The FD5 has been my everyday listen for the last 3 months, so wee update. They are amazing. I had a love hate affair at first, but finding the right tips helped keep that bass in check, which I found loose at first. They also seemed to get better over time, well over 100 hours, so burn-in may have been a factor. Luckily tho, last week I was giving a friend an old portable amp for his phone (the Topping NX2) and to make sure it worked still, I paired it with my FIIO M6. in LO. OH MY GOD... what was I missing. I genuinely thought the M6 in Headphone Out was a powerful enough source, but how wrong I was. The NX2 - although old - is ruler flat in output. It's just power and it has plenty of it. I only stopped using it as it doesn't pair well with Wifi devices close to it, you get some annoying noise. I love the FIIO M6, it's portable, and you can use Tidal in download mode. It's also got a nice laid back, but detailed enough balance to it's sound. For everyday use, i hate having an amp glued to it tho lol. BUT WITH AN AMP...
All of a sudden the top end... which I couldn't understand why owners were saying it could be overwhelming - truly opened up. Like night and day, veil lifted stuff. Now I still don't think it's fatiguing like some have said, and I don't feel I need to change to copper cables, the provided one is fantastic... but I am 43, so younger ears may find them fatiguing I guess. I have heard some sibilance where I didn't before with from HO in M6... but it's not troubling or harsh and it's on songs known for it. With the new pairing tho it's just more premium sounding and I can now appreciate the £250+ price tag now. Before I did think I'd overpaid for it's great, but laid back sound. Soundstage has expanded and now has plenty of air. I found that it sounded a bit within the head before, similar to the FH3.
But the best part is I'm hearing MUCH BETTER levels of detail and separation. Resolution greatly benefits from the right source and is now more akin to a £250+ earphone. What I can say is I'd never call them bright and the recessed mids from before are no longer an issue for me, as they are more forward and present. Still a slightly V shaped listen tho, bass is till slightly loose and fluffy at times, but an AMP has tightened them up. They will always be more musical than analytical, regardless of source.
Sooooo, make sure you power these properly. I feel like I'm hearing them for the first time again. Don't use a warm or laid back source, something neutral or flat really is that sweet spot. I can maybe appreciate that brighter sources could overwhelm the top end, so perhaps that's why some users find it fatiguing or sharp.
EDIT : My friend didn't get the nx2 btw