Midrange And High Frequency Drivers - JBL D208H Instruction Manual

Fine Tuning An Enclosure If you are using the detailed plans contained
in the JBL Enclosure Construction Kit, follow the porting information
provided; it has been validated by the JBL engineering stafl. When
constructing an enclosure of your own design, use of the porting chart for
home entertainment loudspeakers (included in the JBL Enclosure
Construction Kit) will result in excellent bass reproduction. Since each
recommendation in the chart is averaged for the range of enclosure
volumes indicated, the audio perfectionist may wish to further tune his
enclosure in order to achieve optimum bass potential. The fine tuning
procedure is also useful when dealing with an irregularly shaped enclosure
for which calculating the internal volume would be difficult.
The fine tuning procedure is described in the JBL Enclosure Construc-
tion Kit. In most instances, following the porting chart will result in a
measured tuning frequency within 10% of the optimum recommended for
the loudspeaker (see chart below), and therefore, the improvement realized
by completing the fine tuning procedure may not always be audible.
Recommended Tuning Frequency For
Model
124H
I36H
LESI H
LE10H
LE14H
LE15H
D130H
130H
D208H
I) system tuning is higner than recomn-eindcd for the loudspeake' covai a portun pi the non or lengthen ihe duct
il one Is used. Conversely, if system luniity id kJwar than recommended ma«o 1r-<j pert terser or ahoitan Ilia duel.
When tuning a pass-vc radiator. begin with 'e^ver w t T f l v.ctgnts than recommended for ttte enclosure volume Add
iveights J syslsm luning is higher Ilari recommended remrjve weights it the system tuning .u lortor than desired
A passivo rad atcr can be lemporanty rrounled inside PUT so ihc luning weights are easily accessible Additional
washers used in conjunction win the •/.eights supplied vvitl aid in obtaining precise tuning.

Midrange And High Frequency Drivers

The LE5H, LE21H, 075.and 077 mount directly to the enclosure baffle
panel, and compression drivers are bolted to their appropriate horns. Com-
ponents and horns intended for enclosure mounting are provided with a
tubular vinyl flange gasket for an airtight installation. Large freestanding
horns, of course, do not require such a gasket.
With the exception of freestanding horns, a high frequency unit is
normally positioned on the baffle panel directly above or below the bass
loudspeaker, and slightly to the side if necessary to accommodate panel
dimensions. If the distance between the pair of enclosures is limited, the
high frequency units can be mounted on the outboard side of their
respective bass loudspeakers; conversely, if the enclosures are further
apart than average, the high frequency units can be mounted on the
JBL Loudspeakers
Description
300 mm (12 in) low frequency
380 mm (15 in) low frequency
200 mm f8 in] full range
250 mm [10 in) low frequency
360 mm C 1 4 in) low frequency
380 mm (15 in) low frequency
380 mm (15 in) extended rango
380 mm (15 in) lowfrequency
200 mm (6 in) extended range
fcncfosure
tuning
Frequency
26 Hz
32 Hz 32 Hz
45 Hz
Hz
5 5