The Bang & Olufsen Beoplay H9i is 24Ω with a sensitivity of 95.0 dB/mW, which is 111.2 dB/V. To reach 100 dB SPL — genuinely loud, louder than most people listen — it needs 3.2 mW, or 0.28 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, 260 have at least 10 dB of headroom and another 20 have enough. The cheapest portable source that does the job is the Apple USB-C dongle (US) at $9.
Sensitivity here is in dB per milliwatt. Why the unit matters.
Bang & Olufsen publishes this directly as 95 dB/MW (@ 1 kHz +/-3 dB), per milliwatt, so nothing was converted.
Source: assets.ctfassets.net. How this data was built.
| As it is labelled | As printed | Tolerance | Standard |
|---|---|---|---|
| Frequency range | 20 Hz – 22 kHz | not printed | not printed |
Bang & Olufsen prints 20 Hz – 22 kHz for the Bang & Olufsen Beoplay H9i, under the heading “Frequency range”. Source: assets.ctfassets.net.
No tolerance is printed with it, so “20 Hz – 22 kHz” says nothing about how loud this headphone actually is at 20 Hz.
Only what the maker printed; maker by maker.
| Level | What it is | Power | Voltage | Current |
|---|---|---|---|---|
| 85 dB SPL | quiet background listening | 0.10 mW | 49 mV | 2.0 mA |
| 95 dB SPL | normal listening | 1.0 mW | 0.15 V | 6.5 mA |
| 100 dB SPL | loud listening | 3.2 mW | 0.28 V | 11.5 mA |
| 105 dB SPL | very loud | 10 mW | 0.49 V | 20.4 mA |
| 110 dB SPL | peaks on dynamic music | 32 mW | 0.87 V | 36.3 mA |
Most people listen between 75 and 85 dB; the 100 dB row leaves room for peaks.
The 15 cheapest of the 280 sources here that reach 100 dB SPL into 24Ω 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.
| Source | Type | Price | Power into 24Ω | Headroom | Verdict |
|---|---|---|---|---|---|
| FiiO SnowSky Tiny A | USB dongle | $22 | 37 mW | +11 dB | Comfortable |
| FiiO SnowSky Tiny B | USB dongle | $22 | 45 mW | +12 dB | Comfortable |
| FiiO KA11 | USB dongle | $29 | 212 mW | +18 dB | Comfortable |
| Tanchjim Stargate II | USB dongle | $40 | 76 mW | +14 dB | Comfortable |
| ddHiFi TC35AL | USB dongle | $46 | 158 mW | +17 dB | Comfortable |
| ddHiFi TC35Air | USB dongle | $46 | 158 mW | +17 dB | Comfortable |
| Fosi Audio N3 | Bluetooth receiver | $50 | 104 mW | +15 dB | Comfortable |
| Hidizs SD2 | USB dongle | $50 | 52 mW | +12 dB | Comfortable |
| FiiO BTR13 | Bluetooth receiver | $59 | 105 mW | +15 dB | Comfortable |
| iFi GO link | USB dongle | $59 | 52 mW | +12 dB | Comfortable |
| Kiwi Ears Allegro Pro | USB dongle | $60 | 51 mW | +12 dB | Comfortable |
| ddHiFi TC35Pro (Mountain2) | USB dongle | $66 | 49 mW | +12 dB | Comfortable |
| iBasso DC03 Pro | USB dongle | $69 | 74 mW | +14 dB | Comfortable |
| DUNU DTC 480 | USB dongle | $70 | 49 mW | +12 dB | Comfortable |
| EPZ TP35 Pro | USB dongle | $70 | 84 mW | +14 dB | Comfortable |
Hiss. At 111.2 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 19 dB SPL in these headphones — clearly audible in quiet passages. Check your own source.
Output impedance. At 24Ω these want a source output impedance below 3.00Ω to satisfy the one-eighth rule; 35 of the 192 sources that publish one miss it. Check yours here.
12Ω · 101.5 dB/mW · Easy
See requirements →12Ω · 92.0 dB · Easy
See requirements →48Ω · 98.0 dB/mW · Easy
See requirements →50Ω · 98.0 dB/mW · Easy
See requirements →40Ω · 97.0 dB/mW · Easy
See requirements →40Ω · 97.0 dB/mW · Easy
See requirements →Compared with its stablemates: vs Beoplay H95.