TD-000141-00 - QSC Service
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
Cinema Loudspeaker Systems User Manual
LF-4215 Low Frequency Loudspeaker
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 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 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 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 transducers, 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 systems.
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 permanently 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, 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-000141-00 rev.A
© Copyright 2003, 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
Normal Connection
The LF-4215 has barrier strip screw terminals for connection. The terminals accept
up to #10 AWG stranded loudspeaker wiring. Use the largest wire size and shortest
wire length possible for a given installation. Observe the polarity markings and
keep polarity consistent throughout the
system for best performance.
Normal Connection Example:
Parallel Connection of Second SB-5218
The terminals marker SPK2 may be used to
connect another LF-4215 in parallel. Connect the wires as shown in the illustration,
at right. Note: If the LF-4215’s internal wiring 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.
Parallel Connection Example:
Individual Transducer Connection
(requires modification)
The transducers are wired in parallel
inside the enclosure. If individual transducer 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.
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.
4 ohms nominal
3.4 ohms minimum , 150 Hertz
25 ohms maximum, 22 Hertz
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 (per LF-4218)
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 Parameters for alternative processing hardware are available
upon request.
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 yellow jumper wire on internal-side of terminal cup and mark enclosure accordingly.
Two 15” (381mm) high efficiency low frequency transducers featuring vented 4” (100mm) copper voice coils on Kapton® formers. High excursion/low distortion design, with extremely high power handling, and low thermal and port
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.
30” wide X 36” high X 21” deep (762 mm X 910 mm X 516 mm)
195 lbs. shipping, 172 lbs. net (88/78 kg.)
Warranty (USA only; other countries, see your dealer or distributor)
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 limited 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 warranty statement, please visit Contact us at 800-854-4079 or visit our website at
Contacting QSC Audio Products
Mailing address:QSC Audio Products, Inc.
1675 MacArthur Boulevard
Costa Mesa, CA 92626-1468 USA
Telephone Numbers:
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
Facsimile Numbers:
Sales & Marketing Fax(714) 754-6174
Customer Service Fax(714) 754-6173
World Wide
E-mail:[email protected]
[email protected]
QSC Audio Products, Inc. 1675 MacArthur Boulevard Costa Mesa, California 92626 USA
©2003 “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.
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