JBL W10GTi, W15GTi, W12GTi owner manual The Official Brand of Live Music, Enclosure Construction

The Official Brand of Live Music

Enclosure Construction

5. Use PVC or ABS plastic pipe for ports.

Dual Coil Versus Differential Drive®

Figure 2. Conventional dual-voice-coil design

Please observe the following suggestions when building an enclosure for GTi Series subwoofers.

1.	Choose an enclosure design from the
	Enclosure Design Sheet included with
	your subwoofer.
2.	Use at least 3/4" (19mm) MDF (medium
	density fiberboard) or marine birch
	plywood to build the enclosure.
	Enclosures for 12" and larger
	subwoofers and smaller woofers driven
	by high-power amplifiers should be
	constructed using 1" (25mm) material.
3.	Join pieces of wood with glue and

Keep in mind that the openings at either

end of the port must be at least one port

diameter away from any obstruction.

6. Use the 10/24" machine screws and

T-nuts provided to mount the woofer to

the baffle. See Figure 1.

(patent pending)

Conventional dual-voice-coil woofers use a pair of voice coils “interwound” on the former and centered in the magnetic gap. The two coils may be connected in series or parallel in order to maximize an amplifier’s output power. Both coils drive the cone forward and rearward. Xmax (one-way-linear) is determined by the amount of voice coil exposed above and below the top plate. A conventional voice coil is made up of several layers of windings, each transferring heat to the winding next to it until the heat is finally

BOTH COILS DRIVE CONE FORWARD AND REARWARD

CONE

SPIDER

OVERHANG DETERMINES

Xmax

TOP PLATE

MAGNET

screws; do not use nails. Once the box

has been tested, seal all joints inside

the box with silicone caulk.

4. Fill the enclosure with damping material

(dacron, fiberglass insulation or

long-fiber wool) according to the design

you have chosen from the Enclosure

Design Sheet. “0% fill” indicates

that no damping material

Figure 1. Mounting the GTi woofer

in its enclosure

dissipated by the outside layer through the top plate, magnet and backplate. This arrangement is inefficient, and results in low thermal power handling. See Figure 2.

POLE PIECE / BACKPLATE

JBL GTi Series subwoofers employ Differential Drive, a technology developed by JBL Professional. Differential Drive employs two voice coils positioned at opposite ends of the former, each suspended in a separate magnetic gap. These two coils may be connected in series or parallel, like a conventional DVC woofer,

should be used; “50% fill” indicates that all interior walls except the baffle should be lined with 1" thick damping material, and “100% fill” indicates that the box should be loosely stuffed with damping material.

10/24"

SCREWS

(PROVIDED)

to maximize an amplifier’s output power. Both coils MUST be connected to the amplifier in correct polarity! At low power, both voice coils drive the woofer’s cone, and any motor nonlinearities are cancelled by the out-of-phase coils and gaps. As power input increases so that one coil rides completely out of its gap, force is still applied to the cone by the other coil. At extremely high power, each coil will enter

	T-NUTS
04
	(PROVIDED)