I've been meaning to check out the advanced lambdas given their departure from ye olde lambda design to see how Stax is doing and where they're taking their products. And so I picked up a SRS-3100 a little while ago. After spending some time with the SR-L300, I find it's two steps forward, one step back. Sonics first, then a once-over outside and in. Reference is another basic lambda, a SR-202 with SR-507 pads.
The most significant change to me was in terms of staging and imaging, as you may have expected with the new angled baffles. Space in all directions is pushed out a tad, left/right channels are pushed forward slightly, and the space between L/R and center is better filled in. So with a top-down perspective, suppose one was to represent the 202's acoustic volume as bounded by the aquamarine trace, relative to that the azure trace would be the L300. Nice job by Stax here.
Response from 2 to 4kHz is reduced a bit, resulting in things like vocals being a bit less upfront. This would be a welcome change for those who can do with a bit less shout and glare present in the upper midrange with previous lambdas. Bass on the 202 starts gradually rolling off at 80Hz, reaching down to 30Hz though at which point it's nothing more than a mere sputter. With the L300, roll off starts lower at 70Hz but drops off a cliff after 50Hz. In listening, I find bass on the L300 to be preferable, with a bit more thump.
With the redesign Stax dumped the "Basic" moniker and made a couple changes to the labelling. The serif font used struck me as slightly out of place, especially since everything on the box is in sans-serif fonts, apart from the Stax logo of course. The serial number sticker is now located at the bottom of the left baffle, instead of underneath the headband arc. Considering your eligibility for after-sales service is partially determined by this serial number, putting the sticker here where it's more susceptible to wear doesn't seem wise. And then there's the asymmetry.
On the gimbal you can see a vestige of the old design, a recess that mates with a restraining tab on the driver cage. A similar tab is now on the baffle instead and bumps up against the inside of the gimbal. Pads are now flat with the baffle responsible for driver angling. This allows for the drivers to be positioned at a more forward angle vs previous lambdas, thus, most likely, the change in staging mentioned previously. Initially I was concerned by how thin the pads were and if it would affect seal, but they posed no problems in and of themselves in practice. Apart from being angled, the baffle is also flared along the rear edge. Unfortunately, the sum of these design choices cause a critical problem with fit, at least for me, in that they restrict the top of the housing from rotating past the gimbal. As a result, clamping pressure is concentrated along the top, and the bottom of the pads will not sit flush against my cheeks. Weirdly, this also makes the sound seem as if it's coming from slightly above, since the drivers are no longer parallel to my ears, but at a slight downward angle. I'm a bit surprised that Stax made this design error considering they should be sensitive to this issue, what with their experience with the 4070. I assume this is common to all the advance lambdas.
A couple last points before taking things apart, the cabling is now the wide low-capacitance type, and the driver dust cover is a thinner more transparent mesh with plastic edging. Not sure why one side of the edging needed to be wider.
Another nice new feature is that the pads are easily removable. Taking off the pads, you can see that the baffle is hollow with ribs to support the structure. The pads are attached to mounting plates, held in place by pins that go into the baffle. Even with pads in place, the new design means that there is a gap between plate and baffle on the inside rim. On the baffle, you'll find a couple of ports that go through to outside air. Of course all this means that bass will suffer vs the old design where the pads are glued directly onto solid baffle plates, but my sonic impressions suggest Stax was able to achieve an acceptable result.
Lastly, Stax gives us encapsulated drivers screwed to the baffles similar to the rest of the advanced lambdas. Stax transitioned to these resin encased assemblies for all models with the previous SR-X07 generation whereas earlier lambdas (eg SR-202) had bare drivers glued to the baffles instead. Still nice to see this kind of build even in a basic lambda.
So what did I learn? Well, it's encouraging to see that Stax continues to innovate and evolve their sound. There are some compelling ideas represented in the L300, but the execution leaves something to be desired. It seems to me their attention to detail is not quite up to the same standard of excellence as in the past. From a few recently published interviews and factory tours, I understand Stax has been hiring new employees, perhaps in an effort to get younger as their older original personnel must be hitting retirement now. It wouldn't surprise me if they were tasked with certain aspects of the advanced lambda project. Hopefully with future products we see a return to the impeccable craftsmanship Stax has so far cultivated.
A brief note on the SRM-252S since it's part of the SRS-3100 after all. For the tiny footprint, it's performance is not bad at all in driving lambdas. With the SRM-1/MK-2, there are subtle improvements in depth of image, clarity of sustain and decay, and dynamics in general, with more control at louder volumes. I'd expect even better results from the SRM-323X that is the current option a tier up from the basic amp but on the whole the SRM-252S is a perfectly capable little unit.