BoxLab: Speaker Box Designer

Design speaker boxes and passive crossovers from your driver's Thiele-Small parameters — sealed, bass reflex, bandpass, passive radiator and horn. BoxLab runs the real acoustic math on your phone, offline, with no ads and no subscription.

No simplified formulas: exact Small 1974 model for the passive radiator, true Webster 1D simulation for the horn, driver impedance with motional impedance, baffle diffraction, group delay and phase on every design.

✦ PRO-GRADE MATH
• Passive radiator — Small (JAES 1974) pressure transfer function with double notch: ωp loaded on the driver cone excursion + ωr free-air on the SPL response
• Horn — 1D Webster equation solved via cascaded ABCD matrices over 60+ segments, terminated by piston-in-baffle mouth radiation (Bessel J1 + Struve H1 series)
• Exact horn profiles: exponential, Salmon hyperbolic, analytic tractrix, Le Cléac'h, conical (linear radius)
• Alignment helper B4 / QB3 / C4 / SBB4 with suggested Mmp and target Vb

✦ ENCLOSURE DESIGN
• Sealed box — Qtc, Fc, F3 with Butterworth / Chebyshev alignments
• Bass reflex — 5 alignments (B4, QB3, C4, SBB4, EBS) + port velocity check
• 4th-order bandpass with internal divider and port shown in 3D section
• Passive radiator with Fp tuning and added-mass suggestion
• Front / back-loaded horn with compression chamber and rear chamber

✦ PASSIVE CROSSOVER 2/3-WAY
• Butterworth, Linkwitz-Riley, Bessel filters (1st–4th order)
• Real driver impedance Z(f) with motional impedance Bl²/Z_mech
• Zobel network + L-pad for tweeter attenuation
• Manual override of every L/C component
• Baffle diffraction — Vanderkooy edge model: baffle step, ripple and the arrival-time offset between drivers

✦ MULTI-DRIVER CONFIGURATIONS
• Parallel, Series, Series-Parallel
• Isobaric Series / Parallel — Vas halved, enclosure half the size
• Push-Pull with HD2 harmonic cancellation (~12 dB)

✦ INTEGRATED 3D RENDERING
• Oblique projection for sealed, ported, PR
• Side section for bandpass (2 chambers + divider) and horn (chamber + actual flare from profile)
• 6 ratio presets: Golden, EBU, Sepmeyer, Louden, Cube, Custom
• Internal / external dimensions, panel area for material estimation

✦ MEASUREMENT & DISTORTION (PRO)
• Real-time SPL meter A/C/Z + LAeq, 1/3-octave spectrum 16 Hz – 16 kHz
• In-room measurement: pink noise / sweep + mic with overlay measured vs predicted
• HD2 / HD3 / THD distortion vs frequency with push-pull toggle
• Microphone offset calibration

✦ DATABASE & PROJECTS
• Unlimited driver database (Pro)
• Driver import via datasheet copy / paste — the parser extracts Fs, Qts, Vas, Bl, Re, Sd, Mms, Cms, Xmax, Pe
• Save projects and Systems (woofer + midrange + tweeter + crossover + cabinet)
• PDF export with vector charts, sharing and printing

✦ OFFLINE, ZERO TRACKING
• 100% offline, no internet connection required
• No accounts, no registration, no login
• No data collected, no analytics, no ads
• 9 languages: IT, EN, DE, FR, ES, JA, ZH (Simplified & Traditional), KO

✦ PRO ONE-TIME PURCHASE
The free version includes sealed box, bass reflex, 2-way crossover, 3D dimensions, SPL meter, and up to 3 saved projects. Pro unlocks bandpass, passive radiator, horn, 3-way crossover, in-room measurement, distortion analysis, multi-module systems, PDF export, and unlimited projects. Pay once, no subscriptions, no renewals.

Mathematically validated: 51 unit tests cover Thiele/Small, vented alignments, Small 1974 PR model, horn profiles and Webster simulation.

For: DIY hobbyists, builders, audio engineers, acoustics students, sound engineers looking for a precision tool outside the studio.