|Here is where I first saw it ... |
However that was before Apple took over Beats. I also read an article which stated the W1 was an off-the-shelf CSR product but I've yet to come across that one again. In looking for this, I find a lot of articles saying AirPods use a new W1 chipsets. It might well be that the original W1 chipset (ie in acquired Beats headsets) had CSR silicon which Apple subsequently exchanged for in-house product with the same name when Air Pods arrived. I'll keep looking though.