SRH145 vs SRH940: which needs more amplifier?

The Shure SRH145 is 34Ω at 100.0 dB/mW; the Shure SRH940 is 42Ω at 100.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.

In amplifier terms these two are the same headphone. The gap between what they need for 100 dB is under half a decibel, which is smaller than the step between two clicks of most volume controls.

Side by side

The numbers that decide it

Specification	SRH145	SRH940
Impedance	34 Ω	42 Ω
Sensitivity	100.0 dB/mW	100.0 dB/mW
Sensitivity (voltage)	114.7 dB/V	113.8 dB/V
Power for 100 dB	1.0 mW	1.0 mW
Voltage for 100 dB	0.18 V	0.20 V
Current for 100 dB	5.4 mA	4.9 mA
Highest source impedance that leaves them alone (one-eighth rule)	4.25 Ω	5.25 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 SRH940 under the one-eighth rule but not for the SRH145 (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 SRH940 is more demanding than 60% of the 567 non-electrostatic models in this database; the SRH145 than 55%.

dB SPL	SRH145 power	SRH145 voltage	SRH940 power	SRH940 voltage
80	0.01 mW	18 mV	0.01 mW	20 mV
85	0.03 mW	33 mV	0.03 mW	36 mV
90	0.10 mW	58 mV	0.10 mW	65 mV
95	0.32 mW	0.10 V	0.32 mW	0.12 V
100	1.0 mW	0.18 V	1.0 mW	0.20 V
105	3.2 mW	0.33 V	3.2 mW	0.36 V

What drives both

The cheapest source that satisfies both

Source	Price	Headroom, SRH145	Headroom, SRH940	Output impedance	Noise
JadeAudio JA11	$20	14.5 dB	13.6 dB	0.5 Ω	1.7 µV
FiiO KA11	$29	22.7 dB	21.8 dB	0.7 Ω	1.7 µV
FiiO BTR11	$36	14.5 dB	13.6 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 14.5 dB of headroom on the SRH145 and 13.6 dB on the SRH940, its output impedance is 0.5 Ω against a one-eighth limit of 4.25 Ω and 5.25 Ω, and its noise figure puts the hiss floor 21 dB and 22 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
SRH145	25 to 18,000 Hz	not printed	not printed
SRH940	5 to 30,000 Hz	not printed	not printed

Shure prints 25 to 18,000 Hz for the SRH145 and 5 to 30,000 Hz for the SRH940.

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: Shure SRH145 and Shure SRH940. Every figure on this page comes from what Shure published, or is derived from it — what that maker publishes, counted.