Nio vs U18s: which needs more amplifier?

The 64 Audio Nio is 6Ω at 105.0 dB/mW; the 64 Audio U18s is 8Ω at 106.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.

The Nio needs 1.0 dB more than the U18s to reach the same loudness — 0.32 mW against 0.25 mW.

Side by side

The numbers that decide it

Specification	Nio	U18s
Impedance	6 Ω	8 Ω
Sensitivity	105.0 dB/mW	106.0 dB/mW
Sensitivity (voltage)	127.2 dB/V	127.0 dB/V
Power for 100 dB	0.32 mW	0.25 mW
Voltage for 100 dB	44 mV	45 mV
Current for 100 dB	7.3 mA	5.6 mA
Highest source impedance that leaves them alone (one-eighth rule)	0.75 Ω	1.00 Ω
Sources that reach 100 dB out of 280	280	280

What separates them

Where the two part company

Every source in the database that drives one of them drives the other. On power, the choice between these two changes nothing about what amplifier you need.

37 sources are low enough in output impedance for the U18s under the one-eighth rule but not for the Nio (FiiO SnowSky Tiny B, FiiO KA15, FiiO BTR15, 34 more).

280 of the 280 sources here reach 100 dB on both.

At the level you actually listen at

What each one needs from 80 to 105 dB

The U18s is more demanding than 9% of the 567 non-electrostatic models in this database; the Nio than 8%.

dB SPL	Nio power	Nio voltage	U18s power	U18s voltage
80	3.2 µW	4 mV	2.5 µW	4 mV
85	0.01 mW	8 mV	7.9 µW	8 mV
90	0.03 mW	14 mV	0.03 mW	14 mV
95	0.10 mW	24 mV	0.08 mW	25 mV
100	0.32 mW	44 mV	0.25 mW	45 mV
105	1.0 mW	77 mV	0.79 mW	80 mV

What drives both

The cheapest source that satisfies both

Source	Price	Headroom, Nio	Headroom, U18s	Output impedance	Noise
JadeAudio JA11	$20	12.5 dB	14.8 dB	0.5 Ω	1.7 µV
FiiO KA11	$29	24.6 dB	26.9 dB	0.7 Ω	1.7 µV
FiiO BTR13	$59	21.5 dB	23.8 dB	0.6 Ω	1.0 µV

Of the 280 sources here, 280 reach 100 dB on both. 32 of them also publish an output impedance low enough for both under the one-eighth rule and a noise figure that stays below the audible-hiss threshold with both.

The cheapest of the 32 is the JadeAudio JA11, at $20. It leaves 12.5 dB of headroom on the Nio and 14.8 dB on the U18s, its output impedance is 0.5 Ω against a one-eighth limit of 0.75 Ω and 1.00 Ω, and its noise figure puts the hiss floor 8 dB and 8 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.

Try any other source.

Frequency response

What each sheet prints, and what it is worth

Model	As printed	Tolerance	Standard
Nio	10hz – 20kHz	not printed	not printed
U18s	10hz – 20kHz	not printed	not printed

64 Audio prints the same thing for both the Nio and the U18s: 10hz – 20kHz.

Neither range has a tolerance printed beside it, so the matching numbers say little.

Not a measurement; maker by maker.

Both pages in full

Both have a page of their own. In full: 64 Audio Nio and 64 Audio U18s. Every figure on this page comes from what 64 Audio published, or is derived from it — what that maker publishes, counted.