Bass Loudspeakers - JBL D208H Instruction Manual

For connections up to 15 m (50 ft). 1 mm (#18 AWG) insulated wire
(ordinary household lamp cord) is the minimum size recommended. For
longer distances, we recommend the following minimum sizes: 1.3 mm
(#16 AWG) up to 30 m (100 It),and 1.6 mm (#14 AWG) up to 60 m (200 ft).
If lamp cord is used, wires can be differentiated by noting that one of the
insulating jackets is smooth, while the other has a distinct ridge.
Locate the loudspeaker output terminals on the back of the receiver or
power amplifier For each loudspeaker system, connect the "black" wire to
the amplifier output terminal labeled "common:' "ground" or ( - ) , and the
"red" wire to the remaining 8-ohm speaker output? The specified 8-ohm
impedance raling is a nominal figure which suggests a connection giving
the most efficient power transler between amplifier and loudspeaker system
Note that many amplifiers have a chassis grounding terminal which is
usually separated from the other connectors. This should not be confused
with the "ground" designation sometimes used to describe one of the two
terminals for each loudspeaker connection.
It is good practice to keep a loudspeaker in its original carton or placed
face down on a clean surface until installed in order to prevent accidental
cone damage. The aluminum center dome ot an extended range loud
speaker is particularly fragile and should not be touched. A grille on the
front of the enclosure will restrain the curious once the loudspeaker
system is complete
Mounting In An Enclosure Widest sound distribution will be realized
and response through the midrange region will be just a little more natural
and transparent when a loudspeaker is mounted to the front, rather than
back surface of the baffle panel. Use of T-nuts and machine screws,
provided within the carton packing material, allows the loudspeaker to be
removed and reinstalled repeatedly without damaging the enclosure. A
second, larger sei of hardware is supplied for rear mounting 300 mm
(12 in) units.
The seal between the loudspeaker frame and baffle panel must be airtight
When front mounted, a seal is achieved by fitting the white tubular vinyl
gasket into a groove on the back of the loudspeaker frame. (A flat, fiber
gasket is supplied with the D208H.) Loudspeakers that can be rear mounted
are provided with a facing gasket to form a seal. An airtight seal must also
be maintained where the input wires enter the enclosure.
When installing the loudspeaker, tighten the mounting screws evenly to
avoid the possibility of frame warpage. Avoid excessive force; tighten the
screws just enough to prevent air leaks between the frame and the
enclosure,
2 Connecting both speakers as described will insure proper in-phase operation:
i e.. iheir cones will respond to a monophonic signal by moving simultaneously in
the same direction, and not opposite to each other Inadvertent out-ol-phase operation
(which occurs when one set ot speaker wires is reversed v/ith respect to the other)
will not harm the system, but will cause some acoustical cancellation which will have
the audible effect ol reducing low Iroquency response.

Bass Loudspeakers

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