The HEDD Audio HEDDphone TWO is 41Ω with a sensitivity of 89.0 dB/mW, which is 102.9 dB/V. To reach 100 dB SPL — genuinely loud, louder than most people listen — it needs 13 mW, or 0.72 V across the drivers.
That is a moderate load. Most USB dongles handle it without complaint; the weakest phone outputs will run out of volume before they run out of quality. 261 of 280 sources here have enough headroom. The cheapest portable source that does the job is the Generic CX31993 dongles at $12.
Sensitivity here is in dB per milliwatt. Why the unit matters.
HEDD Audio publishes this directly as 89 dB SPL (at 1 mW), per milliwatt, so nothing was converted.
Source: hedd.audio. How this data was built.
| As it is labelled | As printed | Tolerance | Standard |
|---|---|---|---|
| Frequency Range | 10 Hz - 40 kHz | not printed | not printed |
HEDD Audio prints 10 Hz - 40 kHz for the HEDD Audio HEDDphone TWO, under the heading “Frequency Range”. Source: hedd.audio.
No tolerance is printed with it, so “10 Hz - 40 kHz” says nothing about how loud this headphone actually is at 10 Hz.
Only what the maker printed; maker by maker.
| Level | What it is | Power | Voltage | Current |
|---|---|---|---|---|
| 85 dB SPL | quiet background listening | 0.40 mW | 0.13 V | 3.1 mA |
| 95 dB SPL | normal listening | 4.0 mW | 0.40 V | 9.9 mA |
| 100 dB SPL | loud listening | 13 mW | 0.72 V | 17.5 mA |
| 105 dB SPL | very loud | 40 mW | 1.28 V | 31.2 mA |
| 110 dB SPL | peaks on dynamic music | 126 mW | 2.27 V | 55.4 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 41Ω 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 41Ω | Headroom | Verdict |
|---|---|---|---|---|---|
| FiiO KA11 | USB dongle | $29 | 156 mW | +11 dB | Comfortable |
| ddHiFi TC35AL | USB dongle | $46 | 164 mW | +11 dB | Comfortable |
| ddHiFi TC35Air | USB dongle | $46 | 164 mW | +11 dB | Comfortable |
| Tempotec Sonata BHD Pro | USB dongle | $60 | 219 mW | +12 dB | Comfortable |
| JDS Labs Atom+ (2nd gen) | desktop amplifier | $99 | 853 mW | +18 dB | Comfortable |
| Schiit Magni Heresy | desktop amplifier | $99 | 1.9 W | +22 dB | Comfortable |
| ddHiFi TC44 Pro E2 | USB dongle | $99 | 195 mW | +12 dB | Comfortable |
| Fosi Audio SK02 | desktop amplifier | $100 | 148 mW | +11 dB | Comfortable |
| FiiO KA15 | USB dongle | $109 | 140 mW | +10 dB | Comfortable |
| Onix Alpha XI1 | USB dongle | $109 | 140 mW | +10 dB | Comfortable |
| Schiit Magni+ | desktop amplifier | $109 | 1.6 W | +21 dB | Comfortable |
| Schiit Magni Unity | desktop amplifier | $119 | 1.9 W | +22 dB | Comfortable |
| JDS Labs Atom Amp 2 | desktop amplifier | $129 | 2.1 W | +22 dB | Comfortable |
| Tanchjim LUNA | USB dongle | $140 | 227 mW | +13 dB | Comfortable |
| FiiO K11 | desktop DAC/amp | $143 | 407 mW | +15 dB | Comfortable |
Hiss. At 102.9 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 11 dB SPL in these headphones — clearly audible in quiet passages. Check your own source.
Output impedance. At 41Ω these want a source output impedance below 5.12Ω to satisfy the one-eighth rule; 34 of the 192 sources that publish one miss it. Check yours here.
300Ω · 97.8 dB/mW · Moderate
See requirements →300Ω · 97.8 dB/mW · Moderate
See requirements →300Ω · 97.8 dB/mW · Moderate
See requirements →32Ω · 88.1 dB/mW · Moderate
See requirements →60Ω · 91.0 dB · Moderate
See requirements →300Ω · 98.0 dB/mW · Moderate
See requirements →