How to Use Thiele/Small Parameters to Determine Subwoofer Enclosure Size

Thiele/Small parameters are useful in determining enclosure size.

Thiele/Small are measurements, both electrical and mechanical, that are used to determine the correct box size for subwoofers. The parameters were developed in the 1970s by Richard Small and A.N. Thiele and make it much easier for the casual user to determine the exact enclosure volume that their subwoofer will operate best in. Most subwoofers will provide the measurements in their specifications sheet or manual.

Things You'll Need

• Speaker enclosure building software

Instructions

1. Consult the manual or specifications sheet for your speaker for the Thiele/Small parameters. Look for the following information:

   Electrical resistance of voice coil -- Re

   Resonant frequency of loudspeaker -- Fs

   Electrical Q of speaker -- Qes

   Mechanical Q of speaker -- Qms

   Total Q of speaker -- Qts

   Equivalent air volume of moving mass suspension -- Vas

2. Download a software program for determining enclosure size. The Windows-based WinISD is a good choice that is well-regarded.

3. Enter the elements into the program to determine the enclosure size for your speaker.

Tips & Warnings

• The Thiele/Small database lists the parameters of thousands of speakers.

References

• "Car Stereo Cookbook"; Mark Rumreich; 2005
• The Subwoofer DIY Page Definitions
• WinISD program

Resources

• The Thiel/Small speaker database