“Ultimately, your studio’s monitoring set up and listening environment plays the biggest role in the accuracy of this plugin.
The Car Test plugin is designed to simply provide you with a similar frequency response to that of modern car speakers, so you can get a rough idea of what your mix can sound like inside of them.
To use the Car Test Plugin, it’s as simple as pressing the “Power” button.
However, it is equally important that you adjust the output gain using the “Level” knob, so that your mix doesn’t clip. The Car Test plugin’s algorithm will gain specific frequencies, so it will likely clip your mix if it’s input is not reduced accordingly.
Car Test works on both Mac and Windows operating systems”
Source : rocketpoweredsound.com