SPL Testing @ Ultra Low Frequencies                  Testing your car audio system  at its Peak SPL and at four set frequencies of  40Hz   33Hz   25Hz   20Hz  ////////////   The pd SPL format started booming in the U.K. in 2008.  Created by Marcos H Barnes A.K.A. Mega Heavy Bass. A former SPL competitor.//////////  dB readings are taken from the vehicles Head Rest    The doors and windows are allowed to be opened.   Like to know more?       ...Then please feel free to browse this site.       Thank You For Your Interest.           Copyright © 2011 by "Marcos H Barnes"
Copyright © 2011 by "Marcos H Barnes" 
Born in the U.K.!!
Propper Droppers is the only SPL format that measures a car audio system using a fixed set of  low bass frequencies.

40Hz- 33Hz - 25Hz - 20Hz and PEAK SPL

The SPL sensor is attached to the headrest which  helps to represent the listeners normal position.

There are 7 categories to suit most U.K. systems.
Boot Boomers 1 - 2to3 - 4+ and Boot Extreme,
Nowall, Walled, Walled+
If you like to rumble and boom then this format will show you just how well your system performs whilst doing it.