Having trouble with sound deadening

Not easily but there are devices, passive or active, that will absorb bass energy.
What is your goal? Acoustical isolation or sound quality?
What have you done so far?

lots of sacks of salt.

Mass, distance, and de-coupling (the least of these three) are the variables that are in play for lessening bass transfer. Unfortunately, bass hitting hard surfaces will vibrate all through the rest of the structure. Bass waves are also VERY LONG, and will easily go through drywall/joist structures, and pass to the next adjoining spaces.
It's not easy to isolate the bass, without dealing with the entire space. Building a studs/drywall "room within a room" structure in the existing basement, will actually help the sound out in a lot of aspects, but cause other compromises potentially. Still, if you can't decouple the room from the upstairs, you'll have little success in your endeavor.
Lots of info on doing just this on forums, sound treatment webpages, pro audio acoustics papers, home theater architect write-ups, etc.
How far are you willing to go here? ..is what I'd ask myself

Yes, if the room is finished with sheetrock you remove the sheeetrock and extend it away from the studs with absorbing material instead of screwing the sheetrock directly to the studs.

The more absorbing material you have the higher you have to turn up the volume and the higher you turn up the volume the more absorbing material you will need.