Headphone underamping signs

[Blank Verse]

Are there any telltale signs of headphone underamping? Is there a fast rule to determine this from listening, or will different headphones exhibit different symptoms? Uncontrolled bass, distortion, low highest output (the obvious one), and flat sound (lack of bass) is what I have heard.

I'm asking because I have been driving a vintage 300 ohm headphone with 94dB sensitivity with a device which uses an AAA battery, and it sounds great. To be honest, I'm struggling to find any issues with the output, yet it defies explanation how this combo should sound so good.

Besides the signs, are there any songs that you dig for which are specifically challenging for a headphone and might show symptoms of underamping clearly?

 

[solderdude]

Depends on the listening level and your age as well as the output voltage.
With a single 1.5V battery and SE output one can only reach 0.45Vac, 6dB less than your typical smartphone.
However, it is possible to build an amplifier running of 1 AAA battery (1.5V) that outputs 10Vac for instance by using a DC/DC converter internally.
94dB... 94dB/V or 94dB/mW ?
94dB/mW = 99dB/V and amps have an output voltage.

The onset of clipping isn't very audible.