Volume control on Perfeo Water Dancing speakers?

Question

Do it yourself

Perhaps not quite a standard question, but I hope there are experts.
Bought Perfeo Water Dancing speakers from ebay. They dance beautifully, of course, but the sound leaves much to be desired. The girl played a little with them and threw them into the far corner, after some time I felt sorry for them and I decided to connect them to the computer. Now there is a 2.1 system, I switched the mode to quadraphonic and everything seems to be fine, but there is one caveat. The height of the fountains depends entirely on the volume, but there are no volume settings on the speakers themselves, and the volume on the computer is usually set to 5-10. Accordingly, there is no hint of jumping fountains.
Hence the question. Perhaps someone knows how this system can be arranged and how the sensitivity of the fountains can be increased? Or, in extreme cases, reduce the volume of the speakers itself, and leave the fountains at the same level? If needed, I can cut it open and take a picture of what's inside.