Stax SR-003 Electrostatic In-Earspeakers

The purpose of this article is to give both an introduction to Stax headphones (electrostatic technology) and a review of an entry level (price wise), yet outstanding unit, the SR-003, which performs better than several other models in the same family. I know the SR-003 deeply and across the years I have listened to them with several sources, ranging from cheap M-Audio 2496 soundcard and AMB Gamma 1 dac, to geeky tweaked mp3 players (iMod), to Yulong DAH-1, Museatex Bitstream, Assemblage 3.0.
I had been using the following amplifiers: SRM-252, SRM-1 Mk2 Pro, SRM-717, and two custom modded portable amplifiers (see below).

Stax SR-003
This is called in-earspeaker, a tiny electrostatic transducer placed inside the ear canal, with open back (offering no isolation from the outside world). The SR-003 can be used either with the headband, that makes the earpieces put pressure against the ears, quickly getting painful or without the headband, by pushing the silicon tips (two different sizes) inside the ear canal.
There is a portable version of the same canalphone, the SR-001 MkII, with a dedicated portable amp (SRM-001) and cable connector. The SRM-001 is considered an inferior amp to the SRM-252 (usually bundled with the SR-003), but mods have been performed and documented (Head-Fi member Audiocats) which improve the sound of portable amplifier to very large extents.

The Stax SR-003 have a unique sound for a lesser Stax headphone. While most of the ‘cheaper’ Stax are said to have weak bass and bright highs, the SR-003 are warm and bass oriented headphones.
They have very pleasant lower midrange. Depending on wearing them with/without the headband, the midbass can be big and bloomy (with the headband) to linear (without it), but in both cases extremely fast and detailed. Instead of making things bloated or muddy, it’s the pavement where all other sounds are etched on for a wonderful picture. The SR-003 have extreme instrument separation and clarity, and are one of the fastest Stax headphones thanks to the very thin diaphragm.
Electrostatic headphones have the highest resolution capabilities compared to dynamic headphones and orthodynamics.
Artifacts in a digital file can be spotted by the SR-003 and made distinct like under a magnifying glass.
The treble area is slightly subdued around 8-10 kHz and linear past that region. The “human” translation for this, generally, is that sibilance is attenuated, as well as metallic details and cymbals energy. The dip is not excessive, especially without the headband, but gets more significant with the headband: the sound, while being in both case warm and with upfront, beautiful vocals, tends to lushier, fuller and a bit too midbassy/smoothered with the headband, and more linear/precise without the headband. The latter kind of usage is, in my opinion, the better one. Unfortunately, using the SR-003 without the headband (so, inside the ear canal and not against it) brings a few shortcomings: the soundstage gets smaller (using the headband places the drivers further away from the eardrum and the sound is bigger; this is also enhanced by the more powerful midbass); the lack of deep bass (anything below 60 Hz) is more evident (the SR-003 don’t have deep bass, but the midbass exaggeration, when used with the headband, masks it most of the time); it’s easy (for me and the shape of my ear canals, at least) to lose the ‘seal’, and need to readjust the in-earspeaker inside the ear canal. This can be very distracting if happening too often.
Usage with the headband makes the tonal balance more irregular (big midbass quantity and subdued high frequency in the 8-10kHz region – around 6dB dip), although still very pleasant (and still amazing for the price and against much more expensive dynamic headphones), and chances are high for the ear canal entrance to ache in a matter of half a hour. Wearing them with the headband increases the spacial perception, especially because the bass hits out of the head (while vocals and trebly details are, in both cases, in the head), acting like an “external pavement” for the rest of the picture.

Instrument placement, in any cases, is razor sharp. The SR-003 are very good for rock, as they are never harsh and they give it a full bodied character. Plus, the fact that ’60s-’70s rock recordings hardly have deep bass makes the limit negligible. They make listenable Ornette Coleman too, whose sounds are usually shrill and painful.
In general, though, I consider them perfect for most music where deep bass reproduction is not mandatory. The limitations underlined in this sound descriptions, are “deviations from perfection”, and they are not only a bargain, but also a sort of doom: upgrading from the Stax SR-003 means skipping all the Lambda range, and only few, much more expensive electrostatic headphones give a real benefit over them.

They are more sensitive to source changes than amp changes: higher end sources like the custom upgraded Museatex Bitstream and Assemblage 3.0 made a huge difference in the final sound over cheaper, more digital sounding sources.

External resources (regarding mods to the portable SRM-001 amplifier and a review of the modded portable unit):


Stax SR-003