Loudspeaker enclosure
The box a driver is mounted in. Its job is to stop the cone's rear wave from cancelling its front wave in open air, and — done well — to shape the low-frequency response. Which box, and how big, is set by the driver's Thiele/Small parameters and solved with a calculator like micka-enclosure-calculator.
The main alignments
- Infinite baffle (the ideal). A wall extending forever, so the rear wave never reaches the front. Unbuildable, but the reference the others approximate loudspeaker-primer-hackaday.
- Sealed / closed box. A practical infinite-baffle approximation; the trapped air adds a spring, raising system resonance. Its tuning is captured by Qtc (a sealed-box design knob in micka-enclosure-calculator). Tends to suit higher-Qts drivers; gentler rolloff, tighter transient.
- Vented / bass-reflex. A tuned port reuses the rear wave to extend bass output near tuning (Bullock alignment in the calculator). Tends to suit lower-Qts drivers; more output, steeper rolloff below tuning.
- Passive radiator. A vented box's cousin: instead of a port, a motor-less diaphragm (a "drone cone") tuned by its mass and compliance reuses the rear energy. Same bass- extension goal as a vent, no port to chuff or grow unwieldy — handy in a small cabinet (chesky-audio-lc2 uses twin 8″ radiators to reach 40 Hz in a bookshelf box).
Construction
The cabinet itself must not sing along: it needs mass and rigidity to avoid resonating, typically MDF, often filled with acoustic wadding to damp internal reflections loudspeaker-primer-hackaday. Mass isn't the only route: chesky-audio-lc2 instead uses a 3D-printed, double-walled, acoustically-inert composite cabinet plus a solid aluminum baffle to kill resonance by material and geometry rather than sheer MDF weight — a real-world attack on the "cabinet as a second instrument" problem. Rockport's Andrew Payor (rockport-enclosure-design-interview) gives the same problem its sharpest statement: stiffness and damping are "mutually exclusive attributes in a single material", so a sandwich composite (stiff skins over a heavy, lossy core) is the way to have both, and a sandwich panel's stiffness rises with the cube of its thickness. His second point is that shape is a separate design axis from stiffness — edge-diffraction and the baffle step are decided by chamfers and baffle geometry, not by mass — and that both are first-party claims resting on one borrowed measurement.
How you choose
Qts points you at sealed vs. vented, Vas sets the ballpark volume, and Fs sets how low it can usefully go. A designer simulates the frequency response, impedance, step response, and group delay for candidate boxes before building micka-enclosure-calculator.
Two things the simulation doesn't know: the room, which adds its own rise below the frequency that fits in it (room-gain), and the tuning frequency's effect on timing — a port's group-delay penalty tracks where the box is tuned, not merely that it has a port (svs-sealed-vs-ported).
Related
edge-diffraction · rockport-enclosure-design-interview · thiele-small-parameters · loudspeaker-driver · micka-enclosure-calculator · group-delay · room-gain · loudspeaker-primer-hackaday · synthesis