The Adam A7X's do have weaknesses in the low-end, but I believe it's something that plagues all speakers of that size or smaller. I think you can look at some of those mastering engineers' speakers for ideas. I know Bob Ludwig uses these:
[[url=http://[/URL]="http://egglestonwor…"]The Ivy Signature - EgglestonWorks – Quality Loudspeakers[/]="http://egglestonwor…"]The Ivy Signature - EgglestonWorks – Quality Loudspeakers[/]

Anyway, I really doubt that a 2-speaker monitoring system in a typical room can cover down to 20Hz. If I could get my monitoring system (that includes the room) sounding flat down to maybe around 32Hz, I'll be celebrating :D

your gonna need some big ol mains, and a room that could deal w/ it. the ueri 813s will go quite low +/- 3 40hz-15khz), but they aren't really accurate by today's standard. you can make them more accurate by having an efficient power amp/eq setup. where you have a way way overpowered amp so the amp doesnt' come close to distortion at any listening level (headroom). if your room is bottom heavy, you can eq out some lows, this can allow more efficiency, because the speakers aren't trying to reproduce inaudible frequencies, which is perceived as distortion.

you need a serious pro level room for something like this. a really nice amp is gonna run you in the 2-5k range, the speakers, if you can find 'em will be around 2k, the eq, at least 1k, then you'll probably want to tweak the crossovers. there's a whole lot more bass trapping necessary, than for a pair of 8's.

if you want accurate big speakers, your looking around 20k for a pair and that's not the upper end either.

why are you against a subwoofer(s)?

an advantage to them is you can move them around in the room, and find the best place for your lows, w/out compromising your imaging and other mid/high related things.

a buddy of mine uses the adams for their up-front mid range for really picky stuff like noises ect, and a pair of dynaudio 8's for general mixing, he has commented on their powerful low end numerous times. you might wanna check 'em out.

if you want a great pair of nearfields that go low acurately, the meyer hd1's are very nice. not cheap, but i really really like them. quested has a nice 8" speaker that has a more exaggerated low end, the vs2108's i belive is the model #. only use the quested a dozen times or so.

what kind of music are you doing that you need that low octave? alot of electronic stuff?

i did sound, and system tech, for a few years at a dance style night club, and even in the huge room like 200x125x18, w/ 6 jbl cabs w/ dual 15's, 6 18" subs w/ folded horn boxes, tons of crest power amps. (around the 40x30 dance floor) the subs crossovers were somewhere between 50 and 80, (i forget it was a few years ago, and i did it by ear) but i think it was 65, or 70/75. i used the dbx driveracks, 'sub harmonic synth' to artificially boost the 40 hz range . bascially adds a 40hz tone. even tho the settings went down to 20 there wasn't much there. even the "feel" lost it's attack, it's musical emphasis this low. there was much more oooph and booty shakin bass in the next octave up, and even that was really low, the 60 hz range was really where it all revolved around. FWIW.

just not sure it's practical, or even possible to have a flat 20-20 system, but more importantly, if its even useful to have, since most won't experience it.

not being discrouraging man, just think ya might wanna just get a pair of nearfields you like better, or add a sub. IMHO

Urei 813 must be flush mounted or at least they are most often flush mounted . Fist question that pops into mind is budget? Monitors can become very expensive. All this being said, this is the kind of problem that a mastering engineer should be able to remedy.

20 Hz is a LOT to ask of any p/b system, even one with a sub. the best i recall went down to 30 Hz.and that's almost to the point where you do not hear it.

i don't think any really needs that unless they are recording a pipe organ in a cathedral or they are doing de tuned 808s to play in a car forcing everyone for a two block radius to listen to BOOOM! BA BOOM BOOM BOOM!, BOOOM! BA BOOM BOOM BOOM!, BOOOM! BA BOOM BOOM BOOM!.

those morons should be shot .... and the only saving redemption is they probably will be at some point.

Even the Westlake reference series only claims -/+3db @ 34 hz. But, for what its worth, a fairly flat and accurate 34hz is going to give you the ability to seriously mix low-end extensions with lots of fidelity. Its all about accurate crossovers with minimal slewing and superior imaging.

Okay okay...
I'm obviously dreaming of a monitor WAY out of my price range.