Here is the problem that everyone who metal detects faces when looking for aftermarket wireless headphones (aftermarket as in not built by the manufacturer...XP Deus, Minelab CTX3030, Whites V3i):
The latency of the signal response and the build quality/freq response of the phones.
Those AKG's are nice phones for listening to music in the house but they are using "Kleer" 2.4ghz technology and that signal latency lag is awful. About >50ms of signal delay.
That same technology is used in some other headphones too. I have tested them out and their published >30ms of delay latency which I think is much longer is the equivalent of hearing the signal about 10" away from where the target actually is.
So as you swing, with a target sitting right on the surface, you hear the sound about 10" on either side of the actual spot where it sits.
Some guys say they get used to it - but for me it just wasn't right. Plus the phones are really geared to music (20-20,000hz) and not the freq range of our detectors which is from 200-3200hz.
I would stay tuned because something exciting is coming real soon regarding wireless headphones specifically geared for metal detectors...