Impedance: confused! MDR-7506 and KNS-8400

[Kontrary]

Hello everyone, I have not found anything related to this so decided to create an account post here.
 
I have a pair of KRK KNS-8400, and also a pair of Sony MDR-7506.
 
The Sony's are supposed to be 63 ohms and the KRK's 36 ohms. It is my understanding that more ohms = more power required to drive them.
However, if I try both using the same song, sound, etc. without changing the volume on my laptop, the Sony's are actually LOUDER than the KRK's despite being nearly double the ohms.
 
I purchased the 7506's from a U.S. seller on ebay and from what I found online including these forums, they are completely legit, although I have not listened to any other pair of 7506's other than these.
 
So either I have fake Sony 7506's or there is something else I am missing. Hopefully someone can help me out!

 

[jodgey4]

There's another spec, sensitivity (usually given as db / 1mW), that explains the difference. Many planar models are low impedance, but very low sensitivity (90 db/ 1mW). Some high impedance models are high in efficiency like the Audeze Z prototype (1200 ohm, could be driven still by many amps with ease) or Beyer T5.

 

[Kontrary]

  There's another spec, sensitivity (usually given as db / 1mW), that explains the difference. Many planar models are low impedance, but very low sensitivity (90 db/ 1mW). Some high impedance models are high in efficiency like the Audeze Z prototype (1200 ohm, could be driven still by many amps with ease) or Beyer T5.

Hmm, okay! I have nothing to worry about then?
 
This is what I found: 
 
KRK: Sensitivity (1mW): 97 dB SPL
 
Sony: Sensitivity (1mW): 106 dB/W/m
 
Does that info justify what I am experiencing? 

 

[jodgey4]

Yep! Though db/W/m is a speaker measurement for dB/ Watt / meter... so I think the site means 106 dB/ mW.
 
From the same amp, the the Sony should get ~6db louder if I'm thinking straight, which I think sounds twice as loud to the human ear? Anyways, yes, the numbers add up .

 

[Kontrary]

  Yep! Though db/W/m is a speaker measurement for dB/ Watt / meter... so I think the site means 106 dB/ mW.
 
From the same amp, the the Sony should get ~6db louder if I'm thinking straight, which I think sounds twice as loud to the human ear? Anyways, yes, the numbers add up .

Alright, thank you!