[reticon]

I'm writing because I am confused about something. With my full-size headphones, Ohms is pretty straight forward. If I plug in a set that is about 20 ohms like my Beyerdynamic T70p, it will be loud, however if I plug in a set that is 50 ohms like my Senny 380 Pro, I will need to raise the volume on my iPod to get the same volume level.
 
Onto my Shure se535, they are around 50 Ohms, compared to my Westone UM1 which are about 25 Ohms. However the Shure se535 are much louder and I wish my iPod could go lower. This should be the opposite, right? 
 
What changes things? Is it the triple amature of the Shure vs the single amature of the Westone UM1? Thanks in advance!

 

[NA Blur]

The resistance ( Ohms ) is more a measure of how the headphone resists the free flow of voltage / power from a source.  If the source is decent enough or if the headphones are around 50 Ohms this should not be an issue provided the sensitivity is high.
 
Sensitivity ( dB/mW or dB / mV ) which equates to how many volts or how many watts must I drive into a headphone to get to a particular loudness.  This is almost always what you should look at when purchasing a headphone because it directly equates to loudness.  If I tell you that my headphones are 250 Ohms and ask how loud will they be on my iPod you simply cannot tell me.  Resistance tells nothing about loudness.  Because most battery sources can produce a ton of current ( Amps ) into a headphone having a variable resistance is not a problem as long as the resistance is not really low like 16 Ohms or less.
 
If I tell you that I have a headphone with an 80dB sensitivity ( knowing that this is really dB/mV or dB/mW ) then that tells me that to get to 80dB of loudness I will need to produce 1mW of power or 1mV of voltage depending on how the manufacturer measured the sensitivity.  Let us use mW for our example.  Now if another pair of headphones has a sensitivity of 105dB that immediately tells us that it takes 1mW of power to deliver 105dB of loudness.  That means that with the same amount of power you get louder music.
 
I think the Shure SE535 has a 119dB rating while the Westone UM1 is 114dB.  The extra 5dB on the Shures is at least part of the extra loudness.

 

[reticon]

Quote:

The resistance ( Ohms ) is more a measure of how the headphone resists the free flow of voltage / power from a source.  If the source is decent enough or if the headphones are around 50 Ohms this should not be an issue provided the sensitivity is high.
 
Sensitivity ( dB/mW or dB / mV ) which equates to how many volts or how many watts must I drive into a headphone to get to a particular loudness.  This is almost always what you should look at when purchasing a headphone because it directly equates to loudness.  If I tell you that my headphones are 250 Ohms and ask how loud will they be on my iPod you simply cannot tell me.  Resistance tells nothing about loudness.  Because most battery sources can produce a ton of current ( Amps ) into a headphone having a variable resistance is not a problem as long as the resistance is not really low like 16 Ohms or less.
 
If I tell you that I have a headphone with an 80dB sensitivity ( knowing that this is really dB/mV or dB/mW ) then that tells me that to get to 80dB of loudness I will need to produce 1mW of power or 1mV of voltage depending on how the manufacturer measured the sensitivity.  Let us use mW for our example.  Now if another pair of headphones has a sensitivity of 105dB that immediately tells us that it takes 1mW of power to deliver 105dB of loudness.  That means that with the same amount of power you get louder music.
 
I think the Shure SE535 has a 119dB rating while the Westone UM1 is 114dB.  The extra 5dB on the Shures is at least part of the extra loudness.

Wow! Thank you x100,000 my friend, you rock! I totally know what to look for now.