Polaroid LF-4215 - Manual

*TD-000141-00*

Cinema Loudspeaker Systems User Manual

LF-4215

Low Frequency Loudspeaker

Introduction

The LF-4215 dual 15” (381mm) low frequency enclosure is designed specifically for cinema
applications. Meeting cinema requirements for extended low frequency response differenti-
ates the LF-4215 from more conventional “rock-and-roll” woofer systems. The LF-4215 cov-
ers the frequency range from 35 Hertz to 1000 Hertz, depending upon the high frequency
system requirements. Close Coupled Woofers (CCW), with its tight spacing between woof-
ers, improves coupling and keeps coverage angles wide over a greater frequency range than
more widely spaced designs.

The two custom 400 watt, 15” transducers were developed especially for cinema use. They
feature extremely large 4” (100mm) voice coils and a multi-vented pole piece to ensure cool
operation, even at high power levels. Cooler temperatures increase transducer lifespan and
decrease the problem of power compression at high power. An undercut pole piece ensures
the voice coil operates in a Symmetrical Magnetic Gap (SMG), reducing second harmonic
distortion.

The enclosure is constructed of high quality MDF panels and features Single Woofer Cham-
bers (SWC, separate chambers for each transducer). In the rare event of a transducer failure,
this prevents over-excursion of the remaining transducer caused by improper box loading.

Large, Fully Radiused Ports (FRP) ensure smooth air flow through the ports, especially at
higher power. This prevents potentially audible port turbulence noise. Both internal and
external port openings are fully radiused.

With Symmetrical Port Loading (SPL), bass ports are evenly spaced on each side of the trans-
ducers, making internal pressure more uniform across the back surface of the transducer.
This prevents the cone from being displaced to one side or another by unbalanced forces,
reducing the chance of driving the voice coil out of the center of the gap at high power.

Three T-nuts in the top of the enclosure provide easy mounting of QSC’s HF-75 high fre-
quency system, or MH-1075 mid-high system.

Enclosure is not designed to be suspended, flown, or rigged. Do not sus-
pend, fly, or rig this enclosure.

This product is capable of producing sound pressure levels that can perma-
nently damage human hearing. Always keep sound pressure levels in the
listening area below levels that can damage human hearing.

Install in accordance with QSC Audio Product’s instructions and a
licensed, professional engineer. Only use attachments, mounts, accesso-
ries, 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 installa-
tion.

TD-000141-00 rev.D

© Copyright 2003, 2004, QSC Audio Products, Inc.

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

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

1675 MacArthur Blvd., Costa Mesa, CA, 92626 USA
Main Number (714) 754-6175 Sales & Marketing (714) 957-7100 or toll free (USA only) (800) 854-4079
Customer Service(714) 957-7150 or toll free (USA only) (800) 772-2834

Mounting points for high
or mid-high system