JBL is big in the pro audio market and is building momentum on the car side with the development of their GTi line of speakers. Just over a year ago, JBL introduced the revamped GTi subwoofer series, subs designed to handle power, lots of it! SPL was not the only goal in the design; the idea behind them is to reproduce sound with low distortion and a big emphasis on sound quality, all the while maintaining high output. That means you need a clean, powerful amplifier to go with it. Now this is not the company's only car audio line, just the most prestigious. On a previous trip to the JBL facility in New York, we asked Chris Dragon, director of brand marketing for the mobile division, how their component speaker line compared to other brands. Exuding confidence he replied that JBL could stand toe to toe with anyone, producing equivalent, if not better, sound quality and with less cost to the consumer. He was basing that, he said, on JBL's superior manufacturing facilities and the untouchable technological know-how of a company that dominates nearly every dimension of the pro audio business. For instance, if you've heard live music, chances are you've listened to JBL loudspeakers. After hearing such assured claims we made a note to ourselves to definitely do a little more investigation.
JBL/Crown Connection
So we made our way to Elkhart, Indiana, a very "down home" town off the beaten path. The best way to get there is to fly into Chicago (they know how to land planes in the snow, you dig) and make the two-hour drive. Elkhart is the kind of place that reminds you of a simpler time; that is, before a global economy and the concomitant marketing hype. If you were to get the plain honest truth, as they say, anywhere, then this seemed to be the place where you'd find it. Casey Thorson and I, laser sight pens and a grid-map plot paper in hand, went off in search of the 6,000-watt beast! Driving into Elkhart we had the feeling we were on an X-file mission; a small group hunt (by invite only) with only one shot to get our mark. No professional K.C. registered hunting dogs allowed.
Joking aside, the company we were searching for was Crown International. This company is well known in the world of pro sound and live performance because of their amplifiers. Since this is the sound we car audio folks dream to re-create in our cars, it makes sense to turn for a bit of advice to the people that help make the live music happen. If you are JBL, a fish in the pond of the Harman International Company, why not use the technology from those who know amps best? This is exactly what the people at JBL did with the new addition of Crown International to the Harman family.
When the JBL and Crown folks set out to design this new car audio-specific amplifier, it was decided that a car-specific engineering team would be put together to work under Gerald Stanley (see side bar). Making Bob Chadderdon Product Development Manager for the car audio division was the just the start. Then they would collect three young ambitious engineers. Fresh out of college, Robert Siegel, Jeremy Bules and Brian Wachtman were hired to develop an arbitrarily large amplifier. Large may be an understatement as this amplifier is set to eclipse the closest competitor with over double the power. JBL raised the power bar high, 6,000 watts high. This may seem a bit extreme, but the company is out to prove two points: one, it has the technology and resources to build an amp of such incredible power; two, JBL has the know-how and experience to build a subwoofer to handle such an amplifier.
Building an amplifier of such high power using conventional technology is exceptionally difficult and many factors must be considered, such as choosing a class designation to start with. Typically, Class AB amplifiers have an efficiency rating that is not acceptable for an amplifier of this stature in the car environment. Class D amplifiers generally lack sound quality with a low damping factor, slow slew rates, a high THD and a physical design that can be a challenge for full range applications. JBL understands this well and this is the main reason they joined forces with their sister company, Crown. With the mastermind Gerald Stanley behind the technology, Crown has reached a milestone with a new topology referred to as Class I (Interleave) which is used in many of their pro audio amplifiers. Crown refers to this technology as BCA(TM) (Balanced Current Amplifier).
The benefits of Class I (BCA) are numerous:
· Efficiency is as good as or better than Class D.
· Superior damping factor.
· Linearity is very high.
· Low THD.
· Simple output filtering and increased bandwidth feedback result in greater fidelity.
· PWM supply switching allows for full range output.
The benefits of Class I make a 6,000-watt RMS amplifier possible. And Crown is not a foreigner to the technology or producing big power amps. This is their bread and butter. So taking on the request was not a question of whether or not Crown could produce this amp, but how quickly they could do it.
But before all this design process began, this newly formed car audio team spent some time studying the market and going out to the competitions and listening to all the competitors and their concerns, with note pads in hand of course.
With their notebooks full, they set about designing the amplifier. It started life on the computer and quickly the team realized from looking at it on the monitor that the size would be quite large; so to get a physical feel, cardboard, Styrofoam and wood were used to mock up the parts that would make up the amplifier. This was also a good case study due to the development of a new amp design for the 12-volt market. While most amplifiers will have a fist-sized torroid in the power supply, the newly developed one for the JBL/Crown project is the largest car audio amp we've seen! Even larger than the standard commercial concert models! It looks like something the power company should be using to power a small city such as the one we were in.
In an upcoming issue we will have the coveted opportunity to lay this behemoth on our test bench and see what is beneath the wild exterior, which we anticipate conceals an even wilder side of technology.