Speaker makes a crackling noise

Hi guys!

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.

Hi!
When reading what you describe, we can think to a mechanical problem with the speaker such a misaligned coil, or a damage coil due to a too loud use… Now (maybe) the paper that support the coil rubbing the magnet. Or check (if you can) that there no acoustic insulation piece that moved and touching the membrane.

Thanks Balbuze for your interest.

I know that everything points to “you blew the speakers”, but I’m quite surprised of having done that, as I am using a “25W” amp and a “60W, 30Wrms” speaker (quotes on the power ratings, as I know that you have to take them with a pinch of salt). I use it on a 4x4m room and I always listen to moderate volume levels. Plus, if it was a overdriving issue, I guess that the chances of blowing the two of them would be quite high (but I also understand that it one thing doesn’t exclude the other).

In any case, the faulty one clearly makes a rubbing sound when the membrane is pushed by hand, whereas the good one doesn’t, so either the coils are blown or something is broken or loose inside.

To sum up, I just want to know what did I do wrong, in order to not do it again. It’s hard to believe for me that I blew a hefty 5" speaker weighing around 1kg with an amp that doesn’t even have a heatsink (I know it’s a class D amp, and thus doesn’t require them, but even though…), listening to music at reasonable levels (and by reasonable I really mean it!).

Hi… I using raspberry pi 2 with volumio 1.55. sometime automatic speaker make cracking noise. why it happen with my set up?

Popping sounds can be caused by a poor connection between the speakers, speaker cables, and amplifier.