Short answer, absolutely! I agree with your assessment on the 'rattle' not being a rattle or 'distortion'. I too experienced this odd handling of the bass on the deep end with games and movies, as well as music that has a lot of sub-bass (Freezepop, KMFDM, Juno Reactor). I would call it kind of a 'thud' or 'cupping' sound' when the bass gets deep and the volume is higher than normal.
When I first started listening to the HD598 I actually used (and recommended here a few pages back) a parametric EQ and set up a 'low shelf' to compensate. However, this anomaly has since disappeared completely. I mean 100% GONE! As well, I found the bass in the beginning to be somewhat dry and boomy/thumpy with little resonance. Now all I hear is 'musical glue'. I just finished doing a test just for you good folk, and I will say that the HD598 can handle bass, and DEEP bass with ease.
My normal listening volume on my Yamaha receiver is about -25dB, which is considered to be (by me) a notch below really loud. Bass is set to -6 and treble is set to 0. For my music test I set the volume to a defining -10dB and used the 'Music Enhancer' setting (smart loudness) set to low. Treble and bass are at 0 (equivalent to the 12 o'clock position on a knob). For my movie test, I set 'Music Enhancer' to high and turned up the bass to +2.
I first listened to the album "Bass Power", vol. 2 of Audio's Audiophile 24 volume CD set. I used this CD because it contains a good mix of 'real' bass. One word; Wow! Whether the bass is coming from a drum, bass guitar (acoustic and electric), synthesizer, strings, horns, or the human voice, the HD598 simply outputted bass with authority! No distortion, no rattle, no odd cupping sound, just clean and powerful bass with great extension, texture, and surprisingly good reverberation; Not just for a closed back headphone either. Never did the bass sound 'boomy', 'muddy', 'thumpy', or distorted. My next test I focused on the 'artificial' bass. I listed to a good random mix of my "Freezepop" collection. Simply put, "Bring the boom baby!". The bass and sub-bass was so powerful when I placed my hands about 10" from the grills, I could literally feel the sound pressure the HD598s emitted. Again, very clean, and driven with authority. Switching things up a bit I listened to KMFDM on random. Being an industrial band, quality plays as much of a role as quantity because the genre demands 'texture'. Absolutely perfect. I think my eardrums were "torn a new one".
Moving on to movie watching, only 15 minutes of one movie was needed for this test; Pacific Rim.
Holy Moly Wowy Zowy! Christ Almighty! For an open backed set of headphones, the HD598 really know how to give you that big theatre experience when it comes to the dynamics of the bass. Whether is was the growl of the Kaiju, the clapping of the thunder, the heavy foot-steps of the Jager, even the kick-drum of the background track, the bass was powerful, big, and LOUD. Again, no rattle, clicking, or distortion.
All in all, I think I did a good mix of bass tests, and simply could replicate nor hear what not only I heard in the early days of listening, but what other Hi-fiers have reported as well. I do however want to mention that even after my glowing review on bass, the HD598 are not bass monsters, they have very neutral, linear bass. They are about equivalent to the Momentums in quantity, losing out in the sub-bass department only slightly due to their open design. The HD598s can go DEEP, just not
DEEP DEEP; they roll off at about 26Hz.
P.S. Do NOT EQ the bass, at all. You will get nothing but poop. In fact, I highly recommend using a Hi-Fi receiver.
