Horns And Acoustic Lenses - JBL D208H Instruction Manual

LEI75.LE85 And 376 Compression Drivers A compression driver
musi be bolted to the appropriate high frequency horn, which in turn, will
be mounted to the baffle panel or freestanding on top of the enclosure.
Bolts (%-20. 'Aè' hex head) supplied with the driver should be tightened
evenly, and just enough to achieve a snug fit without overtightening. The
perforated center section o( the fiber gasket on the mating surface of the
driver must be removed before installation. It is good practice to cover the
exposed throat opening with plastic electrical tape whenever the driver is
not actually installed on a horn to prevent foreign matter from entering
the driver, particularly iron filings or chips which can be attracted by the
strong magnetic field which exists in the driver throat

Horns And Acoustic Lenses

A horn/lens assembly couples the output of a compression driver to the
air in the listening environment and spreads the sound outward throughout
the room in a predetermined pattern.The smaller horn/lens assemblies
are usually mounted to the enclosure baffle panel; the larger horn/lens
assemblies will be freestanding on top of the enclosure.
Caution: When a horn is mounted to a sturdy baffle panel of the recom-
mended thickness, it will not be necessary to support the driver However,
the driver must be separately braced or removed from the enclosure
whenever the loudspeaker system is transported, since under such circum-
stances it is possible lor the weight of the driver to pull the horn from
the baffle panel.
HL87 Perforated-Plate Horn/Lens The HL87 mounts from the front of
the enclosure in a 134 mm (5%? in) diameter baffle cutout. It is secured
by four machine screws and T-nuts. After making the baffle cutout, place
the HL87 in position and use it as a pattern to mark the location of the
holes for the mounting screws. The drill bit size required for the T-nuts
is 8 mm in).
(Me
HL88 Perforated-Plate, HL89 Serpentine And HL90 Slant-Piate
Horn/Lens Assemblies These large horn/lens assemblies mount on top
of the enclosure. The mounting brackets must bo assembled to the
horn/lens per the accompanying illustrations. The HL89 is shown with the
MA25 installation kit, consisting of mounting brackets and a baffle which
is required for optimum performance. It is also possible to mount an HL89
on the enclosure baffle panel using the cutout illustrated.
HL91, HL92 And HL93 Slant-Plate Horn/Lens Assemblies The HL91.
HL92 and HL93 mount on the enclosure baffle panel, as illustrated- The
baffle cutout is 108 mm (4% in) in diameter. Countersink the four 7 mm
0& in) holes for the flathead mounting screws The white vinyl ring gasket
should be placed on the horn mounting flange to insure an airtight seal.
(Continued on page 12.)