Power rating is the wattage required for what SPL?
I realize now that I was looking at the 90dB and 105dB columns as watts instead of milliwatts. Whoops!
power rating is the (max) Wattage that the headphone can handle.
No manufacturer ever mentions whether this is continuous or music power.
Continuous power is when a constant sinewave is applied and the voice coil isn't fried.
With music power I mean the following:
When a headphone is rated at 200mW (0.2W) and the average level is 50mW the peaks (which can be very short) could easily be 500mW.
That is if the amp can supply this, a 200mW rated headphone thus can handle short peaks exceeding that of the rating without damage.
For electrostats this is different as you run the risks of sparks punching holes in the membrane.
Efficiency = in dB/mW and is a normalized value and differs from the often used dB/V (which usually is a much higher number)
In the table the dB/V values have been converted to dB/mW
xx dB/mW means when you apply 1milliWatt the headphone will put out xx dB
xx dB/V means when you apply 1Volt the headphone will put out xx dB
The question is how the manufacturer measured it... at 1kHz or with white or pink noise or another method.
We will never know..
The numbers thus aren't telling that much but they do tell us ballpark figures.
Max SPL is simply a calculation based on the power rating and efficiency but as said peak SPL may even be above that value.
Also as this is merely a calculation it isn't written in stone as at higher SPL distortion sets in and the output will most likely compress so when 125dB is calculated a headphone may well put out 122dB instead where the same one will give 100dB SPL in reality and calculated.
These numbers say nothing about how GOOD the headphone sounds, it only says something about how loud it goes, not how loud it is perceived as distortion levels play a role here as well.
Also note that some numbers are supplied by manufacturers or other sources (Tyll's plots are such a source) and when you look at the numbers of similar headphones in Tyll's plots it is easy to see these numbers sometimes are far apart for similar headphones.
Sometimes they are closely the same as the one the manufacturer provides sometimes they differ many dB's.
Also there is a question whether manufacturers have changed the driver (silently) over time.
Much uncertainties...
I also have written some articles on power and impedances etc.
No idea if or not I can place a link to my website but the little globe-icon below on the left will take you there.
in 'Technical explanations | power, impedance etc.' there are links to those articles.
NwAvdeuce certainly doesn't agree with everything I wrote in there.
