Moondrop Armature Art 24: how much amplifier do you need?

The Moondrop Armature Art 24 is 5.8Ω with a sensitivity of 96.6 dB/mW, which is 119.0 dB/V. To reach 100 dB SPL — genuinely loud, louder than most people listen — it needs 2.2 mW, or 0.11 V across the drivers.

That puts it in the easy category. A phone, a laptop headphone jack or the cheapest USB dongle will drive it to painful levels. Of the 280 sources in the database, 207 have at least 10 dB of headroom and another 65 have enough. The cheapest portable source that does the job is the Apple USB-C dongle (US) at $9.

The two numbers that decide everything

Impedance5.8 Ω
Sensitivity96.6 dB/mW
Sensitivity (voltage)119.0 dB/V
Power for 100 dB SPL2.2 mW
Voltage for 100 dB SPL0.11 V
TypeIn-ear monitor
Easy to drive — anything will do it
All 280 sources at 100 dB SPL into 5.8Ω
Comfortable 207Enough 65Marginal 7Not enough 1
Cheapest portable source that does it
$9 · USB dongle · +4 dB headroom
Cheapest desktop amp with 10 dB to spare
$75 · desktop DAC/amp · +11 dB headroom

Sensitivity here is in dB per milliwatt. Why the unit matters.

Where this sensitivity figure comes from

Moondrop publishes this as 119 dB/Vrms ((@1kHz)) — a figure per volt, not per milliwatt. At 5.8Ω the two differ by 22.4 dB, so the 96.6 dB/mW above is that published number converted, not a different measurement.

This is the conversion that online calculators skip. Quote the per-volt number as if it were per-milliwatt and this headphone looks 22 dB easier to drive than it is — which is roughly the difference between a dongle being enough and not being enough.

Moondrop prints the impedance as 5.8Ω±15% (@1kHz), not as a bare number. Everything on this page is calculated with the nominal 5.8Ω, and the rest of that line is quoted here rather than tidied away, because how a figure is qualified is part of the specification too.

Source: moondroplab.com. How this data was built.

What is printed there, and what it is worth

As it is labelledAs printedToleranceStandard
Frequency Response Range7Hz-35kHznot printednot printed
Effective Frequency Response Range20Hz-20kHz (IEC60318-4, -3dB)-3 dBIEC60318-4

Moondrop prints two frequency ranges for the Moondrop Armature Art 24. The wide one carries no conditions at all; the narrow one names a measurement standard and a tolerance. Only the second is a specification — the first is a headline.

This is one of only 58 models — out of the 490 whose maker prints a range at all — that also print the tolerance. That is what makes it a specification rather than a headline.

Only what the maker printed; maker by maker.

Power, voltage and current by listening level

LevelWhat it isPowerVoltageCurrent
85 dB SPLquiet background listening0.07 mW20 mV3.5 mA
95 dB SPLnormal listening0.69 mW63 mV10.9 mA
100 dB SPLloud listening2.2 mW0.11 V19.4 mA
105 dB SPLvery loud6.9 mW0.20 V34.5 mA
110 dB SPLpeaks on dynamic music22 mW0.36 V61.4 mA

Most people listen between 75 and 85 dB; the 100 dB row leaves room for peaks.

The cheapest sources that drive them with room to spare

The 15 cheapest of the 280 sources here that reach 100 dB SPL into 5.8Ω with at least 10 dB of headroom and no known hiss or output-impedance problem with these headphones. All 280 sources, judged for these headphones.

SourceTypePricePower into 5.8ΩHeadroomVerdict
Tanchjim Stargate IIUSB dongle$4030 mW+11 dBComfortable
ddHiFi TC35ALUSB dongle$4638 mW+12 dBComfortable
ddHiFi TC35AirUSB dongle$4638 mW+12 dBComfortable
Fosi Audio N3Bluetooth receiver$5025 mW+11 dBComfortable
FiiO BTR13Bluetooth receiver$5944 mW+13 dBComfortable
Tanchjim SpaceUSB dongle$7023 mW+10 dBComfortable
Aiyima A2 Prodesktop DAC/amp$7527 mW+11 dBComfortable
ddHiFi TC44 Pro E2USB dongle$9945 mW+13 dBComfortable
Onix Alpha XI1USB dongle$10933 mW+12 dBComfortable
Hidizs S9 Pro PlusUSB dongle$13925 mW+11 dBComfortable
Topping L30 IIdesktop amplifier$1491.3 W+28 dBComfortable
Shanling H2portable amplifier$169123 mW+18 dBComfortable
xDuoo MT-604desktop amplifier$169363 mW+22 dBComfortable
TempoTec Variations V3 Blazeportable player$179150 mW+18 dBComfortable
Surfans F28portable player$18023 mW+10 dBComfortable

The three ways a source goes wrong

Hiss. At 119.0 dB/V these are sensitive enough to reveal a source's own noise floor. The noisiest source in the database, the Schiit Mjolnir 3, would put its hiss at roughly 27 dB SPL in these headphones — clearly audible in quiet passages. Check your own source.

Output impedance. At 5.8Ω these want a source output impedance below 0.72Ω to satisfy the one-eighth rule; 90 of the 192 sources that publish one miss it. Check yours here.

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