Can you explain this? One of my friends has an Emotiva amp and although it sounds great with the HE-4, I really need to turn down the source's digital volume to get the HE-4 to sound quiet enough for my listening sessions (otherwise my ear drums would blow out).
Planar magnetics needing a speaker amp to sound their best is a myth to me. I just tried the Emotiva with the the V-MODA Crossfade M-100. The M-100 has a dynamic driver and is not a difficult load on the amp at all. The same effects I heard from the HE-4 from the O2 to the Emotiva can be heard with the M-100; so headphones don't require a powerful amp at all. Heck, the O2 gives me plenty of head-room to play with even at 1.0x gain: I was running it with the volume knob at around 12 o'clock with most of my music.
To get the full explanation you'd have to get the input of an amp builder, which I'm not. But I'll try paraphrasing what some people here on Head-Fi who are no fools explained and what a personal friend of mine who's a conductor and owns audiophile equipment worth a rather big house + an engineer have explained me. But first two points in the interest of full disclosure:
1. I currently drive my HE-6 with the Violectric V-200 fed via XLR from my V800 DAC. The V200 delivers 2750 mW into the HE-6's 50 Ohm. Until recently I was of exactly the same opinion as you are,(headphones don't require a speaker amp) just check some previous posts of mine. If you go by the numbers and do the math, that's a very reasonable conclusion, the Vio should drive the HE-6 without any problem at all and with headroom to spare. Hell, even the O2 looks (marginally) doable on paper. I've since talked to many people who presented imo good arguments to the contrary suspended judgment and ordered a FirstWatt F3 amplifier. It's designed to drive high efficiency speakers. It outputs 15W into 8 Ohm. Do the calculations and you'll say that at 50 Ohm it will certainly not do better than the Vio. Yet, people who own even less powerful FirstWatt amps and who have owned the Vio swear to me that they get superior results. A fellow Head-Fier drives them from an F1-J model of the same brand with a 10W output in 8 Ohm. Note: The firstWatt amps are not your typical speaker amps, if you want to know more about the design, check www.firstwatt.com
2. I've heard the HE-6 with a couple of conventional (high powered) speaker amps and some of them sounded like crap, high noise floor, distortion...but in all likelihood that's because they had a lot of gain (as the HE-6 and HE-4 are planar magnetic designs we can largely discount impedance mismatch, certainly if we're not talking tube amplifiers). Headphones don't require massive gain, nor do they require huge current. What they require is sufficient
power to drive them well and sufficient
power reserve on tap at all times. With designs like the 6 and to a slightly lesser extent the 4 I believe that the problem lies there: not enough power 'on tap' to deal with dynamic range. On modern pop records that's mostly not such an issue but with classical music for instance it is (you'll have to take my word for it or do some digging). If you take a look at most headphone amp measurements (for the rare brands who don't outright fudge the numbers or present them in a very selective way) then you'll see that what they post as performance is typically a static picture (power output into a specific load with distortion measured at a certain frequency etc). But they don't take dynamics and fluctuation into account. Simple observation, look for yourself. If you run efficient cans from a decent headphone amp then typically you won't run into a problem but with extreme cases and dynamic music, despite the static measurement data showing all's well, the amp will simply not be able to timely deliver sufficient power (the 'power reservoir' so to speak being too small). That's where the advantage of speaker amps lies imo.
Again, I'll let you know once I received my FirstWatt and I've gained some experience + the 'new toy' syndrome has blown over. It's an experiment but the explanations I've heard (and which I probably didn't accurately reproduce above) sound plausible to me. Plausible enough to sink about 3000 USD into this little experiment anyway.
In short: I'm not claiming that a speaker amp may be required let alone the best for any and all headphones, I'm not claiming that just hooking up any 100 WPC amp is a shortcut to nirvana, I'm not saying that all headphone amps are crap (I own several and with the right cans they're very good). But I do think that it's plausible that with insensitive designs such as the HE-6, HE-4, HE-5...speaker amps can bring something to the table that most headphone amplifiers cannot due to their form factor if for nothing else: massive power on tap and instantly available. It's not about driving them 'loud', that's gain and comparatively easy to accomplish, it's about driving them to their max potential and getting the very best out of them.
I hope the above makes some sense but if you want the full technical explanation I'll gladly hook you up with some guys who have a more solid theoretical basis.
