COSMO vs VENUS: which needs more amplifier?

The Moondrop COSMO is 15Ω at 81.8 dB/mW; the Moondrop VENUS is 18Ω at 82.6 dB/mW. This page covers what they ask of an amplifier, not how they sound.

The COSMO needs 0.8 dB more than the VENUS to reach the same loudness — 66 mW against 55 mW.

Side by side

The numbers that decide it

Specification	COSMO	VENUS
Impedance	15 Ω	18 Ω
Sensitivity	81.8 dB/mW	82.6 dB/mW
Sensitivity (voltage)	100.0 dB/V	100.0 dB/V
Power for 100 dB	66 mW	55 mW
Voltage for 100 dB	1.00 V	0.99 V
Current for 100 dB	66.4 mA	55.3 mA
Highest source impedance that leaves them alone (one-eighth rule)	1.88 Ω	2.25 Ω
Sources that reach 100 dB out of 280	188	225

What separates them

Where the two part company

37 of the 280 sources have the power for the VENUS but not for the COSMO — FiiO SnowSky Tiny B, Fosi Audio N3, iBasso DC03 Pro, 34 more.

3 sources are low enough in output impedance for the VENUS under the one-eighth rule but not for the COSMO (Astell&Kern HC3, RME Fireface UFX II, RME Fireface UFX III).

188 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 COSMO is more demanding than 99% of the 567 non-electrostatic models in this database; the VENUS than 98%.

dB SPL	COSMO power	COSMO voltage	VENUS power	VENUS voltage
80	0.66 mW	100 mV	0.55 mW	99 mV
85	2.1 mW	0.18 V	1.7 mW	0.18 V
90	6.6 mW	0.31 V	5.5 mW	0.31 V
95	21 mW	0.56 V	17 mW	0.56 V
100	66 mW	1.00 V	55 mW	0.99 V
105	209 mW	1.77 V	174 mW	1.77 V

What drives both

The cheapest source that satisfies both

Source	Price	Headroom, COSMO	Headroom, VENUS	Output impedance	Noise
FiiO KA11	$29	5.4 dB	6.3 dB	0.7 Ω	1.7 µV
FiiO BTR13	$59	2.3 dB	3.2 dB	0.6 Ω	1.0 µV
FiiO KA3	$79	2.3 dB	3.4 dB	0.5 Ω	1.7 µV

Of the 280 sources here, 188 reach 100 dB on both. 66 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 66 is the FiiO KA11, at $29. It leaves 5.4 dB of headroom on the COSMO and 6.3 dB on the VENUS, its output impedance is 0.7 Ω against a one-eighth limit of 1.88 Ω and 2.25 Ω, and its noise figure puts the hiss floor 35 dB and 35 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
COSMO	13Hz- 58kHz (IEC61094, Free Field)	not printed	IEC61094 (free field)
	20Hz- 20kHz (IEC60318-4, -3dB)	-3 dB	IEC60318-4
VENUS	6Hz-80kHz	not printed	not printed
	20Hz-20kHz (IEC60318-4, ±3dB)	±3 dB	IEC60318-4

Moondrop prints two ranges, “13Hz- 58kHz (IEC61094, Free Field)” and “20Hz- 20kHz (IEC60318-4, -3dB)”, for the COSMO and two ranges, “6Hz-80kHz” and “20Hz-20kHz (IEC60318-4, ±3dB)”, for the VENUS.

Both sheets print a tolerance, which is rare enough to be worth pointing at: only 58 of the 490 models with a printed range do. These two ranges can be set against each other, because each of them says how far down the response is allowed to be at the ends.

Not a measurement; maker by maker.

Both pages in full

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