M-audio BX5 buzzing problem

[Somervre]

Disclaimer: I’ve already fixed one of these speakers (it had a really loud buzz) by replacing the 2 bad 4700uf caps. Now my other one has same problem. However…something else too.

So I replaced the 2 bad 4700uf caps in this one as well. Turned it on and the loud buzz was gone but now there was a moderate to soft buzz. About 56 db and was around the 750-900 Hz range (constant). I did not notice anything else obvious other than this little

 

[Delta Prime]

Are any of these the one you’re working on?
M-audio BX5 D2
M-audio BX5 D3
M-audio BX5 Carbon Black

About 56 db and was around the 750-900 Hz range (constant).

How old is your unit, high probability it is your transformer primarily caused by magnetostriction a common problem with steel and/or (ferromagnetic) cores expands and contracts 95Hz to 160Hz due to the AC magnetic field degrading overtime, causing “audible” high harmonic distortion around 600 to 120kHz.
You might want to check solder connections because poor solder connections, could overload the transformer increasing magnetic flux.
I would reflow solder and clean up the board using isopropyl alcohol 90% or higher.
As an example circled in yellow, I am sure there are more that are out of focus.See below photos…

 

[Delta Prime]

causing “audible” high harmonic distortion around 600 to 120kHz.

Correction:600 to 1.2kHz.