Does the Shure Aonic 5 need an amp on an Audient EVO 4? The unit is ambiguous, the 50 Ω output is not
«Sensitivity at 1 kHz — 119 dB SPL/MW» is 14.4 dB away from its other reading, and on the EVO 4 the verdict is the same either way: the interface publishes a 50 Ω output against a 36 Ω balanced-armature load. Here the output impedance outranks the unit.
Two readings of the sensitivity, 14.4 dB apart, and the same verdict both times — because on this interface the unit is not what decides.
The Aonic 5 guide prints «Impedance at 1 kHz — 36 Ω» and «Sensitivity at 1 kHz — 119 dB SPL/MW». MW is the megawatt in SI; mW, the milliwatt, is meant. Audient publishes for the EVO 4: «Max Level Into 600ohms: +10.1dBu», which is 2.48 V, and «Output Impedance: <50 Ohm».
Read as milliwatts, which we store. S_V = 119 + 10·lg(1000/36) = 133.44 dB/V. A 110 dB peak needs 0.067 V, 1.87 mA and 0.13 mW. The EVO 4's 2.48 V across a 50 Ω output into a 36 Ω load delivers 1.038 V — 133.8 dB SPL, +23.8 dB of level. But the damping ratio is 36/50 = 0.7 against a rule that wants 8, so the verdict is damping risk.
Read as volts. The peak needs 0.355 V, 9.86 mA and 3.5 mW, and the chain reaches 119.3 dB SPL, +9.3 dB — and the verdict is still damping risk. Fourteen and a half decibels of ambiguity change the headroom and change nothing about the answer.
Read literally, as megawatts. S_V = 43.44 dB/V, the peak would need 2128.88 V, and the EVO 4 would deliver 43.8 dB SPL, −66.2 dB. Arithmetic disposes of that one.
How to judge the unit. Shure's SE215 and SE846 guides on the same server print «107 dB SPL/mW» and «114 dB SPL/mW» in correct lower case, while all three Aonic guides use the upper-case form — a capitalisation slip confined to one document family. Milliwatts.
The pearl: for a multi-driver balanced-armature in-ear, the output impedance is a bigger question than the unit, and it is the question nobody asks. A balanced-armature array has a crossover, and its impedance is not flat with frequency; a 50 Ω source in series with it does not merely lose level, it re-weights the response wherever the load impedance rises or falls. That is why «does the Aonic 5 need an amp» is the wrong question. Move it to a Lewitt CONNECT 2 — 2.19 V, published 1.9 Ω — and the same earphone reads +29.8 dB per milliwatt or +15.4 dB per volt with a damping ratio of 18.9, comfortable under both readings. The Aonic 5 does not need more voltage. It needs a source that publishes a low output impedance, and most do not publish one at all.