[DangerClose]

 
I've heard the Q701's referred to as bass-light, but surely they must have more bass than the AD700's? 

Not really.  Not stock anyway.  If you do the bass mod, you'll probably have all the bass you could want.  A full mod might be overly boomy though.  Read the bass mod thread and see what you think about the opinions.  
 
And remember the Q701 is kind of opposite of the ad700.  The AD700 is 3-D, the Q701 is more 2-D.  The AD700 has more of a diffused sound, the Q701 is pinpoint accurate.  The Q701 has more separation and is more analytical.  The AD700 is like putting your head in a round fish bowl, but the water you're immersed in is sound.  
 
I'll cover the expected "get an AD900x."  If you want to try an AD900x, just eq a V on the AD700 with a 3 or 4db spread, except drop the 16k 4db.  That's pretty much the AD900x.  Well, compared to the AD700x.  From lots of reading but never hearing the AD700, I'm thinking the AD700x might have at least a little more bass already over the AD700.
 
DT990 also has big bass.  And Superlux EVO.  DT990 is better, but the EVO is really something for the price.  I often eq the bass down on both of them.  You might like the DT880 too.  

 

[Draulius]

  The Q701 definitely has more bass than the AD700, especially subbass! It can actually kick and rumble, unlike the AD700. It doesn't sound bass-light with "natural" sounds and real recordings, but it kinda falls behind when it comes to synthetic stuff. I actually like it for some of my technoey music, such as 'Infected Mushroom' because the bass never gets in the way. It's fast and tight, yet still punchy. In addition to some more bass, you will get a lot more treble though. I hope you don't mind more shimmer and sparkle^^.
 
The Fidelio X2 is completely different. Its bass is the main thing. It is POWERFUL. It's fantastic for gaming and movies, because it can really rumble. But at the same time, the mids and treble are there, nice and clear. The bass comes first, then the treble, and finally the mids. So its frequency response curve is "U-shaped." Its best thing, besides the bass, is its soundstage. It is at least as big as the AD700's. It's amazing!
Q701 soundstage might sound more 2D at first. But it sounds very sharp, very defined. And it IS fantastic for gaming, as forum member Mad Lust Envy says.
 
If you just want more bass, go for the Q701. It has all the bass.
But if you want fun, exciting bass, go for the X2.

 
I'm more concerned about the quality of bass rather than the quantity. And a 3D-sounding soundstage would be nice since I'm so used to the AD700's. And last but not least, the X2's look like they have better build quality and possibly more comfort. Maybe I should just go with the X2's?
 
I've listened to the K712's before and didn't like them. I was hoping the Q701 or K702 might be better for me, but I'm not sure. Something in the mids, I think the lower-mids, felt recessed on the K712. Unlike the mids, the highs felt more forward and made the headphone sound less balanced to me, and I found my AD700's more "clear" sounding in comparison. Maybe they needed more burn-in time, but it doesn't matter since I felt them uncomfortable for long periods. I could have made them more comfortable by getting the Q701's angled pads, but this made the price of the K712 unjustified for me.

 

[CaveManta]

If the K712 sounded recessed in the mids, I don't think the Q701 would be much better. Although I don't hear any recessions in the mids of the Q701..Hmm.. The timbre is slightly different in some of the upper mids, compared to my warmer cans..
 
If you want comfort, the X2 is the way to go. It is the most comfortable can I've ever had. Its bass might get in the way of mids at times though.
If you're worried about recessions in the mids, the Q701 will be good. It has some great mids! But it's just not very comfortable. Oh, and its soundstage is more 2D.
 
You know, do the AD900X trick that DangerClose just suggested. It sounds like a great idea.
The AD900X has more bass punch than the Q701(thanks to new earpads,) it's more comfortable, it's cheaper(debatably,) and its soundstage is more 3D. It just might be a winner.
Oh, but its cable sucks! It likes to coil itself up(which might be a good thing =P.)

 

[Draulius]

  If the K712 sounded recessed in the mids, I don't think the Q701 would be much better. Although I don't hear any recessions in the mids of the Q701..Hmm.. The timbre is slightly different in some of the upper mids, compared to my warmer cans..
 
If you want comfort, the X2 is the way to go. It is the most comfortable can I've ever had. Its bass might get in the way of mids at times though.
If you're worried about recessions in the mids, the Q701 will be good. It has some great mids! But it's just not very comfortable. Oh, and its soundstage is more 2D.
 
You know, do the AD900X trick. The AD900X has more bass punch than the Q701, it's more comfortable, it's cheaper(debatably,) and its soundstage is more 3D. It just might be a winner.
Oh, but its cable sucks! It likes to coil itself up(which might be a good thing =P.)

The cable on my AD700 doesn't coil up. If the AD900X's is the same one then it should be fine. I was seriously considering the AD900X but I wanted to learn more about how it compares to the AD1000X and AD2000X first, particularly in the soundstage department. And there doesn't seem to be many comparisons of that I can find. I wouldn't want to purchase the 1000X or 2000X and find that they're great for music but worse for gaming and movies.
 
You think the Q701's soundstage is more 2D than the X2's?

 

[DangerClose]

   
I'm more concerned about the quality of bass rather than the quantity. And a 3D-sounding soundstage would be nice since I'm so used to the AD700's.

 
If you want a 3-D soundstage, you're on the wrong path with the Q701.  

 

[Draulius]

   
If you want a 3-D soundstage, you're on the wrong path with the Q701.  

What other open-back headphones offer a 3-D soundstage besides the Audio-Technica AD series?

 

[Me x3]

   
If you want a 3-D soundstage, you're on the wrong path with the Q701.  

 
My K702 has one of the biggest and most 3-D soundstages I've ever tried.
Q701 should be similar.

 

[Shaffer]

My K702 has one of the biggest and most 3-D soundstages I've ever tried.
Q701 should be similar.

It is similar.

 

[DangerClose]

  What other open-back headphones offer a 3-D soundstage besides the Audio-Technica AD series?

Sounds like a question with long answers for another thread.  For what you've said so far though, I'd put the DT990 on your short list.  
 

   
My K702 has one of the biggest and most 3-D soundstages I've ever tried.
Q701 should be similar.

As 3-D as your HD600?  The sounds on my HD580 are like physical objects compared to my Q701.  

 

[Me x3]

 
As 3-D as your HD600?  The sounds on my HD580 are like physical objects compared to my Q701.  

 
The perception of soundstage is one of the most complex topics around the headphone hobby. It involves a lot of variables such as the form of our body, the way we wear the headphones, listening levels, the recordings used, the source (DACs, Amps, etc), our brain...
 
Here's a Stax SR-007 review often labeled as the most epic headphone review ever written.
http://www.head-fi.org/a/stax-sr-007-omega-ii-a-review-after-4-years-of-ownership-darth-nuts-epic-review
There you can find a very interesting perspective about soundstage and how complex and subjective can be.
 
I've compared K702 with HD600 for several minutes to answer your question from my perspective. The answer only strictly applies to me right now, it might be representative or not, so please take this with a grain of salt.
 
Setup:
Foobar 2000 ----> Schiit Modi 2 Uber ----> Schiit Asgard 2 ----> HD600 / K702
 
Recording used:
Verdi's Rigoletto - Act 1 - Scena E Duetto - Giovanna, Ho Dei Rimorsi (DG)
 
I've picked this recording because it's short, both female and male vocals are present and there's also orchestra. Everything sound clear with precise imaging.
I'm used to this recording and I think that's a plus when it comes to analyze and compare headphones.
 
I've simplified my impressions in this picture:
 

 
The soundstage on HD600 is just a tad more intimate and just a tad less frontal to my ears.

I suspect, the soundstage on K702 can be slightly harder to 'decode' for people used to HD600, since it's bigger and the headphone is lighter in terms of tonality.
I find that K702's separation push the headphone to demand quality recordings with coherent placement.

HD600 is intimate and clear so it's possible that it's slightly easier to put everything in place in our minds, even the first time we use it.
 
Last but not least, K702 seems to put more space between the listener and the music. I've checked this with "A Kiss to Build a Dream On" by Amber Rubarth (Chesky Records' superb binaural recording). As far as I know Amber was singing pretty close to the dummy head but there was still a distance between them. I think the K702 renders better the sense of frontality and the space between Amber and the dummy head (I forgot its name).
 
These (HD600 and K702) are very nice headphones in my opinion and although slightly different, I enjoy both soundstage presentations and both manage to provide a "3D like" imaging from my perspective.

 

[DangerClose]

 
These (HD600 and K702) are very nice headphones in my opinion and although slightly different, I enjoy both soundstage presentations and both manage to provide a "3D like" imaging from my perspective.

It's surprising to hear HD600 and K702 soundstages described as only slightly different.  I don't have those, but I have the similar HD580 and K701 and Q701, and they are worlds apart to me.  The 701 of course has a wider soundstage, one of the widest available in any headphone other than a few exceptions as far as I'm aware.  The DT990 easily has a wider soundstage than the HD580, and the 701 has a bit wider soundstage than the DT990.  
 
But, the depth.  If I watch a movie with lasers shooting at me, or something big crashing through a wall right at the camera, the difference between the 701 and the other two is obvious.  Obvious to the point where, despite enjoying the huge 701 soundstage width, and being in awe of the separation (probably enjoying it more on a technical level than on a musical level), I don't use them as much for movies anymore.  It's like someone squished and compressed the soundstage front-to-back to make it squirt out the sides left-to-right more. 
 
Lack of depth is also my main problem with the Superlux EVO.  Though now that I think about it, I removed the front foam on the EVO, so to be fair to them I should probably put the foam back in to make sure my modding didn't cause their lack of depth.  

 

[Me x3]

  It's surprising to hear HD600 and K702 soundstages described as only slightly different.  I don't have those, but I have the similar HD580 and K701 and Q701, and they are worlds apart to me.  The 701 of course has a wider soundstage, one of the widest available in any headphone other than a few exceptions as far as I'm aware.  The DT990 easily has a wider soundstage than the HD580, and the 701 has a bit wider soundstage than the DT990.  
 
But, the depth.  If I watch a movie with lasers shooting at me, or something big crashing through a wall right at the camera, the difference between the 701 and the other two is obvious.  Obvious to the point where, despite enjoying the huge 701 soundstage width, and being in awe of the separation (probably enjoying it more on a technical level than on a musical level), I don't use them as much for movies anymore.  It's like someone squished and compressed the soundstage front-to-back to make it squirt out the sides left-to-right more. 
 
Lack of depth is also my main problem with the Superlux EVO.  Though now that I think about it, I removed the front foam on the EVO, so to be fair to them I should probably put the foam back in to make sure my modding didn't cause their lack of depth.  

 
What DAC and amplifier are you using to drive your AKGs?
 
Have you tried different positions?

 

[Evshrug]

Not that Draulius is reading anymore, but going from AD700 (3 years of ownership) to Q701 seemed like a pretty natural progression. Not all Q/K701 sound the same (revisions, but especially pad wear), but when I first got my Q701 I felt I had a very similar sound balance WITH more solid bass extension, and almost as good of a soundstage as the AD700. The Q had juuuuust slightly less depth to the soundstage (oval) on the FiiO E5 amp I had at the time, but later when I got a tube amp and a few good condition tubes I feel like the soundstage became better rounded. I like to game with surround processing, and the Q really did a great job while also being more enjoyable and especially involving while listening to music.

I really do feel the Q and similar top AKGs are among the elite in headphone soundstage spaciousness (among the bright AD700, kinda dull Sony MA900, and ones I haven't heard but believe in like the Senn HD800). The HD700 and DT880 had similar depth but not the same width (more "in-head" experience), and the HD700 had a thicker sound and wasn't as good as the Q or DT880 at separating sounds and layers of depth. I would say the DT880 has good imaging of where something is positioned but not the sense of spaciousness and size for me to consider it "elite," and it made my ears produce lots of earwax and pain besides.

Everyone is different and (assuming the K712 you heard wasn't defective) the mids of the K712 shouldn't be much different from the Q. I found the K612 to have just slightly more forward mids and slightly smaller soundstage size (some would call it better balanced), but FYI that 120 ohm headphone (with also relatively low sensitivity too) needed a higher volume dial position than the HD700 and around as much as the DT880 600Ohm, definitely can hear a flawed presentation when used with a weak amp. The K612 and K712 scale really well with a Theta basic II DAC and a nice 70's vintage Russian military tube, but also sounded good out of a Turtle Beach DSS as a starter setup.

 

[DangerClose]

 
What DAC and amplifier are you using to drive your AKGs?
 
Have you tried different positions?
 

Positioning helps on the Sony MA900.  Probably because the drivers are so close to the ears.  I haven't noticed much difference on the 701s.
 
I assume my amps will get the blame since I use a Xonar DG and a handful of old stereo receivers.  The receiver made a noticeable difference over the DG with the HD580.  They sound good on the DG, but on the receiver they gain some 3-D'ness and are more alive.  (I'd have to A-B again, but I think DT990 only had a slight bass quality improvement.)  Could the receiver be enough for the HD580 but not for the 701?  Maybe.  But the receiver only needs to be less than 1/4 volume to make me deaf.  And there's a lot of comments about 701 being "dry."  And there are comments like this:
 

  Why this is generally true and a good thing to consider, the E9 despite it's 10ohm output doesn't even remotely mess with the Q701's signature. It doesn't with my HD-598 and not even with my DJ100 that's 38 ohms. In fact, the DJ100 loves the E9.
 
I actually tried my Q701 with an old Technics receiver from 93 using the headphone jack. Sounded amazing with no change in it's signature. I was shocked to find that the headphone jack has a 330ohm output impedance!! Even my DJ100 sounded the same. Makes no sense.
 

 
He goes on to say, and I've seen other people say similar, about some amps coloring the sound, but comments about depth changes are less common.
 

when I first got my Q701 I felt I had a very similar sound balance WITH more solid bass extension, and almost as good of a soundstage as the AD700. The Q had juuuuust slightly less depth to the soundstage (oval) on the FiiO E5 amp I had at the time, but later when I got a tube amp and a few good condition tubes I feel like the soundstage became better rounded. 

 
Evshrug says his Q701 had just slightly less depth than his AD700.  While hooked to an E5.  That's a pretty weak amp, isn't it?  I'm wearing AD700x right now hooked to the Xonar DG, and sound is pretty much everywhere.  The soundstage is deep at the sides and then loses depth as it gets to the center.  I think the center depth could use a little help actually, but that's compared to certain other headphones like the HD580.  
 
Depth imo is easier to gauge with action movies instead of music, so if most people base their opinions off of music, maybe that's part of the difference of opinion. 

 

[Me x3]

  Positioning helps on the Sony MA900.  Probably because the drivers are so close to the ears.  I haven't noticed much difference on the 701s.
 
I assume my amps will get the blame since I use a Xonar DG and a handful of old stereo receivers.  The receiver made a noticeable difference over the DG with the HD580.  They sound good on the DG, but on the receiver they gain some 3-D'ness and are more alive.  (I'd have to A-B again, but I think DT990 only had a slight bass quality improvement.)  Could the receiver be enough for the HD580 but not for the 701?  Maybe.  But the receiver only needs to be less than 1/4 volume to make me deaf.  And there's a lot of comments about 701 being "dry."  And there are comments like this:
 
 
He goes on to say, and I've seen other people say similar, about some amps coloring the sound, but comments about depth changes are less common.
 

 
Jacks on receivers usually have really high output impedance. Since K/Q701 have a relatively flat impedance, the frequency response of the headphone is pretty much unaltered when plugged into a high output impedance amplifier, but the change in frequency response is not the only effect of a low damping factor.
 
I've used my K702 plugged into a Yamaha A-S500 (470 Ohm). The Yamaha worked very well with the Beyer DT880 and to a lesser extent with the Beyer DT990, both sounded (and measured) significantly warmer, but still clear. On the other hand, the 702 measured pretty much the same but sounded more diffuse. At that time I was comparing with a trusty Fiio E10. I won't say the difference was like worlds apart, I didn't noticed at first, but careful listening (and even sort of blind comparisons with my brother) revealed the fact that the Yamaha A-S500 wasn't a great pair for the K702. Then I started using K702 with Fiio E10 which sounded clearer and tighter all across the spectrum (yes, also just a tad drier). Then got the Magni and the K702 sounded even more clear and refined, specially in the treble region, which improved the soundstage a little bit. Then got the Asgard 2 and Modi 2 Uber, and the K702 improved in most regards included soundstage and imaging. I'm pretty sure there's not much room from improvement from now on, so for now I'm done!
 
Not to say that you MUST find depth in your K/Q701s don't get me wrong. It can be that the headphone doesn't fit you well physically, or sonically. As I've said before, the perception of soundstage is a really complex and subjective topic.
Just give them the benefit of doubt if you haven't tried them on a more refined setup yet. I might surprise you!
 
Note: The Magni is a superb amplifier, although it appears just tad more splashy/forward in the treble than the Asgard 2 (although both measure perfectly flat).
By comparison, the Asgard 2 gives the impression of a slightly heavier, more mid-centric sound, which I find very 'non distracting' and lead me to perceive soundstage more naturally.
 
PS. Yeah, I've been quite skeptical about differences between different quality SS amps, don't blame you if you're still like I was before having quite a few amplifiers to compare. Differences are there, not huge for sure, but sometimes a little difference can make a big impact on how we perceive fine details in the deep of our recordings.