FCC Licensed Amateur Radio Operator, Extra Class

Hacking an Altec-Lansing ATP3 Subwoofer for Stand-Alone Operation

I realize this isn’t directly ham radio-related. Well, actually it sort of is, because this project involves a subwoofer which is now part of the system I use for producing amateur radio-related instructional and informational videos, for monitoring DMR radio activity, and other fun stuff.

Altec Lansing ATP3 subwoofer purchased at a thrift store but missing part of the system

This little project started when I ran across an Altec Lansing ATP3 Powered Subwoofer at a Goodwill store for only $7.97. No doubt they had the thing priced dirt cheap

Altec-Lansing ATP3 Powered Subwoofer. I do love discovering the occasional project item at Goodwill or other thrift stores, etc.

because the two external speakers (left and right) were missing; therefore, there were no controls to turn the subwoofer and its internal amplifier on or off or make any level adjustments at the subwoofer because those are actually located one of the two external speakers. I had been watching for an affordably priced (okay, “cheap”) powered subwoofer to use with a Pioneer surround-sound receiver with Dolby 5.1 Digital processing and digital fiber optic inputs and outputs which I had purchased at that same Goodwill store for only $15.91 (knowing it most likely needed some sort of repair, given the el-cheapo price, plus it was missing the very specialized remote control.) I repaired the Pioneer audio processor/surround sound receiver at a cost of about thirty cents (the cost of a voltage regulator IC) and had purchased a factory remote on eBay for about $20. I already had all the speakers I needed for it, but that model Pioneer receiver/amp does not provide direct power for a subwoofer — it only has a dedicated “line level” subwoofer signal via an RCA-type jack on the rear panel. I really, really wanted a powered subwoofer, but was not going to spend a ton of money on one. All that said, I could not pass up what looked like a possible solution, even if it meant doing a little “hacking” to make the subwoofer independent of the missing speakers and controls.

The factory DIN connector pinout for the Altec Lansing ATP3 Subwoofer

Pinout for the Altec Lansing ATP3 Powered Subwoofer female DIN connector.

It took a little research and some “Googling,” but I finally figured out all of the pins on the factory DIN connector, which are shown here. Despite having tons of parts and connectors around, I did not have the right male DIN connector to make an external control box for the subwoofer. Not wanting to spend another $10 to order a couple of the DIN connectors, I just opened up the subwoofer and removed the circuit board.

Hacking the Altec Lansing ATP3 Subwoofer for stand-alone use without the external speakers

With the circuit board completely out of the subwoofer, I carefully desoldered and removed the female DIN connector assembly completely. Using a few bits of small wire

Altec Lansing ATP3 Powered Subwoofer circuit board landings for the DIN connector, with functions labeled.

salvaged from a CAT5 cable, I “pigtail” wired the lines needed to run to an external control box, which I put together using stuff I already had on hand. All it took was a small plastic box, a SPST slide switch, and a 10K potentiometer and in a few minutes time… “voila!” I had the ability to turn the subwoofer on and off and to control the bass level/volume with a potentiometer.

I’ve included a schematic/diagram showing the actual circuitry and interconnection to the homebrewed external control box.

The thing works great and actually pretty decent bass reproduction. If I crank it up a bit, it literally vibrates a bedside table at

A quick bit of breadboarding confirmed that my design for external controls (a.k.a. “my hack” of the Altec Lansing ATP3 Subwoofer) would work. Time to make it more permanent using just three items I already had in my parts inventory.

the far end of my house, which ain’t bad considering my house is built on a concrete slab with carpet and padding throughout. The subwoofer is most definitely “air coupling”

Removing the DIN connector from the circuit board in the subwoofer created a convenient place to bring out the pigtail wires for adding a homebrew power and control box for the Altec Lansing ATP3 Powered Subwoofer, eliminating the need for the original external speakers and control circuitry.

the bass to the walls, ceilings, etc. even though it’s sitting in the floor on top of that carpet and padding.

The bass output really thumps when playing one of my videos put together with Dolby 5.1 encoding, watching a Dolby or THX trailer, movie, etc.

Oh… you should also hear the audio when I fire up a web browser and listen to fellow ham radio operators talking via DMR by visiting the Brandmeister DMR “hoseline” on their website. The difference between listening that way vs. listening through the little 1.5″ or so speaker in the average handie-talkie is beyond description and much more pleasant when just wanting to listen without running the H/T batteries down.

Homemade external control box for the Altec Lansing ATP3 Powered Subwoofer.

Schematic and diagram for converting the Altec Lansing ATP3 Powered Subwoofer for stand-alone use, providing power and level controls for the subwoofer without the need for the original left and right external speakers and controls.

Too bad the Pioneer receiver, subwoofer, and all the other speakers are just a tad too big and heavy to strap to the TYT MD-380 radio and go portable. 😉

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