How to disturb a loud speaker sound from distance with any electronic device?

Wait ‘til it is dark, then sneak out and cut the cable.

Use a gun. If it needs to be magnetic, use a railgun.

I assume a subsonic rifle shot is out of the question.
Push a pin through the wires and clip it off flush with sidecutters so it cannot be seen.

Like this

Can you have it legally turned off? What is it broadscasting, (on public tuft, I assume)?
And on whose authority?

Can you round up the neighbors, who might be equally annoyed, for a joint effort?

I’m sorry but a magnet will not do it for you. Your only chance is if the speakers have amps built right into the housing. If that is the case you can transmit your own sufficiently large signal that would be picked up by the wires going to the speaker. You will have to match the length and orientation of the wires going up the tower to the speakers.
If there is no onboard amp you are out of luck. The speakers are most likely 8 ohm or less so anything you transmit will be overpowered.
Who was in the neighborhood first you or the speakers?