Using 2 Subwoofers

I am in the process of picking out a new subwoofer and not sure if I want to go for 1 or 2???

Seems like the general consensus is that 2 are better than 1, but I am not sure if my room needs an additional subwoofer. The room is aprox. 14x14 but it is not closed in, since the kitchen is attached and hallway.

I am choosing between, HSU-ED-SVS-Outlaw etc.
2 subwoofers are better than 1 as 3 are better than 2 and 4 are better than 3.

The most common misconception about multiple subs is that is will be too loud. The truth is that multiple subs reduce distortion and take care of multiple room modes which is trying to make bass even around the room.

Some people are lucky and get excellent bass response in there room with 1 sub but that is not common but rather the exception. You will have to experiment in your room and find out what works for you.
with a room that size-
get one and be done with it-
get a used JL Audio 112-
you will thank me later.
Buy two, try them out, then try one and if not much difference, return one. I have two and gave the dual set the edge. The only way to nail the issue is to actually have the two initially. But remember, placement is everything.
I second the JL Audio brand recommendation but I think (hear) that bass is stereo, too just like the rest of the spectrum. I use a pair of JL F110's and love the sound. Had one larger sub before these and two are definitely better than one for my system. When I got them I unpackaged them, put them in place, used the auto room optimization, slightly repositioned them once, and was done. Just like that. In my experience with two you can run at a lower level which makes them easier to integrate and avoid common sub issues.

Bass below 100Hz or so become nondirectional. If you can hear the bass from the sub, either your crossover frequency is too high or the sub generates too much high order hormonic.

I am aware of all the tech reasons you're referring to. In my room I can't place the sub in the middle because there's a large aquarium smack in between the speakers (has been for the last 35 years in a number of homes). With a single sub on the left or right I didn't necessarily hear the sub but with stereo subs I DO hear a broader and deeper soundstage particularly with classical music. I "know" the rules but I "experience" the effect of stereo subs-it sounds wonderful.
If you're trying to smooth the bass response without EQ, then multiple subs is worth considering. I would expect a modern HT to provide room correction, so for a room your size a single quality sub should suffice.
My room is very similar in size to yours, and I find my single Velodyne F1500R is more than enough bass. Location is on one side, in the center it did not produce much bass. My main speakers are ADS 1590/2's, full range in their own right. But still the sub is needed. I can't imagine sticking 2 subs in a room my size!
Multiple subs, placed asymmetrically should even out some nodes....bumps and dips.
Equalization will help for a small area at the expense of larger peaks or dips elsewhere. For a single listener, a single equalized sub should work. In my room, where I have the TV, I got lucky and have a wacky, 8 sided room with an off-center vaulted ceiling. I've looked (listened, actually) for bass bloom and suckout without much luck. I also crossover below 40hz and run my panels full range.....That, too, may help.
One of the advantages of using 2 subs is you can get away with smaller drivers.
A room that sounds good with a big 12, or 15" sounds even better with 2-10" subs.
You pick up alittle speed, and your room does not have to compensate for such nodes (trying to support 30hz clean).
A stereo 50hz, sounds alot cleaner than a mono 30.
I once had 2 Klipsch 8" powered subs hooked up, and they sounded better than all the premium single (12&15") subs I have owned, especially on 2ch music.
Just my opinion, I am no expert by anymeans.
I agree with Bob. To restate and expand on his point.

If you have Audyssey or similar digital room correction (DRC) in your HT electronics, a single well chosen sub (SVS and JL are highly regarded for dual music and HT use) should be more than enough for your space. The DRC will correct for destructive room effects, so you needn't worry about addressing that issue via strategic placement of multiple subs.

The ability to address room issues via strategic placement is the primary reason I'd choose multiple subs. In this respect, DRC or multi subs are an either/or solution to the same problem. You can use both (I actually do so, but for quirky system and room specific reasons), but you usually needn't do both for smooth FR in the deep bass.

While it's also true that multiple subs will - all else being equal - provide higher output for any given distortion level, in your smallish space a single high quality subwoofer should not be remotely stressed into audible misbehavior.

I'm going to be a bit contrary. I have a similar sized room and it is also open on one side. I have a JLf112 that I placed in front just inside my right main speaker in a position commonly recommended byt JL , THX, etc. I ran the JL equalization and the pioneer system and decided the JL system resulted in slightly better performance. I have on several occasions tried listening in all areas of the room and while I can hear a difference, in my case is is not huge and frankly no big deal (YMMV or course). I would suggest trying one and seeing what you think. Than again I also find that not having a matching center ( I do, but ran non matching for some time) was less traumatic than I thought it might be.
Marty, thanks for providng the additional details -- you do a great job.
I own two 15" non-ported audiophile subs and have them placed on either side of the room. One in back and the other in front next to my towers. For two channel music I turn off the sub in the back, because I prefer all the sound coming from in front of me. For movies both subs are set to levels that make you feel like a neutron bomb was dropped on my house.

Therefore, I recommend two... you can always turn off the second one.
I use 2 JL F110's in the A/V room - and I can say that 2 subs sound a lot better than one. The overall response is smoother - there is no localization - and it's a huge presentation - Just a solid Wall of bass - One is good but it looses that magic
Dovjm, I have a SVS PB13 Ultra in a room really close to yours and it works extremely well. 14x19 roughly with 1 doorway and open to dining room on other end. I keep the volume at center on back of sub and my pre measures from -15 to +15 and that's set at -9. All other output settings within sources are center -0-. I recommend the SVS....Bob Reynolds recomended it to me in one of my forums and love it. Thx Bob....

Regards Bacardi
I found in my 11X15 room,one sub was nice,but with two it
adds a real nice blanket of bass for the music to lay on.
It definately sounds complete.
I also noticed alot with one sub DD-15,if you moved from your listening spot even 6"the bottom end would change,thnner,less ect.
Two subs are superior to one and it's not loudness superiority
it's an eveness across the whole room and for me that's a
completeness you can't get with one.
Borrow another and you will hear it for yourself and YOU WILL KNOW.
100 % agree with Drummermitchel
does using two subwoofer increase the range of frequency response?