QSC Audio HF-75 User Manual

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*TD-000149-00*
Cinema Loudspeaker Systems User Manual
HF-75 
High Frequency Component
Introduction
The HF-75 is the high frequency component of the SC-412 and SC-422  two-
way, biamplified screen channel loudspeakers for high performance cinema 
applications. The system is shipped as two separate components: the HF-75 
high frequency system and the LF-4115 or LF-4215 woofer system.
The HF-75 high-frequency system features a large format, 3” (75mm) tita-
nium diaphragm compression driver mounted on a custom designed high-
frequency cinema horn with an adjustable pan and tilt bracket. The horn fea-
tures broad horizontal and vertical coverage angles to ensure coverage of 
every seat in the auditorium. The horn is a low-distortion waveguide provid-
ing highly articulate dialogue without the “honky” coloration associated 
with conventional horn loudspeakers.
The HF-75 includes a driver protection and equalization network. DC block-
ing capacitors protect against DC or low-frequency signals that would likely 
destroy an unprotected driver. Power limiter circuitry protects the driver from 
over-powering and a response correction filter smoothes the frequency 
response of the horn/driver combination. The driver and equalization net-
work provides for more reliable operation, ensuring the show will go on.
The HF-75 components come pre-assembled to reduce field assembly time. 
Three bolts are all that are required to secure the HF-75 to the top of the low 
frequency enclosure.
Mounting
Refer to the illustration for mounting information. The HF-75 attaches to the 
top of the LF-4115 or LF-4215 with three 5/16-18 bolts, 0.75” long, with lock 
washers. We recommend the use of serviceable thread locking compound 
when installing the bolts to prevent loosening due to vibration. Aim the horn 
in the horizontal plane (pan) before tightening. Adjust the vertical tilt with 
the bracket adjustment.
Install in accordance with QSC Audio Product’s instructions 
and a licensed, professional engineer. Only use attachments, 
mounts, accessories, or brackets specified by QSC Audio 
Products, Inc. Refer all servicing to qualified personnel. Ser-
vicing is required when the apparatus has been damaged in 
any way.
WARNING! Before placing, installing, rigging, or suspending 
any speaker product, inspect all hardware, suspension, cab-
inets, transducers, brackets and associated equipment for 
damage. Any missing, corroded, deformed or non-load rated 
component could significantly reduce the strength of the 
installation, placement, or array. Any such condition 
severely reduces the safety of the installation and should be 
immediately corrected. Use only hardware which is rated for 
the loading conditions of the installation and any possible 
short-term unexpected overloading. Never exceed the rating 
of the hardware or equipment. Consult a licensed, profes-
sional engineer when any doubt or questions arise regarding 
a physical equipment installation.
TD-000149-00 rev.D
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