B-Pillar - The B-Pillar is the portion of the automobile where the front door latches are located. We use the leading edge of this pillar (also called the "doorjamb" in this rule book) to define an imaginary plane that is used to determine compliance with the "String Test".
C-Pillar - The portion of the vehicle where the rear-most door latches are located.
Certified Class - The standard class that a competitor competed in when establishing their Certified SPL.
Certified Event - Any multi-point dB Drag Racing event.
Certified SPL - The competitor's highest winning score at any multi-point event.
Commercial Vehicle - A vehicle that is not intended for use in consumer applications. Examples include Cargo Vans, Ambulances, Panel Trucks, School Buses, etc.
Competitor / Contestant - The sole operator of the sound system (not a teammate.)
Conductor - A conductor is a single wire (solid or stranded) that is used to carry electrical current. A traditional speaker wire consists of two conductors (one positive and one negative).
Consumer Removable Component - The dBDRA defines a consumer removable component (such as a seat) as an OEM component that was designed for removal as a part of the normal operation of the vehicle.
Discrete Voice Coil - The dBDRA defines a discrete voice coil as one that is electrically isolated from other voice coils in the woofer. A maximum of 2 binding posts or terminals (+ and -) are allowed per discrete voice coil. The dBDRA reserves the right to determine the actual number of discrete voice coils contained in a woofer.
Jump Seat - The dBDRA defines a "jump seat" as an OEM seat that was designed to be folded up against the side or back of the pickup's passenger compartment.
Metering - This is the process where the Sound Pressure Level or SPL of your vehicle is measured. The resultant score in decibels (dB) is your score.
OEM Equivalent - Please refer to Section 3-8 for more specific information.
Normal Use - Most of the classes in dB Drag Racing require the vehicle to meet certain "Normal Use" requirements. Please refer to Section 3-8 for more specific information.
Passive Radiator - A passive radiator is a diaphragm that is made like a woofer but has no coil or magnet. Woofers may not be used as passive radiators in dB Drag Racing.
Power Rating - When amplifier power limits are specified, the dBDRA will use an approved power clamp meter to verify compliance during competition. If power meters are not available, the dBDRA will use the maximum published RMS rating for the amplifier. (The dBDRA reserves the right to verify the accuracy of any published rating.)
Speaker - The dBDRA defines a conventional loudspeaker as a sound reproducing electro-mechanical transducer that incorporates a cone, surround, basket, and voice-coil.
SPL - Sound Pressure Level - This value is expressed in decibels or "dB" for short. The higher the number, the louder the sound. An increase of 3 dB represents a doubling of acoustic energy. An increase of 10 dB represents a tenfold increase in acoustic energy and will sound twice as loud to the human ear.
Standard Battery - The dBDRA defines a "standard battery" as a battery that has a nominal terminal voltage of 12-Volts, consists of 6 internal series-connected cells, and is lead/acid or gel-type in nature. This battery is used as the primary battery in the vehicle (either OEM or an aftermarket replacement) and is permanently connected to the vehicle's electrical system.
String Test - Two judges position themselves on opposite sides of the vehicle. A string (or wire) is passed through the open doors of the vehicle. Both judges pull the string so that it is taught. Next, the judges move the string in unison so that the string slides along the trailing edge of each judge's respective doorjamb. If the string does not touch the enclosure (or loudspeakers), then the test passes. (The specifics for this rule may be found in section 6-2.)
Wall - The dBDRA defines a speaker wall as any subwoofer enclosure and / or baffle board that meets one or more of the following conditions...
Enclosures that are greater than 30 inches (76.2 cm) in height.
Enclosures that encroach upon "Normal Use" requirements for the passenger compartment.
Any installation which results in a vertical clearance between the top of the enclosure and the headliner of 13 inches (33 cm) or less. (This clearance requirement also applies to any equipment which may be mounted to the enclosure.)
Wall Test - The judge shall use a mic jig (or other appropriate measuring device) to verify a vertical clearance of 13 inches (33 cm) exists between the highest point on top of the enclosure (and any equipment attached to the enclosure) and the headliner directly above that point. (The judge will select the highest point on the enclosure that is most advantageous to the competitor. This will normally be in the center of the vehicle.) The judge will then verify (if necessary) the height of the enclosure to ensure that it is less than 30 inches (76.2 cm) in height.
Wall Test Hatchback Examples
Case 1 - The subwoofer enclosure is located ENTIRELY underneath the rear hatch OR the highest point on the enclosure is located underneath the hatch.
In this example the judge will measure from the highest point on the enclosure (including amps, accessories, woofer surrounds, etc.) to the horizontal plane defined by a point located at the top center of the hatch opening. (Please refer to Figure 106-6, 106-7a, and 106-7b.)
Case 2 - The subwoofer enclosure is NOT located entirely underneath the rear hatch. In addition, the highest point on the enclosure is located directly beneath the headliner.
In this case the standard wall test technique will be used. (From the highest point on the enclosure to the headliner.) Figures 106-6, 106-7a, and 106-7b do NOT apply in this case.
Woofer - A loudspeaker designed for the reproduction of bass. Also referred to as driver, subwoofer, or subs. The dBDRA considers speakers with maximum diameters of 10 inches (25.4 cm) or larger to be woofers.
Vehicle Skin - The dBDRA defines the "skin" of the vehicle as the external shell (top, front, back, and sides) of the vehicle's OEM body that gives the vehicle its distinctive appearance. This is also the part of the vehicle that is normally painted. The underside or undercarriage of the vehicle is not considered to be a part of the OEM "skin".
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