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.
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
thiele-small-parameters · loudspeaker-driver · micka-enclosure-calculator · group-delay · room-gain · loudspeaker-primer-hackaday · synthesis