System Design Using the GTH400 | JBL GTH400-20107 specification

GTH400-20107 06/03/98 15:49 Side 6

3.System Design Using the GTH400

3.1 Speaker Requirements

When used in the non-bridged mode a group-channel of the GTH400 can easily drive two 2-ohm speaker loads. When only one speaker is connected to the left and right outputs of a group, virtually any conventional speaker may be used. When two speakers are connected in parallel to a single output (left or right) of a given group, each speaker must have a minimum impedance of at least 4 ohms. This ensures that the combined load will not drop below 2 ohms. Although the amplifier will not be damaged, load impedances lower than 2 ohms will eventually cause the amplifier to overheat, activating the protection circuits and causing the unit to shut off until it cools down sufficiently.

Parallel Wiring

(+)
(+)
2 ohms	4 ohms	4 ohms
Nominal	4 ohms	4 ohms
Impedance

(–)

Series Wiring

(+)

4 ohms

8ohms Nominal Impedance

(–) 4 ohms

When a group of the GTH400 is in bridged mode, the combined impedance of the speaker (or speakers) connected to the bridged channels should be at least 4 ohms. As in the example above, sustained operation of the GTH400 in bridged mode with less than 4 ohms will likely cause overheating.

The GTH400 must not be used with speakers that have either one of their input terminals wired to the frame of the speaker or to the chassis of the vehicle.