Originally Posted by Keithpgdrb
I've researched, but I'm still at a bit of a loss. Here is the riddle.
Hifiman he-6 Impedance: 50 Ohm - efficiency 83.5
Grado impedance: 32 Ohm - SPL 98
Sennheiser Impedance: 300 Ohm - SPL 97
Beyer DTxxx Impedance: 250 Ohm version SPL 96
The Hifiman cans are the most difficult to drive.
Is the impedance measured on a different scale for orthos? Efficiency plays a part here, but I still remain confused as to how to use these numbers when picking an amp for any of these.
I'm sure this is a thread that has been up before, but with the BS search on head-fi, I cant find it.
Impedance is the measure of electrical resistance.
Efficiency is how much of the power consumed actually does work.
Sensitivity, or load, is how much work is done at a given power level.
Ohm's are related to how much sound you get at a given mw only because it impacts how many mw your amp can deliver.
What you are seeing with the orthodynamics being insensitive is their power requirements. They are doing more work and so require more power.
In terribly simplistic terms think of it like this:
You have a 9 volt battery and 2 motors.
Motor #1 is very small, like a little PC fan but because it has a low number of windings it has a high impedance and so when you connect it to the battery it spins at 10,000rpm. It is not doing as much work because it is small, there for it doesn't need as much power. If it were more efficient then the battery will last longer but it will spin at the same speed. And sensitivity, in the case of a fan would be the amount of air it moves relative to how much power it consumes.
Motor #2 is larger than the first one, like a much larger pc fan and has more windings which makes it have less resistance, but since the motor is much larger it takes more work to make it move so it only spins at 7,000RPM on the same battery. It has less resistance but it is doing more work and so it requires more power. Higher efficiency means the battery will last longer but it will still only spin at 7,000RPM. And sensitivity, in the case of a fan would be the amount of air it moves relative to how much power it consumes.
Therefor if you want to power it to the same level as motor #1 you need a more powerful power source.
A high impedance dynamic headphone does not require as much power as a low impedance orthodynamic and so you must use a 'bigger battery' more powerful amplifier to drive the orthodynamic to the same sound levels as the dynamic.
Try not to confuse sensitivity with efficiency. A highly sensitive headphone will produce a lot of sound without a lot of input. A highly efficient headphone will not run your battery down in your phone as much as an inefficient headphone driven to the same level, all other things being equal.
Edited by Kodhifi - 1/21/13 at 12:20pm