WinISD

All my Subwoofers were designed using the free WinISD software from Linearteam in Finland.

Make sure you download the Pro variant. The current alpha version (0.50a7) calculates box volumes for ported and sealed enclosures using an easy to use interface and also calculates vent lengths. Many graphs are available, including the three I show in the projects section, ie Sound Pressure Level, Vent Air Velocity and Cone excursion, all relative to frequency.

An extensive database of drivers is included and it is easy to add your own entries. This lets you compare different drivers before you go out and spend any money. It is surprising how the final box size and response varies with the driver chosen. Bigger and dearer isn't always the best. Choose wisely, grasshopper!

Screenshots

Some screenshots showing the different screens WinISD uses to access all its features

Modelling Filters

The effects of using filters can be shown. This allows the exploration of solutions to excessive cone excursion in ported systems by utilising a High pass filter

Modelling Boost

The effect of boost can be modelled with the Parametric EQ filter, to allow for amps such as the Jaycar 350w plate

Case Study

A case study used to prototype the snorky design ilustrates the use of WinISD

Signal Generator

A signal generator is also included for testing speakers via your sound card and has a range of control options including selecting the frequency from the cursor position on the response graph. If using this function, be careful not to overdrive the output

Help file and FAQ

The help file and FAQ has all you need to know in order to use the software. If that isn't enough, the site also runs a discussion forum. This is well supported and was very helpful with the queries I had regarding design of the hi-pass filter. WinISD is freeware with a facility to make a donation

Entering driver parameters

Driver parameters can be a pain to enter into the database. If you're having trouble getting it to accept parameters, follow this advice from one of the authors....

Try entering just Qms, Re, Mms, Cms, Bl, Sd, hg, hc, Xlim (optional) and Pe. Do not change any parameters the program calculates. That way the data is consistent. You can of course add the dimensional parameters if you like

Additional WinISD resources

Steve Dart's excellent tutorial on using WinISD including entering driver parameters without errors
A few observations about the various graphs can be found in this discussion at Speakerplans.com
Janne Ahonen, one of the authors of WinISD, has published this paper describing how WinISD compares with other software when it comes to calculating port lengths
You can download a heap of drivers at Tempe's WinISD Pro Parameter Files
If you're having troubles finding T/S parameters, give Thielsmall a go!
If you have only some of the required T/S parameters, and can't find the missing ones anywhere, you may find it useful to try this Driver parameter calculator
If you don't have windows, you can use an online version of WinISD. It takes Vas, Qts and Fs, and gives you designs for sealed, ported, 4th and 6th order bandpasses.

WinISD Overview