JBL 4348 owner manual Attenuator Adjustment, Attaching the Grills

III. Bi-amp Configuration Using Two Power Amplifiers and Internal Networking

Remove the short wires with the gold plated ring sleeves, and connect the high-frequency and low-frequency amplifiers to their respective terminals. Although the two power amplifiers do not need to be identical, they should have similar output performance and same gain, or gains set to the same level in advance, through input adjustments

IV. Bi-amp Configuration Using Two Power Amplifiers and a Commercial Channel Divider

Using a Phillips screwdriver, remove the screws on the subhatch located towards the top of the back panel. Remove the hatch.

Switch the mode switch inside to "Biamp" using a flat-head screwdriver, then screw the hatch back on.

Remove the short wires with the gold plated ring sleeves, and connect the high-frequency and low-frequency amplifiers to their respective terminals.

If you are using a channel divider that has a high-frequency level controller, the gain on the two amplifiers do not need to be the same.

*Caution

Except for bi-amp configuration with a channel divider, always keep the mode switch in the "Normal" position.

The positive terminals of the speaker have a red ring, and the negative terminals have a black ring. Be sure to connect with out mistaking the polarity. The speakers are designed so that when a positive signal is applied to the positive terminal, the woofer moves in the forward direction (positive phase operation).

When using the short wires with the gold plated ring sleeves, be sure that both the sleeves and the conductors are securely fastened to the terminals. In addition, use extra caution so that the cable conductors do not touch other sleeves and short out.

In order to safely and securely connect to the terminals, we recommend that you use the Y terminals or banana plugs on the cable ends.

5. Attenuator Adjustment

Independent, continuous variable attenuators are used for each unit to adjust the MF (mid-frequencies), HF (high- frequencies) and UHF (ultra-high-frequencies) levels to the speaker’s woofer level. The 0 dB position for each volume knob indicates a flat-level position in a test room, where there is little reverb. Make adjustments appropriate to the reverb in the actual room, and to your liking. In general, for most speakers, it takes about 1 – 2 months after initial use until the unit's vibration system yields optimum performance. As the level balance is expected to initially change with use, we recommend that you readjust the level accordingly.

6: Attaching the Grills

The speakers are shipped with the grill installed.

The purpose of the grill is to protect the units. The grill may be removed and re-attached as necessary.

The speaker has separate UPPER and LOWER grills. Furthermore, the UPPER and LOWER parts each have a top side and a bottom side, so attach them according to the figure to the right.