Converting electric powered speaker to USB functional

I was looking for external speaker for my desktop computer to listen music while on work. I looked in office store if there are any unused ones. I found a pair of speakers without use. I connected to the computer but did not hear sound. When I checked the small lamp, it was not lighting. I checked the power and it was due to power problem. After opening the speaker, I saw broken AC converter. I recalled my secondary school knowledge: the AC converter converts the normal incoming electricity to DC. I knew the normal desk top computer connected speakers use around 9-12 volt and usually USB work on same range. Hence, I removed the electricity connecting wire and AC converter from the speaker. Now there are two wires remained to provide DC volt to the speaker. I tried connecting those two with the USB cable. Wow! The speaker light turned on. I checked the speaker sound with volume icon of taskbar. It worked with music and other sounds. I looked for old USB cable and found a broken mouse. I cut the cable and connected blue cable of USB to one DC cable of speaker and Brown cable of USB to other cable of speaker. I taped the connecting and put inside the box and screwed the cover of speaker. Now the speaker is totally converted to USB functional. I can use this speaker to any USB hub and enjoy the music. If you have any broken speaker and USB cable, you can reuse it like I did. Please remember to remove the AC converter and its wire before proceeding for USB connection. Try this only if you have basic knowledge of AC, DC and electric connection.