Speaker Port Velocity Calculator

Direct answer. Enter a modeled cone area, one-way peak excursion, frequency and driver count, then the clear dimensions and count of the ports. The tool estimates peak volume flow, mean speed through the total port area and Mach number.

Method. For sinusoidal piston displacement, peak volume flow is Q = 2 pi f Sd Xpeak N. Mean port speed is u = Q / Aport,total, and Mach is u / c. Calculations use SI internally; air temperature changes the modeled speed of sound.

Sources. OpenStax University Physics derives sinusoidal peak speed as amplitude times angular frequency, with omega = 2 pi f. NASA Glenn defines Mach as flow speed divided by local speed of sound. The port-flow equation applies that kinematics relation to piston area.

Worked example. At 30 Hz, a 530 cm² piston moving 12 mm one-way peak produces about 0.120 m³/s peak flow. A single 100 mm port gives about 15.3 m/s in the uniform-flow estimate; two equal ports halve that speed.

Interpretation. The comparison field is your own project reference. Use it to compare alternatives consistently, not as proof that a port will or will not be audible.

The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.

Measurement units

Metric: cm² and mm

Port shape

Round

Effective cone area Sd

530 cm² or in²

Modeled one-way peak excursion

12 mm or in

Modeled frequency

30 Hz

Identical in-phase driver count

1

Round-port inside diameter

100 mm or in

Slot inside width

200 mm or in

Slot inside height

40 mm or in

Identical port count

1

Air temperature

20 °C

Your comparison Mach value

0.1

Primary result: Estimated peak port air speed: 15.26 m/s.

• Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
• Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
• When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.

This is a uniform, incompressible-style mean-flow estimate driven by an entered excursion scenario. It does not predict actual driver excursion, port compression, turbulence, boundary-layer loss, flare behavior, resonances, bends, nearby-wall effects or audible chuffing. Real flow varies across the port and over the waveform. Validate the finished enclosure with an electro-acoustic model and measurement.