T50RPmk4Q vs T60RP: which needs more amplifier?

The Fostex T50RPmk4Q is 28Ω at 97.0 dB/mW; the Fostex T60RP is 50Ω at 92.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.

The T60RP needs 5.0 dB more than the T50RPmk4Q to reach the same loudness — 6.3 mW against 2.0 mW.

Side by side

The numbers that decide it

Specification	T50RPmk4Q	T60RP
Impedance	28 Ω	50 Ω
Sensitivity	97.0 dB/mW	92.0 dB/mW
Sensitivity (voltage)	112.5 dB/V	105.0 dB/V
Power for 100 dB	2.0 mW	6.3 mW
Voltage for 100 dB	0.24 V	0.56 V
Current for 100 dB	8.4 mA	11.2 mA
Highest source impedance that leaves them alone (one-eighth rule)	3.50 Ω	6.25 Ω
Sources that reach 100 dB out of 280	280	280

What separates them

Where the two part company

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.

1 source is low enough in output impedance for the T60RP under the one-eighth rule but not for the T50RPmk4Q (Shanling H5).

1 source stays below the audible-hiss threshold with the T60RP but crosses it with the T50RPmk4Q (Schiit Mjolnir 3).

280 of the 280 sources here reach 100 dB on both.

At the level you actually listen at

What each one needs from 80 to 105 dB

The T60RP is more demanding than 88% of the 567 non-electrostatic models in this database; the T50RPmk4Q than 65%.

dB SPL	T50RPmk4Q power	T50RPmk4Q voltage	T60RP power	T60RP voltage
80	0.02 mW	24 mV	0.06 mW	56 mV
85	0.06 mW	42 mV	0.20 mW	100 mV
90	0.20 mW	75 mV	0.63 mW	0.18 V
95	0.63 mW	0.13 V	2.0 mW	0.32 V
100	2.0 mW	0.24 V	6.3 mW	0.56 V
105	6.3 mW	0.42 V	20 mW	1.00 V

What drives both

The cheapest source that satisfies both

Source	Price	Headroom, T50RPmk4Q	Headroom, T60RP	Output impedance	Noise
JadeAudio JA11	$20	11.2 dB	4.8 dB	0.5 Ω	1.7 µV
FiiO KA11	$29	20.1 dB	13.1 dB	0.7 Ω	1.7 µV
FiiO BTR11	$36	12.1 dB	4.8 dB	0.5 Ω	8.0 µV

Of the 280 sources here, 280 reach 100 dB on both. 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 cheapest of the 69 is the JadeAudio JA11, at $20. It leaves 11.2 dB of headroom on the T50RPmk4Q and 4.8 dB on the T60RP, its output impedance is 0.5 Ω against a one-eighth limit of 3.50 Ω and 6.25 Ω, and its noise figure puts the hiss floor 23 dB and 30 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.

Try any other source.

Frequency response

What each sheet prints, and what it is worth

Model	As printed	Tolerance	Standard
T50RPmk4Q	10–40,000 Hz	not printed	not printed
T60RP	15 to 35,000 Hz	not printed	not printed

Fostex prints 10–40,000 Hz for the T50RPmk4Q and 15 to 35,000 Hz for the T60RP.

Neither range has a tolerance printed beside it, so a wider range on one sheet is not deeper bass or more treble.

Not a measurement; maker by maker.

Both pages in full

Both have a page of their own. In full: Fostex T50RPmk4Q and Fostex T60RP. Every figure on this page comes from what Fostex published, or is derived from it — what that maker publishes, counted.