Do- It-Yourself

WOOFER POWER

Fabricating a ported subwoofer  enclosure for maximum bass with minimum cost

By Cesar Alvarez

(Photos by Bruce W. Smith)

One of the attributes of a pro-level sound system is its ability to produce crisp, clean notes with the power to seemingly shake the earth.

Such acoustic energy is a product not of the speakers or the amps powering them, but rather the speaker enclosures and how they are tuned for the vehicle in which they are mounted.

This is especially true of a subwoofer, which needs to be mounted in a box designed specifically for the air space the sound system is operating inside be it in a compact car, SUV, motorhome or big-rig.

A subwoofer also needs to be mounted in a speaker enclosure that maximizes the speaker’s ability to move a lot of air, and the most efficient way to move air is with a vented, or ported enclosure. (Think of utilizing ported woofer enclosures as turbocharging your audio system.)

In fact when it comes to a custom rig with a sleeper, one well-designed 12-inch subwoofer box will outperform multiple subs mounted in sealed boxes. It’s one of those audio anomalies where less is more.

Think of a speaker port not as a vent in terms of a path for air to move in and out of the box, but rather as an extra cone area propagating acoustic energy from the enclosure to the cabin.

The air within the cavity of the port is fixed; it’s trapped within the confines of the speaker box walls.

When the subwoofer cone moves there is a corresponding change to the pressure in the box, which causes the trapped air in the port to move either forward or backward. This air mass moves as one solid unit exactly like the speaker cone.[kaltura-widget wid="afuba7eer4" width="260" height="211" addpermission="" editpermission="" align="right" /]

So when you build a properly vented enclosure, it’s like a two-for-one special because the port is essentially another woofer. The port not only provides added output, it also provides more low-frequency extension. Your audio system gets louder and lower at the same time.

To help shortcut the sub-box building process of measuring the air volume of the cab and so forth, here’s a ported, 12-inch woofer enclosure designed specifically for use in custom rigs with flat-top sleepers and 200-500 Watts (RMS) power.

This enclosure is simple to build and delivers exceptional sound performance in a big rig sleeper. We also have two cool videos in our “how-to” videos section showing this build. Enjoy!

Special Thanks:Tripe R Diesel (www.triplerdiesel.com);Airbrush & Design (210.710.2629); and Sun-Masters (210.520.1551)

(About the author: Cesar Alvarez is a professional car audio designer/installer in San Antonio who also competes at the highest levels of audio competitions across the country. He designed and installed the 6,000-watt sound system in the Texas Chrome Shop’s Project One limited-mileage 379 Peterbilt.)

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