Subwoofer box calculator: real simulation, port sizing and a cut sheet. Free.
Boxsmith designs subwoofer and speaker boxes the way desktop tools do, on your phone: it
simulates how your driver plays in a sealed, ported or bandpass box, sizes the port, and draws up the
cut sheet. Every feature is free. No subscription, no account, no paywall on the results, and it works
offline.
SIMULATION, NOT JUST A VOLUME
- Full Thiele-Small model of the driver and box, the same family of model WinISD uses
- Graphs: response (SPL), maximum SPL, cone excursion against Xmax, port air speed, impedance and
group delay
- Set the amplifier power, a subsonic filter, a low-pass, bass boost and car cabin gain, and see the
effect at once
- Overlay up to four designs to compare them
- Tap or drag any graph to read exact values
THE RIGHT BOX FOR YOUR SUB
- Sealed, ported and 4th-order bandpass boxes
- "Suggest a box" finds flat, deeper-bass and compact designs for your driver with the simulation,
keeping the port buildable
- Warnings in plain words: past Xmax, a port that will chuff, a load too low for the amp, more power
than the drivers are rated for
- Multiple subs in one box, single or dual voice coils, every wiring option with its final load
PORTS DONE PROPERLY
- Slot or round ports, one or several, with the end correction included
- Port length for any tuning; one tap sizes the port to stay under the air-speed limit
- Tells you when the port needs an L-shaped bend
BUILD IT
- Enter the width and height that fit your trunk or room and fit the depth to the volume
- Wedge (sloped back) boxes for trucks and hatchbacks
- Net volume after the drivers, port and bracing are taken out, checked against the design
- 3D preview with the drivers and port on the baffle
- Cut list in inches and fractions or millimetres, double baffle, port panels
- Sheet layout on 4 × 8 ft or metric sheets with your saw kerf
- Cut sheet as a PDF to take to the shop
YOUR DRIVERS
- Type the T/S parameters from the spec sheet in any common units; Boxsmith works out the rest
(Qts, Mms, Cms, Bl, efficiency, sensitivity, EBP)
- Every value is cross-checked: it warns when Qts disagrees, when Vas looks like cubic feet typed as
litres, or when Xmax looks peak-to-peak
- Share a driver as a file with a friend; import theirs
- Example drivers to try it straight away
TOOLS
- Subwoofer wiring calculator for every combination of subs and voice coils
- Port length and port tuning calculator
- Box volume calculator, including wedges
- Quick sealed box from Fs, Qts and Vas
- Passive crossover values (1st to 4th order, Butterworth and Linkwitz-Riley), L-pad and Zobel
YOUR DATA STAYS YOURS
- Everything is stored on your phone: no account, no cloud
- Back up every driver and design to one file and restore it on a new phone
Imperial (inches, cubic feet) or metric (cm, litres). The simulation uses the standard lumped model
with 25 °C air; real boxes differ a little, so check your build before you cut.
Subwoofer box calculator, speaker box design, ported box calculator, port length calculator, sub box
builder, car audio enclosure design: Boxsmith, free and ad-supported, from Fernhart Labs.