I refurbished an old radio. My setup is a raspberry pi 2 with volumio 1.55 and the hifiberri amp+. I’m using a couple of Monacor 5" speakers (SPH 60, goo.gl/bs3kVY). Everything has been working nicely for a while, but last week I noticed a crackling sound. I experimented a bit, and found out that is caused by low freqs:
Playing this video (youtube.com/watch?v=M8gjsefNYpE, a tone from 2KHz to 0Hz) makes the crackling appear at around 225Hz and it’s specially noticeable from 50Hz and below. I tried different songs and when they are relatively quiet, the bass parts cause the crackling (but some songs might be able to mask the noise).
So far, only one of the speakers present the problem, and when switching the outputs (left speaker to right and vice versa) the behaviour is the same (the same speaker fails, the other works perfectly), confirming that only one of the speakers present the problem, and that the amp+ board is working. I checked the speaker and nothing seems to be out of the ordinary: wiring is still firmly soldered, no cracks in the cones, rubber parts are in perfect condition.
Given that I’m not knowledgeable at all in this matters, is something wrong with my testing? Should I try to do something else to confirm that the speaker is the problem? Sadly, I don’t have any other amps at hand to test the speaker.