User manual JBL 660GTI

[. . . ] 60TH ANNIVERSARY EDITION 560GTi/660GTi COMPETITION SPEAKER SYSTEMS OWNER'S GUIDE FOR MORE THAN 60 YEARS, JBL ® HAS DELIVERED PRODUCTS THAT EXEMPLIFY THE TECHNOLOGY AND EXPERTISE GAINED THROUGH A LEADERSHIP ROLE IN PROFESSIONAL SOUND REPRODUCTION. THE JBL NAME HAS BEEN SYNONYMOUS WITH THE PRECISE, NATURALLY ARTICULATED SOUND FOUND IN MANY OF THE WORLD'S MOST PRESTIGIOUS LOCATIONS, INCLUDING CLUBS, CINEMAS AND RECORDING STUDIOS, AND LIVE-MUSIC REINFORCEMENT IN VENUES RANGING FROM CONCERT HALLS TO OUTDOOR STADIUMS. JBL LOUDSPEAKERS ARE FOR THOSE WHO WON'T COMPROMISE ­ IN THE STUDIO, AT HOME OR ON THE ROAD. MORE THAN ANY OTHER COMPONENT, SPEAKERS DEFINE THE SOUND OF AN AUDIO SYSTEM. THEY ARE THE CRITICAL CHOICE THAT DETERMINES ULTIMATE PERFORMANCE. [. . . ] Neodymium Magnet: Provides high flux density. Also allows more room for larger steel motor components to provide critical heatsink mass for the voice coil. Vented Gap CoolingTM Ports: Provide movement of air over the voice coil for superior power handling. Flux Stabilization Ring: Provides global stabilization of the static magnetic field and works with the copper cap to minimize coil inductance during inward movement of the voice coil. Voice Coil: Long, over-hung 2" diameter, aluminum edge-wound voice coil provides high excursion for improved low-frequency capability. Reduces distortion at low frequencies and high input power. Vented Voice Coil Former: Minimizes distortion from mechanical noise. Screw-Down Terminals: Ensures reliable high-quality connections. Kevlar Dustcap and Cone Body: Ultrarigid Kevlar dustcap and cone body minimize unwanted cone flexing for smooth frequency response. ® 1 2 3 4 5 6 7 8 9 10 11 12 13. Cast-Aluminum Basket: Provides a rigid support for motor and moving assembly. Figure 1 13 6 TWEETERS, WAVEGUIDES AND OPTIMAL FREQUENCY RESPONSE The dispersion pattern of the sound produced by a speaker is different at low frequencies than at high frequencies. At frequencies with wavelengths greater than the circumference of the speaker's cone ­ the speaker's piston range ­ the sound is radiated in all directions. At higher frequencies, the dispersion pattern narrows. At frequencies for which the circumference of the speaker is about five times the sound's wavelength, the coverage area narrows sharply and the off-axis sound contains far less high-frequency content. This phenomenon occurs for every speaker. For multi-way speaker systems, designers have to contend with this condition for each driver in the system. What makes matters more difficult is that in the crossover region between a large low-frequency driver and a small high-frequency driver, the speakers' behaviors are opposite ­ the dispersion pattern of the woofer is narrow and the dispersion pattern of the tweeter is wide (see Figures 2 and 3). A multi-way speaker that is designed using only measurements of the on-axis response can sound terrible. An analysis of the frequency response of many speakers designed this way reveals a big hole in the off-axis response at the crossover frequency, where the woofer's output is focused into the forward angles (see Figure 4). dBSPL On Axis Off Axis 0° 0 ­10 30° 60° ­30 270° Figure 2. We make measurements of the speakers in two semicircular patterns along the horizontal and vertical axes of the speaker (Figure 7). With those measurements, we determine the size of the optimal listening window and calculate the sound power of the speaker. We then compare the sound power to the response in the listening window and plot the directivity index for the speaker system's frequency response. [. . . ] Woofer aimed across the car, and tweeter aimed at a point between the driver and passenger. Woofer coverage provided by a single window. Tweeter coverage provided by separate listening windows. Listening window illustrated in three dimensions. +65° +35° +5° 0° -5° Figure 18. [. . . ]