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.
It is unavoidable, the only thing you could do is to check the Tweeters periodically, recommended 2 months once. This is part of maintenance of Swiftlet farm . If you don't do it you would loose out to your neighbors.Now you don't have to climb up and down the ladder to check every single tweeter. You can use the Sound detector. It can be nicely fitted onto the aluminium painting poll. All you need to do is to point the Sound Detector to the mouth of the tweeter. If its blink that means the tweeter is OK.
Get one and do some checking today and you would discover many tweeters in your Bh are malfunction. (at least 20%).Good swiftlet farming all!