You will need a subwoofer that you can take apart, some wire, as many LEDs as you wish to use, as many clear pen tubes as LEDs, water, and whatever material you want to make a stand out of
Step 2: Tools
Tools you will need are: wire strippers, wire cutters, needle nose pliers, soldering iron
Step 3: Subwoofer
Take the subwoofer apart (or on some just unscrew the subwoofer speaker).
The only thing you need to focus on is the red and black wire attached to the speaker.
Strip half an inch off of the end of 2 of your wires. You should mark which wire is negative(black) with a felt pen along the length of the wire.
Now solder the unmarked wire onto the positive (red) wire. Next, solder the marked wire onto the negative (black) wire.
Before you put the case back together, use your wire cutters to make a small nick in the case so that you can fit your wires through so that the case doesn't damage the wires
Put the case together.
Step 4: Holder
You can use anything you want to build the holder. I used Lego because its cheap and super easy to work with.
The holder should be able to fit your clear pen in it lengthwise. And hold the pen straight as there is going to be water in it.
Once your enclosure is complete, fill your pen tubes with water and place them in the holder
(Note: I taped my pens to make the LEDs brighter. In some cases it may not be neccassary, it depends on the LEDs used)