If you have a noisy transformer in your Dell MMS-5650 speaker unit it can be quite annoying.
These units internally run on 19 Volts – the same as most laptops.
You can remove the rear screws and pop off the front panel to free up enough wire to access the power connector, then solder a spare Laptop power supply onto the relevant rails.
Ideally you’d use a 90 Watt PSU if you really want it loud, although a 65 Watt one will suit.