I came across this blog post made by the makers of the 5K about power requirements for high-impedance headphones.
https://post.naver.com/viewer/postView.nhn?volumeNo=28984863&memberNo=49910556
Human translated by yours truly:
The Sennheiser HD600 is an old name among headphones, but it still has a strong following among audiophiles. It is also the most cited model for a high-impedence, low sensitivity pair of headphones.
*SENNHEISER HD600*
*- 300-ohm impedance *
*- 97dBSPL/mW sensitivity*
The following graph shows the required voltage level to achieve a given SPL (sound pressure level). For comparison's sake, the HD600 is compared with the SE846 IEM, a low-impedance, high sensitivity IEM.
https://cdn-cms.f-static.net/uploads/2697343/2000_5db51be13ba1f.png
As you can see from the above graph, an SPL of approximately 102dB can be achieved with the output of a 1V RMS amp. (based on playing a full scale sine wave)
*1V*_*RMS* *Output*
Power = V^2 / R = 1^2 / 300 = *3.33 mWatt *
Required current = *3.33 mA*
Sound Pressure Level --> *102.2 dB SPL*
*2V*_*RMS* *Output*
Power = V^2 / R = 2^2 / 300 = *13.33 mWatt *
Required current = *6.66 mA*
Sound Pressure Level --> *108.2 dB SPL*
SPL level (source: Shure) (graph is missing)
As seen above, 108dB is a very high SPL.
However, since most audio sources are not full scale sine waves, and have some degree of headroom, the actually possible SPL is about 102dB, a difference of 6dB. Under most circumstances, the HD600 requires an RMS of at least 2V to attain a certain degree of loudness.
The HD600 has an extremely high impedence. Hence, it does not require a lot of current. The following graph indicates the amount of current needed. Like above, the HD600 is compared with the SE846, a low-impedance, high sensitivity IEM (green).
https://cdn-cms.f-static.net/uploads/2697343/2000_5db51c289d426.png
As shown above, there isn't a big difference in required current flow between the HD600 and the SE846.
Many people understand that the HD600 requires a high-output desktop amplifier, but this is incorrect.
The HD600 requires a small 10mWatt of power to run. It requires a minimum of 2V RMS, but in comparison, it requires little current.
Since high-impedance headphones like the HD600 do not require a lot of horsepower to run, it is easy to pair with an amp if the amp can provide at least 2V RMS. Furthermore, high-impedance headphones are barely affected by an amp's output imedance and cable impedance, which proves to be an advantage.
Advantages of high-impedance headphones
- Its actual required amp output is around 10mWatt
- It does not require a lot of current
- As it can be easily run by an amp, the amp can operate within optimal parameters
- Battery life can be maintained for portable amps
- It is barely affected by amp output impedance
- It is barely affected by cable impedance
Disadvantages of high-impedance headphones
- At least 2V RMS is needed in order to achieve a level of volume
High-impedance headphones like the HD600 can be run to some degree on portable amplifiers. Of course, absolutely speaking, high-performance amplifiers should be used in order to maximize sound quality and performance. However, it is wrong to make a blanket statement that the HD600 must be paired with a desktop amplifier because of low power, which can be confirmed with simple calculations as shown above.
We strongly suggest that users of high-impedance headphones like the HD600 use balanced cables. As mentioned above, high-impedance headphones are barely affected by cables, so there is no need to buy expensive cables. Cheap balanced cables can bring a clear improvement to performance.
The HD600 has maintained its popularity because of these aforementioned reasons. Headphones aren't all-time bestsellers solely because it has objectively superior specifications. Headphones must work well regardless of what amplifier the user pairs it with. The HD600 can be used to some degree even with a 1V RMS output from a phone if SPL needs are not high.
Thoughts?
