The COPP is 16 ohms, not 32, and the DT 990 Pro clearly lists 250 in the linked specs.
WHAT OHMS RATING MEANS: how much power the headphones (or speakers) need to sound decent, at a given volume level. The higher the number, the more power they need. As a baseline, portable headphones designed to work anywhere have 4-8 ohms.
The COPP should be fine with any non-portable device. The AD900X are borderline; I have 38 ohms phones myself (Audio-Technica ATH-M50x) and my high-end Yamaha AV1040 receiver provides just about enough power for them. Forget about the DT990 Pro, 250 ohms is absurd, you need a dedicated headphone amplifier for those. Or wire them up to main speaker outputs.
I own a pair of HD280 Pros, AKG K26Ps and some PX200s. Of the three, the AKGs are my favourite because they’re warmer and have more power/presence. The 280s and 200s may be more balanced but they sound very… ‘thin’ and lifeless to me in comparison, even after dicking around with an EQ. The 280s aren’t especially comfortable either with that clamp, all the pleather is falling to bits (same on the 200s and the original buds on the AKGs) and they get sweaty after a while. They also have a coiled cable which drives me mad because it’s heavy and gets snagged on things. Time for a change I think.
Thin and lifeless. HD280 Pro = 64 ohms. That’s a lot. Right, that will sound thin and lifeless without a headphone amplifier. PX200 = 32 ohms. That’s okay but around the upper limit, and in this tiny design proper seating is an issue. AKG K26P = 32 ohms but with a notoriously bass-heavy design. Bass is the first thing to fall out when there’s insufficient power for your phones. In this case the design compensates, that’s why they sound warmer and more powerful. (I’m guessing you perceive them as just right rather than “booming bass” because your output is actually a bit too weak for them!)
I have a Xonar DX and a Yamaha AV receiver so I have two options when it comes to driving them. Still, I’m not too sure how capable either are. The Xonar has 100ohm impedance, I think, and the Yammy has “Headphone Jack Rated Output/Impedance CD, etc. (1 kHz, 50 mV, 8 Ω) - 150 mV/100 Ω” I have no idea what that means. I know sensitivity is also important but, again, I’ve no idea what that means.
Nothing, sadly. Real HP output specifications for a real dedicated HP amplifier look like this: “Output Power: [email protected] / [email protected] (RCA input), [email protected] / [email protected] (XLR input).” Same as the output power rating that your receiver provides for speakers (only). Don’t bother looking, integrated headphone outputs are almost never properly rated like that. You’ll have to try for yourself how high you can go, but from your experience so far I’d say “not very.”
At present I’m leaning more towards the Custom One Pro Plus because they’re easy to drive, have solid bass control, are customisable with easily replaceable parts, a straight cable and a mic socket if I ever need one. Only problem is they’re closed and use pleather which from experience always seems to degrade into flaky bits (see above)! Velour sounds nice which features on the open AD900X and DT990 Pros as standard.
Anybody have experience with any of these?
No experience but your intuition is correct, it’s by far the most frugal of the bunch and clearly you need that kind of headphone on your relatively weak output.