2018 Rules

New for 2018 highlighted in RED

General SPL Rules

Section 1 – General Rules

1-1   Competitors may use any audio format they choose to achieve their highest Sound Pressure Level (SPL). This includes test tones, sine sweeps, MP3’s, commercially available CD’s and burned CD’s. Competitors in the Basic and Advanced Divisions may choose to “burp” their system for a few seconds or play all out for the full 30 seconds. Competitors in the Midwest Street, Xtreme, and Kaos Divisions must play music.

1-2   When music is required to be played, no test tones, sine sweeps, or music with a single continuous tone will be allowed. The song must have a visible variation in frequency or amplitude on the TermLab metering screen. In some cases a 2/3 vote by judges will be required to determine legitimate music.

1-3   Music played through mids/highs must be audible outside the vehicle during the run. (Intent: audible music must be coming from within or outside the vehicle).

1-4   Competitors are required not to use any audible music with foul language, profanity, or lewd & suggestive lyrics at any time or place during the event. If an issue arises, a competitor may be required to play a different song, not compete, or may be removed from the event.

1-5   The audio format must be played through an audio device such as a CD player, CD Changer, MP3 player, flash drive or hard drive.

1-6   There is an 80 Hz limit in all peak SPL classes.

1-7   The competitor may have their vehicle running during their run as long as the following requirements are met:

  • The emergency brake must be set and function correctly
  • The wheels are chocked or blocked
  • A maximum approximate engine idle speed is not to exceed 2000 RPM. Over revving is not permitted. Competitors who over rev their engines based upon judges discretion during qualifying may be asked to re-qualify. Over revving during eliminations rounds may result in a loss.
  • The use of accelerator/idle adjustments is permitted. Accelerator props must not exceed 1”x1” square.
  • Competitors that choose to idle up their vehicle MUST have a tach installed.

1-8   Only the person operating the sound system is allowed to sit in the vehicle. Anyone choosing to sit in the vehicle during the run must be of legal age to operate a motor vehicle. Those sitting in the vehicle must sit on the driver’s side. Competitors sitting in the vehicle may not sit in such a way as to manipulate their SPL score. Typically, this is the center cross line of the vehicle. This is up to the discretion of the head judge.

1-9   Competitors may choose to open their doors, windows, and other openings of the vehicle during the metering process, however doors and other openings are not to be slammed during this time.

1-10   Once the SPL metering process begins, competitors will have a specified time limit to achieve their highest SPL. Any adjustments can be made to the sound system before, during, and/or after that time. Additional runs may be allowed if time permits.

1-11   When safety is an issue, it shall be up to the judge’s discretion to append or modify a rule on a case by case basis.

Section 2 – Vehicle Interior Requirements

2-1     No obstructions or modifications can affect the placement of the sensor and/or manipulate the SPL reading. This includes any items ( seats or other obstacles ) within 12” of any part of the sensor. In case of dash pods, sensor placement will be 12″ to the left of pod.

2-2     Standard sensor position will be at the “legal” position 12” from the passenger A pillar ( horizontal ) and 4” off of the dash ( vertical ) unless otherwise noted by class division.

2-3     All window and door/hatch openings need to function normally unless otherwise noted by class division. They must be able to open and shut and also roll up and down. Silicone used on windows ( to prevent water leaks ) needs to prove that the modification doesn’t affect the SPL score. Sun/Moon roofs/vents in walled vehicles do not need to function and will be treated as if they don’t exist. Exceptions to these rules are listed in Section 7. No taping or sealing of window openings.

2-4     The vehicle must have front seats. If the OEM seats came with headrests and/or armrests then those items must remain in place. Seats, Seat brackets or other seating mounts may not be modified unless noted otherwise .

2-5     Front seats may be folded and adjusted for competition but may not be removed from the vehicle.

2-6    Rear seats, if intended, may be folded during competition. Rear head rests may be removed if this is part of the normal operation of folding the seats and at the competitors discretion removed from the vehicle. Modifications allowing the rear seat to partially stay open must be made in the cargo area and must not prevent the normal opening and closing of rear seat.

2-7     Rear seat backs in trunk vehicles may be folded. Solid non/folding trunk vehicles may unbolt / latch their rear seat back. The unbolted seat back must remain in the vehicle on top of the bottom seat as if folded.

2-8     Second row seating in vans and SUVs must remain in the OEM location. If designed to do so, they can be folded but not removed. Third row seating may be folded or removed from vehicle.

2-9    If the vehicle is an extended-cab or king-cab pickup truck you do not need to be able to fold the rear ( side or forward facing ) seats as normal operation. Seats may not be removed from the vehicle, but may be folded up during competition.

2-10     All interior panels/carpet, including those in the trunk, hatch or cargo area must remain in OEM position unless custom trim panels are used.

Notice – The spare tire cover, spare tire and tools may be removed.

2-11   Interior modifications are limited by the class the competitor competes in.

Notice – Examples of interior modifications (but not limited too):

  • Replacing/Modifying the OEM windshield/side windows
  • Replacing/Modifying the OEM dash and components
  • Replacing/Modifying the OEM seats
  • Replacing/Modifying the OEM door panels
  • Replacing/Modifying the OEM headliner
  • Replacing/Modifying the OEM floor
  • Replacing/Modifying the OEM carpeting
  • Replacing/Modifying any OEM interior panels

Notice – Seat Limitations

  • Seats not allowed: Go-Cart seats, arcade game seats, dune buggy seats, etc. They are not considered OEM equivalent.
  • Aftermarket seats or those from another vehicle are allowed provided they approximate both form, size and function of the original OEM seat. Seats must remain in the forward facing position.
  • Seats must be fully bolted and secured.
  • OEM seats must remain in their original place.
  • Replacement seats must be bolted in the rear most OEM bolt hole location.
  • Custom seat brackets will be at the sole discretion of the head judge.
  • Modifying seats in order to fold or slide forward past their original OEM specification is prohibited.
  • If the vehicle came with floor pedestals ( to raise the seat ), then those are required to stay in place when replacing seats.

2-12     Door panels must not be glued, overly screwed or siliconed on. In other words, they can not be sealed to the door and must be easily removed in similar mode/ fashion and ease of OEM panels if required.

2-13     Custom interior panels must be covered or painted. Modifications are allowed provided they accommodate accessories, sound, video system or for cosmetic reasons; as long as they are constructed and utilized from  the original OEM panel. Custom cargo/hatch trim panels must be covered or painted. Modifications are allowed provided they replicate original panels and designed to be visible. Audio speaker installation is prohibited in the headliner. Custom door panels must not be taller than the OEM panel.

2-14     Custom dashes must resemble the original dash in size, form and function. Structural reinforcement is allowed only to those areas where aftermarket accessories, sound or video systems are installed.

2-15     Custom center consoles are allowed as long as they are not designed to manipulate the interior of the vehicle to increase the competitors score. This will be at the discretion of the head judge.

Section 3 – Vehicle Requirements

3-1     Each vehicle must be capable of being registered, licensed/tagged to drive on a Highway.

3-2     The vehicle must be capable of driving into the judging lanes. In other words, the vehicle must be able to propel itself using the engine and OEM or equivalent drive train.

Notice – If the vehicle breaks down at the show or on the way to the show or if foul weather does not permit the driving or unloading of a vehicle, then the vehicle may enter the judging lanes by any means possible. This is at the sole discretion of the head judge.

3-3     Modifications to the body of the vehicle are not allowed if the modification will increase the vehicle’s interior volume. This includes, but is not limited to: cutting of the floor, wheel wells and other areas that will change the interior volume of the vehicle. Air ride suspension modifications are allowed.

3-4     The judge must be able to see inside of the vehicle during the metering process to observe the metering equipment. This includes sides or front window. If the window tint is considered to dark competitors may be asked to remove film in order to compete. Vehicles are not allowed to be covered at an event.

3-5     People are allowed to hold or sit on the vehicle while being metered provided no other rules are broken. The competitor takes responsibility for all parties involved. ( See Xtreme rules for further details )

3-6     OEM or equivalent door and hatch seals must be in place. They may not be added to or modified, unless specified by a particular division.

3-7     Standard door and window openings may not be sealed ( taped or siliconed shut ) during the run unless otherwise noted. For safety reasons, if a window is broken/shattered, windows may be taped to prevent further breakage of glass or flying glass particles. ( Exception – no more than 6″ of accumulated tape width per door is allowed to hold a side window from falling down during the run ( not seal )

3-8     A competitor may switch vehicles at any point during the season. No borrowing, renting or switching vehicles for finals.

3-9   National competitors may not share the same vehicle at the same event. However, they may create a “team name “ and run under that name. Only 1 vehicle per division may be assigned to a particular individual competitor and/or team per show.

Example: Competitor A may not share their vehicle with Competitor B at the same event. Also, Competitor A may not allow Team C to use their vehicle as a “team vehicle”. However, one competitor may use 1 vehicle in one division and another vehicle in a different division.

Section 4 – Equipment Requirements

4-1     The audio equipment must be designed for use in a 12-Volt automotive environment.

4-2     The audio equipment must be available for purchase through legitimate auto sound businesses.

4-3     Use of wireless remote controls, IR repeaters, Bass Knobs and/or podiums are allowed in all classes.

4-4     The subwoofers must be powered by the audio amplifiers in the vehicle.

4-5     The maximum voltage of the vehicle’s electrical system can not be higher than 15.5 volts in any national class during the entire run. In most cases this measurement will be taken at or near the amplifier. In some situations due to install or other unforeseen issues, the measurement can be taken elsewhere. This is at the judges discretion.

Notice – Battery Limitations

  • Aftermarket batteries are allowed.
  • Capacitors are allowed
  • Custom home-made batteries/lithium batteries are not allowed.
  • Additional batteries may be mounted in a cargo area and/or under the hood. No battery boxes, trays or racks underneath the vehicle permitted.
  • Vehicles with batteries installed in an unsafe manner, according to the judge, will not be permitted to compete.
  • All lithium battery terminal connections will be required to be protected by durable, non conductive material. IE: Wood, plastic, rubber. All season.
  • FINALS ONLY – All battery/capacitor terminal connections ( lead acid, AGM, caps, etc. ) will be required to be protected.

4-6     The use of aftermarket alternators and external voltage regulators are allowed provided no other rules are violated. There is no limit on the number of alternators used.

4-7     External generators, battery chargers and other charging devices ( excluding primary vehicle’s alternators ) may not be used in the judging lanes or while the vehicle is being metered.

4-8    Passive radiators are allowed provided they are commercially available. They are not considered woofers and will not be counted. Custom or homemade passive radiators are not permitted.

4-9    Subwoofers installed in an isobaric formation will be counted by cone area individually ( not as 1 woofer )

Section 5 – Installation Requirements

5-1     Nothing in the sound system may interfere with the normal daily use and/or operation of the vehicle. This includes equipment on the floor or seat and seating position of passengers. See specific divisions for details.

5-2     Amplifiers mounted in the passengers compartment must meet the following guidelines:

  • Amplifiers may be installed under front or rear seats as long as the installation doesn’t interfere with normal operation of the seat
  • Amplifiers may not be installed where the seat folds/lays directly on top of the amp.
  • Amplifiers must be securely fastened and protected from unintentional damage or abuse.

5-3     No aftermarket sub amps and/or batteries may be mounted in the center console or center console area. However mid/high amplifiers are allowed as long as no other rules are violated.

5-4     Additional batteries may not extend forward past the B-pillar in the passenger compartment. unless the space behind the seat is no longer considered “passenger” area IE: wall vehicle.

5-5    Subwoofer and Subwoofer enclosures are required to be located behind the edge of the driver’s door to the edge of the passenger door referred to as B-Pillar and/or doorjamb.

Notice – The following test may be performed – “B” pillar test: A string is passed through both doors and ran up and down the doorjamb. No part of the subwoofer enclosure or anything attached to the enclosure may interfere with this test. OEM trim panels attached to the enclosure are not counted.

Notice – Non-Wall Pickup Trucks :

  • Single cab pickup trucks (not an extended-cabs or king-cabs and only those with 2 doors) with the subwoofer enclosure behind the front seats, the subwoofer enclosure can not be in front of the “B” pillar by more than 3″ at any point.
  • All other pickups ( extended-cabs, king-cabs, or those with 3 or more seats, etc. ) the “B” pillar test is required.
  • In the Basic Division all equipment must reside within the cab of the vehicle except for batteries.
  • In the Basic Division full size trucks with forward facing rear seats, the enclosure shall be under, behind or in front of the rear seat, but not on top of. Rear seats may be folded during competition but must be in its OEM location and not removed.
  • In the Advanced No Wall Division, pickups are allowed to remove or modify any part of their back seats to incorporate the sound system. Enclosure, amps, batteries may reside in the bed of the vehicle as long as the equipment doesn’t extend above the side bed rails.

Notice – Wall Pickup Trucks :

  • In the Advanced Divisions all equipment can be in the bed of the truck provided a commercially available bed cover or camper shell is used.

5-6     Competitors are encouraged to mount/secure subwoofer enclosures and other equipment  for safety.

5-7     The cargo area in vans and SUVs is defined as behind the second row seating. If the vehicle does not have second row seating in place, then that vehicle can not compete in the basic division unless otherwise noted.

5-8    In the Basic Division, two seat vehicles such as CRX, EXP, RX7 or Corvette, all equipment ( excluding source unit, EQ, processors and battery under hood ) must be behind the B-pillar and can’t be setting behind the front seats on the floor. Equipment location is subject per division.

5-9   A speaker wall is any subwoofer enclosure that is taller than the top of the rear seat back (not including head rests) or taller than the bottom of the rear side windows which ever is lower.

Notice – No Wall Division

  • If the vehicle has no side windows and the enclosure up to the B-pillar, then the box height will be at the opening of the drivers and passenger window at the B-pillar.
  • If the vehicle is a 4-door car, the the box height will follow the trailing edge of the rear drivers and passenger side windows.

Notice – Box Height

  • Anything that is attached to or setting on the subwoofer enclosure including, but not limited to, speakers, surrounds, amplifiers, processors etc., is considered to be a part of the subwoofer enclosure and will count towards the “wall” test.
  • Any aftermarket audio components installed to increase the competitors SPL score, that is installed in non OEM locations will be counted towards the wall test. Components installed for Mids/Highs purposes will be permitted upon judges discretion.
  • If the vehicle is a two seat vehicle such as a CRX, EXP, RX7 or Corvette (excluding pick up trucks), then the maximum height of the enclosure shall be 16” measured at its tallest point from the bottom of the floor. Floor build-ups in relation to box height will be at the sole discretion of the head judge.
  • Vehicles such as standard cab, extended cab and king cab pickups the maximum box height will be at the bottom of the rear window.

5-10     Trunk vehicles may port through the rear deck utilizing existing openings only. Modifying or cutting the rear deck or OEM package tray cover is prohibited. The only allowed modification is the unbolting and laying forward of the back of the rear seat in non-folding vehicles and/or rear speakers.

5-11     Competitors may install additional equipment in the spare tire well. This includes but is not limited to: amps, batteries, wiring, CD changers, speakers and enclosures. This area must also be available for inspection.

5-12     There is no limit on the amount of sound damping. All sound damping must be installed in such a manner that the OEM door panel/panels and headliner must attach normally using the factory OEM tabs/screws. Rear deck lid or other places in the cargo area where there is not an OEM cover may be used. Sound damping must be used in accordance to the manufacture’s recommendation. No sound damping shall be visible or placed on top of interior panels. Products such as Dynamat, Road Kill and Accumat are considered approved materials. Home made “sound damping” materials are not allowed.

5-13     The use of duct tape or other adhesive tapes is not permitted within view of the passenger compartment or cargo area to hold panels in place, to seal gaps between panels or to cover vents

5-14     The use of, but not limited to, glue, silicone and/or additional screws is not permitted to attach OEM panels in place.

5-15     Expanding foam may only be used in limited amounts in front of the B-pillar and may not be used to fill any large voids such as under dashes or doors, or headliner.

5-16     Competitors are required to mount all batteries and capacitors safety and securely.

5-17     Competitors may not share same equipment unless one competitor is out of the competition.

5-18     All subwoofer speaker wires must be capable of being inspected from the sub amp to the enclosure.

5-19    In the power divisions, competitors are required to use only a single strand of speaker wire per output terminal on the amplifer. Speaker wire distribution blocks or connections may be used as long as the metering equipment can be placed between them and the amplifier.

5-20     In the power divisions, competitors are required to have all (+) positive speaker wires going to the enclosure(s) ran in such a way that they can all be clamped at one time.

5-21     Competitors are strongly encouraged to have their installations neat in appearance especially at finals. Bare wood or unfinished materials are discouraged. Recommended finish materials are: paint, carpet, Formica, Plexi, stainless steel, aluminum and vinyl. Competitors taking the time to do so will be rewarded by having photos of their vehicles posted on the official website www.midwestspl.com and other forms of media used by Midwestspl.

Section 6 – Classification

6-1     Competitors are classified by the components of their sound system and modifications to the vehicle.

6-2     Subwoofers mounted behind the “B” pillar in the competitor’s vehicle will be counted to determine what class they can compete in. Subwoofers mounted in an OEM center console will not be counted. Competitors may be asked to disconnect or make inoperable subwoofers 10” or larger mounted in front of the “B” pillar,   during the run.

6-3     In some classes a power rating along with the sizes of subwoofers is used. The higher of the two ratings will determine a competitor’s class.

Example: Competitor “A” has 2-12” speakers and 2,000 watts. The entry level class allows for 2-12’s and 1,000 watts therefore the competitor would be moved up into the class that allows for 2,000 watts. However, competitors may choose to turn down their 2,000 watt amp to produce 1,000 watts of power during their run and remain in the entry level class.

Example: Competitor “B” has 1,000 watts and 4-12’s; this competitor would be in a larger class because of the number and size of subwoofers.

6-4     Each competitor may compete in only 1 class per division ( IE: Basic, Advanced, Xtreme and Kaos ) at a regular season event as long as their particular audio system installation and vehicle regulations meets each class’s requirements. See rule 10-3 regarding finals participation.

Section 7 – Instructions per Division

Midwest Street Division

MSD – Classes are for beginner and entry level competitors only. Manufacturers, retailers and professionals are prohibited from participating in these classes. This includes but not limited to: Anyone that has competed at ‘any’ World Finals, anyone that is a current member of another sound off organization or someone that has higher skills or knowledge than others in their class. Moving someone out of these classes is at the sole direction of the event promoter or judge. Local level rules and classes may vary from event to event.

These are typically offered at most Midwestspl Events. All MSD competitors are required to play music ( no tones or sweeps ).

Typical Classes Offered ( could change depending on the needs of the retailer):

  • MSD 1 – Up to 1-12, 2-10’s or 3-8’s ( peak score )
  • MSD 2 – Up to 1-15, 2-12’s, 3-10’s or 4-8’s ( peak score )
  • MSD 3 – Up to 1-18, 2-15’s, 4-12’s ( peak score )
  • MSD 4 – Unlimited

The rules for the MSD are suggested rules and can vary from show to show depending on the specific needs of the retailer/show promoter. The following rules are typical of what you will see:

  • Doors and windows may be open
  • Engine RPM limit 2000
  • Parking break must be set
  • Walls are permitted
  • Vehicles must have 2 front seats

Basic Division


  • Basic 1 – Up to 1-15, 2-12’s, 3-10’s or 4-8’s, 7-6.5’s up to 1,000 watts ( max clamped )
  • Basic 2 – Up to 1-24, 1-21, 1-18, 2-15’s, 4-12’s or 6-10’s, 9-8’s, 14-6.5’s up to 2,000 watts ( max clamped )
  • Basic 3 – Unlimited Speakers, up to 4,000 watts ( max clamped )
  • Basic 4 – Unlimited Speakers, up to 8,000 watts ( max clamped )
  • Basic Trunk – Unlimited Speakers, up to 2,000 watts ( max clamped )

7-1    CRX’s or any vehicle not originally designed for the US domestic market are not allowed in Basic 1 or 2. – MidwestSPL defines a vehicle not originally designed for the US domestic market as a vehicle not originally offered for widespread sale as new by an OEM (Original Equipment Manufacturer) in the United States. This includes, but is not limited to, Fiat Panda’s, Seat Marbella’s, and Seat Terra. Proof of OEM sale availability may be required upon inspection of vehicles in question.

7-2     Structural modifications to the passenger or cargo compartment are not permitted.

7-3     Custom installations and/or custom panels are permitted provided no other rules are violated.

7-4     Subwoofers and enclosures must be in the “cargo” area.

7-5     Subwoofers and enclosures may not set on top of a folded rear or 2nd row seat.

7-6     Seats and seat backs must be fully functional when the enclosure is in its competition position. If the vehicle is an extended-cab or king-cab pickup truck you do not need to be able to fold the rear ( side or forward facing ) seats as normal operation.

7-7     Enclosures may be “built” into the trunk of the vehicle. However, the construction may not be permanent and the competitor must easily be able to return the vehicle to its original/OEM condition. Competitors may be asked to provide proof that the installation meets these guidelines.

7-8     Speaker walls are not permitted.

7-9   Any audio equipment used to produce SPL must be below the window line referred to as the wall test.

7-10   Two seat vehicles such as a CRX, EXP, RX7 or Corvette, may have equipment, excluding the subwoofer(s) and enclosure, up to the B-pillar. The enclosure and anything attached to it must be 15” behind the B-pillar.

Exception: If the two seat vehicle has less than 24″ of maximum B-pillar to back depth in the cargo area, then that vehicle may use all of the cargo area for the subwoofer enclosure and equipment installation provided no other rules are broken.

7-11   Commercial vehicles, those with no rear 2nd or 3rd row seating and/or have floor cuts such as handicap van or an ambulances are not allowed.

7-12  Sensor placement in the legal position

Advanced No Wall Division


  • Advanced No Wall – Unlimited Speakers, Unlimited Power

7-12     Structural modifications to the passenger compartment are not permitted in front of the “B” pillar. Interior modifications are allowed provided the modification is behind the “B” pillar and under the “wall test”.

7-13     All windows and openings need to function normally in front of the “B” pillar and above the widow line.

7-14    Cut throughs in pickups are permitted.

7-15     Speaker walls are not permitted.

7-16     Commercial vehicles that have floor cuts such as handicap van or an ambulances are not allowed.

7-17     Two seat vehicles such as a CRX, EXP, RX7 or Corvette, may have all equipment up to the B-pillar.

7-18  Sensor placement in the legal position

Advanced C Division –


  • Advanced C – Up to 1-24, 2-21’s, 2-18’s, 4-15’s, 6-12’s, 9-10’s, 14-8’s, 21-6.5’s up to 4,000 watts ( max clamped )

7-18     Subwoofers and enclosures must be behind the “C” pillar or 2nd row seat which ever us furthest back.

7-19     If the vehicle only has 1 “C” pillar, then the “string test” will be replaced with measuring ( with a tape measure ) from the “B” pillar back to determine box location.

7-20     2nd row seating must remain functional. Reclining 2nd row seat not required.

7-21     Structural modifications to the passenger compartment are not permitted in front of “C” pillar.

7-22     All windows and openings need to function normally in front of the “C” pillar.

7-23    Speaker walls are permitted but not required.

7-24  Two seat vehicles are not allowed.

7-25  Sensor placement in the legal position

Advanced Division


  • Advanced 1 – Up to 1-24, 2-21’s, 2-18’s, 4-15’s, 6-12’s, 9-10’s, 14-8’s, 21-6.5’s up to 4,000 watts ( max clamped )
  • Advanced 2 – Up to 2-24’s, 3-21’s, 4-18’s, 6-15’s, 9-12’s, 13-10’s, 21-8’s, 31-6.5’s up to 8,000 watts ( max clamped )
  • Advanced 3 – Unlimited Speakers, Unlimited Power, 15.5 Volt

7-25     Structural modifications to the passenger compartment are not permitted in front of “B” pillar.

7-26     All windows and openings need to function normally in front of the “B” pillar ( excluding sunroofs ).

7-27     Speaker walls are permitted but not required.

7-28    Two seat vehicles such as CRX, EXP, RX7 or Corvette, may have all equipment up to the B-pillar.

7-29  Sensor placement in the legal position

Xtreme Division

Xtreme 1 & 2 use Basic Rules, Xtreme 3 & 4 use Advanced Rules for the following:


  • Xtreme 1 – Up to 1-15, 2-12’s, 3-10’s or 4-8’s, 7-6.5’s / Unlimited Power
  • Xtreme 2 – Unlimited Woofers / Unlimited Power
  • Xtreme 3 – Up to 1-24, 2-21’s, 2-18’s, 4-15’s, 6-12’s, 9-10’s, 14-8’s, 21-6.5’s/ Unlimited Power
  • Xtreme 4 – Unlimited Woofers / Unlimited Power

7-29    All passenger side doors must remain shut during the run, but other windows ( including passenger side ), doors and other openings can remain open.

7-30    Scores will be averaged for 30 seconds during the run.

7-31     Xtreme Division will measure the audio system’s SPL 12” from the opening of the front passenger’s door window, centered left to right of window opening, level with the opening ( window seal ) outside the vehicle.

7-32     Competitors/Spectators may not crowd around or “cup” the sensor during the metering process. The distance away is up to the head judge. At finals, only the operator of the vehicle may stand “between the bumpers”. Competitors and teams are allowed to sit on top of the vehicle as long as no other rules are violated.

Kaos Division

Kaos 1 & 2 uses Basic Rules, Kaos 3 & 4 uses Advanced Rules – Except for the following:


  • Kaos 1 – Up to 1-15, 2-12’s, 3-10’s or 4-8’s, 7-6.5’s / Unlimited Power
  • Kaos 2 – Unlimited Woofers / Unlimited Power
  • Kaos 3 – Up to 1-24, 2-21’s, 2-18’s, 4-15’s, 6-12’s, 9-10’s, 14-8’s, 21-6.5’s / Unlimited Power
  • Kaos 4 – Unlimited Woofers / Unlimited Power

7-33    Scores will be averaged for 1 1/2 minutes minutes  ( 90 seconds ) during the run.

7-34    The SPL sensor will be placed inside the vehicle on the center of the windshield centered horizontally and vertically.


Additional Classes

At some events, additional classes may be offered. These classes are for fun and do not accumulate points for finals.

  • Loud N Low – This format requires the competitor to play 4 tones ( 20hz, 25hz, 30hz & 35hz ). The scores from these tones will be averaged together to achieve a final score. Sensor placement is in the center of the windshield measured vertically and horizontally. Advanced Division rules apply.
  • Top Dog – This format uses track 19 on the Midwestspl CD. The track highlights frequencies between 30-50hz. Competitors must play this track for at least 30 seconds while the computer takes an average score. Sensor placement is in the center of the windshield measured vertically and horizontally. Advanced Division rules apply.
  • S.L.A.M ( Sound Looks and Modifications ) – This is a car show style format. Competitor’s vehicles are judged on all aspects of their vehicle as the title says. The more done to the vehicle, the cleaner it is and the better it sounds will allow the competitors to achieve the highest score possible.
  • Mayhem – Three minute music average class! Anything goes! This is a class to see who’s system can last the longest! The SPL sensor will be placed inside the vehicle on the center of the windshield centered horizontally and vertically.
  • Benefit Class – Each year, Midwestspl chooses a benefit to help raise money for. The format is simple, the sensor may be placed anywhere in the vehicle to achieve the highest SPL. As long as no device goes “into” the sensor competitors are allowed to do what ever they want.

Section 8 – Inspections & Protest

8-1     Vehicle inspections will take place at Finals prior to qualifying. The registered competitor must be with their vehicle during this process. If an issue arises where judges need to address installation legality, only the registered competitor ( not team or friends ) may be involved in a private discussion. Team vehicles will designate one person to be the spokesperson.

8-2     Midwestspl and its judges reserve the right to audit a competitor’s vehicle. During an audit the competitor will be asked to show the vehicle and its audio sound system. If the competitor does not allow the judge to verify their vehicle then the competitor’s score shall be eliminated and the competitor disqualified from the event and no refund given.

8-3     Audits may include, but not be limited to, the following inspections:

  • The vehicle’s electrical system
  • The vehicle’s sound system
  • The subwoofer enclosure
  • The interior panels
  • Competitor’s media

8-4   Competitors may protest another competitor at finals

  • Competitors may ONLY protest by filling out a protest form
  • You may only protest someone else in your class.
  • Protest forms must be filled out completely.
  • You must provide your name ( or competitor number ), the name of the competitor being protested, the rule in which they are in violation of, the action you would like to see taken and the time.
  • Judges will review each protest form as they are submitted and take action.
  • After brackets are made, protest forms may ONLY be turned in as long as the violation has occurred AFTER the competitor has qualified. ( IE: The competitor qualified legally, made changes and now is illegal )

Section 9 – Other Information

9-1     All rules will be enforced based upon their intent and the ruling of the head judge is final.

9-2     At times there may be certain rules or guidelines that are not printed in this rule book. There also may be times that certain rules need amended, modified, changed, reworded or added too in an effort to keep within the spirit or intent of Midwestspl.

9-3     In some cases a competitor meeting will take place prior to the event. It is your responsibility to know the information discussed at this meeting. Meetings will be announced prior to the event date.

9-4     A competitor caught tampering with the judging equipment will be disqualified and removed from the event with out refund.

9-5     A competitor caught deliberately cheating will be banned from competing at any Midwestspl event.

9-6     Groups or “teams” are encouraged to wear matching shirts or clothing in an order to have a more professional appearance at events.

Section 10 – National Finals

10-1    Midwestspl National Invitational information can be found online at www.midwestspl.com or you can contact our offices for further information.

10-2     Invitations to the Midwestspl Nationals will be awarded as follows:

  • Competitors must earn the requested total number of points. For this season the total is 100.
  • Competitors must earn 50 points to qualify in the class they wish to compete in at Nationals.
  • Competitors must attend a minimum of 3 events during the season no matter how many points they earn to be eligible to attend finals.
  • Competitors must be a member of Midwestspl to compete at Nationals.
  • Example: A competitor can have 60 points in Basic 1 and 40 points in Xtreme 2 to equal 100 points. They would receive 1 invite to finals. A competitor can have 60 points in Advanced 3 and 60 points in Xtreme 3 to equal 120 points. They would receive 2 invites to finals.

10-3    Participation at National Finals:

  • You may only compete in either 1 Basic or 1 Advanced class at Nationals
  • You may only compete in 1 Xtreme class at Nationals
  • You may only compete in 1 Kaos class at Nationals

10-4   Competitors must use their own vehicle or the vehicle they competed with the most during the year at finals. No borrowing, renting or switching vehicles at finals.

10-5     The vehicle must carry valid insurance.

10-6    Vehicles and systems must remain view-able to all competitors and spectators at finals. Vehicles may be shut or locked when not supervised.

10-7    Photos of all vehicles, participants and attendees at finals may be taken and posted on the main site www.midwestspl.com and on various other websites and used for marketing purposes.

Section 11 – State & National Records

11-1     State Records may be set at any event. The competitors highest winning score of the event will be counted. Scores will be posted on the official website www.midwestspl.com.  Certificates will be handed out at Finals to those who have the current record at the end of the season.

11-2     National Records may only be set at Progressive Events. The competitors highest winning score of the event will be counted. Scores will be posted on the official website www.midwestspl.com. Plaques will be handed out at Finals to those who have the current record at the end of the season.

11-3    At the end of each season, records will be reset

Section 12 – Max Wattage

12-1     Some classes require a Max Wattage measurement to be taken. This is how Max Wattage is derived:

  • Termlab Probe Meter voltage leads is placed on the speaker leads coming out of the amplifier.
  • Termlab Probe Meter Ammeter/Current meter is “clamped” around the (+) speaker lead coming out of the amplifier to speaker lead(s). Competitors are asked to have these wires accessible.
  • During the run, Termlab measures the wattage used to achieve the highest SPL ( Sound Pressure Level ).
  • In the event of equipment failure or other unforeseen circumstances, other power metering equipment may be used ( IE: Flukes )

12-2    Competitors are encouraged to run the proper size speaker wire ( or larger ) and have it accessible to placement of the judging equipment. If wires are unable to be “pierced” or the judge feels they can not get a proper measurement, then the competitor must either run a non-power class or make changes if time permits.

12-3     In some cases, an amplifier’s power output may not be able to be recorded correctly due to unforeseen circumstances in the design of the amplifier and/or installation. When an issue arises, Midwestspl reserves the right to either not allow this particular amplifier or installation in its power classes or use additional measurement equipment and means to determine power. This will be judged on a case by case basis. Competitors are encouraged to use only amplifiers in which their power can be properly measured at an event.

Section 13 – Judging Format

13-1     The judging of the event will be easy provided competitors are aware of the rules and prepare their vehicle accordingly. We encourage all competitors to fully read these rules to completely understand their intent.

13-2     When qualifying for the event the competitor will open their vehicle for the judge or official to place the proper measurement equipment inside their vehicle. This includes:

  • SPL Sensor to measure the Sound Pressure Level
  • Termlab Probe Meter will be installed to measure wattage ( power class verification ONLY )
  • Judge may verify installation of equipment.

13-3    The judging equipment may not be touched by the competitor after it is placed in the vehicle.

13-4    After the run, the judge will determine: (1) if competing in a music class if music being played is allowed, (2) Termlab verification of power.

13-5     If there is equipment failure after the first qualifying attempt, competitors will have a predetermined time to fix or replace damaged equipment before they run again.

13-6     Competitors may receive up to 2 qualifying attempts.

13-7     The competitor, if he/she chooses, will qualify a second time to re-establish their class or to improve their score. If the competitor’s wattage class does not change then that competitor will automatically be in that designated class. If the competitors score improves then the higher of the two scores will be kept unless the result is a class change then that competitor can choose to have the newly established score nullified.

13-8     Additional qualifying attempts to change a competitor’s class or to improve a competitors score may be allowed and subject to an additional entry fee or re-run fee. The time in which a competitor may take their rerun will be at the discretion of the head judge

13-9     Once all competitors have qualified for their class, the top 4 competitors ( sometimes 8 depending on size of event ) in each class will compete for 1st, 2nd and 3rd place. First place qualifier goes against eighth place qualifier and second place qualifier goes against seventh place qualifier, etc. The winners will advance to the next round ( semi finals ) where another bracket will take place. The person with the higher incoming score ( quarter finals win ) that loses in Semi Finals will get 3rd place. We do not track or count losing scores. The winners of the semi final rounds will advance to finals to compete for 1st place.

13-10     Eliminations are single elimination format. Competitors will not be allowed to re-run during this time. Situations may arise where a re-run might be allowed due to failure in metering equipment or other unforeseen situations that the competitor or team are not responsible for. This is at the discretion of the head judge.

13-11     If there is judging equipment failure in a competitors vehicle, that vehicle/competitor may need to re-run in order to get a legit score. If the failure happens after a score is posted, then the judge may or may not require the competitor to run again. If a re-run is required the competitor in opposite lane may choose to keep their original score and not run again OR delete their score and re-run to obtain a new score.

13-12    When in the case of a broken or cracked windshield, the sensor may be attached to the window via any means possible in order to hold in place to ensure a safe and accurate reading.

13-13     In case there is a tie in elimination rounds, the win will go to the competitor with the lowest power. If a tie results in a non power class, then the round will be re-ran.

13-14     If both competitors in elimination exceed their class’s power limitation, then both competitors will re-run until one competitor has an official score.

13-15    If there is a dispute regarding the competitors own score or power, it must be made immediately aware to the judging staff after the run. Once the competitor leaves the judging lanes, he or she acknowledges their run was accurate and complete.

13-16  If the judging staff deliberates and makes a decision contrary to the outcome of the run, then both competitors will be notified of the outcome.

13-17   Competitors & teams in the lanes must remain with the vehicle being judged during the judging process ( before, during & after ) until after scores & wattages are verified by judges. During set up and tear down, competitors, teams and family members are asked to step away until all equipment is removed from the vehicle. If a judge feels that a competitor or team has violated this rule, then disciplinary actions might take place. One or both vehicles re-run, scores dismissed, person/competitor removed from judging lanes.

Section 14 – Points

14-1     Points will be awarded to the top 8 competitors at an officially sanctioned Midwestspl event. Points are as follows:

  • First Place: 20 Points
  • Second Place: 15 Points
  • Third Place: 12 Points
  • Fourth through Eighth: 10 points

14-2     Progressive Event points value will reflect the total number of unique competitors: Example 19 unique competitors =1 times the points; 24 unique competitors = 2 times the points; 46 unique competitors = 4 times the points.

  • 1-19 unique competitors = 1X
  • 20-29 unique competitors = 2X
  • 30-39 unique competitors = 3X
  • 40-49 unique competitors = 4X
  • etc., etc., etc.

14-3   Individual Memberships

  • Points are tracked by the competitor’s name.
  • A person may only purchase one (1) Individual membership for themselves.
  • You may NOT use a “team” name as part of your membership name.
  • You do not need to be a member in order to accumulate points.
  • You MUST be a member prior to competing at National Finals.
  • Each competitor MUST be onsite and present at the event in order to accumulate points. Note – This does not mean that the person accumulating points has to be the person running the vehicle.

14-4    Team Memberships

  • Teams must consist of active participants in the construction of the vehicle.
  • Must be a Team Member prior to accruing points at any event.
  • All names of authorized operators of the team vehicle must be on the Team Membership card.
  • Team Memberships are $50 per season ( for 2 people ) Each additional competitor will add $10.
  • Teams must be setup/bought 60 days prior to season cut off date ( July 31st ).
  • Team Membership card must be present upon registration at each event.
  • Team Membership card must specify team vehicle.
  • A $20 fee will apply to change team vehicle on Team Membership Card.
  • A $20 fee will apply to change/add names on membership card.

14-5   Competitors may earn additional points by participating in multiple divisions at each event.

14-6     Competitors can not share, exchange or give points away.

14-7    If Midwestspl feels that a particular event results are in error, Midwestspl has the right to modify that event results and competitors points accordingly.

Section 15 – Points Cup

This years points cup is sponsored by Incriminator Audio ( see www.incriminatoraudio.com ).

The Points Cup is a race to see who can have the most points at the end of the season. After the conclusion of the season at Midwestspl National Finals, the winner will be presented with the Incriminator Audio Points Cup for their achievement.

How to win: Attend as many shows as possible and enter as many classes as allowed.

Competitors points will only come from:

  • (1) one Basic or (1) one Advanced class
  • (1) one Xtreme
  • (1) one Kaos

Incriminator Audio Points Cup points will be awarded as follows:

  • 1st – 5 points
  • 2nd – 3 points
  • 3rd – 1 point

We will take the highest points from either Basic or Advanced class, but not both. Max points awarded from each show shall be 20 points.

Points Multiplier ( Progressive Events ) will not count towards the points cup.