RobsonI don't own the Hi-Fi man but I have the Fostex Thx0 Purpleheart, AKG Kxx and Audio Technica ATH 900x. I would say don't waste your money on anything but the Fostex. Everything about them is great and the bass is the way it should be.
RobsonI don't have the T-X0's, but I have a pair of modded T50RP Mk3's (clay around the driver per Mayflower [that I'm not sure did anything...], foam strips in cups, cotton circles behind drivers, no stiff foam attached to the back of the driver like so many do). I find the Fostex to have a bit less treble than the 4xx, and I feel like transients are faster, maybe due to the smaller driver. I use the Fostex mainly with my Burson Conductor SL on my nightstand connected to an RPi Zero running Volumio, so I don't bug my wife when I need some tunes on at night to help control my thinking, and I often use that setup just to listen. They're 'semi-open' but I think more accurately described as 'mostly closed' or maybe 'vented'. Oh, I almost forgot the most important mod, the Mr Speakers leather headband, the best mod ever for these. I think the T-X0's already have a leather strap.
The 4xx is brighter, but not piercing or anything. I like it more than the Fostex overall. I have it paired with a Geek Pulse hooked up to my PC. I played a little Forza Horizon 3 with then when I first got them, sounded wonderful. But I don't have much time for gaming, so I'm not really going to comment on their gaming prowess. I love them for all types of music. Could they reach a bit deeper for electronic stuff with a lot of sub-bass? Sure, but really, what can couldn't? To me, these have great quality bass that reaches quite low, but if you're a basshead looking to get your head pounded by those low frequencies, maybe look elsewhere. For the price, these are simply sublime, and I feel they punch far above their weight. I almost forgot to mention that I've changed the pads to angled Brainwavz hybrid pads with the perforated insides, and I added a ZMF pilot pad because I found the headband wasn't quite padded enough for my apparently sensitive skull after probably too many hours of wearing at a stretch.
I like both pairs, but be aware the 4xx is fully open, you get about as much sound emitted outside as you do into your ears. My wife always thinks I have them way too loud. Because of that, the soundstage feels quite large, where the T50 is more intimate.
Sorry for the rambling and incoherent nature of this. I just kept adding things as they came to mind!
ryanaehHey thanks for the extensive reply. I already have the t-X0 and was considering putting them up for sale for these, but now they are sold out so I will wait and see if they come up again. Comparing the frequency traces of the 2 headphones the Massdrop/Fostex are flatter, but that doesn't mean that much... Never had planar magnetics of any kind before.
Thanks for your input
RobsonYou're welcome. I had joined the first 4xx drop, felt bad about missing the T-X0, so got the T-50 and modded away. I must admit I didn't think the stock sound was bad, just needed some help. Those stock Fostex pads, on the other hand, well, they hardly deserve to be called pads! I almost bought the T-X0 off eBay a couple of times, but didn't because I was too worried it wouldn't sound much different than my T-50s, but I sure like the look of the X0.
ryanaehIf you feel any better, I can tell you the stock sound of the T-X0 is pretty bad: they have huge resonance-like sound (it's like listening in a bathtub), bass is bloaty, sub-bass is lacking, mid is congested and upper range is both recessed and have a spike around 8kHz that causes some fatigue. On the other hand, response is fast (as expected from a planar driver) and detail is surprisingly good (they're monitoring headphones for a reason). I see huge modding potential, didn't started modding yet because I don't have the time right now, but with some EQ the sound improves noticeably.