QSC LF-4215 User manual

*TD-000141-00*
Cinema Loudspeaker Systems User Manual
LF-4215and LF-4215-8 Low Frequency Loudspeakers
Introduction
The LF-4215 dual 15” (381mm) low frequency enclosure is designed specifically for cinema
applications. Meeting cinema requirements for extended low frequency response differentiates
the LF-4215 from more conventional “rock-and-roll” woofer systems. The LF-4215 covers 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 woofers, improves
coupling and keeps coverage angles wide over a greater frequency range than more widely
spaced designs. The LF-4215-8 is an 8 ohm version of the standard 4 ohm LF-4215.
The two custom 400 watt, 15” transducers were developed especially for cinema use. They fea-
ture extremely large 4” (100mm) voice coils and a multi-vented pole piece to ensure cool opera-
tion, 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 Chambers
(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 frequency
system, or MH-1075 mid-high system.
Enclosure is not designed to be suspended, flown, or rigged. Do not suspend,
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 lis-
tening 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, accessories, or brack-
ets specified by QSC Audio Products, Inc. Refer all servicing to qualified per-
sonnel. 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 hard-
ware which is rated for the loading conditions of the installation and any pos-
sible 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-000141-00 rev.E
© Copyright 2003, 2004, 2007, 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 [phone] Sales & Marketing [phone] or toll free (USA only) [phone]
Customer Service(714) 957-7150 or toll free (USA only) [phone]
Mounting points for high
or mid-high system

Connections
Normal Connection
The LF-4215 has barrier strip screw termi-
nals for connection. The terminals accept
up to #10 AWG stranded loudspeaker wir-
ing. Use the largest wire size and shortest
wire length possible for a given installa-
tion. Observe the polarity markings and
keep polarity consistent throughout the
system for best performance.
Parallel Connection of Second LF-4215
The terminals marker SPK2 may be used to
connect another LF-4215 in parallel. Con-
nect the wires as shown in the illustration,
at right. Note: If the LF-4215’s internal wir-
ing has been modified in any way, this may
not function. If this is the case, remove the
terminal cup and verify the presence of the
factory yellow jumper and blue jumper
wires; remedy as required or have the
loudspeaker serviced.
Individual Transducer Connection
(requires modification)
CAUTION! Requires removal of
terminal cup and cutting of
both the yellow and the blue
jumper wires that connect the
SPK1 and SPK2 terminals.
The transducers are wired in parallel
inside the enclosure. If individual trans-
ducer connection is required, remove the
terminal cup and remove the yellow and
the blue jumper wires that are connected
between the SPK1 and SPK2 terminals.
Replace the terminal cup and mark the
enclosure with a note of the modification.
Normal Connection Example:
Parallel Connection Example:
Individual Transducer
Connection Example:

LF-4215 Specifications (subject to change without notice)
Frequency Range: 38 - 1300 Hertz (±3 dB)
30 - 1400 Hertz useable range (-10 dB)
Nominal Coverage: 100° horizontal X 55° vertical at 600 Hertz
Maximum Output: 134.5 dB SPL calculated peak, 1 meter, half space, at rated rms power with 6 dB crest factor pink noise input, 25 - 250 Hertz.
128.5 dBA SPL calculated maximum continuous, 1 meter. The dBA scale is typically used to identify sound sources
which can cause permanent hearing loss.
Impedance: 4 ohms nominal (8 ohms nominal, LF-4215-8)
Maximum Input Power: 800 watts rms (100 hours of 6 dB crest factor pink noise, 30 - 500 Hertz)
1000 watts rms (2 hours of 6 dB crest factor pink noise, 30 - 500 Hertz, AES method)
recommended amplifier power capability- 1600 watts rms maximum into 4 ohms (LF-4215) or 8 ohms (LF-4215-8)
Sensitivity: 99.5 dB half space, 93.5 dB full space, 35 - 1000 Hertz, 1 watt, 1 meter
Recommended Processing: Subsonic filter below 30 Hertz, >18 dB per octave, maximum recommended crossover frequency is 1000 Hertz. QSC
DSP configurations are available at www.qscaudio.com. Parameters for alternative processing hardware are available
upon request.
Connectors: Barrier strip screw terminals accept up to #10 AWG stranded wire. Four terminals: (two INPUT and two PARALLEL
OUT). Drivers are internally wired in parallel. For independent transducer connection, remove blue jumper wire and yel-
low jumper wire on internal-side of terminal cup and mark enclosure accordingly.
Transducers: Two 15” (381mm) high efficiency low frequency transducers featuring vented 4” (100mm) copper voice coils on Kap-
ton® formers. High excursion/low distortion design, with extremely high power handling, and low thermal and port
compression.
Enclosure: Quasi B4 alignment, ported enclosure with fully flared ports, low turbulence symmetrical port design, tuned to 36
Hertz, constructed of medium density fibreboard and heavily braced. Features vandal resistant woofer mounting bolts.
Size: 30” wide X 35” high X 20” deep (762 mm X 889 mm X 508 mm)
Weight: 195 lbs. shipping, 172 lbs. net (88/78 kg.)
SPL and Impedance vs. Frequency
Frequency (Hertz)
SPL (dB)
Impedance (ohms)
SPL 2pi
LF-4215-8 Impedance
SPL 4pi
LF-4215 Impedance

Warranty (USA only; other countries, see your dealer or distributor)
Disclaimer
QSC Audio Products, Inc. is not liable for any damage to amplifiers, or any other equipment that is caused by negligence or
improper installation and/or use of this loudspeaker product.
QSC Audio Products 3 Year Limited Warranty
QSC Audio Products, Inc. (“QSC”) guarantees its products to be free from defective material and / or workmanship for a period
of three (3) years from date of sale, and will replace defective parts and repair malfunctioning products under this warranty
when the defect occurs under normal installation and use - provided the unit is returned to our factory or one of our authorized
service stations via pre-paid transportation with a copy of proof of purchase (i.e., sales receipt). This warranty provides that
the examination of the return product must indicate, in our judgment, a manufacturing defect. This warranty does not extend
to any product which has been subjected to misuse, neglect, accident, improper installation, or where the date code has been
removed or defaced. QSC shall not be liable for incidental and/or consequential damages. This warranty gives you specific
legal rights. This limited warranty is freely transferable during the term of the warranty period.
Customer may have additional rights, which vary from state to state.
In the event that this product was manufactured for export and sale outside of the United States or its territories, then this lim-
ited warranty shall not apply. Removal of the serial number on this product, or purchase of this product from an unauthorized
dealer, will void this limited warranty. Periodically, this warranty is updated. To obtain the most recent version of QSC’s war-
ranty statement, please visit www.qscaudio.com. Contact us at 800-854-4079 or visit our website at www.qscaudio.com.
Contacting QSC Audio Products
Mailing address:QSC Audio Products, Inc.
1675 MacArthur Boulevard
Costa Mesa, CA 92626-1468 USA
Telephone Numbers:
Main Number [phone]
Sales & Marketing [phone] or toll free (USA only) [phone]
Customer Service(714) 957-7150 or toll free (USA only) [phone]
Facsimile Numbers:
Sales & Marketing Fax[phone]
Customer Service Fax[phone]
World Wide Web:www.qscaudio.com
E-mail:[email protected]
[email protected]
QSC Audio Products, Inc. 1675 MacArthur Boulevard Costa Mesa, California 92626 USA
©2003, 2004, 2007, “QSC” and the QSC logo are registered with the U.S. Patent and Trademark Office.
Kapton® is a registered trademark of E.I. du Pont de Nemours and Company.