De-smarting the Marshall Uxbridge Bluetooth speaker
36 comments
·January 11, 2025mysteria
zxcvgm
I have the same thoughts about the approach, and I'm actually working (on the back burner) a similar thing. It's a harman kardon "smart" speaker with a similar design where the brains are on a separate daughterboard and that's now fried.
I've already figured out the control signals and have designed a new daugterboard with an ESP32 to drive the I2S output. I just need to figure out how to downmix the audio to mono and to DSP the L/R channels into tweeter/bass outputs, or to find some code already out there that does this. Any help/pointers here would be appreciated!
f1shy
> The reason powered boxes sound decent despite their relatively cheap hardware is because of the extensive processing they have in the background to compensate for any hardware defiencies.
I will not argue that that could be one ingredient, but a couple of months ago I did a toy for my kids, I bought decent speakers, placed them in a cheap plastic box, and was absolutely amazed bybthe sound quality. The amplifier is a sub 1 dollar class D bought in a Raspberry Pi shop. No processing at all. If the box is sturdy and sealed, and the speaker is good, is incredible what you can do.
acchow
I'm interested in which speaker and amp those were. Also, the plastic box :)
bayindirh
Not the OP, but if you have a little budget, HifiBerry's AMP2 [0] sounds great. After my dad gave his Hi-Fi stack to me (due to having no space at home), I built a small system with this and connected to a set of passive 2.1 Kenwood Hi-Fi speakers for him. They sound amazing, plus HiFiBerry OS is superb for connectivity.
I just want to note that software is built with collaboration of Bang & Olufsen. Both hardware and software oozes quality.
[0]: https://www.hifiberry.com/shop/boards/dealing-with-blocked-p...
bayindirh
Marshall speakers, from my experience, has a brand sound signature, and that tuning is not very optimal for every genre of music.
Replacing the DSP with a simpler amplifier may allow to get more detailed sound from the drivers and the box themselves and may create a more pleasant listening experience.
From what I have seen, the drivers seem pretty full-size for that box, and any disturbing sound characteristic can be tuned with a simple equalizer. A more dynamic approach might create audibly weird sound profile if done wrong.
Modern DSPs are magic, but I still prefer an audio pipeline where things show their deficiencies and not hide things real-time.
AstroNoise58
I assume you mean AD85050 (rather than AD8255). And yes, the last paragraph before "Going all-in" is about the idea of driving the I2S. But the I2C config sent to the ESMT chip would have had to be reverse-engineered as well...
mysteria
Fixed, thanks. Somehow the title of the datasheet pdf is AD8255 despite the chip being a AD85050.
gavinuhran
I have this speaker and cannot believe how annoying the smart features are. I'll be talking on the phone in my apartment and the speaker will think I'm trying to prompt it.
"SORRY. YOUR DEVICE IS NOT CONNECTED TO THE INTERNET. PLEASE CHECK YOUR BLUETOOTH SETTINGS AND TRY AGAIN." (at max volume!)
It's unbelievable. I'm not an EE, but would love to know how I can disable these incredible unsmart features.
seba_dos1
There's an article that tells you that. I believe it's linked somewhere above this comment.
bonzini
The article removes all the smart features (not just the annoying ones) and requires pretty serious knowledge of analog electronics. Probably it doesn't fit the bill for the parent comment.
dheera
I mean, it's a speaker in a box, so you could also just snip the speaker wires, ditch the circuit board, solder some extension wires, and plug it into an external audio amplifier box of your choice.
If you go that route you don't really need much EE knowledge.
(This is also only if you already have this box and want to reuse it. Otherwise I would just go to your next neighborhood garage sale and pick up some good speakers for $10)
emidoots
Return that crap and buy something like Audio Pro speakers instead
tlhunter
Lately I've been wondering if there's a way to do this to Smart TVs. Personally, I like the name "stupify" better ;)
rotifer
A year or so ago I bought a Hisense 65U88KM, which comes with Google TV. During the setup procedure it asked me if I wanted to enable the "smart" features, such as Google TV, the camera and microphone, or connect it to a network. I said no to all of them, and that was that.
Now it just acts as a dumb screen for my Apple TV box.
05
There’s a project to load OpenWRT onto LinkPlay A31 [0], might be easier than basically replacing the insides..
Mathnerd314
I'm curious about price - sure, the speakers were free ($240 value), but I don't think printing up a PCB is cheap, and those are some pretty big capacitors.
jdietrich
JLCPCB have changed the game. Five 2-layer PCBs of up to 100x100mm cost just $3.50 including global shipping. Things get more expensive if you stray from their standard specs, but you're still looking at just a few dollars per board.
The biggest electrolytic caps in this circuit cost $3.29 each in qty 1, but they're fancy "audio-grade" Nichicon caps; a standard-grade capacitor of that size would cost you $1.68 if you want a Japanese brand, or as little as $0.36 if you can settle for a Chinese brand.
f1shy
And you can even order all or the SMD components soldered for less money that you can buy solder and other consumables for soldering never mind the time.
stavros
A PCB like that would cost around $1 each, if you got 10 or so, so it's not expensive at all. I don't know how much assembly costs, but I'd be surprised if the total was over $20.
MrBuddyCasino
This looks an EE‘s approach who hasn’t had a lot of exposure to speaker design. You need to consider Thiele/Small parameters of the chassis, enclosure volume, baffle design and a million other factors to design a proper crossover. You can’t just ltspice your crossover and call it a day. VituixCad would be a more appropriate solution. And then you actually have to measure!
Replacing and amp and „smart“ crap is easy if there is an analogue crossover you can reverse-engineer, if it was just some DSP things get difficult quickly (unless its just a single broadband chassis, but even then…).
And no, you can’t use pre-built „standard“ crossovers or some calculator on a website either.
But other than that, nice that he saved some hardware.
AstroNoise58
Do not underestimate audio circuit tuning based on listening tests. Good ears and patience can substitute a lot of lab equipment dollars, especially for a hobbyist.
ipsum2
You seem to be very knowledgeable about this subject. I have some Google Nest Audio speakers that sound fantastic, but have the same problems as bluetooth speakers, and lack a 3.5mm input jack to convert into normal speakers. Do you have any recommendations on how to do this, for someone with minimal audio knowledge and some basic EE?
liminalsunset
The Google Nest Audio speakers are kind of a special case. They only sound good because they use a sealed, extremely rigid cast aluminum sealed enclosure with a high excursion driver. The performance of these speakers with a regular crossover and amp will be poor, due to the low efficiency of the enclosure/small driver.
To get around this, Google put in the TI TAS5825M smart audio amp. By measuring the speaker parameters through V/I measurement and a model, it drives the speaker in a closed loop way with far more power than it would actually be able to handle nornally to compensate for the resistance from the enclosure air pressure, and throttles to maintain the coil at a safe temperature. The chip also does DSP to compress the audio signal, cutting the peaks off the bass as needed when the volume is turned up so volume is maintained at the cost of bass.
One way to explore could be to just feed I2S audio from an I2S ADC i.e. PCM1808 to the digital input of the amplifier. The processing is internal to the amp so theoretically you won't lose the tuning. However this may turn out to be a relatively annoying reverse engineering project with fine magnet wire involved.
Note: I2S is different from I2C - the amp will likely have both. You will likely need to keep the original system around to program the amp over I2C (or capture the transaction and replay it) - otherwise you will likely get no audio.
The "raw" audio performance of this device (just an amplifier connected directly to the internal speaker and dsp on the computer) is impressive, kicking out bass down to 40Hz. It will, however, not last long like that. Reports online are that these blow speakers easily even when used with the default amplifier.
I would recommend that if 3.5mm input is desired, to replace them altogether with the IK Multimedia iLoud Micro Monitors. These have sound quality just as good as the Google at similar size, with the same DSP tricks, but have regular inputs and no smart features.
ipsum2
Thanks for the comprehensive answer, I'll look into the I2S audio solution.
You're right that iLoud Micros sound similar, they're 3x the price (The Nest Audios were sold at $50/each on sale). Definitely worth it, I just like tinkering with things.
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encom
>You can’t just ltspice your crossover and call it a day.
I'm sure that's true, but how important is that really for a set of crappy plastic speakers?
Slava_Propanei
[dead]
mgaunard
what exactly is the problem with smart speakers? Most people just want to stream Spotify
ipsum2
It's mentioned in the article, but briefly 1) latency (300ms+) and 2) random voices at max volume while you're trying to listen to music.
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netsharc
"We are delighted to announce an update to our smart speaker line: we are sunsetting the online services for this model. Your devices will be disabled in March 2025. They will no longer work, and please bring them to an electronics recycling center near you.
You are eligible for a voucher to get a discount when you upgrade to a newer model."
mynameisvlad
This is pretty much word for word what has already happened at least once.
Sonos at least reversed their decision to disable the devices when they sunset S1. They just made them incompatible with their current system but allowed people to download the old apps.
Unfortunately, devices that were already marked for trade-in before they made the decision are still completely bricked.
f1shy
I bought a Yamaha CD-N301, came with a web radio, where you could setup a user, and make an index of URIs with webradios. After that you could select the station from a menu in the front. 3 months after purchase, the service started costing 3 dollars per month. I only use the CD function now.
I contacted Yamaha, the answer was “it still works, we never promised it would be forever free” PoS
lelandfe
"Sustainability is non-negotiable!" was my favorite platitude from their website at that time. As Sonos needlessly condemned 6 year old speakers to the landfill.
If you're going through all the effort to design a PCB have you thought about driving the I2S input digitally? I skimmed through the AD85050 datasheet and it has internal DSP functionality which would have been already tuned for the drivers and box by Marshall. The reason powered boxes sound decent despite their relatively cheap hardware is because of the extensive processing they have in the background to compensate for any hardware defiencies.
As the AD85050 has a stereo I2S input there's a possibility for the actual crossover to be either done on the amp chip itself (with the same signal driving both channels) or done on the Amlogic SOC. The latter would be ugly as you would need another DSP chip on your board to do the crossover functionality, or perhaps you could program the AD85050 via I2C to add the appropiate low and high pass filters.
A two channel A/D converter would work on the front end, as you could drive both channels with a single analog input to get a stereo I2S out with duplicate channels to drive the amp. A USB input would be much messier if you want true stereo using two speakers unless you plan on doing routing on the software side. With SPDIF you probably could get away with splitting the signal and using a SPDIF to I2S converter chip in each speaker, but you would still need some way to separate out the left and right channels. The AD85050 has mixing functionality via I2C which may help with that.
And of course, all this might be more work than desigining an amp in the first place, and it really depends if you want to explore the analog or digital side of things.