Originally Posted by Intrepidman09
...I also covered the walls and ceiling with 1" soundboard and an additional 1/4" drywall, so the room is 'dead'....I have to keep turning the sound down because of the bass. Or am I just kidding myself, and I'm missing out on true bass?...
It sounds like you've added sound isloation to the room, meaning that the room is not "dead" but rather "quiet." If it were truly "dead" in the sense of very low reverbration time, you'd never turn "...the sound down because of the bass."
Far more likely that by soundproofing the room, you increased RT, especially at low frequencies, and so have a strong set of room modes. It's the old "reflection + transmission + absorption = 1" principle. By reducing transmission (the goal) without increasing absorption, you've increased reflected energy, and not uniformly at all frequencies. I have a room about 2/3 your size, but it's leaky, with several features that absorb or leak bass. My single 15" will make you jump if you're not expecting it, but it's hardly overpowering.
The solution is to find out what your RT looks like vs. frequency, then add acoustic absorbers of the appropriate type to flatten out the RT vs. frequency curve. Bass needs special attention as the vast majority of acoustic treatments aren't terribly effective in the range where room modes dominate. Then there's the room dimensions...
23.5 | Adjacent mode spacing
26.9 | 3.4
47.1 | 20.2
53.8 | 6.7
70.6 | 16.8
70.6 | 0.0
80.7 | 10.1
94.2 | 13.5
107.6 | 13.5
117.7 | 10.1
134.5 | 16.8
141.3 | 6.7
141.3 | 0.0
This shows the room modes below 150Hz from the Harman "roomcalculator.xls" which you cna easily download. Ideally, room modes are evenly spaced. Yours are not: L and W are close, and H is 3x the other two, so modes coincide. Note that this assumes rectangular room with 6 flat, parallel walls. Any departure from that adds complexity, thus the recommendation to do some RT measurements at the low end to see what's actually present in the room. Without measurement, you may be able to confirm aurally, by changing locations to verify which mode you're hearing. My bet is that the 70-80Hz trifecta is killing you.
If this makes sense, here's a link to the master reference where you can find out how to measure, and what you cna do to address the issues, if room treatment is, in fact, the solution.