Sony MDR-MV1 on an EVO 4: loud enough and still the wrong output
24 Ω headphones on a published output impedance of up to 50 Ω: the level still lands 4.3 dB above target, but the ratio is 0.5 where the rule asks for 8. This is the failure that «is it loud enough» never catches.
- Gear in this setup
- Audient EVO 4Check price at Thomann
- Sony MDR-MV1Check price at Thomann
Level: fine, 114.3 dB against a 110 dB target. Damping: 0.5 against a required 8. The verdict here is not about volume.
Sony rates the MDR-MV1 at 24 Ω and 100 dB/mW, which is 116.2 dB/V — a 110 dB peak needs only 0.49 V, 10 mW, 20.41 mA. Audient publishes +10.1 dBu into 600 Ω for the EVO 4, i.e. 2.48 V, and — unusually — also publishes an output impedance: «<50 Ω». That 50 Ω and the headphone's 24 Ω form a voltage divider, so of the 2.48 V only 0.804 V ever reaches the driver. That is still 4.3 dB above what the MV1 needs, which is exactly why this problem survives every «does it go loud enough» thread.
What the ratio of 0.5 does. A dynamic headphone's impedance is not flat: it peaks at the driver's bass resonance, often to several times the nominal figure. Feed it from a source whose own impedance is comparable, and the divider passes more voltage exactly where the impedance is highest — the bass rises and loosens. The 1/8 rule asks for a source at or below 3 Ω for this 24 Ω headphone. 50 Ω is sixteen times that.
The pearl: the EVO 4 loses more to its own output impedance than it differs from its bigger brother. Audient's own iD4 MkII publishes 5.46 V — 6.86 dB more than the EVO's 2.48 V. But the EVO's 50 Ω divider costs 9.78 dB into 24 Ω, more than the entire gap between the two boxes. On a low-impedance headphone the output impedance is the bigger number, and it is the one almost nobody reads.
And the honest asymmetry. The EVO 4 looks bad here only because Audient published the figure. For the iD4 MkII no output impedance is published at all, so we cannot say whether it clears 3 Ω, cannot rule out the same problem, and cannot claim the tonal balance is safe — we can only say its 5.46 V puts the level at 130.9 dB, which is 20.9 dB of headroom nobody needs. A published bad number is worth more than an absent good one. The same 50 Ω appears in Focusrite's Scarlett 2i2 4th Gen manual, where it produces the identical picture: 114.2 dB of level, a ratio of 0.5.