Nope. They can't. The hd650 has better bass quality, and still falls short and sounds muddy. Just less so. It's a problem ubiquitous among open dynamics. The ones that can keep it under control are the sole exceptions.
Take a planar design and pump up the nether bass through and through via EQ. The distortion on the common dynamic driver in the bass region is such that any full sized headphone will sound awful muddy. Dynamics will always have that sort of hump going on for them.
On the topic, the d1100 I don't recall being that able with the subbass. Plenty of distortion, though at least it reached down low. The k550 had a murderous spike around 6khz.
Except that is his square wave reference, for a start. If you don't drive really loud, it still performs admirably with low bass. And as for its impedance, while it does have an unusual swing for a single driver design, it still has a relatively high output impedance. Compared to an "ideal" load, sticking 30ohms worth of resistor wouldn't even change the FR at ~100hz by .5db.
Selling my EX1k, for the usual head-fi reasons*. Lightly used, though the paint on the right housing has been chipped. Unfortunately, I don't have the carrying included with the EX1000, and only have the S/M/L hybrid tips for it.
May be interested in a trade for a Hifiman RE-272.
*Head-f i reasons may include but are not limited to the desire to eat better than instant noodle flaring up, new FOTM out of reach, general disuse and dislike of signature,...
Not quite. There are plenty of very strong values, that are still very good today, independent of price. Just that expecting to be able to pay away the flaws in your listening experience is a fool's errand. All headphones have shortcomings, some more blatant than others, and as one goes away, more pop up to take their place.