Televisions, refrigerators, alarm systems, doorbells, garage doors — it seems like everything is getting the smart home treatment these days. These systems are undoubtedly useful (well, some of them, anyway!), providing us with conveniences that were unthinkable not so long ago. But does everything really need to be so smart? Does a coffee maker really need voice recognition capabilities? Maybe we would like to simply press a button from time to time, rather than yelling out voice commands after being misunderstood for the umpteenth time.
A Swedish software engineer and hacker named Tom Szilagyi recently came across a very nice pair of Marshall Uxbridge speakers after spelunking in a dumpster. These happen to be smart speakers, but they are not just junky speakers trying to cash in on a trend — Szilagyi found them to be of excellent quality. But the smart features themselves proved to be quite a drag.
The original electronics — thanks, but no thanks (📷: Tom Szilagyi)
After powering one up, it immediately requested that it be set up to work with a companion app. No thanks, said Szilagyi, who found that they seemed to work just fine as plain-old Bluetooth speakers. But after playing with it for a while, it started complaining about a lost connection. Furthermore, the speaker had a significant delay that was apparent when watching videos. And when you have a pair of speakers, of course you are going to want stereo, which is not going to happen with a Bluetooth connection — at least not without them being out of sync.
This situation clearly called for some “de-smarting”. Where are the good old-fashioned RCA plugs when you need them?
Szilagyi jumped right in to set things straight. The process began with disassembling the speakers’ enclosures and studying the internal components, including the main board, power supply, and speaker drivers. Recognizing that the existing digital amplifier and smart module were tightly integrated, Szilagyi opted to remove the original electronics entirely. He then designed and built a new circuit centered around an LM1875T analog power amplifier and a custom Linkwitz-Riley active crossover filter, which splits audio frequencies for the woofer and tweeter.
The new electronics have been installed (📷: Tom Szilagyi)
The design prioritized simplicity, using readily available components, and retained compatibility with the existing power supply and speaker connections by using the same JST connectors. A new RCA input was added, replacing the dreaded Bluetooth button, with airtight sealing to maintain the enclosure’s acoustic properties. During assembly, minor mechanical adjustments were made to fit the new circuit board.
The result was a de-smarted analog speaker system that delivered superior audio fidelity, sharp stereo sound, and reduced noise and distortion compared to the original configuration. By tailoring the analog filters to the specific speaker components, Szilagyi achieved audiophile-quality sound, and he was able to do it in an eco-friendly way by repurposing discarded — yet perfectly good — electronics.
The schematics have been published under a permissive MIT license, so if you come across a speaker like this and are disappointed with the smart add-ons, don’t be dismayed. Just get hacking and you will have a great speaker before you know it.
