Ported vs. Sealed
Which enclosure design reigns supreme in the low-end kingdom?
In the audio community, few topics spark as much passion as the enclosure type of a subwoofer or loudspeaker. On one side, we have the Sealed (Acoustic Suspension) purists, and on the other, the Ported (Bass Reflex) power-seekers. To choose the right one, we have to look at the physics of air pressure and group delay.
Sealed
Often called “Acoustic Suspension,” these enclosures are completely air-tight. The trapped air acts like a spring, helping the driver return to center.
- Tight Response: Better transient speed.
- Musicality: Accurate phase and timing.
- Small Footprint: Requires less box volume.
Ported
These enclosures feature a “vent” or “port” tuned to a specific frequency, allowing the rear energy of the driver to reinforce the front.
- High Output: Massive SPL at tuning freq.
- Efficiency: Less power for more bass.
- Deep Extension: Hits the sub-sonics harder.
The Roll-Off Factor
The biggest technical difference lies in how the bass “rolls off” as frequencies drop. Sealed enclosures have a gentle 12dB/octave slope, allowing them to benefit from “Room Gain.” Ported enclosures stay louder for longer but drop off a cliff with a steep 24dB/octave slope once they go below their tuning frequency.
Group Delay & Transient Response
Group delay is the time it takes for a frequency to reach your ears. Sealed boxes have near-zero delay, while ported boxes introduce a slight “smear” near the port frequency.