Hello millercarbon,
You know we both completely agree, based on personal experience, about how exceptionally effective the 4-sub DBAs are in virtually any room and with any pair of main speakers.
The topic on this thread had switched a bit and was recently about whether anyone knew of any commercially available music recordings that contained bass below 20 Hz. Phusis then posted some comments that raised the issue again about whether or not deep bass under 80 Hz was recorded in true stereo and whether individuals can localize bass below 80 Hz even if the music was actually recorded in true stereo bass.
I think we both know how extremely rare it is for anyone being able to identify a single music recording that's commercially available with any bass content below 20 Hz and that, even if one is proven to exist, I think the odds that the bass was also recorded in true stereo below 80 Hz and not summed to mono, is lroughly zero.
My current concern is that we're veering away from the main subject the OP, smodtactical, is concerned with. His main concern seems to be how he can achieve very good bass response in his future very large 30'x30' room for music that will also perform very well for HT use. Can he achieve this using large subs or will it require smaller, sealed subs to perform very well, especially on music. Smodtactical, please correct me if I didn't summarize your main concerns correctly.
My suggestion is that you'll likely find it easier to get very good bass performance in your future large room than it would be in a smaller room. This belief is mainly based on the fact that bass soundwaves are omnidirectional, are physically much longer and behave much differently in any given room than midrange and treble soundwaves behave. Midrange/treble soundwaves are highly directional, physically much shorter and, therefore, behave much differently in any given room than bass soundwaves do.
In smaller sized rooms,I've found it's best to get the bass sounding right in the room first and then optimally position the main speakers in the room, in relation to the designated listening seat, for midrange/treble and imaging performance. 'm not certain this approach works as well in larger rooms but I don't see why it wouldn't. In theory, I believe it should be easier.
Smodtactical, I think you have several options to get the bass right in your future room. But I realize I'll need to more specifically need to understand your goals and budget to best tailor the options I'm thinking about to your requirements. Generally, I'd like to know if your priority is quality or cost and how important convenience is to you in terms of setup and use.
My options all consist of a minimum of 2 subs. I know that 2 subs will perform about twice as well as a single and 4 subs about twice as well as 2.
Here are some of the general options I'm currently considering for your room:
1. Start with a pair of Captivator RS2 or similar large subs and position them each optimally in your room using the crawl method. If you only use a pair of subs, the optimum positioning of each sub is very important and unlikely to consist of just positioning one by each of your main speakers. You'll need to be open to placing each sub sequentially in your room where the bass sounds the best to you at your listening seat and not where they conveniently fit in your room. This could require rearranging furniture and other room décor.
A variation on any of these options is to add a 3rd and even 4th sub to to create what's called a distributed bass array (DBA) system. The advantages of a DBA system are that the bass will have increased bass power and bass dynamics capacity when the content calls for it since the bass is cumulative, each sub will be operating well below its limits for lower distortion, the bass will be perceived as smoother, faster, more detailed, even better integrated with the main speakers and this high quality bass will be perceived throughout the entire room, not just at the designated listening seat.
2. Start with a pair of smaller REL 812S subs optimally positioned using the crawl method. If this is deficient in any way, you could add a 3rd and even 4th 812S sub until it meets your requirements. I believe using smaller and less expensive subs as additional subs might work almost as well as additional 812S subs. I also believe the 812S subs have the very convenient advantage of offering wireless connections.
3. Start with a pair of Syzygy SLF870 subs as a less costly option. These are newer subs that have received very good reviews and are also offer wireless connections. I believe the guy who started this company formerly worked for REL. Here's a link to their site:
http://syzygyacoustics.com/4. Buy a complete 4-sub DBA system for about $3K total, such as the Audio Kinesis Swarm or Debra bass system. This is what I use in my smaller 23'x16' room and it works spectacularly well. I know these are designed to provide high quality bass performance similar to being in a bigger room, but I think this system would work at least as well in a larger room such as yours. However, I'd suggest contacting Duke or James Romeyn at AK to make sure they agree. Here's a review of the Swarm in The Absolute Sound that I found gives a very accurate description of the bass performance level to expect:
https://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/Best of wishes,
Tim