From what you've described, you're getting a very non-linear response with your current positioning. Have you been able to measure your frequency response at your primary seat and other seats yet? I'll be it looks like a wild roller-coaster
The larger the room, the less intense the various cancellations and peaks will be. Simply by virtue of the sound waves travelling a greater distance before they reflect off of a wall or ceiling surface and bounce back into the room, those reflection waves will have less energy in a large room vs a smaller room. So in that sense, yes, "more air" does help. It's just a simple matter of reflections and the strength of those reflections. More distance? Weaker reflections.
I know you've been having a lot of trouble getting your new PC13-Ultra to perform the way you want. I'm sure, by now, you're well aware that putting out LOUD, deep bass is not an issue for the sub itself! But getting the sub to work well with your room acoustics and your seating position is what's holding you back now.
Very important to keep in mind that with a lone subwoofer, the best you can get is quite linear, flat, accurate frequency response at ONE seat using some EQ (the PC13-Ultra has two bands of EQ built in, so that's a big help already, but more EQ might still be necessary for flatter response). At other seats, the best you can hope for is...something less than linear response...possibly MUCH less linear. But when you're mostly concerned with one "sweet spot" "throne" seat, a single sub can work well, but you HAVE to position it properly and then EQ.
So the trick is to find the spot in your room where there are no big dips at your primary seat. Big peaks, while not desireable, are "treatable" with EQ. And as for any seats OTHER than your primary seat - they're pretty much out of luck. They're going to have their own unique dips and peaks - which can be huge - and there's nothing you can do about that other than adding more subwoofers.
But for your primary seat, one sub is perfectly capable of delivering good response. You just have to find the right spot for it! If there is NO spot in your room where you can physically place your subwoofer and get response at your primary seat that is free of any big dips, then you need to move your seat. Even 6 inches can dramatically change the response, so it isn't necessarily rearranging the entire room or anything, just moving the seat and trying again...and again and again and again, until you find a combination of seating position and subwoofer position that produces a response that is free of any big dips at the primary seat.
Once you managed that, use the EQ to tame down any big peaks and you'll be good to go
Nothing you can do for your other seats without adding more subwoofers, but at least the primary seat can enjoy linear bass.
Adding passive bass traps alters the room's acoustics. In a very rough sense, adding bass traps is akin to making the room bigger - in other words, you decrease the strength of the reflections, so it's similar in effect to simply moving the walls further away. Thus, passive bass traps can significantly help in reducing the severity of the peaks and dips. Ultimately, the dimensions of your room are still the same, so the peaks and dips will occur at the same frequencies whether you have passive bass traps or not. But you can decrease the strength of the reflections and thus, reduce the interference between reflected waves and the waves that are coming directly from the subwoofer.
If nothing else, run a sweep - like the THX Optimizer bass sweep from 200Hz down to 20Hz and simply listen to that sweep in your primary seat with your current sub location. I think you'll find that it sounds very uneven the way you have things positioned right now, with the sweep getting much louder at some parts and much quieter or even silent at others.
As for the SubDude, I'm happy that it reduced the structure-borne transmission somewhat. That's what it's meant to do, afterall
It doesn't stop the bass from travelling through the air at all though. With dance music and other strong bass, you're certainly still going to hear it in other rooms simply because the air-borne sound is enough to penetrate normal walls as well as travel via any flanking paths. The SubDude should reduce the physical transmission of vibrations from the sub to the structure. If you noticed a decrease in bass in other rooms, that's the SubDude doing its job. But it can't prevent regular air-borne sound. To do that, you have to actually soundproof the room itself so that all vibrations - both air-borne and structure-borne - are contained within the theater room as much as possible.
