The Hidizs MP145 PRO is 30Ω at 104.0 dB (no reference unit printed); the Hidizs MS2 PRO is 17Ω at 111.0 dB (no reference unit printed). This page is only about what they ask of an amplifier — not how they sound, which no specification on either sheet can tell you.
The MP145 PRO needs 7.0 dB more than the MS2 PRO to reach the same loudness — 0.40 mW against 0.08 mW.
| Specification | MP145 PRO | MS2 PRO |
|---|---|---|
| Impedance | 30 Ω | 17 Ω |
| Sensitivity | 104.0 dB | 111.0 dB |
| Sensitivity (voltage) | 119.2 dB/V | 128.7 dB/V |
| Power for 100 dB | 0.40 mW | 0.08 mW |
| Voltage for 100 dB | 0.11 V | 37 mV |
| Current for 100 dB | 3.6 mA | 2.2 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 3.75 Ω | 2.12 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
One caution before reading the rows. Hidizs MP145 PRO and Hidizs MS2 PRO printed a decibel figure with no reference unit, so this page reads it as per milliwatt. If it is really per volt, each of them needs far more than the table says. Why the two readings differ by so much.
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.
19 sources stay below the audible-hiss threshold with the MP145 PRO but cross it with the MS2 PRO (FiiO BTR11, Fosi Audio SK02, FiiO K11 R2R, 16 more).
280 of the 280 sources here reach 100 dB on both. That count is about power only — the output-impedance and hiss lines above are separate questions, and a source can pass this one and fail those.
The gap between these two in decibels does not change with volume — it is a property of the two headphones. What changes is the size of the numbers, and it changes fast: every 10 dB costs ten times the power. The row that matters is the one nearest the level you listen at, and for most people that is nearer the top of this table than the bottom.
The MP145 PRO is more demanding than 35% of the 567 non-electrostatic models in this database; the MS2 PRO than 5%. Both figures use the same measure as the rest of the site: whichever runs out first against a 2 V, 100 mW dongle, voltage or power.
| dB SPL | MP145 PRO power | MP145 PRO voltage | MS2 PRO power | MS2 PRO voltage |
|---|---|---|---|---|
| 80 | 4.0 µW | 11 mV | 0.8 µW | 4 mV |
| 85 | 0.01 mW | 19 mV | 2.5 µW | 7 mV |
| 90 | 0.04 mW | 35 mV | 7.9 µW | 12 mV |
| 95 | 0.13 mW | 61 mV | 0.03 mW | 21 mV |
| 100 | 0.40 mW | 0.11 V | 0.08 mW | 37 mV |
| 105 | 1.3 mW | 0.19 V | 0.25 mW | 65 mV |
105 dB is included because forum power figures are usually quoted there or higher. It is also a level that damages hearing in minutes — how many minutes is its own calculator.
| Source | Price | Headroom, MP145 PRO | Headroom, MS2 PRO | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 18.5 dB | 23.0 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 27.1 dB | 34.8 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 24.0 dB | 31.7 dB | 0.6 Ω | 1.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. That is the easy axis. 53 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 rest either fail one of those or never printed the number at all, and 208 of them are in the second group.
The cheapest of the 53 is the JadeAudio JA11, at $20. It leaves 18.5 dB of headroom on the MP145 PRO and 23.0 dB on the MS2 PRO, its output impedance is 0.5 Ω against a one-eighth limit of 3.75 Ω and 2.12 Ω, and its noise figure puts the hiss floor 16 dB and 7 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
Cheapest that satisfies three published numbers is not the same as best, and none of it is about how either headphone sounds. To put either model against a source this page does not mention, or to change the target loudness, use the amplifier matcher.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| MP145 PRO | 20Hz to 40kHz | not printed | not printed |
| MS2 PRO | nothing printed | — | — |
Hidizs prints 20Hz to 40kHz for the MP145 PRO and nothing at all for the MS2 PRO.
MP145 PRO: Hidizs prints this figure in the body copy of the product page. The only specification table on that page belongs to a different product — one of the company’s DAC dongles — and there is no frequency row in a table for this model.
MS2 PRO: The page does carry a specification table with a frequency-response row — but that table is for one of the company’s DAC dongles, not for these in-ears.
So one side of this comparison has a frequency-response number and the other does not — which changes less than it looks. The range printed for the MP145 PRO comes with no tolerance beside it, and a range without a ±dB figure says nothing about how loud the headphone is at either end of it: thirty decibels down at the bottom and the sentence would still be true. On the only reading that would have made it a specification, the two sheets say the same amount: nothing.
None of this is a measurement. What each maker publishes, and what it is worth, is set out in the frequency response audit.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: Hidizs MP145 PRO and Hidizs MS2 PRO. Each figure on this page is labelled on those pages with where it came from, including the ones Hidizs never published — what that maker publishes, counted.