Bluetooth Adapter and Wireless Audio Receiver with Microphone and 2.5mm Jack for Sennheiser HD598 / HD598Cs / HD598SE / HD595 / HD599 / HD559 / HD569 / HD579 / HD518 / HD558 Headphones

I bought this despite reading other reviews in which people reported that it lacked the Sennheiser proprietary twist lock interface, because *some* people indicated that the product *they* received *did* have the right connector. I took the risk, and paid the price. No luck. Just a pure black cylinder with no little grooves/channels to accommodate the twist interface.

This deserves more praise - works with my HD 598 flawlessly, and working perfectly as described.1) I just received it so I cannot comment on the battery life yet2) So far the audio quality is excellent, identical to that of connections with cables.3) There is not a delay as obvious as your typical bluetooth speakers, and I can almost say that latency would not be an issue even for games - I'll test it out myself4) The proprietary plug was a non-issue as they have dealt with that in their design already, it fixes itself into my HD 598 without any issue5) For those who suffered terrible sound quality, disable your mic (voice input) from the bluetooth connection (AF Lossless Hands-Free AG Audio output), as well as limiting the output to only the AF Lossless Stereo. The terrible audio comes from the "AF Lossless Hands-Free AG Audio output", and it is a common thing for bluetooth audio devices, not a device-specific issue.

The product worked for the first day, then began providing sound occasionally, i.e. this hour and not the next, this day and not the next. As of 05/15/2025, it has completely stopped functioning. The product was purchased about 14 days past.

Ive been using this bluetooth adapter for a year now before writing this review. I can confirm this is the best upgrade ever for my Sennheiser HD 518 & 599! I get to keep the quality sound/design that I like so much about Sennheiser headphones, but now have the added convenience of wireless audio tooMusic through bluetooth audio sounds just as great as plugging straight into the headphone jack. Admittedly the sound quality is just a tiny bit better when using a wired connection, but honestly you'll barely hear a difference. My headphones still reproduce high quality detailed sound regardless if they're wired or wireless. I dont know much about amplifiers and DACs, but I can tell they put alot of thought into this adapter so that it provides ample power for the headphones they're designed to plug intoBattery life last about 6 hours straight in my experience of spending half a day watching Youtube videos, listening to music, and sitting through online meetings. Not bad

The connection drops for about a second ever 2 - 3 minutes. I also can't keep a connection to these unless I'm in the same room as my phone. I can easily be 4x the distance and keep a reliable connection with other cheap bluetooth headphones.With the dropped/freezing issue, it got bad enough that I restarted my phone, restarted this little thing, and then started counting off how often it happens. This was with my phone being 3 feet away from the headphones, Sennheiser DC 599s. This issue does not occur when I have the headphones corded. This issue does not occur with other, cheapo $20 bluetooth headphones connected to the phone. Through this process of elimination, combined with being ale to tick off dozens of times it dropped / froze for a second over two different 1 hour listening sessions on two separate days, I am convinced that the issue is with this product.

Update: turns out the range and connection stability leave much to be desired. And probably the audio quality, considering this is for people who own Sennheiser wired headphones. So I hope they will improve this product's innards because the concept really fulfills a need.I wanted a product like this for a long time because great headphones should last a very long time, but bluetooth tech gets outdated and lithium ion batteries wear out. This lets use your favorite headphones through several generations of bluetooth tech.This unit sounds great and connects easily to my Android device and my Apple Watch. I haven't tested range. It remembers multiple devices, but I haven't tested simulaneous connection. The form factor is pretty much perfect for not hitting you in the shoulder but also positioning the mic well. No complaints about voice pickup or quality from people on phone calls.The only thing I've identified that would improve it would be USB-C charging. I had nearly eliminated all micro USB from my setup, but oh well. I decided not to take off a star for that, but it's a little unfortunate.

Does NOT fit Sennheiser HD 579's as advertised. The 2.5mm aux port is too short and does not connect unless a ton of force is continuously applied to the headphone's aux port.

As far as headphone bluetooth adapters go i guess this is as good as it gets for sennheiser. every once in a while i have to reset my computer to make the headset pair and work properly, not often , but often enough to mention. also the mic is not bad, but if you play any games and try to use this as a "computer gaming" headset your audio will cut out when you use your mic. all in all it works better than most bluetooth devices. to make it work so i actually use it i bought a yeti blue mic and have that hard lined in and sitting on my desk and use this as a wireless headset only . this allows me to be "wireless" and walk around without unplugging or setting anything down which is what i was after.