[eyal1983]

Hi all,
 
I connected the Sennheiser HD439 (112db, 32ohm), and the Koss KSC75 (60ohm, 101db) to the same source.
 
the Sennheiser has lower volume than the koss.
this is because of the Impedance, right?
 
Now then, the Sensitivity only shows the volume potential it can reach to ?
 
And if i want to match the volume, need I of an ohm resistor adapter ?
 
 
thanks!

 

[mikeaj]

Sennheiser usually lists it in dB SPL / 1 V input. Many others do dB SPL / 1 mW input. It's not a fair comparison. With 1 V input, KSC75 would get 16.666 mW power so 113.2 dB SPL. That's the number that's comparable to Sennheiser's listed 112 dB SPL. Note that manufacturer specs might be off or not measured in the same way, and there are differences from unit to unit.
 
These might be able to go louder (but will heavily distort, possibly before that range too). The more power you put it, the louder the sound you get out, at least until the point of extremely heavy distortion and maybe it burning.
 
Note that if the source's own output impedance is not negligible, it will transfer a lower percentage of its output voltage level to the HD 439 (because of its lower impedance) than to the KSC75. Hence you get relatively less volume for the HD 439 in that case. For a given source, adding the correct resistor to the KSC75 could normalize the volume. But depending on the headphone, it could alter the sound some.
 
I ought to head to bed now, so I'll cut it here and leave you with this:
http://www.head-fi.org/t/607282/headphone-amp-impedance-matching-basics-you-need-to-know
http://www.head-fi.org/t/668238/headphones-sensitivity-impedance-required-v-i-p-amplifier-gain

 

[eyal1983]

Thanks !!!