taken from some forum somewhere....a review
A few thoughts:
While the alarm is LOUD, it can also be muffled quite a bit just by pressing one's hand or thumb over the speaker hole. That's okay by me, as I don't really view the alarm as a theft deterrent. Rather, it is the best prevention I've seen against accidentally riding off without first removing your disc lock. Although some other locks have "features" designed to prevent this embarassing mishap, they all require that the user remember to use them religiously (e.g. attaching that springy orange "telephone cord" to your handlebars). Seems dumb to me: if you're forgetful enough to ride off without first removing your lock, you're probably also capable of forgetting to set up the reminder device.
With XENA locks, this is never a problem. Attach the lock to your bike and it automatically arms itself. When you return, getting on the bike will definitely trigger the alarm, well before you have time to get on and (try to) ride away.
Now, for most of us this isn't a big problem. But I must admit that the XENA has saved me from making this mistake once or twice, usually on days when I had too many other things on my mind to remember a tiny disc lock. On that basis alone (and given the negligible difference in price between the XENA and non-alarmed disc locks) choosing the XENA was easy. And who knows? Setting off an unexpected and attention-gathering alarm might also just be enough to make a casual thief (like a tank-bag snatcher, say) give up and move along. I doubt it would deter a pro, but then again, what would?
As for sensitivity, my previous XENA was definitely more touchy than my new one, an XN15. The XN15 seems both more sensitive (sometimes just lightly touching my bike is enough to set it off) as well as less prone to false alarms. Also the XN15 is beefier, and looks far tougher to break. I purchased it with a chain combo, allowing me the option of just using the disc lock, or chaining the bike up to something and using the disc lock to secure the two ends of the chain together. I really like that flexibility, as it allows me to moderate the level of security I think I need for the situation. Heading to dinner in Marin County? Disc lock only, small enough to fit in the pocket of my Hein Gericke. Leaving the bike overnight in East Oakland? Disc lock and 4' chain attaching the bike to a telephone pole.
