Oct 4, 2011

The OPPO BDP-95, BDP-93, and BDP-83 Blu-ray players don't include a headphone output jack. A headphone output capability is included with many players and in stereo amplifiers and receivers. Owners of high-performance players which don't include a headphone output will often use a separate headphone amplifier unit. However, for very high sensitivity headphones (>110 dB SPL) in the 30 - 60 ohm impedance range, the headphones can in fact be driven directly from the player line-out, using a very simple passive voltage divider network, preserving the exceptional audio performance that these OPPO players provide. The divider circuit and the range of resistor values which are suitable for this usage are discussed. A convenient script calculator is included which facilitates converting headphone specifications (sensitivity and efficiency) and displaying dBSPL listening level achievable with any player, headphones and circuit component values.

In order to facilitate comparison with other headphones, it is important to know how to convert headphone

dBSPL(1mW) = dBSPL (1Vrms) - 10*log(1000/R) = dBSPL(1Vrms) - 30 + 10log(R)or, for the HD 598 headphones:

dBSPL(1mW) = 112 - 10*log(1000/50) = 112 - 30 + 17 = 99 dBTherefore any headphones with an impedance of 50 ohm and an efficiency of ~ 100 dBSPL(mW) should perform similarly to the Sennheiser HD 598 when used in the voltage divider circuit discussed above.

As another example, the Sennheiser HD 650 and HD 800 headphones both have an impedance of 300 ohm and a sensitivity of 102 dBSPL (1Vrms) or an efficienty of 97 dBSPL (1mW). Using the divider circuit above with modified component values of R1 = 300 ohm and R2 = 1 kohm, these headphones will provide a sound level of 100 dBSPL when used with the OPPO players at full signal analog output level. (the maximum internal voltage of the OPPO players are 2.2Vrms, and the voltage divider circuit, including the OPPO internal 100 ohm resistance, provides 0.81Vrms at these headphones which is about 2dB lower level than for a 1Vrms signal).

The calculator below converts headphone efficiency to sensitivity or vice versa.

- Enter the headphone impedance Rphones in ohms.

- To convert sensitivity to efficiency, enter the sensitivity value (dBSPL / 1Vrms) and click Get Efficiency.

- To convert efficiency to sensitivity, enter the efficiency value (dBSPL / 1 mW) and click Get Sensitivity.

Headphone Sensitivity / Efficiency Converter and dB SPL Calculator | ||
---|---|---|

Rphones (ohms): | Sensitivity (dBSPL/1Vrms): | Efficiency (dBSPL/1mW) : |

Vs(Vrms): Rs(ohms): | R1 (ohms): | R2 (ohms): |

dBSPL (Circuit): | Phones Voltage (Vrms): | Phones Power (mW): |