WinISD Alternative
A Browser-Based WinISD Alternative That Works on Mac
WinISD is still the most-cited free subwoofer simulator. It is also Windows-only, last updated in 2016, and requires driver library setup before your first simulation. RokketBox works in any browser, any OS, from the first tab.
WinISD vs RokketBox
| Feature | WinISD | RokketBox |
|---|---|---|
| Platform | Windows only | Any browser, any OS |
| Installation required | Yes — .exe installer | None — open a tab |
| Last updated | 2016 | Active development |
| Enclosure types | Sealed, ported, bandpass | Sealed, ported, bandpass |
| Frequency response simulation | Yes | Yes |
| Cut sheet output | No | Yes — panel dims, port routing, kerf bends |
| Port length calculation | Yes | Yes |
| Driver database | Large — community-maintained since the 1990s | Curated + manual T/S entry |
| Mac and mobile support | No | Yes |
| Price | Free | Free (account required for cut sheets and CAD) |
What RokketBox Does Differently
Browser-based physics simulation
RokketBox runs a full equivalent circuit model in your browser with no server round-trips for simulation. The engine evaluates 500 frequency points per sweep using the complete electroacoustic circuit — voice coil impedance including lossy semi-inductance via the Wright model, moving-mass mechanics with radiation loading calculated from Bessel and Struve functions, and acoustic output through the box model. For ported enclosures, port turbulence is solved iteratively until the velocity estimate converges. All of this runs client-side in TypeScript — simulation results are immediate and no audio data is sent to a server.
Cut sheets — the real gap in WinISD
WinISD tells you the box volume and port dimensions you need. Then you are on your own working backwards to actual panel sizes. RokketBox closes that gap with a cut sheet output that lists every panel with its exact width and height, the full port path including any internal routing detail, corner strip positions, and kerf bend specifications for curved enclosures. The sheet is formatted for print and designed to sit next to you at the table saw — no back-calculation required, dimensions are ready to mark out. The Free tier includes one cut sheet export per month. Paid plans extend that limit and add DXF export for CNC work.
Thermal, Le, and cabin gain modeling
At moderate to high power levels, three effects that WinISD ignores or simplifies become significant. Voice coil heating raises Re, which shifts Qts and changes the low-frequency rolloff — RokketBox applies thermal compression to Re at the rated input power. Inductance is not constant across frequency; the Wright semi-inductance model captures the impedance rise shape accurately and affects response above a few hundred hertz in typical woofers. Finally, in-vehicle use adds 6–12 dB of cabin gain at the lowest octaves from room gain and standing waves; RokketBox models this as a bounded acoustic space so you see the in-car response directly rather than anechoic and having to guess the lift. These additions matter most when you are borderline on excursion or tuning a bandpass for maximum in-cabin output.
Moving from WinISD
If you have been using WinISD and want to replicate a design in RokketBox, the parameter handoff is straightforward.
Step 1 — Find your T/S parameters in WinISD
Open your WinISD project and go to Driver > Driver Parameters. You need: Fs, Qts (or Qms + Qes separately), Vas, Re, Le, BL, Mms, Sd, Xmax, and Pe. Most driver datasheets list all of these; WinISD shows whatever was entered when the driver record was added. Note the values — you can also export the driver to a text file from the Driver menu.
Step 2 — Enter them in RokketBox
In RokketBox, open the Driver panel and choose "Enter manually". Type in each parameter value from your WinISD record. The field labels and units match the standard T/S parameter set — Fs in Hz, Vas in litres, Re in ohms, Le in mH, Sd in cm², Xmax in mm, Pe in watts. If WinISD gave you Qms and Qes separately, RokketBox will calculate Qts for you, or you can enter Qts directly.
Step 3 — Match your box volume and tuning
Enter the net box volume and port tuning frequency from your WinISD design. The frequency response curve should closely match your WinISD output. Small differences below about 20 Hz are normal — RokketBox's radiation loading model produces slightly different rolloff shape at the extremes compared to WinISD's transfer function approach. If you see a larger discrepancy, double-check that Re and Le match exactly, as those parameters shift the impedance curve and therefore the transducer loading.
Frequently Asked Questions
Is RokketBox as accurate as WinISD?
RokketBox uses a full equivalent circuit model evaluated at 500 frequency points per sweep. It includes Bessel/Struve radiation loading, iterative port turbulence convergence, BL compression, lossy semi-inductance via the Wright model, and cabin gain with standing-wave modeling. WinISD uses a transfer-function approach that is well-validated for small-signal sealed and vented work. For typical box design the outputs agree closely; RokketBox adds nonlinear compression and thermal effects that become significant at high excursion levels.
Does RokketBox have a driver database like WinISD?
WinISD ships with a larger community-maintained driver library that has been growing since the 1990s. RokketBox includes a curated driver database and a full manual-entry path where you type in Thiele-Small parameters directly from your driver's datasheet. For any driver not in the database, manual entry takes under a minute.
Does RokketBox work on Mac?
Yes. RokketBox runs entirely in the browser — Safari, Chrome, Firefox, and Edge on Mac, Windows, Linux, iOS, and Android are all supported. No emulation layer or Wine required.
Can I export to DXF for CNC cutting?
DXF export is available on the Workshop plan. Every plan (including Free) generates a printable cut sheet with panel dimensions, port routing, and kerf bend specs. Workshop adds a DXF file you can open directly in CAD software or send to a CNC router.
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