Overview

The LF-4215-8F dual 15" (381 mm) low-frequency enclosures are designed specifically for large format cinema applications. Meeting cinema requirements for extended low-frequency response differentiates these products from more conventional “rock-and-roll” woofer systems. The LF-4215-8F cover the frequency range from 35 Hertz to 1000 Hertz, depending upon the high-frequency system requirements.

The LF-4215-8F is an 8 ohm version of the 4 ohm LF-4215-F. Both are designed for safe and easy suspension via M10 fly points. Heavily braced, tour grade construction provides great strength while keeping weight to a minimum.

The two custom 400 watt, 15" transducers were developed especially for cinema use. They feature extremely large 4" (100 mm) 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 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 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 power.

Sixteen M10 mounting points provide safe and secure means to suspend the enclosure via M10 forged eyebolts (not included) or user-supplied brackets. Always consult a licensed structural engineer to approve any mounting method.

Features

• “Flyable” dual-woofer screen channel speaker system
• Constructed of heavily braced, 15 mm tour-grade plywood
• Sixteen M10 fly points per enclosure for safe and easy suspension
• Common dimensions of Mid/Hi and LF enclosures facilitate easy installation in vertical or horizontal arrays

Suspension

The the LF-4215-8F enclosures feature 16 load-rated attachment points. As shipped from the factory, each attachment point has a bolt installed to retain the air-tight design of the enclosure. Never operate the loudspeaker with the attachment points open (unsealed) as it will degrade the performance of the product.

The LF-4215-F, LF-4215-8F, MH-1075C-F and MHV-1090F have the exact same external dimensions and attachment points. They can be supported individually or as a group, depending on what works best for the application. The boxes can be arrayed vertically and horizontally. When paired together, it is recommended that the mounting structure connects both boxes to the suspension system rather than suspending the boxes from one another. Commercially available uni-strut or other custom fabricated brackets can be used.

Suspending the system from the top rear attachment points results in a slight down angle that may be close to the desired aiming for many installations. The bottom attachment points can be used for a pull-back cable to fine tune the tilt of the system.

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 or
placement. 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 regarding physical equipment installation. Ensure that all local, state and national regulations regarding the safety and operation of loudspeakers and related equipment are understood and adhered to.

Connections

Amplifier connections to the LF-4215-8F are made on the rear panel via a Neutrik® NL4P speakON™ connector supplied by the installer. This connector provides power to both woofers via the 1+ and 1- terminals. The woofers are internally wired in parallel. Pre-made speakON™ cables using high grade, 2 or 4 conductor stranded wire are readily available from a number of suppliers and is highly recommended.

Specifications

• Frequency Range
• ±3 dB: 38 – 1000 Hz
• -10 dB: 30 – 1200 Hz useable range
• Maximum Output: 134.5 dB SPL calculated peak
• Impedance
• LF-4215-8F: 8Ω nominal
• Maximum Input Power
• 100 hours of 6 dB crest factor pink noise, 30 – 500 Hz: 800 watts
• 2 hours of 6 dB crest factor pink noise, 30 – 500 Hz, AES method: 1000 watts
• Sensitivity (half space / watt / 1 meter): 99.5 dB half space, 96.5 dB full space, 35 – 1000 Hz, 1 watt, 1 meter
• Transducers
• Two 15" (381 mm) high-efficiency, low-frequency transducers featuring vented 4" (100 mm) copper voice coils. High-excursion/
• low-distortion design, with extremely high-power handling, and low thermal and port compression.
• Recommended Processing: Subsonic filter below 30 Hz, >18 dB per octave, maximum recommended crossover frequency is 1000 Hz. QSC DSP configurations
• Nominal Coverage: 135° horizontal x 50° vertical at 500 Hz
• Connectors: Neutrik® speakON™ NL4, LF 1+, 1-, No Connection 2+, 2-
• Enclosure: Heavily braced 15 mm tour-grade plywood with 16 M10 load-rated attachment points.
• Dimensions (HWD): 40" x 31.5" x 19" (1016 mm x 800.1 mm x 482.6 mm)
• Net Weight: 134 lb / 60.8 kg