I was using my old 8500 (non x50) for something unrelated when i came across a strange occurence i thought i should share.
I don't know if it applys to the x50's or not.
i noticed the 8500 tends to give preference to ka alerts over k band alerts. i found that if i make it alert to even a weak or moderate ka alert, using my tester, that it will not audibly alert to even a full blast k band hit from a radar gun. The only way you would know, is if you are in EXP mode and look at the display and see a full k alert.
I found that if i hold the k alert long enough it eventually overpowers the ka alert and signals, but not until it could be too late.
Now a strong ka alert wouldn't matter, as you would be slowing anyway, but a weak ka hit will mask a full blast k hit, so it's possible if you were driving and started getting a weak ka alert, you could be missing a strong instant on alert on k band.
I also noticed that when the k band signal would finally overpower the ka signal and alert, it would stop displaying or alerting the ka signal, even though the tester was still on. It would take several seconds after the k alert stopped, before it would start alerting to ka again, even though the tester was still on the entire time.
I captured this on video and i'll upload it tomorrow.
Hopefully this isn't a problem with the x50's or even an issue that could happen on the road with an 8500, but i thought i would mention it in case someone wants to test this on an x50 just to be sure.