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Big Audio Dynamite - JL Audio System

Posted in How To on January 1, 2003
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Contributors: Randall JachmannCourtesy Of JL Audio
Photographers: Courtesy Of JL Audio

Here's the scenario: You have your off-roader outfitted with all the bling-bling double throw down hop-ups available. Big lift, wheels and tires, winch, lockers, and so on. One thing is missing: A decent sound system with crisp highs, distinct mids, and thumpin' lows. With the amount of time spent inside the cab, tunes are just as important as everything else.

These days, technology has taken mobile audio systems to a new level. One company that has set high standards in the sound department is JL Audio. Classed as an upper end audio component manufacturing company, JL Audio products are a wise choice for the mobile audiophile. Its product line ranges from amps to specific built Stealth subwoofer enclosure to separate mids, tweeters, and woofers.

When we pitched our story idea of upgrading our Project Jeep Grand Cherokee Limited 5.9. with JL Audio amplifiers and speakers, JL thought this would be great way to showcase its products to the readers of OFF-ROAD magazine.

After going over the blueprint of the vehicle, the tech staff at JL Audio came up with the audio components showcased in this story. We would keep the stock head unit, but would install two new amps: a 500x1 that will power the subwoofer and a 300x4 that will handle the rest of the speakers. A Stealthbox that specifically fits the Jeep houses a 10-inch sub, the XR650 Csi two-way component system, and a set of VR650 Cxi coaxial speakers. Pacific Audio in Fullerton, California, handled the installation of the project.

SpecificationsNominal diameter: 10 inches (250 mm)Continuous power handling: 250 WattsVoice coil: 2.25-inch diameter, four-layer, Kapton formerAvailable configurations: Dual 2 ohm, Dual 4 ohm, or Dual 6 ohmXmax (one-way, linear): 0.51-0.58-inch(13.0-14.7 mm) depending on specific modelSealed enclosure range: 0.60-0.90 cu ft (17.0-25.5 liters)Ported enclosure range: 1.00-1.50 cu ft(28.3-42.0 liters)VRC(tm) technology: Yes

The Amplifiers500 1 Sub Amp300 4 AmpJL Audio subwoofer amplifiers and the subwoofer channel of the 500/5 use a new Class D circuit that represents a significant advance in subwoofer amp design. While Class D amplifiers are well known for outstanding efficiency, they have also been known for less than spectacular sound quality because of weak damping of the driven load. Damping factor is critical to subwoofer amplifier performance as it provides the necessary force to control the high moving mass of subwoofers. Poor damping can result in degraded transient response (sloppy sounding bass) and irregular frequency response.

JL Audio's patented Class D output circuit uses a discrete control section and a unique feedback loop design that results in a damping factor greater than 500 at 4 ohms (250 at 2 ohms). This is vastly higher than other Class D designs and also higher than most Class AB amplifiers. The benefit of this exclusive JL Audio technology is tight, clean bass reproduction with the efficiency advantage of Class D.

JL Audio full-range amplifiers also benefit from an exciting new technology: Absolute Symmetry.

Until recently, the accepted approach for building high-fidelity Class AB amplifiers has been to utilize complementary output stages, which use different types of transistors to push the speaker and pull the speaker. The problem with this approach is that true mirror-image transistors are impossible to create, leading to asymmetrical clipping behavior.

Another approach is to use the same type of transistor for both push and pull but without buffering from the load impedance. This solves the problem of asymmetrical clipping, but leads to huge increases in distortion as load impedance drops (making this design less desirable than the complementary approach.)

JL Audio amplifiers solve the entire issue once and for all with a revolutionary Class AB circuit that employs identical-type transistors for push and pull with true buffering from the load impedance. Jl's design achieves absolute power symmetry and extremely low distortion over a wide range of load impedances. It is the most significant breakthrough in Class AB circuit design in quite some time and it is patented by JL Audio.

R.I.P.S. SystemR.I.P.S. stands for "Regulated Intelligent Power Supply" and is a central feature of JL Audio's new amplifiers.

Regulated means the power supply adjusts its operation so as to maintain the amplifier's rated power output over a wide range of vehicle voltages (11V-14.5 V). Conventional, unregulated power supplies result in significant power losses as battery voltage decreases. With a JL Audio amplifier, the power output remains consistent in real-world systems, resulting in superior fidelity and stability.

The Intelligent portion of the R.I.P.S. System is a circuit that actually monitors output current to optimize the amplifier's output power over a wide range of load impedances (1.5 ohm-4 ohm per channel). Conventional amplifiers are designed to produce optimum power at a particular impedance (2 ohm, for example). When asked to run more than that impedance (say, 4 ohm), these amplifiers lose power (half their power from 2 ohm to 4 ohm). This will not happen with a JL Audio amplifier because the R.I.P.S. System detects the actual impedance being driven and adjusts output rail voltages to deliver optimum output. The entire process is seamless, automatic, and results in incredible dynamics for satellite channels and consistent power output for a wide range of subwoofer configurations. It also takes into account the real impedance of the system, rather than relying on often inaccurate assumptions based on a speaker's nominal impedance.

The bottom line of the R.I.P.S. system is: optimum power at any impedance between 1.5 ohm and 4 ohm per channel at any vehicle voltage between 11 and 14.5V.

XR650 Csi6.5-inch (160mm)Two-Way Component SystemThe XR component woofers are built with suspensions and cones from the leading manufacturer of such parts: Dr. Kurt Muller and Co. These parts are expensive, but they also represent the best the world has to offer and are integral to the incredible sonic quality and consistency of the XR products.

The long-throw component woofer features a mineral-filled, polypropylene cone body with a butyl rubber surround and a highly optimized motor system, delivering stunning midbass impact and midrange quality.

The tweeter is a neodymium magnet, ferrofluid-cooled, 1-inch (25mm) aluminum dome with a synthetic rubber surround that damps unwanted ringing for smooth, non-fatiguing output. The component tweeter features JL Audio's's exclusive RSR mounting system, permitting precise alignment after installation for optimum performance.

High-end, programmable crossover networks with premium polypropylene capacitors, premium inductors, and solid-state tweeter protection round out the package. Crossover networks can be programmed to 15 possible settings (three midrange presence settings, five tweeter level settings). The crossover networks are attractively presented in a smoked acrylic case that complements any installation.

500 1Power AmpSpecificationsRated power: 500-watt RMS @ 1.5 ohm-4 ohm (11V-14.5V)THD at rated power: 0.05% @ 4 ohmS/N Ratio: 95dB below rated powerFrequency response: 5 Hz-500 Hz (+0, -1dB)Damping factor: 500 @ 4 ohm/50 HzInput range: switchable from 200mV-2V RMS to 800mV-8V RMSDimensions: 13.4"L x 9.25"W x 2.36"HFeatures: Differential-Balanced Input Topology:(1 pair of inputs)On-board crossover: fully-variable (40-200 Hz), selectable-slope LP (12 or 24 dB per octave)Preamp output: two-channel (independent active filter, parallel with amp filter or full-range)Bass EQ: parametric with variable boost as much as 15dB and remote bass control (optional)Infrasonic filter: fully-variable 24dB/octave from 15-60 HSignal-Sensing turn-on: permits operation without remote leadDual mono speaker output connections: accept up to 8ga. Wire +12V and Ground connections: accept up to 4ga. Wire

300x4 Power AmpSpecificationsRated power (stereo): 75 W RMS x 4 @ 1.5 ohm-4 ohm (11V-14.5V)Rated power (bridged): 150 W RMS x 2 @ 3 ohm-8 ohm (11V-14.5V)THD at rated power: 0.03% @ 4 ohm S/N Ratio: 108.5 dB below rated powerFrequency response: 5 Hz-30 KHz (+0, -1dB)Damping factor: 200 <\@> 4 ohm per ch./50 HzInput range: switchable from 200mV-2V RMS to 800mV-8V RMSDimensions: 13.4"L x 9.25"W x 2.36"HFeatures: Differential-Balanced Input Topology: (2 pairs of inputs)Front crossover: fully-variable (50 Hz-5 KHz), selectable-slope LP or HP (12 or 24 dB per octave)Rear crossover: fully-variable (50 Hz-5 KHz), selectable-slope LP or HP (12 or 24 dB per octave)Speaker output connections: accept up to 8ga. wire+12V and Ground connections: accept up to 4ga. Wire

SpecificationsTwo-way system6.5-inch (160 mm) woofer1-inch (25 mm) aluminum dome tweeterGrilles included70W continuous power handlingRec. Amp Power: 25-150 watts89.5 dB Efficiency @ 1W/1mFR: 48 Hz - 25 KHz 3 dB

Specifications6-inch (150 mm) coaxialGrilles included60W continuous power handlingRec. Amp Power: 15-100 watts89.0 dB Efficiency at 1W/1mFR: 59 Hz - 22 KHz 3 dB

Sources

Pacific Audio
Fullerton, CA 92831
JL Audio Inc
Miramar, FL 33025-3962

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