Below is the Sound detector I use for checking tweeters in my Bh. It comes with a free battery. It is a must have gadget for all farms. It uses frequency to detect sound and it will blink if the tweeter is in good condition.
The first six months, if the humidity of Bh is high 20-40% of the tweeter will damage. The high humidity causes oxidation at connection point of the tweeters thus caused it to malfunction.