Airfrex 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 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a product like this for a long time because great headphones should last a very long time, but bluetooth tech gets outdated and lithium ion batteries wear out.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.

For all the marketing on this store page that the product is specifically designed for the HD598, it doesn't fit! And I have no clue if I received the correct model (SEHD). There's no model code on the device itself, and the packaging suggests i received the wrong version.The 2.5mm end of the cable that comes with the headphones has two grooves on the side. This is to assist with keeping the cable locked to the headphones. In my photos where i hold the airflex next to the 2.5mm cable, you can see that the airflex has about the same diameter as the 2.5mm cable but doesn't have the grooves, so it won't snap into place.Connecting the device to my phone via bluetooth was very easy. Just a shame i could not hear anything because i can't plug the device into my headphones!

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.

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.