MECA has a SPL class calculator to determine your competition class. MECA and other organizations have online rule books containing all the general rules as well as formats and classing restrictions in each, here some restrictions that are helpful to understand and are pretty standard for most competitions.
TRUNK: Includes builds confined to a sealed of trunk in a car. For most organizations enclosures in the bed of a truck for example are classified in the no wall division.
NO WALL: This is a build in the cabin of a vehicle that is not sealed off at the ceiling or pillars.
WALL: Vehicles that have an enclosure that extends from ceiling to floor essentially “sealing off” the cabin at the B or C pillar is considered a wall.
EXTREME: Extreme class is usually reserved for vehicles with extreme modifications such as a bullet proof windshield, fold out out stunt wall or any modification resulting in a violation of a rule in a smaller class.
Amplifier Power Ratings:
Amplifier Power ratings are listed in 2 ways. Either as the rated amplifier power determined by manufactured specifications or using a clamp to measure the total power being generated by the amplifiers while competing.
Cone Area Restriction
Some audio competitions class their competitors based on the total cone area being used. This can be calculated by: Cone area = pi x (r x r) pi = 3.14 r = radius of sub
Beyond SPL competitions, SQ competitions will often classify or have restrictions on the location and /or total number of speakers being used.
Audio Arena Voceteo Chipeo classes are Doors Only, Doors and Trunk/Cargo Area and Finally extreme.
Audio Arena SQ Grudge includes classes that include audio systems that have speaker mounted on the outside of the vehicle, such as grills and bumpers, as well as one for vehicles that have window pods or enclosures for speakers that fit in the area where the window would be.
SQ Grudge Classes:
AMATEUR : Doors & Bass Only
LIGHTWEIGHT : Doors, Bass and Outside Grills/Bumpers Only
MIDDLEWEIGHT : Doors, Bass, Outside Grills/Bumpers and Window Pods Only
HEAVYWEIGHT : Doors, Bass, Outside Grills/Bumpers, Window Pods and Side/Rear Wall Only
EXTREME: No Rules