Why does my subwoofer make a humming noise? The voltage difference between a subwoofer electrical ground and the equipment ground can cause it to hum. This can happen because of the irregular current flow in your audio cable. Turning on the volume too high can also cause a hum.
Hello Redman, I sent you the link to download the service manual of model B112, it is quite similar
Check for possible false contacts
I hope you can solve the problem
Greetings Franco Dosil
Hola Redman, te envio el link para que descargues el service manual del modelo B112, es bastante similar
Revisa posibles falsos contactos
Espero puedas resolver el problema
Saludos Franco Dosil
https://elektrotanya.com/behringer_eurolive_b112d_sm.pdf/download.htmlhttp://www.uns.nu/pdf/Behringer_Speaker_B115D.pdf
Sounds like an earthing problem , check your cables and make sure none of the cables have strands that could be shorting down to earth causing the buzz