QSC HF-75 User Manual

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Cinema Loudspeaker Systems User Manual

HF-75 High Frequency Component

Introduction

The HF-75 is the high frequency component of the SC-422 two-way, biam­plified screen channel loudspeaker for high performance cinema applica­tions. The system is shipped as two separate components: the HF-75 high
frequency system and the LF-4215 dual 15” woofer system.

The HF-75 high-frequency system features a large format, 3” (75mm) tita­nium diaphragm compression driver mounted on a custom designed high­frequency cinema horn with an adjustable pan and tilt bracket. The horn fea­tures broad horizontal and vertical coverage angles to ensure coverage of
every seat in the auditorium. The horn is a low-distortion waveguide provid­ing highly articulate dialogue without the “honky” coloration associated
with conventional horn loudspeakers.

The HF-75 includes a driver protection and equalization network. DC block­ing 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 net­work 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 LF­4215 enclosure.

Mounting

Refer to the illustration for mounting information. The HF-75 attaches to the
top of the 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. Ser­vicing 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, cab­inets, 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, profes­sional engineer when any doubt or questions arise regarding
a physical equipment installation.

*TD-000149-00*

“QSC” and the QSC logo are registered with the U.S. Pa tent and Trademark Office

QSC® is a registered trademark of QSC Audio Products, Inc.

© Copyright 2003, QSC Audio Products, Inc.

TD-000149-00 rev.A

Connections

The HF-75 has barrier strip screw terminals that accept up to #10 AWG stranded loudspeaker wire.

HF INPUT Terminals

Connect the amplifier’s output signal to the loudspeaker’s HF INPUT terminals. Observe proper polarity; amplifier + signal to loud­speaker + HF INPUT, amplifier - signal to loudspeaker - HF INPUT. Use the largest wire size and shortest length for the application.

NOTE! Maintain proper loudspeaker connection polarity throughout the entire system for maximum performance.
Do not apply full range signal to the HF-75! There is no crossover in the HF-75, only a compensation/delay net­work. All required signal processing must be done upstream of the HF-75.

HF OUTPUT Terminals

The HF OUTPUT terminals are factory-connected to the compression driver. These terminals should ONLY be connected to the HF-75’s
compression driver.