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What is a car audio SPL competition? Tacom 2 and how sound pressure contests work

Short answer

A car audio SPL competition is a contest for the loudest bass inside a car, measured in decibels by a sensor in the cabin. Leagues like dB Drag Racing, MECA, IASCA and EMMA split cars into classes by woofer count, power or budget, and top systems now pass 185 dB. Tacom 2, a 2013 street SPL contest in Tangerang with 75 entrants, was a local version of the same idea.

A car audio SPL competition is a contest to make the highest sound pressure level inside a vehicle, measured in decibels. You play a bass tone or track, a sensor in the cabin reads the peak or average, and the highest number in your class wins.

Tacom 2, short for Tangerang Contest Modification 2, was one of these. It ran on May 25, 2013, at Tangerang City Mall, organized by the Tangerang chapter of Toyota Kijang Club Indonesia, with 75 entrants in street SPL classes (Gerald Julio's blog). Here's how contests like it work.

What SPL means and why the numbers climb slowly

SPL stands for sound pressure level. It's measured in decibels against a reference pressure of 20 micropascals in air (Wikipedia).

The scale is logarithmic, which is why gains are hard. Doubling amplifier power adds about 3 dB, and doubling sound pressure adds about 6 dB (Wikipedia). So going from 150 dB to 156 dB means doubling the pressure, which takes far more than doubling the hardware.

For context, Nationwide Children's Hospital lists a jet takeoff at about 140 dB and fireworks at 150 dB, and says noise above 120 dB can harm hearing right away. Serious SPL cars run well past both.

How a run is measured

A sensor is clamped in a fixed spot in the cabin, the doors are shut, and the competitor plays a tone or track for a set time. The meter logs the result.

Each league fixes the sensor position so scores are comparable. IASCA's 2024 rules put the sensor 4 in above the dashboard and 12 in from the passenger-side A-pillar, set with a certified jig and facing forward. EMMA mounts its sensor on the driver's seat base, pushed back toward where the driver's head would be.

The tone and timing vary too. In dB Drag Racing, the classic run is a short "burp" between 30 Hz and 70 Hz in a sealed vehicle (Wikipedia). IASCA's sound-off format caps frequency at 100 Hz and times runs at 30 seconds. EMMA records the peak with doors closed and a 30-second average with doors open.

Term-LAB is the measurement system you'll see named most, and EMMA's rules refer to Term Lab software too. In 2019, the dB Drag Racing North American Finals ran simultaneously in Louisville, Kentucky, and Sacramento, California, linked through the Term-LAB measurement system (Mobile Electronics).

The main formats and classes

Classes stop a 1,000-watt daily driver from going up against a van full of batteries. Leagues split them by woofer count, cone area, amplifier power or, in Europe, by equipment budget.

League or format

How classes are split

Example classes and limits

Source

dB Drag Racing

Power, woofer count, build type

Street Stock 1K, Pro Stock 2K and 5K, Super Street No Wall, 1-2, 3-4, 5+, X, Extreme NL

Mobile Electronics

dB Drag Bass Race

Score brackets

120.0-129.9 dB up to 150.0-159.9 dB

Mobile Electronics

MECA SPL

Power and build type

Street 1, Modified 5, Radical X, dB1, plus Park and Pound measured 6 ft outside the car

PASMAG

IASCA IdBL Class 1

Cone area and power

Up to 240 sq in (for example 2x12 or 1x15), max 2,000 W RMS, 15.5 V

IASCA

IASCA IdBL Class 2

Cone area and power

Up to 480 sq in, max 4,000 W RMS, two alternators

IASCA

IASCA IdBL Class 3

Cone area and power

Up to 750 sq in, max 6,000 W RMS, three alternators

IASCA

IASCA Advanced and Ultimate

Cone area only

No amp limits, up to 18 V

IASCA

EMMA ESPL

Equipment price and install type

Trunk 3,000 euros, B/R 4,000 euros, W (wall) 8,000 euros, then X

EMMA

"Wall" builds fill the vehicle with speakers from floor to ceiling. dB Drag's Super Street No Wall class bans that layout (The Journal, New Ulm).

EMMA adds limits you won't see in the US. Its 2024 judge book caps voltage at 14.6 V at the amplifier, allows two amplifier channels per woofer and bans self-built or modified amplifiers outside the Unlimited class.

There are also head-to-head formats. IASCA runs Bass Boxing, where the top two qualifiers face off over three rounds, and Demo Boxing, judged on the loudest 90-second final (IASCA).

Typical scores and records

In the results we found, street classes scored in the high 140s to mid 150s. Unlimited builds now pass 185 dB.

Class or event

Score

Who and when

Source

MECA Park and Pound, best of show

138.3 dB

Anthony Caldwell, 2017

PASMAG

MECA Street 1, second place

147.91 dB on 750 W

Davy Weil, 2018

PASMAG

dB Drag Street Stock 1K

154.7 dB, tied world record

Mike Ullrich, one 15-inch sub, under 1,000 W, 2018

PASMAG

dB Drag Super Street No Wall record

166.8 dB

Dan Horner, 2017

The Journal, New Ulm

MECA Modified 5, SPL best of show

167.24 dB

Jeremy Kough, 2017

PASMAG

dB Drag Super Street 5+ record

171.2 dB

Team Directronix, 2019

Mobile Electronics

MECA Radical X, top score

171.91 dB

Joseph Ault Sr., 2017

PASMAG

dB Drag Extreme 9+ winner

173.3 dB

Scott Owens, Ford F-250, 2003

New Atlas

dB Drag Extreme record

185.2 dB

Team Soundcheck, 2022 World Finals

PASMAG

The cost of the top end is huge. Scott Owens' 2003 winning truck used nine 12-inch subwoofers, 36 amplifiers, 72 batteries and three alternators (New Atlas).

PASMAG's 2022 report also says Team Soundcheck went on to 185.4 dB after the 185.2 dB record. It doesn't clear up which figure stands.

Safety rules

The loudest cars are run with nobody inside. Wikipedia notes that no one sits in a dB Drag vehicle during the loudest trials, and IASCA requires any system capable of more than 165 dB to be operated from outside the car.

Below that line, IASCA lets one person sit upright in the driver's seat wearing approved hearing protection. EMMA lets only the person on the volume control sit inside, and says plainly that it takes no responsibility for health effects.

Other common rules: engine speed capped at 2,000 rpm, no external power or trailers, covered battery terminals and an extinguisher if wiring isn't fused (IASCA).

SPL contests in Indonesia

Some Indonesian SPL contests are run by car clubs as part of modification shows. Tacom 2 is a good example. Its three classes were Street SPL Sedan 2 Subwoofer, Street SPL Non Sedan 2 Subwoofer, and Street SPL Free For All, and it followed a first edition in December 2010 (Gerald Julio's blog).

Splitting by two-subwoofer limits and body style mirrors how the big leagues work. Sedans and hatchbacks or MPVs have very different cabin volumes, which changes how pressure builds.

Bigger Indonesian shows now run sanctioned audio contests. BlackAuto Battle 2023 included an audio competition called Black Out Loud with SQ, SQL and SPL categories, run with EMMA, CAN and MECA (Carmudi). Indonesian tuners compete abroad too: Venom Indonesia's Filiphus Sebastian won the President Cup Unlimited category at EMMA, Medcom reported in 2023.

For bigger car shows to plan around, see our tuner event calendar.

How to get started in SPL

  1. Pick a league and download its current rulebook before you buy anything. Class limits on cone area, power and voltage decide your build.
  2. Start in an entry class like IASCA Street (1,000 W RMS, up to 240 sq in of cone) or dB Drag Street Stock 1K.
  3. Plan the electrical system early. IASCA and EMMA both police voltage, and IASCA also limits alternator count by class.
  4. Seal the cabin and reinforce panels and glass. Competition cars are sealed tight to hold the sound energy in (Wikipedia).
  5. Wear hearing protection for every test, and run from outside the car once you're near 165 dB.

Sources

Featured image: Biggest Magnat subwoofer by JosefRousek, CC BY 2.0. Source

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