Size & Space for Audio Racks

By Matt McKay

Audio racks are standard equipment in recording studio and live music applications, but are used in some high-end home audio systems.
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Audio racks come in a variety of sizes and space heights to suit user application and equipment needs. Used to mount audio components adhering to industry width and height standards, racks serve to consolidate equipment in stationary or mobile environments. Racks help minimize cable obstructions by rear interconnection of audio components and allow easy access to device controls and front-mounted patch cable devices.

Audio Rack Width

All audio racks and rack equipment are standardized at 19 inches in width. Smaller components can be rack mounted with the addition of aftermarket rack mount kits or those offered as an option by the original manufacturer (sometimes called "rack ears"). Devices are anchored to pre-drilled and threaded vertical rack rails with 10-32 x .75" metal screws, with nylon washers employed to minimize equipment finish damage. The cabinet housing the rack is larger than the mounting rack itself, and varies with manufacturer design. Some rack cabinets are decorative for home use or utilitarian and rugged for mobile systems.

Audio Rack Height

Audio rack height is measured in "rack space units", designated as "U" for unit, or "RU" for "rack unit. A single rack space is the equivalent of 1.75-inches (1U), with larger units conforming to the height standard with higher numerical "U" designations in multiples of 1.75-inches. Industry veterans often refer to the height of rack gear simply by the number of rack spaces rather than the "U" abbreviation -- "three rack spaces" for example, for the equivalent of "3U" or 5.25-inches.

Audio Rack Depth

While audio rack and component height and width are standardized, rack depth is not and will vary with rack manufacturer. Full sized racks measure 16- to 18-inches in depth or more, with shallow depth racks averaging 12- to 15-inches. This difference is necessary to accommodate equipment of varying depths, dictated by device engineering and based on internal component and circuitry size requirements.

Rack Space Planning

Rack space planning is necessary when shopping for or building a rack. Summing component rack space totals provides an initial estimate, but electronic components require airflow to help cool electrical circuits during operation and must be considered. Rack mount vents and fans placed above heat-producing components -- such as amplifiers and tube preamps -- require one to two additional rack spaces. Rack mount utility drawers and shelves of varying "U" heights serve for tool and small component storage and can be convenient for mobile applications. Take all present and potential needs into account when planning your audio rack layout.