Headphone Cable Trouble Inspires Bluetooth Conversion

Headphones described in article, charging off a powerbank through an orange USB cable

[adblu] encountered the ever-present headphone problem with their Sennheiser Urbanite headphones – the cable broke. These headphones are decent, and despite the cable troubles, worth giving a new life to. Cable replacement is always an option, but [adblu] decided to see – what would it take to make these headphones wireless? And while they’re at it, just how much battery life could they get?

Armed with a CSR8635 Bluetooth audio receiver breakout module and a TP4056 charger, [adblu] went on rewiring the headphone internals. The CSR8635 already has a speaker amplifier inside, so connecting the headphones’ speakers didn’t require much effort – apart from general soldering difficulties, as [adblu]’s soldering iron was too large for the small pads on the BT module. They also found a 2400mAh battery, and fit it inside the headphone body after generous amounts of dremel work.

The result didn’t disappoint – not only does everything fit inside the headphone body, the headphones also provided 165 hours of music playback at varying volume. Electronics-wise, it really is that easy to retrofit your headphones with Bluetooth, but you can always go the extra mile and design an intricate set of custom PCBs! If firmware hacks are more to your liking, you can use a CSR8645 module for your build and then mod its firmware.

12 thoughts on “Headphone Cable Trouble Inspires Bluetooth Conversion

  1. I’ve been doing some stuff like this with headphones too – but the big trouble here in Aus is the battery. Those small lipo batteries are often ‘fake’ – ie will only be usable for about 10 charges, or at best about 50 – and the decent ones you can find online in the USA/EU don’t ship to Australia..

    Every single one I’ve found in Aus so far – including in physical stores – is ‘fake’ ie nothing like what you get in a commercial product.

    If anyone reading this knows a good source in Aus or ones that will ship here, please put a link in!

    1. That’s interesting as it reflects my experience with cheap Chinese wireless headphones. They work great-(ish) until the battery dies after a few cycles.

      Anybody knows what is the cause here? If they generally use the same type of battery, the life time can’t be that much worse, can it?

      1. Often the charging current is too high and the charger has no thermal protection. The LiPo cells inside headphones would probably last forever if they would be charged with 0.1C like we did with NiCd some decades ago.

  2. It really sucks that it’s 2022, and the bluetooth consortium STILL will not let you use stereo audio + a mic channel. And don’t give me that BS about “buut butt bluetooth doesn’t have enough bandwidth!”…garbage.

    1. Bluetooth has supported 24Mbps since version 3.0, plenty for almost any consumer audio use case. Their main failing is that rather than defining the standard with capabilities that are well beyond current use cases (as HDMI and PCIe do), they define the standards to barely meet current use cases. Then there’s the licensing fees that are particularly problematic for small businesses…

      It’s worth noting that back in 2015, Nvidia used Wifi for their Shield TV platform rather than Bluetooth as they found Bluetooth too limiting. As such, they did a proprietary implementation of HD Audio over Wifi which sounded much better than the Bluetooth available at the time. What I would like to see is an open source version that uses ESP32, I really liked Nvidia’s wireless HD audio except for the fact it only works on Nvidia devices.

    2. Totally agree. There are some things that might rectify this issue coming, if I understand the communications properly, but too little too late.

      Even if it DOES work and works great, it’ll be 20+years before a cheapo headset from whoever actually uses it, along with any actual BT that is in the sending device. Apart from phones(well, almost) there seems to be no actual decent working BT available.

      The general stance of the BT consortium seems to be: “but it needs to be low power!!!1” and therefore for example audio is only available in low bitrate and strange compression. Heavens forbidd that you let the users decide and just put a slider there. Or just have a “general data” service where the usecase can decide how much power and data is needed.
      And as if that was not enough, insult is added to injury when the non adjustable audio quality is cut time and time again because the radio is adjusting power levels way too aggressive.

      I’d rather have a shorter battery time than two pieces of useless junk. It only works for 5hrs is way better than it does not work at all.

  3. I replace the cord with standard telephone handset cord. It’s very strong and has reasonable flex. Telcos didn’t mess around with “designer looks” like a single round insulation with hair fine wires inside. Plug is only a centimeter tall, kind to phone in pocket.

  4. Did this project some time ago, with a batteru scrapped from a dead smartphone, and Aliexpress battery charger and bluetooth receiver modules.

    Didnt use the phones too much for the annoying voice at full blast saying “bluetooth mode”, “the bluetooth device is already connected”. Gosh!

  5. I’ve been doing this for ages now. I mage a Sennheiser HD202 for my sister, it uses a DSi battery, charges over USB-C and has a headphone jack that can be used for AUX or if it’s in bluetooth mode you can plug in a second headphone so that two people can listen. Also a mic and call controls.
    For my dad I’ve modified a ’80s Philips can, it charges via a magsafe cable, has a huge analog volume knob and I used a smaller drone battery. It also has a headphone for passthrough but no mic.

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