Beginner’s Guide to SPL Comp

When considering to compete in a Demo or SPL Competition it is important to understand the basics and terminology. There are quite a few SPL Organizations to choose from. We will discuss them briefly in this article, however, for full rules and regulations check out our SPL Org Guide.

***PLEASE NOTE*** All information on this site is for educational and informational processes.  Any guidelines, tips or recommendations are considered general knowledge and we strongly encourage you to consult with a professional before installing, adjusting, or altering a car audio system.

Basic Terms

SPL Meter – Device used in SPL Competition.  The microphone can be placed in various areas of the vehicle depending on format. It measures the sound pressure level of the vehicle.  It is usually placed on the windshield near the dash referred to as a “Legal” or “Dash” Score.  Other common locations are the headrest of the seat, in the “kick” which is the front corner of the floorboard near the door. 

Run – A run is your complete attempt, from start to finish to put up a score on a meter.  Some organizations allow “re-runs”, where you are allowed a second or third attempt on the meter. 

Scratch/DQ – If your vehicle is in violation of any rules or regulations or if you break a rule during your run/attempt your final score may result in a scratch or Disqualification.  

Peak Frequency – The frequency, measured in hertz that your vehicle generates the highest decibel level.  

Example:  Your vehicle does a 145 DB at 39 hertz but only does a 144 or lower at other frequencies.  39 hertz would be your peak frequency.  

SweepA series of tones played in a vast range to determine the peak frequency of the vehicle.  A sweep will play a tone beginning at a low frequency and continue to higher frequencies.  

Peak HoldPlaying tones otherwise known as “burping” is usually scored based on Peak Hold. This is the level at which your vehicle played the loudest and is used to determine your overall score. 

Musical Average – When playing music during the run, the average of the total score maintained through the run is the final score. 

Example: You begin your run at 156 db and as the run continues it continues to lower due to loss of power over the course of the run.  By the end of the run your score is now a 154 db.  Your musical average final score would be about 155 db. 

Knowing the types of metering and scores is just the beginning. Each organization has its own formats which include different locations for the meter sensor, varying time limits on the run, unique classing and in some cases bonus points for playing lower frequencies.

If possible, it is best to do some testing before competition to determine your peak as well as your score in different sensor positions. Some local areas have bass meets or audio shops where for as little as $5 you can meter your vehicle and do sweeps to find your peak frequency. Most SPL Organizations use a meter called the Magnum Termpro which is very accurate and consistent with scores. This equipment is not cheap and may be out of your budget, in that case buying a cheaper version of a meter may be a great alternative for testing purposes such as the SPL Lab mobile meter.

Keep in mind, your exact score may be higher or lower on the Magnum Termpro when competing due to it having a more accurate sensor as well as a judge placing the sensor in a very accurate position. Most judges have a wooden template to help with placing the sensor the exact distance from the dash and pillar of the windshield therefore all vehicles are measured from the exact same spot. Once testing is complete you can decide which SPL format your vehicle would be the most competitive in.

Example: Your vehicle plays very low frequencies well and your electrical is more than adequate to play for several minutes before the voltage begins to drop. In this case you may want to compete in formats such as Psyclone in DB Drag, Bass Battles in USACI or Subsonic Suicide in ISPLL since all of these formats offer bonus points for lower frequencies. So if your competitor plays 25 hertz at 145 db but you play 20 hertz at 140 db, you bonus points result in a higher final score making you the winner.

We have already discussed the meter sensor is placed consistently to keep the playing field even but each organization has classes within each format similar to weight classes in wrestling. Once you have determined the format that you will compete in, it is vital to determine your class. This will help keep all registrations accurate and determine who your direct competition actually is.

So many are intimated by competition but they are missing out on a very cool part of the industry. As an audio enthusiast, competing at least once simply for the experience is something you should take into consideration. Times have changed, and now most competitors are just average Joes, not professional sponsored builds. Even though there are some large builds still out there, thanks to classing the playing field is more even. No need to fear your two 12s going against twenty four 12s because you will most likely be in separate classes. There is an exception to this rule if you have a vehicle that has been modified in several ways but not your average daily driver.

Please note: When considering to compete in a Demo or SPL Competition it is important to understand the basics and terminology. There are quite a few SPL Organizations to choose from. We will discuss them briefly in this series, however, for full rules and regulations check out our SPL Org Guide.

Knowing where you stand can help determine if a small investment is worth it. For instance, if your fellow competitor in 1st place is 5 DB ahead of you, a small purchase will not be ahead to move ahead. If the score difference is marginal, adding equipment to boost your signal or upgrade your electrical can provide the edge you are lacking. It is important to note however, that uncontrollable factors such as weather and more specifically humidity can cause small fluctuations in performance resulting in a lower meter score.

Classing Basics

Each organization has its own rules and regulations to determine your classing but there are some basic terms to help narrow it down. These variations will need to be reviewed directly from the rule book to prevent disqualifications. However, it’s good to have an idea of how to decide which organization would be best first and only read that rule book(s) versus trying to read them all since some are up to 50 pages long. Without a foundation of the terminology as well it can be difficult to understand the regulations.

Build Type – There are several enclosure types such as sealed and ported enclosures, but how your enclosure is installed plays a role in classing. Some organizations classify by vehicle type but in most, it comes down to 4 basic divisions. 

  • Trunk Build / Sealed off from the Cabin of the vehicle
    • This includes vehicles where the cargo/trunk area is isolated meaning the back seat and rear deck prevent access to the trunk area. 
    • In some cases you can have things such as batteries in the cabin but it varies from org to org.  
  • No Wall / Below window line
    • This includes vehicles where the enclosure is in the cabin but is not sealed off from roof to floor
    • Some organizations have limitations such as having the subwoofer enclosure no higher than the bottom of the windows. 
  • Walled Vehicles
    • This includes vehicles where the enclosure is in the cabin and is not sealed off from roof to floor either at the B pillar (Between front and back seating) or the C-pillar (Behind back seats)  
  •  Extreme/No Rules Class
    • These vehicles have extreme modifications such as welded doors, multi layer windshields and in some cases even having tape on your vehicle can bump you to extreme class.  
    • Basically if you are excluded from any of the first 3 classes due to a modification or violation of a class rule, then your vehicle will be put in this class. 

Some SPL organizations even have what is referred to as cone area restrictions. This is referring to the total surface area of all subwoofers, and obviously the larger the subwoofer, the more cone area. The equation for his is: pi = 3.14 r = radius of sub Cone area = pi x (r x r)

Example: Two 12 inch subs is less cone area than one 18 inch subwoofer.

Format Basics

Allow most organizations offer very similar formats that include a 30 second peak hold or a 1 minute musical average to determine your final score, below we will discuss formats in various organizations that are more unique. 

These formats help determine which organization you may consider competing in for an entire season to accumulate points to qualify for finals.  We will discuss points and finals in more detail in a later lesson but for now let’s review formats from various organizations all over the country.  

Organizations such as MECA that offer several formats in addition to a basic 30 second peak hold. Yet in almost every organization there is either a 30 second peak hold or a musical average format and in some cases both. Other organizations offer a similar scoring system, such as a set time limit of 30 seconds with the option of playing a tone or music. These formats may only differ when it comes to where the meter sensor is being placed. In addition to dividing the field by formats, within each format there will be varying classes. Some formats have as little as 2 classes that may only distinguish between a stock build versus an extremely modified vehicle. In most cases however classing is usually based on the amount of subs and amplifier wattage.

The main distinction between your format versus class is that the format determines how the final score is calculated whereas your class is the limitations set in place for your vehicles build type and power capabilities..

DB Drag Bass Battles  – This format is very unique since it is not based on peak hold or musical average but instead you are attempting to reach a specific score.  It begins with your bass battles class based on a decibel range. A unique dynamic to this format is you are not competing individually.  2 competitors are in the lanes side by side.  

Example: The first class is up to 129.99 db meaning, you may be required to play your system up to 129.99 db but nothing higher than that.  

Attend a show and check out the lanes as a spectator and if you are intrigued, pull out and take a run at it. You will find most judges and other competitors are happy to answer any questions you may have but it helps to at least have a foundation.