QSC LF-4215 User Manual

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*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 drive levels. An undercut pole piece  

ensures the voice coil operates in a Symmetrical Magnetic Gap (SMG), reducing second har-

monic 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 drive levels. 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 drive levels.

Three T-nuts in the top of the enclosure provide easy mounting of QSC high frequency sys-

tems.

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.B

© 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

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