# Vented 12-inch subwoofer

> Tune the vented subwoofer example, size its ports, check the duct length and protect the driver below tuning.

Source: https://simulator.00aud.io/docs/cookbook/vented-subwoofer

Use the Ciare 12.00SW in the 55 L vented example to explore three linked decisions: tuning, port area and low-frequency protection. A deeper response is only useful if the port fits and the cone stays within its limits.

- **Starting box:** 55 L net, tuned to 32 Hz
- **Starting port:** One 10 cm round port, 35.6 cm long
- **Comparison conditions:** 100 W, half space at 1 m

## Start with the example

1. **Open the starting design.** [Open the vented example](https://simulator.00aud.io/app?template=vented&power=100), at 100 W. Keep its driver and volume fixed for this comparison.
2. **Read the response and its costs.** Compare **SPL (dB)**, **Excursion** and **Port Velocity**. The cone moves least near tuning, while the port moves much of the air. Below tuning, output falls and cone travel rises.
3. **Keep a reference.** Use **Duplicate** to keep the original before changing the copy. Match input power and environment when comparing.

## Tune and size the port together

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

The app’s controls lower **Tuning** to 28 Hz, then change **Number of ports** to two. The original response stays visible for comparison.

All at 100 W over 10–400 Hz. The port warning is 17 m/s; the driver’s Xmax is 13.5 mm.

| Design | F3 | Each port’s length | Peak port speed | Peak cone travel |
| --- | --- | --- | --- | --- |
| 32 Hz, one port | 30.3 Hz | 35.6 cm | 20.1 m/s at 30.1 Hz | 15.0 mm |
| 28 Hz, one port | 29.6 Hz | 48.3 cm | 18.6 m/s at 26.1 Hz | 15.2 mm |
| 28 Hz, two ports | 29.6 Hz | 102.6 cm | 9.3 m/s at 26.1 Hz | 15.2 mm |

A lower tuning changes the response shape and needs a longer port. Increasing the total port area reduces air speed, but adds still more length at the same tuning. Check **Port length** and **Gross volume** before deciding the change is practical.

> **F3 is not the whole result** A lower tuning can trade level higher in the bass for more output lower down. Compare the full SPL curve over your intended band, not only a single cutoff number.

## Protect the cone below tuning

Now double the drive to 200 W on the 28 Hz design with two ports. Compare it with a 28 Hz fourth-order Butterworth high-pass. The filter reduces low-frequency output as well as travel.

_Figure: Cone excursion of the lower-tuned, two-port design, with and without a high-pass filter, against the driver’s Xmax._

Ciare 12.00SW, 55 L tuned to 28 Hz, two 10 cm ports, 200 W, half space at 1 m. Simulated when this page was built.

| Excursion with and without a high-pass filter | Peak | At |
| --- | --- | --- |
| No filter | 21.5 mm | 10 Hz |
| 28 Hz high-pass | 5.6 mm | 40 Hz |

Across 10–400 Hz, peak travel changes from 21.5 mm at 10.0 Hz to 5.6 mm at 40.2 Hz. Compare that with 13.5 mm Xmax, then inspect the filtered SPL and port speed too. This is a filter comparison, not a certified operating limit.

Add the intended **High-pass** in the enclosure’s filter controls and check **Max SPL (dB)** and **Headroom**. A filter does not remove the need to check the thermal limit and amplifier load. [EQ and filters](https://simulator.00aud.io/docs/guides/eq-and-filters) explains the controls.

## Before you cut wood

- Allow for the air volume, ducts, driver displacement and bracing inside the walls.
- Use end corrections that match the physical port ends. Keep enough clearance around the openings and check the duct’s first resonance against the operating band.
- Save the final driver, port, filters and power together, then measure the finished tuning and response.
- If the required ports cannot fit, compare a larger box or a passive radiator design instead of accepting a noisy port.

**Ask your AI**

> Using 00 Simulator, compare my selected vented enclosure with two ports and a lower tuning without saving. At its current power, report the SPL changes, port lengths, peak port air speed and peak cone excursion. Then compare a high-pass filter and explain the output it gives up.