QSC LF4215-8F User Manual - Introduction
3
Introduction
The LF-4215-F and 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-F and 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
— Figure 1 —
— Figure 2 —