The Grado Signature S950 is 38Ω at 117.0 dB/mW; the Grado SR325x is 38Ω at 98.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.
The SR325x needs 19.0 dB more than the Signature S950 to reach the same loudness — 1.6 mW against 0.02 mW.
| Specification | Signature S950 | SR325x |
|---|---|---|
| Impedance | 38 Ω | 38 Ω |
| Sensitivity | 117.0 dB/mW | 98.0 dB/mW |
| Sensitivity (voltage) | 131.2 dB/V | 112.2 dB/V |
| Power for 100 dB | 0.02 mW | 1.6 mW |
| Voltage for 100 dB | 28 mV | 0.25 V |
| Current for 100 dB | 0.7 mA | 6.5 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 4.75 Ω | 4.75 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
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.
31 sources stay below the audible-hiss threshold with the SR325x but cross it with the Signature S950 (Kiwi Ears Allegro Mini, FiiO BTR11, Fosi Audio SK02, 28 more).
280 of the 280 sources here reach 100 dB on both.
The SR325x is more demanding than 66% of the 567 non-electrostatic models in this database; the Signature S950 than 2%.
| dB SPL | Signature S950 power | Signature S950 voltage | SR325x power | SR325x voltage |
|---|---|---|---|---|
| 80 | 0.2 µW | 3 mV | 0.02 mW | 25 mV |
| 85 | 0.6 µW | 5 mV | 0.05 mW | 44 mV |
| 90 | 2.0 µW | 9 mV | 0.16 mW | 78 mV |
| 95 | 6.3 µW | 15 mV | 0.50 mW | 0.14 V |
| 100 | 0.02 mW | 28 mV | 1.6 mW | 0.25 V |
| 105 | 0.06 mW | 49 mV | 5.0 mW | 0.44 V |
| Source | Price | Headroom, Signature S950 | Headroom, SR325x | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 31.0 dB | 12.0 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 39.3 dB | 20.3 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 36.2 dB | 17.2 dB | 0.6 Ω | 1.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. 42 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 42 is the JadeAudio JA11, at $20. It leaves 31.0 dB of headroom on the Signature S950 and 12.0 dB on the SR325x, its output impedance is 0.5 Ω against a one-eighth limit of 4.75 Ω for both, and its noise figure puts the hiss floor 4 dB and 23 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| Signature S950 | 3.5 Hz – 51.5 kHz | not printed | not printed |
| SR325x | 18-24kHz | not printed | not printed |
Grado prints 3.5 Hz – 51.5 kHz for the Signature S950 and 18-24kHz for the SR325x.
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 have a page of their own. In full: Grado Signature S950 and Grado SR325x. Every figure on this page comes from what Grado published, or is derived from it — what that maker publishes, counted.