+graham kaveman Sure, Mr. Kaveman! All our videos have explanations on the science and how to perform the demo yourself at our website. Here's the link for this particular demo: demos.smu.ca/index.php/demos/modern/18-electronwaves

The one in the video is a little expensive. What I'd recommend is look for an old stereo speaker, which will do the same thing.

@SMUPhysics yes I was afraid you'd say that, so I already got a subwoofer in replacement of that, I also got the ring and something to stand it on.

The subwoofer may not do it. It'll only act at low frequencies and even then, not with much amplitude.

I was planning on using an amplifier, assuming it increases the frequency. Also, to hold and attach the ring to the subwoofer (or speaker if changed), would it be better to use a metal tube or a metal rod, which would transfer the frequency better?

The amplifier will increase amplitude, not frequency. A subwoofer by definition will not vibrate above ~200Hz no matter what you input, so it will severely limit your frequency range. Tube or rod doesn't matter, as long as it is steady.