Stax SR- Lambda vs. SR-LNS vs. SR-303 & Koss ESP/950

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Comparative review

Stax SR- Lambda vs. SR-Lambda Nova Signature vs. SR-303, with special guest Koss ESP/950


For a long time I wanted to do a short comparative review of my Lambda frame headphones, unfortunately I never had time. So instead of doing a full-blown A/B review a decided to listen to each headphone with the same album whenever I had time and afterwards do a fast off the head on the head A/B comparison on a few of my favorite records and songs. As I listened I took notes, but I never formulated them as a review. Only now that I have a little bit of free time I am putting my notes in a “review format”. One of the headphones that I am reviewing, SR-lambda normal bias, is not longer in my possession. After owning it for a year and buying up electrostatic headphones like crazy I had to sell it to bring back some money to finance a new amp. You will see why I made a decision to sell it after reading my review.


Let me first describe my system and music preferences as well as listening habits so that you can take a way the most form this review. I listen mostly to experimental rock, jazz and to lesser degree to electronic music and metal. I almost never listen to pop, singer songwriter, and mainstream rock. I truly hate new light jazz and new rock music, as I am a relic and admire the 70’s Kraut rock and prog rock movements.

I also do not listen to a lot of classical music, with exception to some modern classical music like Cage, Glass and or occasional chamber orchestra piece.

Sample albums:

Naked City (John Zorn) – Radio

Roxy Music – Roxy Music

Andy Summers - Charming Snakes

Wolfgang Muthspiel Trio - Timezones

Art Blakey/Jazz Messengers - A Night In Tunisia

Medeski, Martin & Wood - End Of The World Party

Spazztic Blur - Spazztic Blur

H.N.A.S. (Hirsche Nicht Aufs Sofa) - Küttel im Frost

Moloko - Do You Like My Tight Sweater?


Amps: Stax SRM-1Mk2Pro

Sources: Pioneer PD65, Museatex Bitstream DAC

Cables: Glass TOSLINK, Omega Mikro

With my musical taste out of the way let me describe the system that was used for majority of my listening sections. My source is comprised of Pioneer PD-65 used a transport feeding, via glass optical, a Museatex Bitstream DAC, out of the DAC I use Omega Mikro RCA cable into Stax SRM-1Mk2Pro. Koss is used out of the Stax pro jack with ericj made adapter cable. After selling SR-Lambda I upgraded to SRM-T1S with the rest of the system remaining the same and Stax SRM-1Mk2Pro migrating into my speaker system as a dedicated Stax amp for occasional living room listening sessions.

Let me stop with the lengthy introduction and go into review. I am not going to list the specific songs and or albums and to a step by step walk through I will simply state my impressions about sound signature of each headphone what I like and what I do not like about it. As the last step I will compare them directly.


I had SR-Lambda normal bias for about a year, it was my first real electrostatic headphone. I used it with SRD-6, 7 and SRM-1Mk2Pro. I enjoyed it the most out of SRM-1Mk2Pro.

SR-Lambda is an amazing headphone that has a well balanced and somewhat laidback sound. There is a slight forwardness in the midrange but it is in no way aggressive or abrasive, in fact the mids are smooth and have an excellent tone. The detalization is excellent and the low level details stay in the background as they should but make themselves apparent if one listens for them. The bass is deep and very textured but lucks slam that dynamic headphones are so adept that presenting. On most kinds of music SR-Lambda was able to perform admirably. Music never became a mushy mess, even with very fast and technically demanding music Lambda still was able to keep composure and present all instruments and sounds cohesively. The midrange is where Lambda shines, it sounds very good with vocal tracks; unfortunately I do not listen to a lot of music that takes the best advantage of what Lambda does best. When really pushed SR-Lambda fails at extending as deep or as high as its modern descendants, more about this latter. The speed, decay and attack are excellent as with all electrostatic headphones. Transient response is also amazing. Soundstage that headphones present is wide and deep but not very high and still mostly remain in this defined space slightly large than my head. The instruments are positioned in space accurately but are slightly blurred. Overall SR-Lambda is amazingly good for 30 year old headphones.

SR-Lambda Nova Signature (LNS)

LNS is one of the last electrostatic headphones that I purchased. I was curious about LNS for the long time as it supposedly was an attempt at a different sound signature as compared to SR-Lambda Signature. The first thing that I notice when I plugged LNS in was how linear they were. There where no apparent colorations, bumps in FR or attempts at alter the sound spectrum. They were very polite extended on both ends and flat. The bass was much better than SR-Lambda’s even more texture and even a bit of slam. Overall sound signature is similar to SR-Lambda but without the midrange warmth and slightly soft sound. Soundstage is also larger and more accurate with better positioning and better vertical dispersion. LNS is not an exiting headphone but it is very accurate revealing and has a great quality of being hyper detailed yet a bit laidback. The speed, decay and attack are excellent and are even better that with SR-Lambda. The sound is a bit forward in the mids as far as positioning goes, as with all the Lambdas, but not at the expanse of the soundstage or musicality. Over all LNS is my favorite Lambda frame headphones it does all of the things great and has not glaring issues that would prevent me form enjoying the music and forgetting about the headphones.

Stax SR-303

I got SR-303 after SR-Lambda to see what the modern Stax sound is all about. I do not regret it for a minute. SR-303 has a more aggressive upper midrange and more forward presentation than SR-Lambda and LNS. The bass is about the same as LNS but seems just a bit punchier. The basic Lambda frame signature is here as well as great detalization, attack, decay and transient response. SR-303 is much more colored than LNS and normal bias Lambda, I think they are still less colored than SR-Lambda Signature and SR-Lambda Pro or it could be that I am just less sensitive to the coloration that SR-303 adds to the music. A bit of hotness in the upper mids does not bother me and it gives music a level of aggressiveness that sounds great with very fast rock and metal. The soundstage is a bit better than SR-Lambda but not as good as LNS, as the blurry edges that were gone with LNS are back with SR-303. In the end SR-303 seems to have a sound that is different for the older Lambdas and is at the same time an improvement as well as a step down, I guess it depend on who you ask.

As you can see I like all 3 Lambdas a lot, but when it came down to choose which one had to go I surprised myself but letting go of SR-Lambda. In the end it LNS and SR-303 had all the best qualities of SR-Lambda, but what SR-Lambda did best did not matter to me that much as it excels at vocal dominated music that is seldom my first choice when I reach for a CD or an LP. Another reason for saying bye bye to SR-lambda was Koss ESP/950.

Koss ESP/950

Koss ESP/950 sound very different from Stax amp and for the purposes of this review I will not describe how it sounds out of E/90 amp that came with it.

ESP/950 plugged in SRM-1Mk2Pro is a great headphone. It can do everything a almost any Lambda can but it has more bass slam and seems to be even faster with better attack. The soundstage is also a bit different, as Koss is even more forward in the mids than SR-Lambda. Think of Koss as SR-Lambda on steroids. Well balanced and somewhat laidback, with great tone, but forward mids. With Koss possessing so much of SR-Lambda’s best qualities it brought it up to LNS level but with it different presentation of soundstage and details that gave Koss a nice edge over SR-303 and especially SR-Lambda. I still think LNS is a more neutral and accurate headphone, but Koss seems to be better when it comes to very technical music as it can really become a speed monster no Lambda can.

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