Acoustic Insulated Plenum Box for HVAC Linear Slot Diffusers
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Acoustic Boxes / Plenum Boxes
Our plenum boxes are specifically designed for use with our linear slot diffusers. Their primary function is to equalize the pressure profile within the box, ensuring consistent airflow and even velocity across the full face of the grille diffuser.
Each plenum—also referred to as an “acoustic box”—is equipped with a high-quality foam insert to significantly reduce noise levels caused by airflow. This makes them an excellent choice for projects where acoustic comfort is as important as performance, such as offices, residential developments, hospitality spaces, and educational environments.
For ease of installation, the boxes are supplied with three pre-scored “knock-outs” (75mm, 125mm, and 160mm). This flexible design allows installers to adapt the connection size on-site by fixing spigots (supplied separately) securely to the exterior of the plenum using tech screws.
Key Benefits:
- Provides balanced air distribution for optimal diffuser performance
- Acoustic foam insert minimizes noise for quieter environments
- Flexible installation with three pre-scored spigot options
- Manufactured for durability and long-lasting performance
- Compatible with a wide range of linear slot diffusers
Whether you are working on a high-end interior, a large commercial project, or a bespoke design solution, our acoustic boxes deliver both functionality and reliability.
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Pure Clima is an authorized UK distributor of Ventmann frameless diffusers and gypsum-based products.

