What is WinISD

WinISD is a free loudspeaker enclosure design program that only requires the Thiele/Small parameters typically provided by the driver's manufacturer. These parameters can also be determined if the exact model of driver is unknown. It can facilitate the design of sealed enclosures and ported enclosures, while also providing useful information for less common designs. The picture above shows the results of modeling a Tectonic TEBM28C10-4 planar speaker in a sealed enclosure (blue), a standard ported enclosure (green), and an enclosure featuring a passive radiator (yellow).

WinISD is especially useful when designing high-fidelity speakers, as calculating and tuning enclosure sizes for (sub)woofers is important for extending bass response. The enclosure volume is typically regarded as the critical aspect of any (sub)woofer design, and further tunings such as the addition of a port can offer a designer many degrees of freedom.

While WinISD is fantastic for planning enclosure volumes and getting a starting idea for the port, it is not an all-in-one solution for designing high-fidelity products. Not only is the volume of the enclosure important, but the size and shape of it needs to be designed in a way to avoid resonances, internal standing waves, and vibrations. In addition, the port size needs to be monitored to eliminate the possibility of distortions and non-linearities from being introduced. These ideas, and other aspects of loudspeaker design like the crossover, can be supplemented by other programs. Yet, overall WinISD is a fantastic first step when beginning the design of a loudspeaker enclosure.

Quickstart Guide

Step 1:

Install software

Download the latest version of WinISD from Linearteam.org by clicking the button above.

Run the installer and follow the prompts.

Open the program once installation is complete.

Step 2:

Add driver to the database

If not using a driver already included in WinISD's database, you will have to enter the parameters manually. Skip to step 4 if using a driver already in the database.

In the toolbar of WinISD, click the speaker icon (pictured above) to open the "Driver Database". You can also alternatively press "ALT-D" to open the window.

Enter in the driver's manufacturer and model number.

Click the "Parameters" tab to begin data entry.

Step 3:

Enter in the Thiele/Small parameters

Enter the Thiele/Small parameters in the order specified below:

  1. Enter either Mms & Cms or Fs
  2. Enter Sd, BL, and Re
  3. Enter either Qms or Rms
  4. Enter Pe and either Xmax or Hc & Hg
  5. Enter the number of voicecoils and correct Znom if necessary

Click "Save" to add the driver to the database.

It's important to note that you must enter only the specified Thiele/Small parameters and in the exact order specified, or else you may run into issues of conflicting parameters. This tends to be the first stumbling block users run into, since it's easy to just enter every parameter provided by the driver manufacturer. You should also notice that as you enter in the parameters, other values will start to get calculated. By the time the last specified parameter is entered, almost all of the other values should have been calculated.

Another thing to keep in mind is that the Thiele/Small parameters provided by the driver's manufacturer will most likely differ from the real thing. For example, the specification sheet for the TEBM28C10-4 used in the plots on the top of this page displays a variance on the Thiele/Small parameters - some of these can vary as much as 40%! It is best to either choose a driver from a trustworthy manufacturer that will produce drivers of relatively equal quality, or test the physical driver itself. Thiele/Small parameters can typically be determined using just a standard desktop computer and little to no additional equipment.

Step 4:

Create a new project

In the toolbar of WinISD, click the paper icon (pictured above) to start a new project. Select a driver from the database - if you followed Steps 2 and 3, your custom driver should be listed under whatever manufacturer you entered.

Step 5:

Begin designing enclosure

Select the number of drivers to be in the same enclosure, as well as the placement. WinISD allows for standard placement, as well as the less traditional isobaric placement. Press "Next".

Decide what kind of enclosure you want to design. I only have experience with "Sealed", "Vented", and "Passive Radiator", where each have their pros and cons. Press "Next".

Choose the desired alignment. For a sealed enclosure I recommend the default "0.707 Max flat amplitude response" alignment, and for a vented enclosure I recommend the default "QB3 Quasi-Butterworth" alignment. Press "Next".

Name the project, and press "Create".

Step 6:

Tune the enclosure

If you don't have very any design constraints, go with whatever WinISD has just provided you. However, 99.9% of the time, there are realistic constraints a designer must keep in mind - this is where the art of tuning a speaker enclosure becomes apparent.

Step 6a:

Tuning a sealed enclosure

Tuning a sealed enclosure is typically easier than tuning a vented enclosure, and certainly much easier than tuning a passive radiator. A few things to keep in mind are the volume, stuffing material and amount, and the Qtc of the enclosure. Click the button below for a detailed explanation of the tuning process.

Step 6b:

Tuning a vented enclosure

Tuning a vented enclosure can get a little tricky, especially once we begin messing with the volume. A few things to keep in mind are the volume, tuning frequency of the enclosure, port length, and port air velocity. Click the button below for a detailed explanation of the tuning process.

Step 6c:

Tuning a passive radiator

This process is much messier than designing a sealed or vented enclosure, but can can be very useful for certain applications. When designing vented enclosures for very small drivers, such as those found in Bluetooth speakers, the port length becomes too long and begins to take up too much space. This can be ameliorated by using a passive radiator, which takes up no internal or external volume.

They are also useful when designing (sub)woofer enclosures where the port air velocity becomes too high and introduces audible chuffing. As the enclosure size shrinks, the vent length increases, so the vent diameter decreases. Eventually, this will reach around 5% the speed of sound and manifest as audible distortion. Replacing the port with a passive radiator addresses this concern. Click the button below for a more detailed explanation of the tuning process.