[plakat]

  62 Ohm impedance headphones are not that hard to drive when the headphones have good power sensitivity (105 dB SPL @ 1 mW). In the case of the AKG K7 series the voltage sensitivity is around 117 dB SPL @ 1 Vrms, so they should sound fine with most portable devices, but they will sound a bit better with a headphone amp anyway.
 
(I use the Sennheiser HD 25-1 II (70 Ohm) with my iPhone all the time and they sound loud enough. The HD 25-1 II have a bit more voltage sensitivity (120 dB SPL @ 1 Vrms), so they sound louder than the AKG K7 series).

I read the K7XX sensitivity as 105dB @1V, so its rather low. I'd not expect any wonders driven by a mobile phone etc. It might be loud enough, but most probably the bass will be rather lacking. Once had the K702AE...
 
With an impedance of 62Ohm 1V amounts to 0,016W, i.e. 16mW, that is ~12dB above the level at 1mW. If I calculated that correctly sensitivity would be ~93dB @1mW.
 
Edit: I could not find any data on the sensitivity of the HD25 (only its SPL max of 120dB), but the Beyerdynamic DT1350 is rated at 109dB @1mW and works fine with mobile devices (having 80Ohm impedance).

 

[acme15]

Just ordered myself a pair of these! Sadly I missed out on the first 2000 units, so I had to buy them via a postal forwarding company to get them to me... The whole thing cost about the same though, so no issues. I expect them in March. 

 
They will be taking the place of my Q701 and possibly my X1 as well. 

 

[gabrielnorena]

I read the K7XX sensitivity as 105dB @1V, so its rather low. I'd not expect any wonders driven by a mobile phone etc. It might be loud enough, but most probably the bass will be rather lacking. Once had the K702AE...

With an impedance of 62Ohm 1V amounts to 0,016W, i.e. 16mW, that is ~12dB above the level at 1mW. If I calculated that correctly sensitivity would be ~93dB @1mW.

Edit: I could not find any data on the sensitivity of the HD25 (only its SPL max of 120dB), but the Beyerdynamic DT1350 is rated at 109dB @1mW and works fine with mobile devices (having 80Ohm impedance).

AKG K7 power sensitivity is 105, however, voltage sensitivity is around 117, and that's the one that matters.

 

[plakat]

AKG K7 power sensitivity is 105, however, voltage sensitivity is around 117, and that's the one that matters.

I read the specifications given by massdrop differently. They state
 

 Sensitivity: 105 dB/V

 
AKG states the same for the K712 as well as the K702. Where did you get your information and what exactly do you understand as 'voltage sensitivity' -- maybe we're talking about different things after all?

 

[gabrielnorena]

 
I read the specifications given by massdrop differently. They state
 
 
AKG states the same for the K712 as well as the K702. Where did you get your information and what exactly do you understand as 'voltage sensitivity' -- maybe we're talking about different things after all?

We are talking about different but related things, voltage sensitivity is no the same as power sensitivity. Yes, power sensitivity of the K7 series is 105 dB SPL at 1 mV, but voltage sensitivity of the K7 series is around 117 dB SPL at 1 Vrms.
 
(By the way, Sennheiser HD 25-1 II have voltage sensitivity 120 dB SPL at 1 Vrms).
 
I suggest you read this: 
 
http://benchmarkmedia.com/blogs/news/14017381-headphone-impedance-and-sensitivity
 
"Sensitivity is often expressed as dB SPL at 1 mW (acoustic output as a function of inputpower)."
"In contrast, Sennheiser specifies sensitivity in terms of dB SPL at 1 Vrms (acoustic output as a function of input voltage) Sennheiser's "voltage sensitivity" method takes impedance out of the equation and allows direct comparisons without making calculations."
 
EDIT: In fact K7 series headphones voltage sensitivity is 105 dB SPL @ 1 Vrms. Now AKG states sensitivity as acoustic output as a function of input voltage.

 

[plakat]

It seems we are talking about the same thing. The sensitivity is stated as 105dB/V is not per mW or mV.
 
I did not find a sensitivity for the HD25, only the SPL max (which is 120dB). Still another thing.
 
Feel free to PM me to discuss this matter, as it otherwise might derail the thread otherwise. I think most owners of any K70x would agree that they are not really adequately driven by a mobile device though, regardless of specification calculations.
 

  We are talking about different but related things, voltage sensitivity is no the same as power sensitivity. Yes, power sensitivity of the K7 series is 105 dB SPL at 1 mV, but voltage sensitivity of the K7 series is around 117 dB SPL at 1 Vrms.
 
(By the way, Sennheiser HD 25-1 II have voltage sensitivity 120 dB SPL at 1 Vrms).

 

[gabrielnorena]

  It seems we are talking about the same thing. The sensitivity is stated as 105dB/V is not per mW or mV.
 
I did not find a sensitivity for the HD25, only the SPL max (which is 120dB). Still another thing.
 
Feel free to PM me to discuss this matter, as it otherwise might derail the thread otherwise. I think most owners of any K70x would agree that they are not really adequately driven by a mobile device though, regardless of specification calculations.
 

I know AKG K70x are not the best headphones for mobile device use, but they are no the worst either, i found them somewhat in between... You're right, I assumed that AKG stated sensitivity as acoustic output as a function of input power, but I'm really not sure about that, I guess I'll have to check it out more.

 

[plakat]

  I know AKG K70x are not the best headphones for mobile device use, but they are no the worst either, i found them somewhat in between...

Yes, they are not unusable, though no wonders should be expected... But there are other headphones that would fare much worse, i.e. be actually unusable with mobile devices.
 
a problem might be their really open nature, so while they might be usable driven by a mobile device in a quiet room, out and about is another thing.

 

[gabrielnorena]

 
Yes, they are not unusable, though no wonders should be expected... But there are other headphones that would fare much worse, i.e. be actually unusable with mobile devices.
 
a problem might be their really open nature, so while they might be usable driven by a mobile device in a quiet room, out and about is another thing.

You're right, my mistake, the voltage sensitivity is what AKG use in their specs now days, so the K70x voltage sensitivity in fact is 105 dB SPL at 1 Vrms.

As I said, they will sound better with a decent amp... I never use them with mobile devices anyway, there are other more appropriate closed back headphones for that.

 

[conquerator2]

Or semi open even

 

[redgod7]

Sennheiser's HD 598 were on sale for $99. I got those insted. I hope i dint miss out too much on these  k7xx

 

[mrk]

  Sennheiser's HD 598 were on sale for $99. I got those insted. I hope i dint miss out too much on these  k7xx

Well I used to have the HD598 and my Q701s were better than them in all but one area, the headband comfort.
 
So the K7XX by all counts will be much better than the HD598

 

[ZoNtO]

  Sennheiser's HD 598 were on sale for $99. I got those insted. I hope i dint miss out too much on these  k7xx

 
You did. And you'll regret it for the rest of your life.

 

[money4me247]

You did. And you'll regret it for the rest of your life.

lol

 

[ASMnC]

This will be my first pair of "real" headphones.. (The only other pair I have are QC15's which i like a lot for noise cancelling, though I know the audio isn't that great)

I plan to mainly use this in my home theater setup. I was debating between getting HVL-1 speakers or headphones. Since I can't always use speakers anyway, I decided to get headphones.

Anyway, my question is: can I just connect the headphones to my receiver or do I need some other stuff to drive these. I see a lot of people talking about amps and stuff, i'm a little confused.