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Using the site

Finding enclosures

Catalog #: All enclosures as cards. Filter by category (sub · kick · mid · top) to narrow the list. Each card links to the full design page with spec table, curves, plans, and driver info.
Find by constraints #: Filter on hard numbers: F3, max SPL, internal volume, driver size and count, topology, and tags. Sort by any metric including efficiency densities (dB/L, dB/kg) to find the best design for a given constraint.
Design space #: Scatter plot of any two metrics across the full catalog, with Pareto frontier highlighting. Good for spotting which designs are genuinely best on two axes at once.

Comparing builds

Compare enclosures #: Overlay response curves (SPL, phase, impedance…) from multiple enclosures. Measurements are prioritised over sims when both exist. Optional peak normalisation lets you compare shapes regardless of absolute level.
Compare drivers #: T/S parameters side by side plus a radar chart, up to 4 drivers. Links are shareable via ?ids= in the URL.

Drivers & horns

Driver catalog #: Cone · compression · horn tabs with filter and sort. Each driver page shows full specs, derived hints (EBP, sealed Vb), and every enclosure in the catalog that uses it.
Substitute candidates #: Every driver and enclosure page lists drop-in alternatives (same size for cones, same exit for compression drivers), ranked by parametric similarity and tiered close · usable · risky. Flags warn when impedance, power handling, or Xmax regress.
Horn ↔ compression driver matching #: Horn pages list compatible compression drivers and vice-versa, matched on throat exit diameter. No stored link, derived live from the specs.

Planning a rig

Stack builder #: Assemble a full rig from catalog boxes with per-line quantities. The state is encoded in the URL so builds are shareable. The summary covers cabinet count, weight, transport volume, plywood sheets, bandwidth, and power-summed max SPL with per-category array gain.
Amplifier matching #: For each line, every series/parallel wiring of the cabs is shown with the resulting load rated ok · caution (below 4 Ω) · danger (below 2 Ω) · inefficient (above 16 Ω), plus recommended amp channel sizing.
Crossover suggestions #: One crossover point per adjacent band pair: the enclosure's stated value when available, otherwise the geometric mean of the overlap range, clamped to compression driver protection floors. Spectral gaps are reported rather than papered over.
Predicted system response #: Per-band curves plus a composite. The LR4 toggle applies ideal Linkwitz-Riley 4th-order filters at the suggested crossover points and shows the coherent sum.

Data & provenance

Measured vs sim badges #: Every enclosure is marked measured or sim. Measurements come from REW or Klippel; sims from Hornresp or AkAbak. The two are never blended on the same curve.
Exports #: Compare and stack views export CSV or JSON. The stack also has a print-friendly sheet. Raw data is available via JSON APIs: /api/manifest.json, /api/drivers.json, /api/horns.json, /api/curves/<slug>.json.

Glossary

The vocabulary behind the specs: enough to read a datasheet and size a rig.

Driver parameters

Fs (Hz) #: Free-air resonance of the driver: the frequency where the moving mass and suspension naturally resonate. A driver makes little useful output below Fs in most boxes, a sub driver wants Fs under ~40 Hz.
Qts / Qes / Qms #: How damped the driver's resonance is: Qes is electrical damping (motor strength), Qms mechanical (suspension losses), Qts the combination. Qts is the single most important matching parameter when swapping drivers, a box designed around Qts 0.35 behaves differently with a 0.5 driver.
Vas (L) #: Equivalent compliance volume: the volume of air with the same springiness as the driver's suspension. Together with Qts and Fs it sets the box volume and tuning a driver wants.
Xmax (mm) #: How far the cone can travel (one way) while the voice coil stays in the magnetic gap. Beyond it output stops rising and distortion climbs fast. Xmax bounds a sub's maximum clean SPL at low frequencies.
Sd (cm²) #: Effective radiating area of the cone. SPL capability at low frequencies is set by Sd × Xmax (displaced volume): two 15″ drivers move roughly as much air as one 21″.
Sensitivity (dB) #: SPL at 1 m for 1 W (2.83 V into 8 Ω) input. 3 dB more sensitivity = same loudness for half the amp power. Horn loading trades box size for sensitivity, which is why scoops and horns rule freeparty rigs.
EBP #: Efficiency Bandwidth Product: Fs ÷ Qes. A rule of thumb for what loading suits a driver: under 50 favours sealed, over 100 favours ported/horn, in between works either way.
Min crossover (Hz) #: The lowest frequency a compression driver may be crossed at (with the stated slope). Crossing lower sends excursion the diaphragm can't take, this is how tweeters and CDs die at parties. When in doubt, cross higher.

Box & system figures

F3 / F6 (Hz) #: The frequency where the box's response has fallen 3 dB (or 6 dB) below its average level: the practical lower limit of the cabinet. Lower F3 = deeper bass, usually paid for in box size or sensitivity.
Fb (Hz) #: Port/vent tuning frequency of a ported or horn box. Below Fb the driver unloads, excursion rises fast and Xmax limits output. A subsonic highpass just below Fb protects the drivers.
Max SPL (dB) #: Loudest output at 1 m before a limit is hit. Two independent ceilings: excursion-limited below Fb (cone travel runs out) and thermal-limited above (voice coil heat). The headline figure is whichever applies.
Crest factor (dB) #: Gap between a signal's peaks and its average (RMS) level. Compressed dance music sits around 6 dB; a sine test tone is 3 dB. Your amp must pass the peaks cleanly while the cabs see the average power.
Array gain / coupling #: Stacking cabinets adds output: subs close together couple coherently (+6 dB per doubling, four subs play 12 dB louder than one), while mid/top cabs sum as power (+3 dB per doubling). This is why sub walls work.
Distance loss #: A point source loses 6 dB per doubling of distance: 130 dB at 1 m is ~104 dB at 20 m. Big stacks and walls behave better than this in their coupled range, but it's the safe planning assumption.
Crossover / LR4 #: The filter splitting the signal between sub, kick, mid and top. LR4 (Linkwitz-Riley 4th order, 24 dB/oct) is the live-sound default: each side is −6 dB at the crossover point and they sum flat when time-aligned.
Measured vs sim #: Curves here are either simulated (Hornresp/AkAbak prediction) or measured on a real build (REW, Klippel). Sims are honest starting points; measurements are reality. The catalog never blends the two.

Power & electrical

AES / program / peak power #: AES: continuous power the driver survives (2 h noise test). Program: ~2× AES, the music rating. Peak: ~4× AES, instantaneous. Match amps on continuous power into the real load, not the peak number on the sticker.
Impedance (Ω) #: The electrical load the cabinet presents. Nominal (4/8/16 Ω) is an average, real impedance dips lower with frequency. Halving the load roughly doubles amp power drawn, until the amp runs out of current.
Series / parallel wiring #: Parallel divides impedance (two 8 Ω cabs = 4 Ω), series adds it (= 16 Ω). Most amps are happy at 4 Ω, good ones at 2 Ω; below that you cook the amp. Underpowering with a clipping amp kills more drivers than honest overpowering.

Topologies

Sealed #: A closed box: tight, predictable, compact, forgiving of driver substitutions, but the least efficient way to make bass. Rare in freeparty rigs except for infra duty.
Bass reflex (ported) #: A box with a tuned port that boosts output around Fb. Best extension per litre, easy to build and sim, the default for kicks and tops, common for subs. Watch port velocity (chuffing) at high level.
Bandpass #: The driver fires into a chamber and all output leaves through ports: high output over a narrow band, with the box acting as a filter. Loud but one-note if pushed beyond its band; harder to verify without measurements.
Tapped horn #: A folded horn where both sides of the cone feed the same path. The best SPL per litre and per watt in its passband, but very driver-specific: a tapped horn designed for one driver rarely works with another. Sim before substituting anything.
Front-loaded horn #: A horn in front of the cone (often with a sealed or vented rear chamber): big sensitivity gains and controlled directivity. Needs a large mouth to load low, which is why bass horns are huge or stacked in multiples.
Folded horn #: A horn path folded to fit a transportable box (W-bins and friends). Classic punchy festival kick/bass sound; the fold compromises the top of its range slightly.
Scoop #: A rear-loaded horn open at the front: the freeparty classic. Cheap to build, forgiving of driver choice and build tolerances, very loud per watt, at the cost of muddier, less controlled bass than a tapped horn or reflex. Walls of scoops are a sound system rite of passage.
Transmission line #: A long damped duct behind the driver, ~quarter-wavelength at tuning: deep, clean extension from a moderate box. More a hi-fi/studio choice than a rig workhorse, big for the SPL they make.