Anatomy of a compact powered subwoofer

Fill your vehicle with bass, not equipment


Buck Pomerantz

Buck Pomerantz was born and raised in Philadelphia. His parents bought their first television set when he was born. He figured out how to run it by the time he was two. Besides athletics, his formative interests included electronics, amateur radio, music, and stage crew work. He got his BA in writing from Brown University. Then he joined a rock 'n roll band as their soundman and moved to Charlottesville, Virginia. After that venture failed, he spent time in Boston, New Orleans, and Berkeley. He worked in a music store in Austin manufacturing, installing, repairing, and operating sound systems for recording studios, clubs, and bands. He moved back to Charlottesville, ran a little recording studio and finally joined Crutchfield as a copywriter. He has 2 grown children and 3 grandchildren, but after a good nap he can still rock out.

More from Buck Pomerantz

Sound Ordnance B-8PTD powered sub

Want to restore the bass in your music without a lot of boxes and loud booming? Maybe a compact powered subwoofer can do the job for you, and bring some fun back to your ride. Getting a single, all-in-one unit instead of having to deal with a separate sub, amp, and enclosure will save you cargo space and simplify your wiring requirements.

Sound Ordnance's new B-8PTD powered subwoofer is small enough to fit under most car seats (or in an out-of-the-way location in the cab of a truck), but powerful enough to pump out enough bass to keep up with almost any factory or aftermarket stereo. This little workhorse will surprise you with its impressive bass and its ability to mesh perfectly with the rest of your system.

We took one apart to show you the separate components and how they fit together into a unified subwoofer system. Click on the yellow boxes to read more.


A strong grille protects the cone

The grille isn't as simple as it looks. It has to be strong enough to protect the sub's cone and surround from loose, sharp objects or intrusive fingers and feet, while remaining transparent to the sound. Of course, it's supposed to look good, too, which this one does.


Strong cone for tough play

The sub's stiff 8" aluminum cone holds its shape even when playing hard, helping to keep the lowest notes clean, and ensuring a long life for the sub. A tough, yet supple butyl rubber surround allows the cone the freedom to move in and out reliably, while holding it aligned and under control, so it can pump out lots of distortion-free bass. This component subwoofer is driven by a sensitive motor assembly that pushes a lot of air and sounds louder than what you'd expect from 120 watts RMS.


Speaker-level inputs

A practical feature of the B-8PTD is a built-in line-output converter circuitry, which gives you the option of using speaker-level inputs — getting the signal from your car's existing speaker wiring instead of running long RCA cables to and from the receiver. This also makes it simple to add a B-8PTD to almost any factory stereo system. With a sub like this, there's no excuse for not adding a little bass to your system.


Sealed enclosure produces deep, precise bass

The B-8PTD's tough outer casing of molded ABS plastic serves as the sub's sealed enclosure, so it has to withstand some pretty extreme internal pressure changes without reverberating, buzzing, or falling apart. The bottom is held tight to the upper case with an abundance of furniture-type screws and an airtight gasket system. Every little nut and bolt inside has also been locked down with glue, to prevent anything from vibrating loose. It wasn't easy to take this unit apart. In fact, we couldn't remove the front and back panels without breaking them, so we decided to leave them intact for the photo.


Dialing in bass that blends perfectly

It starts with setting the Level and Bass EQ controls to match your full-range system's output. Doing this lets you take advantage of the sub's full range of power without distortion. You then adjust the low-pass filter Freq knob to eliminate the higher notes, like vocals, that you don't want the sub to play. The adjustable Phase control produces the amazing feat of virtually moving the sound wave of each bass beat for you to place precisely where it makes the most impact in your vehicle.


Big bass from this little amp

The 120-watt RMS amplifier that powers the woofer lives on a compact circuit board mounted inside the enclosure. Class-D amplifier technology, which consists of digital power switching and special output transistors, is the secret to creating such a small, yet powerful, amp. What little heat it generates dissipates via the block-like heatsink just visible under the amp's circuit board. A vibration-resistant bracket holds the amplifier assembly to the sub's shielded steel plate bottom, so the pounding bass won't harm the tiny components.

Sound Ordnance B-8PTD 120-watt compact powered subwoofer

The Sound Ordnance™ B-8PTD 120-watt compact powered subwoofer fits neatly into your trunk or cargo area
See our entire selection of Powered Subwoofers

Products in this article

Find what fits your car