This review covers the Stax Lambda Pro electrostatic headphones and the SRM-1/MK-2 FET-input, pure class-A, DC-coupled amplifier.
Disclaimer: Both units are purchased by the reviewer and are not company-sponsored samples. You can visit the main Stax website here.
To read more about the Stax products we have previously featured on Headfonics click here.
Note, that this article follows our latest scoring guidelines which you can read up on here.
I always felt these were at the pinnacle of the headphone chain. Head-Fi and poisonous impressions from acquaintances here at Headfonics have all added to that longing for a personal electrostatic to satisfy my audio lust.
The weird thing is that this was actually a blind purchase as I haven’t listened to an electrostatic setup before. Glad I went through with this
Packaging & Accessories
The package came with the lambda professional ear speakers – very comfortable, if somewhat fragile-looking, the SRM-1/MK-2 amplifier – long, heavy, sturdy, with separate volume controls for the left and right channels (variable voltage adjustment is a godsend!), and a bonus extension cable.
The black and matte finish is a plus, as it blends well with my desktop. the amp has inputs for normal and pro bias, but the ear speakers can only plug in the pro bias slot so nothing else to tweak here. the back panel of the amp accepts two pairs of RCA inputs.
The voltage selector is also located at the back, as well as the power plug socket. the ear speakers are surprisingly light, lighter than the Beyers actually, and the circumaural pads are comfortable. my only gripe is the feeling that I am balancing a bridge-like contraption on top of my head.
The Beyer and HD650 clamp is much more secure, but comfort wise the level is exceptional. being open and perforated, the ear speakers do let the ears breathe out so no undue sweat accumulation to worry about
I have always wondered how the “effortless” Stax sound really was. My experience with the dynamic headphones had conditioned my hearing, and detail resolution, bass slam, and highs extension were the usual things I attempt to extract for any audio gear I get to listen to. But I was not prepared for the lambda pro.
The airy soundstage was disconcerting: the sound had the feeling of drifting towards my ears instead of being pushed inside. this plus the open design contributes to a very wide soundstage. I am reminded of my brief audition of the K701 and this is beyond the Beyer soundstage easily
Instrument separation is on a whole new level. I have always loved how the Beyer DT880 600Ω gives a separate space for each instrument.
The lambda pro ups the volume of those instruments in the background, bringing them closer to the volume of the vocal, without smearing them against each other, or bringing them forward all at once. Instrument positioning is preserved, and this is so brilliantly done, to an extent past the Beyer or the HD650 separation.
Speed is a new concept I have just recently appreciated with the lambda pros. Musical passages played fast sound really sound just as fast, in contrast to the sometimes congested feeling when listening to guitar runs on the hd650. Detail resolution is simply the best I have heard so far amongst my gear
As for the bass, I initially thought the bass was the sacrificial lamb or the weak point of vintage low-end Stax. Well, the bass was initially lacking slam and intensity, and I even felt the dt880 have more bass.
But turning up the volume increased the bass output and now I have the bass level at a more than ample enough level. Also, these cans respond to EQ easily. A simple bass boost using EQ gave me the DT990 bass quantity.
Mids & Highs
Mids and highs extension is excellent. At times, the highs can be irritating at higher than usual volumes, especially when using the Xonar as a source. The uDAC is a far smoother and more forgiving DAC. The drums are crisper, the guitar is most melodic, and the vocals are more alluring.
I love these pros for everything! Alternative music, R’n’B b, and classical sound awesome. rock and metal seem to be less enjoyable using these compared to the dt990. but overall, the jump in SQ warrants a thorough listen to all of my music!