A WinISD alternative that runs in your browser
If you have designed a box in WinISD, you already know how this works: type in the driver, pick an alignment, read the curves. DIY Sounds solves the same Thiele/Small model and draws the same graphs — then carries on to the cabinet you actually cut.
The same model underneath
WinISD and this calculator are built on the same published science. Both take the driver's Thiele/Small parameters, hang an enclosure off it as a lumped-element circuit, and solve that circuit frequency by frequency. Put the same driver in the same box in both and the curves should land in the same place — if they don't, check the parameters were copied across in the same units.
That means the graphs you read in WinISD are here too, from one solve, so they always agree with each other:
- SPL / frequency response, with the reference level and the −3 dB point marked.
- Impedance, with Re marked — the twin peaks of a ported box and the minimum your amplifier sees.
- Cone excursion, against the driver's Xmax.
- Vent air speed, against a 17 m/s chuffing line.
- Group delay, against a one-cycle audibility line.
Drive level is set in volts, with 2.83 V (1 W into 8 Ω) as the reference, and the calculator warns separately when a box that looks fine at 1 W would run out of excursion or chuff at the driver's rated power.
What it adds
| WinISD | DIY Sounds | |
|---|---|---|
| Runs on | Windows (desktop install) | Any browser — Mac, Windows, Linux, Chromebook, tablet, phone |
| Sealed, ported | Yes | Yes |
| 4th- and 6th-order bandpass | Yes | Yes |
| Folded horn and tapped horn | No | Yes |
| SPL, impedance, excursion, vent speed, group delay | Yes | Yes |
| Round, slot, wall-slot and aero vents | Round and slot | All four, with end correction |
| 3D cabinet you can orbit, section and explode | No | Yes |
| Panel cut list, net and gross volume | No | Yes |
| Curves re-solved from the cabinet as drawn | No | Yes |
| High-pass filters, EQ, Linkwitz transform | Yes | Not yet |
| Works offline | Yes | Needs the page to load |
| Price | Free | Free, no account needed |
The biggest difference is where the design ends. WinISD tells you the box should be 56 litres tuned to 32 Hz; turning that into boards is left to you, and so is noticing that the port you calculated doesn't fit inside the box. Here the same design becomes a cabinet with real panel thicknesses, a driver cut-out and a vent that has to physically fit — and you get the cut list for it.
The box as built, not the box as asked for
A long port often has to be folded or shortened to fit, and the panels, driver and bracing all take air out of the box. None of that shows up in a volume figure. The model editor measures the air your boards actually enclose, chamber by chamber, and the real length and bore of every vent, then solves that cabinet again. The as-built curve is drawn over the design curve, so a lost litre or a shortened port shows up as a curve that moved rather than as a surprise when you measure the finished box.
What WinISD still does that this doesn't
To be straight about it: WinISD lets you put high-pass and low-pass filters, parametric EQ and a Linkwitz transform in front of the driver and see the effect on every curve. This calculator models the box and the driver only. If your design depends on a subsonic filter or a boost, work the box out here and check the filter there — or treat the excursion curve below tuning as the reason to fit one.
Not affiliated. WinISD is a free program by Linearteam. DIY Sounds is an independent tool with no connection to it; the name is used here only to describe what the two have in common.
Frequently asked questions
Is there an online version of WinISD?
WinISD itself is a Windows desktop program with no official online version. DIY Sounds is a free browser-based calculator on the same Thiele/Small model, drawing the same main graphs — SPL, impedance, cone excursion, vent air speed and group delay — with nothing to install.
It is independent and not affiliated with WinISD.
Can I use WinISD on a Mac?
Not natively — WinISD is built for Windows, so a Mac needs a Windows virtual machine or a compatibility layer such as Wine or CrossOver.
A browser-based calculator runs on a Mac, Linux, a Chromebook or a phone with no install, and covers the same sealed, ported and bandpass modelling.
Will I get the same results as WinISD?
For the same driver and the same box the curves should closely agree — both solve the same Thiele/Small equivalent circuit. Small differences come from defaults such as box losses (Ql) and the vent end correction.
A bigger difference is almost always a parameter copied in the wrong units: Vas in litres versus cubic feet, or Sd in cm² versus m².
Does this calculator model horns, which WinISD does not?
Yes. Alongside sealed, ported and 4th- and 6th-order bandpass, it models folded horns and tapped horns, treating the horn path as a transmission line.
Like any lumped model it is most reliable in the bass range, below the box's first internal mode.
Bring a WinISD driver across
Copy Fs, Qts, Vas, Re, Sd and Xmax out of your WinISD driver file and the curves appear in the same shapes you are used to.
More calculators
Ported box calculator
Volume, tuning and vent, with the air-speed check people skip.
Sealed box calculator
Solve the box from a target Qtc, and see where it rolls off.
Bandpass box calculator
4th and 6th order — loud over a band, and quiet everywhere else.
Thiele/Small parameters
What Fs, Vas, Qts and Xmax mean, and which ones decide the box.