T40RP MK3 vs T60RPmk2: which needs more amplifier?

The Fostex T40RP MK3 is 50Ω at 91.0 dB/mW; the Fostex T60RPmk2 is 28Ω at 96.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.

The T40RP MK3 needs 5.0 dB more than the T60RPmk2 to reach the same loudness — 7.9 mW against 2.5 mW.

Side by side

The numbers that decide it

Specification	T40RP MK3	T60RPmk2
Impedance	50 Ω	28 Ω
Sensitivity	91.0 dB/mW	96.0 dB/mW
Sensitivity (voltage)	104.0 dB/V	111.5 dB/V
Power for 100 dB	7.9 mW	2.5 mW
Voltage for 100 dB	0.63 V	0.27 V
Current for 100 dB	12.6 mA	9.5 mA
Highest source impedance that leaves them alone (one-eighth rule)	6.25 Ω	3.50 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 T40RP MK3 under the one-eighth rule but not for the T60RPmk2 (Shanling H5).

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 T40RP MK3 is more demanding than 92% of the 567 non-electrostatic models in this database; the T60RPmk2 than 69%.

dB SPL	T40RP MK3 power	T40RP MK3 voltage	T60RPmk2 power	T60RPmk2 voltage
80	0.08 mW	63 mV	0.03 mW	27 mV
85	0.25 mW	0.11 V	0.08 mW	47 mV
90	0.79 mW	0.20 V	0.25 mW	84 mV
95	2.5 mW	0.35 V	0.79 mW	0.15 V
100	7.9 mW	0.63 V	2.5 mW	0.27 V
105	25 mW	1.12 V	7.9 mW	0.47 V

What drives both

The cheapest source that satisfies both

Source	Price	Headroom, T40RP MK3	Headroom, T60RPmk2	Output impedance	Noise
JadeAudio JA11	$20	3.8 dB	10.2 dB	0.5 Ω	1.7 µV
FiiO KA11	$29	12.1 dB	19.1 dB	0.7 Ω	1.7 µV
FiiO BTR11	$36	3.8 dB	11.1 dB	0.5 Ω	8.0 µV

Of the 280 sources here, 280 reach 100 dB on both. 70 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 70 is the JadeAudio JA11, at $20. It leaves 3.8 dB of headroom on the T40RP MK3 and 10.2 dB on the T60RPmk2, its output impedance is 0.5 Ω against a one-eighth limit of 6.25 Ω and 3.50 Ω, and its noise figure puts the hiss floor 31 dB and 24 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
T40RP MK3	20 to 35,000 Hz	not printed	not printed
T60RPmk2	10～40,000 Hz	not printed	not printed

Fostex prints 20 to 35,000 Hz for the T40RP MK3 and 10～40,000 Hz for the T60RPmk2.

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 T40RP MK3 and Fostex T60RPmk2. Every figure on this page comes from what Fostex published, or is derived from it — what that maker publishes, counted.