This is IASCA ’s SPL competition format. IdBL Divisions (Rookie, Stock, Stock Pro, Advanced No Wall, Advanced and Ultimate) are based on the experience and industry position of the competitor and the level of modifications to the vehicle. IdBL classes are based on the cumulative total of all subwoofer cone surfaces in square inches.
Calculating cone area is quite simple; there are different methods for calculating cone area, depending on the shape of the subwoofer. For round subwoofers, the formula for calculating cone area is Radius squared times Pi (3.14).
Example: Take a ten inch round subwoofer; the radius of all subwoofers is half the diameter, so the radius of a ten inch subwoofer would be 5 inches; the radius squared would be 5 times 5 which equals 25. 25 times Pi (3.14) equals 78.5. And there you have it; the total cone area of a ten inch subwoofer is 78.5 square inches.
It’s even easier for square subwoofers; simply multiply two connecting sides of a subwoofer together (e.g. square 12 inch woofer—12 times 12 equals 144 square inches) and that’s it.
There’s a cone area calculation chart for round subwoofers in the rule book for quick easy reference. Once you know the amount of square inches of subwoofer cone area you have for each size of sub you have, simply multiply that amount by the amount of subwoofers you have in your vehicle and you’ll get the total cone area for your vehicle.
Once you’ve calculated the total subwoofer cone area of your sound system, refer to the vehicle criteria for each IdBL Division to determine what Division you will be able to compete in. And that’s it! You’re on your way to competing in IASCA IdBL competition!
Sound Pressure Level (SPL) measurement in decibels is registered using the IASCA AC-3056 RTA/SPL meter. Determining the winner is simple; the highest score in each class wins!
CD-R’s, CD-RW’s or MP3’s are not allowed to be used in the judging process. In IdBL, any commercially available CD that contains musical tracks or test tone tracks can be used to compete at Single Point (SPE) events. The official IASCA “Max dB2” CD is the required judging software at DPE (Double Point Event) or TKE (Territorial Key Event) events.
Typically, most show promoters will offer two scoring attempts, giving each competitor the opportunity to increase their previous score. The highest score of the two attempts will prevail.