Subpac S2 owner here, have had it over the past 3 months and worked on a few tracks with it for a label, my $0.02:
It’s absolutely bad ass - my reasons for purchasing one:
1.) Architectural issues in the space I produce music makes bass treatment pointless, my room mode is just shot to hell no matter what I do.
2.) Lowering my listening levels and thus protecting my hearing.
3.) Detailed physical feedback while doing sidechain compression adjustments, sculpting bass and kick sounds, and EQing within its designated range (5hz-130hz). Messing around with the RYTM on this thing is a genuine joy.
Overall, I was really pleased and even surprised at how tactile the bass response was simply in terms of articulation. This isn’t exactly a Nintendo 64 rumble pack for your chair, it’s a legitimately useful tool which not only provides physical feedback similar to what you come across on larger sound systems, but also engages your body on another sensory level while you’re working on music. If something is clashing, or feels muddy, you also feel that too - and you can gauge how well something is balanced by how pronounced and separated the vibrations are. The fact it lasts a really long time (like close to 5 or 6 hours sometimes for me on a single battery charge) is really nice. I leave it plugged in overnight and when I get home from work the next day, it’s ready to go again without having to leave it plugged in the entire time.
A word of advice - you NEED to calibrate and dial in the right vibration amount though - a good volume to vibration ratio is key to get the best results from the S2, too much vibration and you’re really missing half the point of it (plus it starts to feel flabby and “dead-woofer-ish”). I barely crank the vibration setting on my S2 past ~20% and that is plenty for me, I can then get even more granular with its vibration feedback by using the secondary headphone output level out on my Mackie BigKnob (which its connected to).
Also, playing games like Grand Theft Auto and Burnout is an awesome experience with the S2. You might even get a murder-boner during explosions and gunfire.