This page does not review anything STAX makes. It counts one thing: how much of what this database says about their products came out of their own documents, and how much had to be worked out or left blank.
| Model | Impedance | Sensitivity | Source of the figure |
|---|---|---|---|
| SR-007A | 170000 Ω | — | Reference not convertible |
| SR-007MK2 | 170000 Ω | — | Reference not convertible |
| SR-009 | 145000 Ω | — | Reference not convertible |
| SR-009S | 145000 Ω | — | Reference not convertible |
| SR-L500 MKII | 145000 Ω | — | Reference not convertible |
| SR-L700 MKII | 145000 Ω | — | Reference not convertible |
Impedance is almost always printed. Sensitivity is the one that goes wrong, because a decibel figure means two very different things depending on whether it is per milliwatt or per volt — about five decibels apart at 300 Ω and eighteen at 16 Ω. The conversion is here.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| SR-007A | 6 to 41,000 Hz | not printed | not printed |
| SR-007MK2 | 6 - 41,000Hz | not printed | not printed |
| SR-009 | nothing printed | — | — |
| SR-009S | 5 – 42,000Hz | not printed | not printed |
| SR-L500 MKII | 7 – 41,000Hz | not printed | not printed |
| SR-L700 MKII | 7 – 41,000Hz | not printed | not printed |
STAX prints a frequency range for 5 of all 6 models here whose sheets have been read, and nothing for the other 1.
Not one of those ranges comes with a tolerance in decibels. Without a ±dB figure a range says nothing about how loud the headphone is at either end of it, which puts STAX with the majority: of the 490 models across this database whose maker prints a range, 58 print the tolerance.
Every range stands under the same heading, give or take a capital letter: “Frequency Response”.
No measurement is published here — only what was printed. The whole count, maker by maker, is in the frequency response audit.
Very little of what this site says about STAX came from them. That is not an accusation about how their products sound — it is a statement about their paperwork, and it is the reason those pages carry so many qualifiers.
The rule used here is the same for every maker and is described on the manufacturer index. Every figure behind it can be opened on the product page it came from, with the document it came from linked.