maximumsidMy pair arrived a few weeks back. I gave them a brief listen with the SoundBlaster E5 and was impressed. Then I saw the advice about 150 hours' break in! This was not a complete surprise, as I'd discovered the need for breaking in planar-driver headphones 30 years ago when reviewing for Stereophile. Playing high-volume noise through them overnight was all that was needed. I found an Advent 300, and started the breakin using KING FM. I stopped at about 100 hours, and tried them directly connected to my Sony D-FJ75TR Discman. Not only was the volume just barely adequate, even with the output all the way up (again, no surprise), but the sound was dull, bass-heavy, and lacking "punch". As the Sony was never designed to drive demanding headphones like the HE-4XX, I connected the D-FJ75R's optical output to the E5 --and there was the sound I'd expected.
I bought STAX electrostatic earphones some years ago. They came with their own high-voltage driver amp (about the size of the E5), but no DAC. At that time, the STAX cost about what the E5+HE-4XX does now. (The STAX currently goes for about 40% more.) The HifiMan is not only more comfortable (the STAX has silicone thingies to make a good seal; a doctor had to remove one that got stuck in my ear), but the presentation is more natural and less in-the-head. My preference is for highly accurate, finely detailed sound. The HE-4XX is warmer, without being dark or murky. I can imagine 'phones that come closer to literal accuracy, but who cares? Without something "better" to compare the HE-4XX with, there is nothing to criticize about their sound. * (That is a compliment, not a waffle.) With a decent amplifier, they're suitable for monitoring. And they're great for listening "outdoors", if you don't mind schlepping such a large pair of cans. In terms of bang for the buck, they outclass the STAX.
* Just to clarify the point... If you know what live instruments sound like, the HE-4XX is obviously a bit on the dark side. This isn't a big deal, especially when you consider that many circumaural headphones sound as if the instruments are right next to your ears.
GrizzledGeezerYes, even I was quite surprised by how good these serve the purpose of monitoring too, I can easily edit the audio for my YouTube videoes, something which isn't easy for open design headphones. These really strike a phenomenal balance of natural presentation and open soundstage while being extremely detailed and tonally balanced at the same time. Even voices in movies/videos sound incredibly detailed, and even the busiest parts of my library are handled perfectly. Almost like upgrading from a 1080p to a 4K monitor. I think mine are burned in for around 50-75 hours by now and they already sound incredible.
I ran them with my Fiio E10K, and the sound was terrible, even though on paper E10K can run HE4XX, then I bought an O2 amp and only then I could appreciate how good these are. Right now I am using Fiio E10K as a DAC, so I am wondering if getting a JDS Labs OL DAC (Or Massdrop SDAC) will make a difference.
Still I find them a little too heavy for when Hi-Fi audio isn't a priority for example while watching videos on YouTube, and since I also like the laid back nature of my HD598, I was wondering if getting HD6XX would be worth it for 'non critical listening'.
I personally found HE4XX to be very neutral, though I only have experience with HD598, my M50x, and my Mackie Monitoring Speakers, and these are my first mid-fi headphones.
maximumsidIf I might add another point... I've owned STAX Lambdas for many years. They're driven by the T1 hybrid amplifier (the all-transistor amp is duller and less-detailed) and the ED-1 diffuse-field equalizer. (Such EQ is needed for any high-quality headphones, but the EQ varies with the 'phones, so it isn't practical to build a "one curve fits all" circuit into headphone amps.) In terms of detail and transparency, the Lambdas are superior to the HE-4XX. The catch is that the Lambdas have a coloration I can only describe as "mechanical". (Don't ask me to explain. I once compared them with Acoustats, and the difference was obvious.)