I used a threaded rod, some weights from a sports shop and bolted it together like this:
https://wolf-u.li/3594/shaker-tuning-mittels-zusaetzlichen-gewichten-fuer-bassshaker-bzw-bodyshaker/ (it's in German)
However, you could also use the EQ function in Voicemeeter to add a low pass and add a bit more punch, my settings for the shaker: