The woofer cabinet is the enclosure loading the bass driver, and it shapes how a speaker rolls off, how it behaves near a wall, and how large it has to be for the bass it produces. It appears in the spec table for the 187 passive speakers and 18 powered speakers here that publish it, of which 136 and 15 respectively use some form of port.
Ported designs dominate because a port buys extra output in the bass for very little cost. The main tradeoffs are a steeper roll-off below tuning and the possibility of port noise. Placement is influenced more by the speaker’s total bass response and nearby boundaries than by whether the port faces forward or backward.
Sealed
A closed box with no port and no radiator. The driver works against the trapped air inside, which acts as a spring.
Sealed cabinets typically roll off at about 12 dB per octave below their system resonance. That shallow slope can combine usefully with low-frequency room gain. A sealed box has no port-clearance requirement, but nearby walls still reinforce its bass and can still produce an uneven in-room response. Claims that sealed bass is automatically “faster” or “tighter” are too broad; the final alignment, resonances, output level, and room all matter.
The trade is efficiency and extension. For the same cabinet size and driver, a sealed design gives up meaningful output in the bottom octave compared with a ported one. Only 10 passive speakers and 1 powered speakers here use a sealed woofer cabinet, which reflects how strongly the market favours the extra output a port provides.
Ported, Also Called Bass Reflex
A box with a tuned port. The air in the port resonates near the driver’s low-frequency cutoff and adds roughly 3 to 6 dB of output in that range, which is a large gain for the cost of a hole and a tube.
Two things come with it. The roll-off below the tuning point steepens to about 24 dB per octave, so output disappears faster once you get below where the port works. The port opening also needs enough space for unobstructed airflow, although its direction alone does not determine how close the speaker may sit to a wall:
- Front ported. The opening is less likely to be physically blocked when the cabinet is near the wall behind it. The wall can still increase bass output and excite room modes. ELAC DBR62, JBL 4367 and Revel F208 are front ported.
- Rear ported. Leave enough room for free airflow, following the manufacturer’s guidance where available. There is no universal six-inch minimum: the required clearance depends partly on the port diameter and design. A rear-ported speaker can work near a wall if the opening is not obstructed and its resulting bass balance suits the room. KEF Blade Two Meta, Wharfedale Linton 85 and Klipsch RP-500M II are rear ported.
- Unspecified. Many records list only “ported” without a position. Where that matters for your placement, the manufacturer’s own page linked from the speaker’s card is usually the fastest way to check.
The practical rule is to judge the complete low-frequency response in the intended position. Leave the port physically unobstructed, then listen or measure at the seating position. If the bass is excessive or uneven, change speaker and seat placement first, use the speaker’s boundary controls if it has them, and apply EQ or room correction where appropriate.
Passive Radiator
An alternative resonant bass-reflex alignment in which an undriven cone, with no voice coil and no magnet, replaces the port. Pressure inside the cabinet moves it the way a port’s air column would move, adding output in a similar range without airflow noise from a port opening.
The trade is cost and complexity, because a passive radiator is a real driver-sized component rather than a hole. 11 passive and 1 powered speakers here use one in the woofer cabinet. It is far more common on portable speakers, where cabinet volume is scarce and a port would be impractically small.
A passive radiator is not counted as a driver, for the reasons set out in speaker drivers explained.
Open Baffle
No enclosure at all in the conventional sense. The driver is mounted on a flat panel, leaving the rear wave free to radiate into the room out of phase with the front.
This produces a distinctive dipole radiation pattern that interacts with the room very differently from a box, and it removes cabinet resonance as a variable entirely. What it demands in return is space, because an open baffle speaker needs real distance from the wall behind it to work, and it gives up low bass output unless the baffle is very large. The GR-Research NX-Treme is the example here.
How This Differs From The Subwoofer Enclosure Spec
Subwoofers carry their own Enclosure spec covering the same physics with a wider set of designs, including horn loaded and in-wall types that do not appear on full-range speakers. If you are reading about a subwoofer rather than a bookshelf or floorstanding speaker, subwoofer enclosure types explained is the more detailed page, including the full sealed versus ported argument and every port position in that data.
Where To Look Next
Cabinet design sets what the bass can do, so it reads alongside bass extension explained and frequency response explained. For the drivers the cabinet loads, see speaker drivers explained. For how the room finishes the job the cabinet starts, see how room acoustics affects speakers.
Every speaker’s woofer cabinet is in its spec table, across large bookshelf speakers, medium bookshelf speakers and large floorstanding speakers.
Frequently Asked Questions
Is a sealed or ported speaker better? Neither is better outright. A sealed cabinet usually rolls off at about 12 dB per octave and has no port-clearance requirement. A ported cabinet adds useful output near its tuning point, at the cost of a steeper roll-off below that point and the possibility of port noise. Both still interact strongly with nearby walls and room modes. Ported designs are far more common because that extra output is inexpensive to obtain.
Does port position matter? It matters when the opening is close enough to a surface to restrict airflow, but it does not create a universal wall-clearance rule. Leave a rear port unobstructed and follow the manufacturer’s guidance. For either front- or rear-ported speakers, boundary reinforcement and room modes usually have a larger effect on bass at the listening position.
What is a passive radiator? A passive radiator is an undriven cone with no voice coil or magnet that replaces a port in a resonant enclosure. Cabinet pressure moves it the way a port’s air column would, adding output around the tuning region without airflow noise from a port opening. It costs more than a port because it is a real driver-sized part.
Why do so few speakers use sealed cabinets? Because a port adds meaningful bass output for little manufacturing cost, and buyers reward deeper bass from smaller boxes. Sealed designs give up output in the bottom octave for the same cabinet size, so they tend to appear where a compact, predictable low-frequency roll-off is more useful than maximum extension.