I see lots of articles saying people are driving 007s and 009s out of the Kingsound M03 portable amp. On the other hand on Head-Fi Spritzer supposedly said its dangerous and you need to install a resistor to do it. Which is true? Is it just a precaution that isnt' necessary?

High end speakers tend to have 3 types of diaphragms, beryllium, diamond, or aluminum coated ribbons.   Now just recently Focal introduced beryllium into the headphone market, in order to chase "electrostatic-like speed."    In terms of speed in term of loudspeaker tweeters it goes like this...