Well guys, I'm back and I've solved both my broken IEMs and my upgrade itch.
Firstly, I decided to buy the HEM8 after having another listening session with the Fiio FA7. I did not think I would enjoy the FA7, with their elevated mid-bass and non-reference tuning. They look and feel amazing though, like a piece of jewelry, with the 3D printed casing and silvery wire.
On to HEM8 impressions though, because that's what this topic is about:
1) They're
super sensitive with the source that you give them. They're super sensitive in general, actually. I guess this explains the wildly different opinions that people have about them. The HEM2 were fine with my Sony XZ3's output. The HEM8 were a muddy mess, with a dark, bassy sound signature and recessed vocals. I was actually disappointed when I first tried them out, since I had already bought them. So I plugged into my ifi idsd nano, to see what they can do in a best case scenario. It's a whole other ball game. Everything opened up, the vocals came forward and let in a very nice sound signature. Not as bright as the HEM2, but very nicely balanced and very detailed. The IEMatch port also works wonders with them, providing a very clean output, with absolutely zero hissing.
Since I needed these IEMs for portable use, the Hidizs Sonata DAC cable is a decent compromise. The sound signature is pretty close to the idsd nano and it's not that much bigger than the passive USB-C -> 3.5mm adapter that I have to use anyway with the phone. Unfortunately, I lose the Sony processing this way and it has a noticeable hiss in some quiet songs. If it had a low/high gain switch for the amp, it would have been perfect. I'm still glad I have it, because otherwise I wouldn't be able to enjoy the HEM8. For 30 bucks, it's a steal.
2) The bass and sub-bass is better than I expected, much better than the HEM2 in general and much more neutral than the Fiio FA7. I find it exactly like
@monsieurfromag3 described it, tight and unforgiving with textures that I didn't hear before. The bassline in Outkast's "Hey ya" is a very good example of this. I realised that it's not just there, it keeps the rhythm with the drums.
3) The tuning is indeed different than the HEM2, but it keeps the good things, like the soundstage and detailed presentation.
As a side-note, the store, being specialized in AV equipment, replaced my HEM2 on the spot. I have to give then props for that. Other places would have asked for me to ship them the product, open an RMA request and then wait for a couple of weeks until they blame me for "improper usage".