dB below half space at the same distance. For horns the difference varies with frequency because the mouth loading changes too.

## Bumps and dips

_Figure: The vented example tuned to 32 Hz and the same box tuned to 45 Hz, which adds a hump above the roll-off._

The same 55 L box and driver at 1 W, half space, 1 m. Simulated when this page was built.

| Tuning | F3 | Hump above the level at 200 Hz |
| --- | --- | --- |
| 32 Hz | 30.3 Hz | none |
| 45 Hz | 40.3 Hz | +4.2 dB at 48.7 Hz |

- _A hump above the roll-off_ means the box is underdamped: a vented box tuned high, or a sealed box that is too small for its driver. Tuned to 45 Hz, the vented example gains a 4.2 dB hump at 48.7 Hz and loses its deepest bass: F3 rises from 30.3 Hz to 40.3 Hz.
- _Ripple and dips inside a band_ come from resonances along a horn’s path, or from two tunings set too far apart in a sixth-order bandpass box. Small ripple is normal; a deep dip is a hole in the band.
- _A dashed line marked PR_ on a vented box is the port’s first pipe resonance, where a real port can add a narrow peak of its own. For the vented example it sits at 482 Hz, well above the band a subwoofer uses.
- Peaks on the **Impedance** tile mark the tunings. The vented example has peaks at 19.1 Hz and 49.9 Hz with a dip at 31.6 Hz, close to its 32 Hz tuning. The sealed example has one peak, at 53.6 Hz: its resonance in the box, not the driver’s Fs.

A room adds peaks and dips of its own, often larger than any here. The simulation shows the speaker, not the room: [From simulation to a build](https://simulator.00aud.io/docs/start/simulation-to-build) covers what it leaves out and how to compare with a measurement.

## Ask your AI

**Ask your AI**

Your assistant reads the same curves through the 00 Simulator connector.

> Using 00 Simulator, simulate my open workspace and tell me each enclosure’s F3 and F10, the level of its loudest octave, and any dip deeper than 3 dB inside its band.