HK Audio SI-SERIES-CM-4-U 4'' Coaxial Ceiling Speaker

4 Inch Coaxial Ceiling Speaker With Backcan For Clean Installed Audio

The HK Audio SI Series CM-4 is a passive 2-way coaxial in-ceiling speaker with an integrated backcan, built for clear music and speech in commercial installs like restaurants, hotels, conference rooms, retail spaces, galleries, and houses of worship. It combines a 4" polypropylene woofer/midrange with a 0.75" aluminum dome tweeter so you get intelligible vocals, smooth background music, and even coverage from a compact ceiling loudspeaker footprint.

Wide 145 Degree Dispersion For Even Coverage Across The Room

The CM-4 is designed to spread sound broadly, using integrated wave guides and a wide 145-degree conical dispersion pattern. That matters when you’re trying to avoid “hot spots” directly under the speaker and keep coverage consistent across seating areas, aisles, or open retail floors. The result is more uniform SPL across the space with fewer speakers compared to narrow-pattern alternatives, depending on ceiling height and layout.

70V 100V And 8 Ohm Switching For Flexible System Design

This ceiling speaker supports both low-impedance and constant-voltage installs, so it can drop into an 8-ohm distributed audio system or a 70V/100V commercial audio system with selectable power taps. A front-accessible rotary switch makes it easy to set taps or bypass the transformer for low-Z operation, which is helpful during commissioning, zone changes, or when standardizing on one speaker model across different projects.

Detailed Crossover And Protection For Reliable Long-Term Installations

A newly developed passive crossover keeps frequency distribution controlled and consistent, with a 3.6 kHz crossover point and a self-healing HF protection circuit to help safeguard the tweeter in fixed installations. That combination helps the CM-4 stay clear at practical listening levels and improves durability for day-after-day operation in background music and speech reinforcement systems.

Metal Backcan Construction And Magnetic Grille For A Clean Finish

A stiffened steel backcan reduces resonance and helps keep the sound tighter and more accurate, especially in ceilings where uncontrolled cavity space can cause coloration. The rimless magnetic grille provides a clean architectural look and makes service access simple. Black and white grille options let you match ceiling finishes without special ordering a separate trim kit.

Installer Friendly Hardware And Connectivity For Fast Ceiling Work

The CM-4 uses front-accessible mounting clamps with a wide grip range for secure installs, plus brackets for safety wires or secondary retention. Two included cover plates support different cable routing preferences, and the speaker uses 2-pole Euroblock connectors for clean, professional terminations—great for contractors who want fast, repeatable wiring in multi-speaker zones.

Emergency Announcement System Support For EN 50849 Projects

For projects that require emergency messaging compatibility, the CM-4 is designed to support use as part of an electro-acoustic emergency warning system in accordance with EN 50849. This makes it a strong option when the install needs to cover both everyday paging/background music and regulated voice alarm or emergency communication requirements, depending on the broader system design and approvals.