Reference · Tiles
TILEREAR PORTM/SPort Velocity (Rear Chamber)
A sixth-order bandpass can have a quiet front port and a noisy rear one. This tile reads the rear chamber’s port independently.
- Shows
- Peak air speed in a bandpass box’s rear-chamber port, in m/s, at each frequency, against the warning line.
- Healthy when
- The curve stays under the line at the power you will actually use.
- If it is not
- More rear port area, less power, or a high-pass below the band you play.
The tile#
Port Velocity (Rear Chamber)
m/s
- One rear port19.8 m/s at 20 Hz
- Two rear ports9.9 m/s at 20 Hz
The rear port peaks at 19.8 m/s near 19.6 Hz. With two rear ports it peaks at 9.9 m/s. Both use the same rear-chamber volume and target tuning.
Use Port Velocity for the front chamber and this tile for the rear. A sealed rear chamber has no rear-port curve. A rear chamber loaded by a passive radiator belongs on PR Excursion instead.
Read the warning at your working power#
The dashed line is the same adjustable port-speed warning used by the front-port tile, 17 m/s in this example. It is a warning threshold, not a prediction of exactly when a particular port will become audible.
| Change on the rear chamber | Trade-off |
|---|---|
| More port area | Lower air speed at the same tuning, with longer ports. |
| Lower tuning | Moves the low-frequency behaviour and increases required port length. |
| Less input power | Reduces both front and rear port speeds, along with output. |
| A high-pass below the band | Removes demand where little useful sound remains; recheck the lower passband edge. |
Start from a 6th-order bandpassThe bandpass example with its 70 L rear chamber ported too: one 10 cm rear port tuned to 30 Hz, and the 50 L front chamber tuned to 70 Hz, at 100 W. Both ports reach the room, and the rear port’s air passes the dashed 17 m/s line. The grey line is an unchanged copy.
Schematic
Simulating…
SPL (dB)
Simulating…
Port Velocity (Rear Chamber)
Simulating…
The live bench shows how both chambers affect the result.
What to try#
| Try | What it changes |
|---|---|
| More rear port area | On the Rear tab, a second port or a wider one slows the air for the same tuning. Each port gets longer. |
| A high-pass below the band | If the peak sits below the band you play, a high-pass there slows the air for little output. |
| Less power | Air speed follows the square root of power: half the power is about 0.7 times the speed, and 3 dB quieter. |
Ask your AI#
Ask your AI
Using 00 Simulator, check both port velocities in my sixth-order bandpass at its current power. Preview more area on whichever port exceeds the warning, keeping the chamber tunings fixed, and report the new speeds and port lengths.
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