I'm doing a side gig reviewing headphones. Companies send me stuff and I give my opinion on things.

I recently got a certain Moondrop Para planar which I thought sounded pretty okay. Then I saw the spec sheet and my hair stood up a bit-

101dB/V at 8 ohms. Or, when converted to actual efficiency figures... 80dB/mW.

My question to the amp gurus here - will this load kill amps? It's a rare case of low efficiency combined with high sensitivity so people will be lulled into thinking that it's an easy load to drive. Like - hurr-durr, pot's only at 9'o clock and it's already hella loud! When in reality you're pushing serious mA and mW.

And I'm not talking about proper beefy discrete output amps. Hard-to-drive cans these days are so rare that everyone's just getting by with opamp-buffer composites or just opamps.

What say you? Will it KEAL?

I’m not sure what point you try to make. Isn’t 101dB/V at 8 Ohms equivalent to 80dB/mW? How can the same spec on one hand ‘low efficiency’ and at the same time ‘high sensitivity’?

dB/V and dB/mW are far from being the same spec. As in - they are the same spec only if the headphone has 1000 ohm load resistance.

It's a simplification but generally sensitivity (dB/V) will tell you how much gain needs to be applied to get to a certain SPL. A high-sensitivity headphone requires very little action on the volume knob to go loud, however it says nothing about the power draw because load resistance is out of the equation. That's why you can sit comfortably at 10'o clock on the knob and cook your outputs due to crazy currents being drawn.

I did not say dB/V and dB/mW are the same spec. I said specifically 101dB/V at 8 Ohms is the same as 80dB/mW. If you know why dB/V at 1000 Ohm is the same as dB/mW, you'll understand the math behind my statement.

Okay, that was an exaggeration on my part. But dB/V (or dB/A for that matter) makes sense only if the load impedance is known. And in my opinion, the utility of dB/V falters if the load can force the amp to exceed the bounds of its current or power delivery. As in - cease being a perfect voltage source.