# Port Volume Velocity

> Distinguish the volume of air flowing through a port from its speed, and see why larger ports can keep the same flow while reducing noise risk.

Source: https://simulator.00aud.io/docs/reference/tiles/port-volume-velocity

This tile shows how much air the port moves each second. It helps explain the port’s contribution to the sound; Port Velocity is the tile to use for air speed and noise risk.

- **Shows:** How much air flows through a vented box’s port each second, at its peak, at each frequency.
- **Healthy when:** It has no limit of its own. The peak sits near the tuning, where the port takes over from the cone.
- **If it is not:** Check the tuning and filters if the curve differs from the alignment you intended. For port noise, read **Port Velocity**.

## The tile

_Figure: Total port volume flow with one and two ports, at the same tuning and power._

Vented example at 100 W, half space, 1 m. Only port count changes. Simulated when this page was built.

| Port Volume Velocity | Peak | At |
| --- | --- | --- |
| One port | 157.6 L/s | 30 Hz |
| Two ports, same tuning | 157.6 L/s | 30 Hz |

The vented example’s total port flow peaks at 157.6 L/s near 30.1 Hz. [Open this example](https://simulator.00aud.io/app?template=vented&power=100). The app uses mL/s, L/s or m³/s to suit the value and shows vented enclosures only.

Volume flow is air speed multiplied by the total open port area. A large opening can carry a large flow at modest speed. There is no warning line for volume flow itself.

## The same flow can need less speed

_Figure: The corresponding air speeds: more opening area lowers speed._

Vented example at 100 W, half space, 1 m. Only port count changes. Simulated when this page was built.

| Port Velocity | Peak | At |
| --- | --- | --- |
| One port | 20.1 m/s | 30 Hz |
| Two ports | 10.0 m/s | 30 Hz |

In these runs the one-port and two-port flow peaks are 157.6 and 157.6 L/s. Their air-speed peaks are 20.1 and 10.0 m/s. More port area must be paired with more length to preserve tuning.

| Change | What moves |
| --- | --- |
| Increase area, keep tuning | Air speed falls; total flow is largely unchanged. |
| Change tuning | The flow peak moves with the new alignment. |
| Change power or EQ | Flow follows the applied signal at each frequency. |
| Read **Cone Velocity** beside it | Multiply cone speed by Sd before comparing it with a volume flow. |

## What to try

| Try | What it changes |
| --- | --- |
| [Compare port sizes](https://simulator.00aud.io/docs/reference/tiles/port-velocity) | At the same tuning a wider port, or a second one, moves the same air more slowly: this curve stays put while **Port Velocity** falls. |
| [Compare with the cone](https://simulator.00aud.io/docs/reference/tiles/cone-velocity) | **Cone Velocity** times the driver’s Sd is the air the cone moves. Near the tuning the port moves far more than the cone. |
| [Change the tuning](https://simulator.00aud.io/docs/boxes/vented) | The peak follows the tuning up or down. |

## Ask your AI

**Ask your AI**

> Using 00 Simulator, preview one and two ports on my vented design at the same tuning and power. Compare total port volume velocity, port air speed and required port length, without saving the change.