Actually, I would like to try wood if it makes it tighter, kaso Publema ko with wood slabs is the possibility of Cracking, which I believe is normal habang nag dry ung wood, especially during subsonic scenes, baka ma accelerate ang cracking ng wood. hehehe.
Baka kasi pag nag crack, mag iba din ang sound, and not for the better.
Lagyan mo muna ng sako ng buhangin sa ibabaw. That's the cheapest test. Pero kung for HT, masarap din naman yun may resonance ang flooring. Hehe! Pero kung for music, parang hindi maganda. Ang worry ko lang, it still won't stop the floor from vibrating because hindi mo pa din na-decouple yun sub sa floor. Baka maslumakas pa ang resonance.
Here are other options:
1. You can also try to put a heavy object underneath your sub instead. Point is, you are trying to put mass under the sub in hopes of hindi kayang galawin ng sub yun heavy mass sa ilalim. Kung hindi niya magalaw, then baka ma-lessen or mawala ang floor resonance.
2. You can try to get hold of Trod93. Dati may project sana kami na for that purpose.