The Beyerdynamic MMX 300 PRO is 48Ω with a sensitivity of 96.0 dB/mW, which is 109.2 dB/V. To reach 100 dB SPL — genuinely loud, louder than most people listen — it needs 2.5 mW, or 0.35 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, 259 have at least 10 dB of headroom and another 21 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.
Beyerdynamic publishes this directly as 96 dB SPL @ 1 mW / 500 Hz (1 mW at 500 Hz), per milliwatt, so nothing was converted.
Source: north-america.beyerdynamic.com, europe.beyerdynamic.com. How this data was built.
| As it is labelled | As printed | Tolerance | Standard |
|---|---|---|---|
| Headphone frequency response | 5 - 40,000 Hz | not printed | not printed |
Beyerdynamic prints 5 - 40,000 Hz for the Beyerdynamic MMX 300 PRO, under the heading “Headphone frequency response”. Source: north-america.beyerdynamic.com.
No tolerance is printed with it, so “5 - 40,000 Hz” says nothing about how loud this headphone actually is at 5 Hz.
Only what the maker printed; maker by maker.
| Level | What it is | Power | Voltage | Current |
|---|---|---|---|---|
| 85 dB SPL | quiet background listening | 0.08 mW | 62 mV | 1.3 mA |
| 95 dB SPL | normal listening | 0.79 mW | 0.20 V | 4.1 mA |
| 100 dB SPL | loud listening | 2.5 mW | 0.35 V | 7.2 mA |
| 105 dB SPL | very loud | 7.9 mW | 0.62 V | 12.9 mA |
| 110 dB SPL | peaks on dynamic music | 25 mW | 1.10 V | 22.9 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 48Ω 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 48Ω | Headroom | Verdict |
|---|---|---|---|---|---|
| FiiO KA11 | USB dongle | $29 | 134 mW | +17 dB | Comfortable |
| Tanchjim Stargate II | USB dongle | $40 | 50 mW | +13 dB | Comfortable |
| ddHiFi TC35AL | USB dongle | $46 | 140 mW | +17 dB | Comfortable |
| ddHiFi TC35Air | USB dongle | $46 | 140 mW | +17 dB | Comfortable |
| Fosi Audio N3 | Bluetooth receiver | $50 | 92 mW | +16 dB | Comfortable |
| Hidizs SD2 | USB dongle | $50 | 47 mW | +13 dB | Comfortable |
| FiiO BTR13 | Bluetooth receiver | $59 | 66 mW | +14 dB | Comfortable |
| iFi GO link | USB dongle | $59 | 49 mW | +13 dB | Comfortable |
| Kiwi Ears Allegro Pro | USB dongle | $60 | 45 mW | +13 dB | Comfortable |
| ddHiFi TC35Pro (Mountain2) | USB dongle | $66 | 43 mW | +12 dB | Comfortable |
| iBasso DC03 Pro | USB dongle | $69 | 65 mW | +14 dB | Comfortable |
| DUNU DTC 480 | USB dongle | $70 | 43 mW | +12 dB | Comfortable |
| EPZ TP35 Pro | USB dongle | $70 | 75 mW | +15 dB | Comfortable |
| Tanchjim Space | USB dongle | $70 | 83 mW | +15 dB | Comfortable |
| Truthear SHIO | USB dongle | $70 | 83 mW | +15 dB | Comfortable |
Hiss. At 109.2 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 17 dB SPL in these headphones — clearly audible in quiet passages. Check your own source.
Output impedance. At 48Ω these want a source output impedance below 6.00Ω to satisfy the one-eighth rule; 34 of the 192 sources that publish one miss it. Check yours here.
48Ω · 100.0 dB/mW · Easy
See requirements →48Ω · 100.0 dB/mW · Easy
See requirements →48Ω · 98.0 dB/mW · Easy
See requirements →47Ω · 96.0 dB/mW · Easy
See requirements →47Ω · 96.0 dB · Easy
See requirements →32Ω · 94.1 dB/mW · Easy
See requirements →Compared with its stablemates: vs DJ 300 PRO X · vs DT 700 Pro X · vs DT 880 Edition (600Ω) · vs DT 990 Edition (600Ω).