I am sorry, I am just a noob. How could I relate the output of amp (for example, e17 has an output of 220 mW@32Ω /> 290 mW@16Ω ) with sensitivity of headphones?
K240 mkii has sensitivity of 104 dB SPL/V, what does it mean?
Heya,
The wattage is just giving you a clue as to how much current the amp can produce at a given impedance (work). The impedance requires voltage to ramp up until it meets that work load. After that, current passes through. The wattage listed is that current passing. You'll note that as impedance (work) rises, current drops. They are inversely related. The more current that is needed, the more work an amplifier has to do. Voltage is easy. Current, takes a lot of work. It requires big power supplies and thermal regulation. Which is why big powerful amps are huge--it's all power supply basically and thermal control.
Sensitivity is efficiency. It's in dB/mW. That's sound pressure given per milliwatt of current. In other words, how loud it can get for the electricity provided. Higher dB/mW is louder for less energy (efficient). Lower dB/mW is less loud for the energy (inefficient). It's not linear either. Each 10 dB basically is
double the perceived loudness to your ear. So even 3~4 dB/mW difference is actually profound in terms of how loud something gets for the energy. This is why something that is 104dB/mW sounds very loud for little volume on your device, and then something that is 86dB/mW sounds like a whisper, as it's almost 20 dB difference, and again, every 10 is like doubling the loudness you perceive, so it's twice that. Hence whisper. The lower the dB/mW (efficiency/sensivity), the more current the device needs to generate it's sound pressure so you can hear it. When you're in the 80's db/mw range, it takes serious current throughput, which means lots of amplification. When it's in the 90's and higher, it takes very little, so it doesn't need serious amplification and works from most things assuming voltage is available to overcome resistance (which is easy, again, voltage ramping is easy on most devices), but extreme impedance (600ohm for exmaple) does need amplification because it needs more energy to raise voltage high enough and most portable devices just can't do that from a cell battery for very long, if at all.
So the E17 spec is telling you that at 32ohms of impedance, it will raise voltage, and allow 220mW of current to pass constantly. At 16ohms, it raises slightly to 290mW. So at 38ohms, expect 200ish mW to pass. The HE-4 needs about 2,500 mW. More than 10 times the power. That's
profound to say the least. You'll notice on some amps the power output will be higher, like a desktop amp, something that does 1.2 watts (or 1,200 mW) at 32ohms for example. This will be much better at driving a headphone with a sensitivity of 89db/mw (HE500), but still not really enough for something that is 86db/mw (HE-4). Again, for 86db/mw you'll need a lot more power, closer to 2.5 watts (2,500 mW) at 38ohms.
Before buying expensive equipment, you should really research what you're getting into in this hobby. The electro-chesmistry is actually 2nd year Chemistry in terms of what all this means, wattage, voltage, amps, impedance, sensivity and the units of measurement involved. Also, how they are related
mathematically because you can tell everything you need from these values in terms of working mechanism. What you can't tell, is if it will sound
good to
you. That's where ears come in.
But mechanically speaking, the E17 just doesn't have the current output to properly power the HE-4.
As for the E09k, don't waste your money. Look at it's spec sheet on their website. 900mW at 32ohms. No where near the 2,500mW needed at 38ohms that the HE-4 is going to need. It's still under powered. Again, this why I'm stressing that this headphone is not typical. It takes a lot, read again, a lot more power than typical entry headphone amps and even a lot of mid-level amps can manage to handle. This is why people use speaker amps for this headphone.
If you want an ortho in this price range that you can actually use, look at the HE-400.
Very best,
It might take me awhile to get hold of an amp because of my exams but I would still like to listen to some music while studying.
