# SPL (dB)

> How to read the SPL tile in 00 Simulator: the level each design plays at your power and distance, its F3 and F10 markers, EQ on the curve and baffle step.

Source: https://simulator.00aud.io/docs/reference/tiles/spl

How loud each design plays at each frequency, at its set power and EQ and your listening distance. It is the tile to judge bass extension and response shape on, and to shape with EQ.

- **Shows:** Sound pressure level in dB at each frequency for every visible enclosure, at its power and EQ, the radiation space and the listening distance.
- **Healthy when:** The curve is smooth through the band you want, and F3 sits where you need the bass to reach.
- **If it is not:** Change the box or tuning for extension and EQ for shape, then check the limits at the power you will use.

## The tile

_Figure: The SPL (dB) tile for the vented example at 1 W, with F3 and F10 marked._

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.

- Vented example, 1 W: loudest octave 88.1 dB

| Curve | Marker | Frequency | Level |
| --- | --- | --- | --- |
| Vented example, 1 W | F3 | 30.3 Hz | 85.1 dB |
| Vented example, 1 W | F10 | 24.9 Hz | 78.1 dB |

The vented example plays 88.1 dB averaged over its loudest octave at 1 W. The level is 3 dB below that at 30.3 Hz (F3) and 10 dB below at 24.9 Hz (F10).

- [Open this example](https://simulator.00aud.io/app?template=vented) in the simulator and switch on **F3** in the tile header for the markers. Hover the curve for the level at a frequency, or click the chart to hold the readout there.
- Each visible enclosure draws its own curve and its own markers, in its colour.
- A multiple-entry horn also draws a dashed line for each amplifier channel beside its solid total. The channels add with their phase, so the total is not the sum of their levels.
- The level is at the **Radiation space** and **Listening distance** set in the **Environment** section of the Driver panel: half space and 1 m unless you change them.

## How to read it

- Read the shape first: where the bass starts to fall, how steeply, and whether there is a hump or a dip on the way. Then read the level.
- F3 and F10 are measured down from each curve’s own loudest octave, not from a fixed level, so a quiet design and a loud one get comparable markers.
- The level follows the power: each doubling adds 3.0 dB. Compare designs at the same power, or on [Transfer Function Magnitude](https://simulator.00aud.io/docs/reference/tiles/transfer-function), which takes the level out.
- This tile does not say whether the driver survives that level. [Excursion](https://simulator.00aud.io/docs/reference/tiles/excursion), [Max SPL (dB)](https://simulator.00aud.io/docs/reference/tiles/max-spl) and [Headroom](https://simulator.00aud.io/docs/reference/tiles/headroom) do.
- It is the response without a room. **Radiation space** adds the gain of nearby walls and floor, but room modes and reflections are not in it.

## F-points

**F3** in the tile header shows or hides the markers. The cog beside it, **F-point settings**, chooses which ones and what they are measured from. On a desktop, **Pin to side** keeps those settings beside the chart.

| Setting | What it does | To start |
| --- | --- | --- |
| **F3**, **F6**, **F10** | Mark where each curve falls 3, 6 or 10 dB below its reference level. | F3 and F10 on, F6 off |
| **Custom** | A level of your own, from 0.1 to 80 dB down. | Off, at 4.7 dB |
| **Baffle step Fc** | Shows or hides the baffle step line, for enclosures that simulate it. | On |
| **Active enclosure only** | Markers for the selected enclosure only, instead of every visible one. | Off |
| **Advanced** › **Reference level** | What the markers are measured down from: **Auto · loudest octave average**, **Selected band average** over a band you type, or **Response peak**. It also lists each enclosure’s reference level and band. | Auto; a typed band starts at 50–100 Hz |

_Figure: The SPL (dB) tile for the bandpass example at 100 W, with F3 and F10 marked at both edges._

B&C 18SW115 in the fourth-order bandpass example, at 100 W, half space, 1 m. Simulated when this page was built.

- Bandpass example, 100 W

| Curve | Marker | Frequency | Level |
| --- | --- | --- | --- |
| Bandpass example, 100 W | F3L | 38.9 Hz | 108.9 dB |
| Bandpass example, 100 W | F3H | 92.2 Hz | 108.9 dB |
| Bandpass example, 100 W | F10L | 27.2 Hz | 101.9 dB |
| Bandpass example, 100 W | F10H | 134 Hz | 101.9 dB |

- Bandpass boxes and horns get two markers for each level, L at the low edge and H at the high edge. The bandpass example is 3 dB down at 38.9 Hz and 92.2 Hz, and 10 dB down at 27.2 Hz and 134 Hz.
- For a narrow bandpass box or a horn with separate humps, **Auto** can pick the wrong octave. Choose **Selected band average** and type the band you mean as the passband; humps outside it are ignored.
- A dip inside the band that falls below a marker’s level does not move the marker: markers show the outer edges, and **Advanced** notes the dip.
- The **Metrics** tile’s F3 and F10 always use **Auto**, whatever this tile is set to.

## Other lines on the tile

- **PR** marks a vented box’s port resonance: the frequency where the air in the port rings like an organ pipe. In the vented example it is at 482 Hz, past the default 400 Hz axis; set **Upper frequency** in **Settings › Display…** to 1 kHz to see it.
- A sixth-order bandpass box marks **Front PR** and **Rear PR**, and a horn with a ported rear chamber marks **Rear PR**. Here PR means port resonance, not passive radiator.
- A box with **Simulate baffle step** switched on, in the **Baffle step** section of the Enclosure panel, gets a line labelled Baffle at its transition frequency.

_Figure: The sealed example’s SPL with baffle step off and on, and the baffle transition line at 364 Hz._

Dayton Audio DCS205-4 in the 15 L sealed example, at 1 W, half space, 1 m. Simulated when this page was built.

- Baffle step off
- Baffle step on, 300 × 450 mm: −6.0 dB at 20 Hz

| Curve | Marker | Frequency | Level |
| --- | --- | --- | --- |
| Baffle step on | Baffle 364 Hz | 364 Hz |  |

On the sealed example, **Simulate baffle step** with the default 300 × 450 mm baffle puts the transition at 364 Hz. Below it the bass wraps round the box instead of going forward: the curve is 3.0 dB lower at the transition and 6.0 dB lower at 20 Hz. The most it takes is **Step depth**, 6 dB to start. It is a smooth shelf; the ripple a real baffle edge adds is not modelled. The [Baffle Layout](https://simulator.00aud.io/docs/reference/tiles/baffle-layout) tile moves the driver on the baffle.

## EQ on the tile

- Every curve includes its enclosure’s EQ and filters that are switched on, whether or not you are editing them.
- Click **EQ** in the tile header to draw the selected enclosure’s filters over the chart and drag them into place. **Exit** puts the tile back.
- Right-click the chart and choose **Add filter** to put a high-pass, low-pass, parametric EQ, shelf or Linkwitz transform at the frequency you clicked.
- The [EQ Editor](https://simulator.00aud.io/docs/reference/tiles/eq-editor) tile is always in this mode. [EQ and filters](https://simulator.00aud.io/docs/guides/eq-and-filters#on-the-graph) covers each handle.

## What moves it

| Change | Effect | Why |
| --- | --- | --- |
| Double the power | +3.0 dB | The whole curve moves with the drive level. |
| Half space to quarter space | +6 dB | One more boundary next to the box. The same at every frequency for a box; a horn’s shape changes too. The app notes the offsets hold best at low frequencies. |
| Double the listening distance | −6.0 dB | Level falls with distance, and the tile reads it at the distance you set. |
| **Simulate baffle step** on | Up to −6 dB below the transition | A box on a stand loses the bass a wall would have sent forward. |
| Tune the vented example to 28 Hz instead of 36 Hz | F3 32.6 Hz → 29.6 Hz | Lower tuning reaches deeper; the port gets longer. |
| A high-pass filter | Less level below its corner | Every filter that is switched on is in the curve. |

## Settings and controls

| Control | Where | What it does |
| --- | --- | --- |
| **F3** | Tile header | Shows or hides the F-point markers. Off on a new tile. |
| **F-point settings** | The cog beside **F3** | Which markers show and what they are measured from ([above](#f-points)). |
| **EQ** | Tile header | Edits the selected enclosure’s filters on the chart. **Exit** leaves. |
| **Y-axis settings** | Tile header | **Auto** fits the curves; **Manual** takes a **Min** and **Max**. Either way the axis stops at 50 dB. |
| **Add filter**, **Add note** | Right-click the chart | A filter, or a note, at the frequency you clicked. |
| **Fix** | Over the chart | A design whose whole response is below 50 dB is left off the chart with a warning in its place. When the cause is a port with no room left (0 L), **Fix** takes you to the port settings. |

## What to try

| Try | What it changes |
| --- | --- |
| [Mark F3 and F10](https://simulator.00aud.io/docs/start/reading-a-response#f3-and-f10) | Switch on **F3** in the tile header to mark where each curve falls 3 dB and 10 dB below its loudest octave. |
| [Shape it with EQ](https://simulator.00aud.io/docs/guides/eq-and-filters) | Click **EQ** in the tile header, or right-click the chart and choose **Add filter**. The curve includes every filter that is switched on. |
| [Check it can play that loud](https://simulator.00aud.io/docs/reference/tiles/max-spl) | This tile is at the set power. **Max SPL (dB)** shows how loud each design can go before excursion or heat stops it. |

## Ask your AI

**Ask your AI**

Your assistant runs the same solver on your own designs through the 00 Simulator connector.

> Using 00 Simulator, simulate my open workspace and tell me each enclosure’s F3, F10 and the level of its loudest octave. Then put the SPL (dB) tile on screen and mark each F3 with a line.