ISPLL has four divisions and each has its own classing system.  We recommend visiting to verify your classing and to familiarize yourself with the general rules of the organization. 

Below is a basic breakdown of the formats offered and a helpful guide to finding the right event for your system.  

In all formats:

  • No reving your engine above 2500RPMs
  • Vehicles must be drivable with th exception of the No Rules Class (NR)
  • Maximum frequency is 70hz

The classing is based on a variety of factors which can be found at .  The most basic of these factors is your amp power based on your equipments rating in the ISPLL Rulebook.  We have included the classing matrix for each event however, please consult your rulebook and/or a organization judge to verify your class as some factors may bump you up such as a no wall enclosure being too tall, alterations in front of the A-pillar, etc. 


ISPLL Subsonic Suicide is a 2 minute musical average using a subsonic track under 32hz. Each 1Hz below 32 you play at will add .25dB to your final score (i.e. you play the 28Hz track, you will receive a 1dB bonus on your final average). If you play the 20Hz track or below, you will receive an additional 2dB bonus to your final score (5dB total bonus). If you play the 15Hz track or below, you will receive an additional 1dB bonus to your final score (7.25dB total bonus). The mic is placed on the dash.  Competitors may open any door, window, hatch, trunk, etc. that they wish to, before and during (AKA “fanning”) the run.

Click Here to Download Subsonic Suicide Tracks


REAL SPL is the only format that uses tones.  Its a peak hold or burp within 30 secs that averages 3 tones to come up with your final score.  Each frequency is 10 cycles apart (example: 24hz, 34hz, or 44hz) so this is a great event for showing off your system’s bandwidth capabilites.   Metering will take place on the passenger side windshield (legal position). All doors, windows, hatches, trunks, etc. must be closed during the runs.


All Around is a 30 second musical average.  The music must be commerically available as in all SPL Competition.  Metering will take place on the passenger side windshield (legal position), passenger seat headrest, and passenger side kick (outlaw position). Only the driver side door OR window may be open during the rounds. The average of these 3 scores creates your final score.  


Demo Showdown is the longest run of all the formats.  It is a 90 second musical average. Metering will take place on the passenger side headrest and the driver side window (approx. 3-6” outside the vehicle). The driver side window location will be as close to the window opening as the vehicle physically allows (the sensor is placed on a microphone stand standing on the ground outside the vehicle, almost against the door). Only the driver side window and/or passenger side window may be open during the rounds, no doors.


For each format you run, you will earn 1 point.  Up to 4 points per show if you run all formats.  2X or 3X shows are limited but available, doubling or tripling your points. 8 points are required to be eligible for finals,  The 8 points must be accured in the same class and format that will be competing in at finals. 

For upcoming SPL shows CLICK HERE