Stats and bass is a somewhat complicated topic. Stats need a good seal in order to get bass extension, and a lot of the measurements that you see - a bump in the midbass followed by deep bass rolloff - are symptoms of a bad seal. When you throw in the fact that many stats are now vintage and pads are starting to deteriorate, it becomes pretty damn hard to get quality bass measurements and nearly every new measurement you see today shows a broken seal to some extent. On top of that, Stax have lately been designing their headphones with an intentionally broken seal, and in that case you do see midbass elevation and deep bass rolloff and there's not much you can do about it except to mod them and improve the seal.
Tyll's old measurement database had plenty of Stax measurements that showed a good seal, and in those cases you mostly saw flat bass down to 20hz and beyond, or maybe a 3-4db bass shelf but with good extension. In these cases, you also saw pretty much negligible distortion in the bass throughout. But when you had a broken seal, you had rolloff, midbass boost, rise in distortion, etc etc. Of course, "flat" in this case doesn't mean Harman flat. But Harman sounds too bassy for me anyway.
Now you can make the argument that a theoretical perfect seal that you can't attain in practice doesn't reflect how those headphones sound in real life, and having seal issues leading to weak bass could simply mean that stats tend to have weak bass, whatever the reason. YMMV.
In terms of impact, stats need power, and Stax amps are generally not up to the task. Give them aftermarket power and impact is much better, though compared to the most punchy dynamics and planars, they're still not quite there. But the L700 Mk2 has very surprising punch and impact, it's a straight up bassy, punchy headphone even in comparison to things like Focals. Now if only the bass quality was better, but that's another story. The old SR-X Mk3 Pro had terrific bass punch and impact, and even the 007, given enough power, has a solid tactile bass though I wouldn't describe it as bassy by any means.
The 007 in particular has a very interesting bass characteristic. The bass has very quick decay, much quicker than any dynamics I've heard thus far. So with material that has well recorded bass that doesn't rely on the system having long decay or excess bloom - like acoustic bass or well recorded bass guitar - it sounds terrific, super taut, punchy, textured, detailed; in this case I can basically follow the bassline melody more easily with the 007 than with any other headphone. But with electronic music that has been mixed for more of a club system, the bass sounds lean and not quite natural, there is initial impact but then it's immediately gone. And when you listen to a sine sweep, or use a tone generator to emulate one, you hear bass pretty much flat down to 20hz, so it's not bass light. It's definitely an unusual bass presentation and somewhat recording dependent.
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