The RDL ST-MX2 is a compact, two-channel audio mixer designed for simple yet effective audio combining in commercial sound systems. Part of RDL's "Stick-On" series, it is housed in a small metal enclosure that can be easily mounted virtually anywhere using adhesive backing or screws, requiring no rack space. This mixer is designed to blend two independent mono audio sources—such as a microphone and a line-level music source, or two microphones—into a single mono or stereo output. Each channel is configurable for either microphone or line-level input via a jumper or switch, providing flexibility for various input types commonly found in paging, background music, and basic presentation systems.

Operation is straightforward, with each channel featuring a gain control to match input levels and a level control to set its contribution to the final mix. The mixer utilizes high-quality, low-noise operational amplifiers to ensure clean audio summing without introducing hum or hiss. Its simple design focuses on reliability and ease of installation, making it an ideal solution for adding a microphone to an existing music system, combining two audio feeds in a retail environment, or creating a basic mix in a small conference room. The ST-MX2 typically operates on a single low-voltage DC power supply (such as 24V), which is often already present in commercial audio racks powering other equipment like amplifiers and DSP units.

For system integrators, the RDL ST-MX2 offers a cost-effective and space-saving solution for basic audio mixing tasks. Its "stick-on" form factor allows it to be discreetly installed inside equipment cabinets, behind displays, or under tables, keeping wiring neat and localized. By providing a simple means to combine audio sources with minimal controls and maximum reliability, this mixer addresses a common need in installed sound without the complexity or expense of a larger, feature-rich mixing console, making it a practical component in many commercial AV designs.