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GTi COMPETITION SPEAKER SYSTEM
TECHNOLOGY
LOW-DISTORTION WOOFER
Distortion – sound produced erroneously – is the enemy of great speaker performance. At its worst, distortion makes speakers sound broken. At more moderate
levels, distortion clouds the midrange, making vocals sound muddy and obscuring the music’s detail. At JBL, we’ve had more practice than any other speaker company
at eliminating distortion, and it shows. GTi competition speaker systems include the lowest-distortion woofers we’ve ever built.
In a loudspeaker, distortion can be produced by the cone, the motor, the suspension and even the movement of air through the speaker’s assembly. In designing the
670GTi woofer, JBL engineers have left no stone unturned. The basket, polepiece and voice coil former all include vents to eliminate any potential distortion caused
by the movement of air trapped within these parts. The ultrarigid Kevlar
®
cone eliminates unwanted cone fl exing (also called modal distortion), which can cause big
peaks and dips in the midrange response. The spider and surround are designed to ensure linear forward and rearward motion, minimizing distortion caused by the
speaker’s suspension. The motor includes a copper polepiece cap and a fl ux stabilization ring that work together to produce a linear voice coil inductance that mini-
mizes intermodulation distortion. Finally, an extralong voice coil ensures that the coil remains in the magnetic gap to minimize distortion at low frequencies and their
harmonics, and during high-output transients. The result is crystal-clear midrange, snappy mid-bass without any audible ringing or hang-over, and a smooth frequency
response that needs no compensation circuitry in the crossover (see illustration, below).
1. Spider-Landing Vents: Minimize distortion from mechanical noise.
2. Nomex
®
Spider: Provides linear force in both movement directions.
3. Nitrile-Butylene Surround: Ensures superior longevity.
4. Copper Polepiece Cap: Provides linear inductance over the full
range of forward voice-coil travel for reduced intermodulation
distortion. Provides crystal-clear vocals and midrange, even during
heavy bass signals.
5. Polished and Flared Polepiece Vent: Provides a low-velocity inlet
and outlet for the movement of air in and out of the motor structure.
Minimizes distortion from mechanical noise.
6. Neodymium Magnet: Provides high flux density. Also allows more
room for larger steel motor components to provide critical heatsink
mass for the voice coil.
7. Vented Gap Cooling
™
Ports: Provide movement of air over the voice
coil for superior power handling.
8. 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.
9. Voice Coil: Long, over-hung 2” diameter, aluminum edge-wound
voice coil provides high excursion for improved low-frequency ca-
pability. Reduces distortion at low frequencies and high input power.
10. Vented Voice Coil Former: Minimizes distortion from mechanical
noise.
11. Screw-Down Terminals: Ensures reliable high-quality connections.
12. Kevlar
®
Dustcap and Cone Body: Ultrarigid Kevlar dustcap and
cone body minimize unwanted cone flexing for smooth frequency
response.
13. Cast-Aluminum Basket: Provides a rigid support for motor and
moving assembly.
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