The Beyerdynamic Custom One Pro Plus is 16Ω at 96.0 dB (no figure from the maker at all); the Beyerdynamic T1 2nd Gen (600Ω) is 600Ω at 102.0 dB (no figure from the maker at all). 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 Custom One Pro Plus needs 6.0 dB more than the T1 2nd Gen (600Ω) to reach the same loudness — 2.5 mW against 0.63 mW.
| Specification | Custom One Pro Plus | T1 2nd Gen (600Ω) |
|---|---|---|
| Impedance | 16 Ω | 600 Ω |
| Sensitivity | 96.0 dB | 102.0 dB |
| Sensitivity (voltage) | 114.0 dB/V | 104.2 dB/V |
| Power for 100 dB | 2.5 mW | 0.63 mW |
| Voltage for 100 dB | 0.20 V | 0.62 V |
| Current for 100 dB | 12.5 mA | 1.0 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 2.00 Ω | 75.00 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
One caution before reading the rows. For Beyerdynamic Custom One Pro Plus and Beyerdynamic T1 2nd Gen (600Ω) the maker publishes no sensitivity figure at all. The number in the table was collected when this database was first built and has never been traced to a manufacturer document, so treat every row below it as an estimate rather than a specification.
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.
34 sources are low enough in output impedance for the T1 2nd Gen (600Ω) under the one-eighth rule but not for the Custom One Pro Plus (Zoom AMS-22, Audient EVO 4, ART HeadAmp 4 Pro, 31 more).
1 source stays below the audible-hiss threshold with the T1 2nd Gen (600Ω) but crosses it with the Custom One Pro Plus (Schiit Mjolnir 3).
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 T1 2nd Gen (600Ω) is more demanding than 91% of the 567 non-electrostatic models in this database; the Custom One Pro Plus than 59%. 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 | Custom One Pro Plus power | Custom One Pro Plus voltage | T1 2nd Gen (600Ω) power | T1 2nd Gen (600Ω) voltage |
|---|---|---|---|---|
| 80 | 0.03 mW | 20 mV | 6.3 µW | 62 mV |
| 85 | 0.08 mW | 36 mV | 0.02 mW | 0.11 V |
| 90 | 0.25 mW | 63 mV | 0.06 mW | 0.19 V |
| 95 | 0.79 mW | 0.11 V | 0.20 mW | 0.35 V |
| 100 | 2.5 mW | 0.20 V | 0.63 mW | 0.62 V |
| 105 | 7.9 mW | 0.36 V | 2.0 mW | 1.09 V |
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, Custom One Pro Plus | Headroom, T1 2nd Gen (600Ω) | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 7.8 dB | 4.0 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 19.9 dB | 12.4 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR11 | $36 | 12.5 dB | 3.8 dB | 0.5 Ω | 8.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. That is the easy axis. 69 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 69 is the JadeAudio JA11, at $20. It leaves 7.8 dB of headroom on the Custom One Pro Plus and 4.0 dB on the T1 2nd Gen (600Ω), its output impedance is 0.5 Ω against a one-eighth limit of 2.00 Ω and 75.00 Ω, and its noise figure puts the hiss floor 21 dB and 31 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.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: Beyerdynamic Custom One Pro Plus and Beyerdynamic T1 2nd Gen (600Ω). Each figure on this page is labelled on those pages with where it came from, including the ones Beyerdynamic never published — what that maker publishes, counted.