Stax SR-L700 Electrostatic Headphone: Review


At about the end of 2015, Stax launched three modes of headphones of Advanced Lambda series, namely SR-L700, L500 and L300. In terms of product positioning, L700 and L500 respectively correspond with SR-507 and SR-407 in the last generation (the full name of this generation is New Lambda). In respect of the core technology, L700 and L500 adopt a stainless holder for diaphragm and a brand-new fixing method. As for L300, may it be a new mode for previous generation? Today we are going to test the highest-end one among them -- SR-L700. Since all Stax electrostatic headphones should use special dedicated amplifiers to power them, we will also test SRM-353x, the special amplifier for L500. By the way, SR-L700 is priced at RMB 7,599 Yuan (about $1,189), and SRM-353X is RMB 5000 Yuan (about $783).

Technology and Appearance

Regarding previous names of Stax electrostatic headphones, ¦Ë and ¦¸ were used at the very first time, and Lambda series also indicates those Stax headphones that own a rounded rectangle diaphragm. Headphones of SR-404/407, SR-507 and so on, all belong to Lambda series. Latter on, SR-009 and SR-007 brought round diaphragms into use, and their positioning is also higher than Lambda. With the release of L700/500/300, the production of SR-407 and SR-507 was stopped. According to an announcement in the Stax official website, there are still some SR-507 in stock being sold, while no other previous Lambda products are being produced any more.

Through the picture Stax SR-407 Electrostatic Headphone - Teardown (by Soomal) in which we tore a SR-407 down several years ago, we can review the basic structure of traditional Stax headphones. As shown in the picture, a rounded rectangle diaphragm should be fixed on a holder. But how can such a thin diaphragm be fixed with evenly deployed force? It is said that this is one of the top secret weapons of Stax. The major change of L700 and L500 this time also lies here. There is a sentence in the first term in official introduction, stating that a new kind stainless material as well as a three-layer fixing method is employed. We have already contacted with someone official to confirm such technology. However, SR-009 seems to use aluminum holder. Compared with SR-009, Lambda series has a diaphragm different in shape as well as a holder different in material. Accordingly, the expressed sound style will be definitely different. Some marketing materials appear to mean that L700 adopts some technologies of SR-009. It seemed to be said so, but now we cannot find similar information in the official website any more.

The differences between L700 and L500 are similar to those between SR-507 and SR-407, among which the most important is cable. By the way, it is said that cable is the main difference between two products in one generation. L700's cable features 6N silver-plated cooper wires (or maybe mixed cooper and silver wires? Seemingly to be mixed pure silver and 6N cooper wires), while L500 adopts new HiFC wires. L700's earpads are made of genuine sheepskin leather, but L500 uses imitation leather. Either is comfortable to wear thanks to their light weights, big sizes and small inner elastic resistant. Being quite fresh, the headphone is also unlikely to squish despite the frictions made by simple holder fixing axis.

Finally coming to the appearance of L700, there are slight changes comparing to previous products, but the old and simple style is still remained. Hardly can the appearance be considered as stereotyped, for the design was quite chic 20-30 years ago. The enclosure, shaped as a brick, is made of plastic. The headband and the two main bodies are fixed simply by a plastic yoke with two holes, making it pretty easy to tear down. In addition, it seems to be quite light for such a big headphone weighted 360 grams, and so is it when being worn on. Anyway, this kind of appearance cannot be described as delicacy absolutely. Instead, it may belong to the kind of ˇ°retro designˇ±, which is further back than retro. A design like this may be scorned 7 or 8 years ago when we tested SR202, but it might be more popular than SR-009 nowadays. Going out with such kind of earspeaker, all you need is only a portable amplifier, which is alleged to be produced. The last two sentences can be read for fun.

For testing L700 this time, we prepare two amplifiers, one of which is Stax SRM-007T. Actually, this 007T of the first generation sounds almost the same with the 007TMKII in hand, but the older one sounds softer while the newer one's resolution is better. The other driver amp is SRM-353X, released together this time, which is a transistor amplifier, with FET (Field Effect Transistor) at first stage as well as Class A direct current at the next stage amplifying output. Older driver amps such as SRM-007T and TA are priced from RMB 5,000 to 6,000 Yuan (about $783 to $939), the brand-new SRM007-T MKII is priced at RMB 10,000 Yuan (about $1,565), and SRM-353X is RMB 5,000 Yuan (there seem to be discount packages). So L700 along with these two amps costs about RMB 13,000 to 15,000 Yuan (about $2,035 to $2,348). It can be quite favored for most audiophiles.

While worrying that run-in process may cause wastes of electronic tube's life, we noticed an interview by a Japanese reporter on the Stax official website, indicating that a 10-day aging test would be carried out for all components after the assembling of diaphragm and electrodes. And also, after assembling the whole units, a 10-day run-in process would be completed for all headphones. So an extra run-in seems to be unnecessary.

The main task today is to compare Stax SR-L700 only with SR-009, so there is little need to talk about the comparatives. As a side mission, we will further compare them to LCDi4 and Hifiman HE1000. For sound generating, we choose Musiland MD30 Plus and Matrix Mini-i Pro 2S audio decoders. As for HE1000 we use self-optimized Tempo Tec Fantasia B-HP headphone amplifier.

Side mission: Firstly we deal with the side mission. During the test of LCDi4, we did not explain the specific differences in treble range between LCDi4, L700 and SR-009 on account of no spoiler. As a matter of fact, we tested LCDi4 and L700 one after another, without detailed comparison, and without testing SR-009. Until recently, to prepare for testing L700, we make comparison carefully.

At that time, the article concluded that LCDi4 had a performance approaching to L700 and even SR009 with its extension in treble range, especially in the highest treble, as well as its resolution in the upper treble. But today, our conclusion is that, thanks to the in-ear design, LCDi4 defeats SR-009 by its extension in the highest treble, resolution in the upper treble, and also transient details. As long as you actually hear through these two headphones, you will not be doubtful about the description above. The advantage is easy to identify without the need for much experience. Yet, there is no surprise here, for resolution cannot fully represent audio quality. The balanced and loose performance of SR-009 and L700 in the whole treble range is better than the in-ear model. Still, LCDi4's performance reflects supreme technology strength.

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