MB Quart RK1-168 5x7/6x8-Inch 2-Way Coaxial Speakers

The MB Quart RK1-168 is a pair of 5x7/6x8-inch, 2-way coaxial car speakers designed as a direct-size upgrade for compatible factory speaker locations. Each speaker combines a woofer and centrally mounted tweeter in one assembly, simplifying an upgrade where separate external tweeters are not desired. The pair is rated at 4 ohms and is intended for use with compatible factory radios or aftermarket amplification.

These Reference Series speakers use lightweight craft pulp cones reinforced with bamboo fiber for midrange and bass reproduction. Their curvilinear cone profile is designed to add strength and reduce cone flex during playback. A rubber surround supports cone movement, while the red woven fiber cotton/poly-blend spider helps stabilize the cone and voice-coil assembly.

High frequencies are handled by 0.75-inch titanium dome tweeters with MB Quart WideSphere technology. This tweeter design is intended to provide broader off-axis high-frequency dispersion, which can be useful in door and rear-deck speaker locations where listeners are not directly in front of the speakers. An integrated 2-way crossover routes the appropriate frequencies to the woofer and tweeter.

The RK1-168 is rated for 50 watts RMS and 100 watts peak power per speaker, or 100 watts RMS and 200 watts peak for the pair. With 88 dB sensitivity and a stated 35 Hz to 20 kHz frequency response, it is suited to balanced full-range playback in a compatible vehicle installation. Power matching should be based on the continuous RMS rating rather than the peak rating.

For durability in an automotive environment, the speakers use high-temperature adhesive at the cone-to-surround connection, molded polymer sealing gaskets, and a PA66 composite frame reinforced with 30% glass fiber. Vents through the spider and frame ribs are designed to exchange air around the voice coil. This pair is a practical option for replacing compatible 5x7-inch or 6x8-inch factory speakers while retaining a conventional coaxial layout.

Key Features

• 5x7/6x8 Fitment: Designed for compatible oval factory speaker locations.
• 2-Way Coaxial Design: Combines woofer and tweeter in each speaker.
• Titanium Dome Tweeter: Handles high frequencies with WideSphere technology.
• Pulp/Bamboo Fiber Cone: Supports midrange and bass reproduction.
• Integrated Crossover: Directs frequencies between the two drivers.
• 4-Ohm Impedance: Matches many car-audio speaker amplifier channels.

Design & Installation

The RK1-168 uses a craft pulp and bamboo-fiber woofer cone, rubber surround, titanium tweeter, and a PA66 composite frame with 30% glass-fiber reinforcement. High-temperature adhesive, a molded polymer gasket, a Kapton voice-coil former, and a ventilated motor/frame structure are part of the speaker construction. Grilles are not included.

Confirm that the vehicle accepts a 5x7-inch or 6x8-inch speaker and verify mounting clearance before installation. The listed top-mount depth is 2 9/16 inches and bottom-mount depth is 2 3/4 inches, so window travel and door-panel clearance should be checked. Connect speaker polarity correctly, secure wiring away from moving parts and sharp metal edges, and use the included mounting hardware where appropriate.