Okay - here's my "feature length" Raal SR1A review. I'll cross post this under Head Gear in a day or two. R-r will be at Canjam Singapore (via SLT technologies) and I'm going to try to talk Danny into getting a booth at Canjam Socal. If you're at either show, definitely go and check them out!
Disclaimer: In exchange for my feedback and testing reports of amp pairings, Danny McKinney provided me with a pre-production SR1A (formerly named SRH1A) loaner unit and, after deciding to pull the trigger, I also received a production version of the headphones at a small discount. Most of this review was written with the pre-production set. However, Danny has assured me that the loaner is identical in design and signature to the final version, and I have not been able to notice a sound difference between the two sets.
Introduction:
The Raal Requisite SR1A review has been a particularly difficult one to write. Alongside the AKG K1000 and Mysphere 3, the SR1A’s are part of a very exclusive group of headphones that have neither earcups nor an enclosure. The soundstage, energy delivery and imaging of these “ear mounted speakers” are different from that of conventional headphones. For the K1000 and Mysphere 3.2, both of which use more-or-less conventional, power-hungry dynamic drivers, that’s where the differences (mostly) end.
Not for the SR1A. The SR1A uses driver technology derived from Raal’s aluminum ribbon tweeters, an unprecedented move among headphones. In more ways than one, the SR1A’s signature is a
massive departure from what we’ve come to expect TOTL headphones to sound like. And while I admit to rolling my eyes whenever I see the words “speaker-like” in a headphone review, I can mostly go straight-faced on the claim that, to some extent, the SR1A’s don’t really sound like headphones.
Adding to the challenge of writing this review is the sheer, electricity-bill increasing amount of power that the SR1A’s require. If you don’t have and aren’t planning to get a speaker amp that’s
at least 150 wpc into 4 ohms, there’s little point in reading any more of this review. The numbers that Raal Requisite list are not general guidelines like the K1000’s 8w+8w sweet spot, they are hard targets that must be hit, or else you may not be able to enjoy them at a comfortable volume. No headphone amp will work with these, and direct A/B’s against other cans become a non-trivial task.
Sufficient to say, this review has forced me to put in work. The short of it is that whether you will like these headphones is largely a matter of both taste and the strength of your source and/or files. Personal preferences aside, the SR1A’s are arguably the single most exciting new development in the summit-fi headphone world since the advent of planar drivers. Raal and Requisite Audio have demonstrated that, in contrast to chasing the relatively incremental on planar and electrostatic designs, radical departures from the norms of headphone design can still lead to radical gains.
I need to give a massive shoutout to Goodwin’s High End, where Alan and Dana practically made this review possible by giving me access to an incredible selection of high-end speaker amps and literally spending hours helping me set up demo systems. If you ever find yourself in the greater Boston area, definitely consider checking their showroom out.
Build quality and Design
The SR1A’s are built like a piece of professional equipment. They don’t quite have the loving craftsmanship and polish of Final Audio or Ultrasone’s limited edition lineup, but the thicker-than-usual steel headband guide and extensive use of carbon fiber lends itself to a sturdy feel. Absolutely nothing on them feels delicate, as if they’re meant to be thrown around in a busy recoding studio. The heavy-gauge Pelican case that comes with the headphones adds to that perception. Opinions might differ, but I like the Pelican's functionality over a wood presentation box. The Pelican is so well-built that I wouldn't hesitate to check it in on a flight.
Adding to that durability is the amazing modularity of these headphones. The cable, cushions, headband, and even the ribbon driver “cartridges” are entirely user-replaced. I mentioned in my Mysphere 3.2 review that I love modularity in headphones, and the SR1A runs with the idea straight to the end zone. Want a plushier headband? Grab any random piece of leather, punch a couple holes, and that’s your new headband. Had the misfortune to blow a driver from an amp short? Cartridges are $150 a pop. I should mention that Raal Requisite is promising a 5-years warranty guarantee on these - a rare thing for headphones.
The cable that I received with the production SR1A’s is extremely stiff, being solid core 24 awg silver plated copper. However, Danny mentioned that he didn’t get the production-version cable material in time for my pair. Subsequent orders should come with a more pliable, stranded cable in the same gauge and material. It should be noted that cable resistance is
critical to the performance of the headphones. The adapter box is design to take 0.2 ohms of net load on the headphone-facing end, and the net resistance of the cable should
absolutely not exceed 0.2 ohms. This means a minimum of 24 awg wire for a cable of roughly 7-8 ft, and a minimum of 20 awg for a cable of 12-14ft.
It should also be noted that the wire goes from dual 3.5mm trs jacks (the supplied jacks are trrs, but the pinout bridges the second r and s) to a
female 4 pin XLR jack, with the male jack on the adapter box. This is to prevent the user from accidentally plugging the headphones into a normal headphone amp. With only 0.2 ohms of total resistance on the cable and drivers, powering an amp on with the headphones directly plugged in will immediately cause it to go into protection. One thing I should mention is that I’ve found it difficult to source high-quality stranded wire that is sufficiently thick for the headphones, but Raal Requisite does offer replacement cables at a variety of lengths and the appropriate thickness.
The supplied, passive adapter box takes in up to 150 watts for the purpose of properly loading up the amplifier and not delivering too much current to the drivers. If I understood Alex’s explanation correctly, the box’s 5.6 ohms of internal resistance effectively turns the voltage-drive of the speaker amp into a current drive system, solving the problem caused by the ribbon drivers being massively
less resistive than the cable itself. The box also limits how much power can be loaded onto the drivers to prevent the drivers from physically hitting the chassis. The downside is that you‘re not only throwing out power from the amp - unless you’re running a Class D amp you’re getting a far greater than 1:1 ratio of heat vs. power delivered - but also up to 150W of excess power from the box. It’s great if you’re in Boston during the winter, not so great if you’re in a warm area during the summer. “That is not an unfortunate circumstance”, as Aleksandar Radisavljević, founder of Raal Ribbon and the lead engineer behind the SR1A says, “systems approach perfection when their efficiency approaches zero”.
(This is the engineering sample pair, with white instead of black foam in the driver baffle)
Ergonomics
Ergonomics are weird, but surprisingly good. The headband allows for an immense amount of adjustability since you can add mounting holes as needed. There is a “reinforcing strap” that goes over the back of your head that is supposed to prevent the headphones from falling off your head. On the production version I’ve found this to be largely unnecessary: the headband does a great job of keep the speaker on your head and properly centered.
As with other fully open designs, my advice is to spend some time figuring out the best configuration for your ears when demo’ing them. The Mysphere 3.2’s, for example, need their drivers to be in a “sweet spot” relative to your ear canals to perform optimally. With the SR1A’s elongated, 4x1 inch drivers, tolerance is much better along the vertical axis but driver placement relative to your ears is still crucial. Opening them up too wide results in a massive horizontal sound stage with no depth, and not opening them up wide enough results in murky imaging as the perceived image from the two drivers overlap. I find myself enjoying them most when the drivers are push forward to the same plane as my temples at a shallow, roughly 35 to 40-degree angle away from parallel, but you experience might vary depending on the size and shape of your ears.
Once you do get the drivers to a good location, comfort is very, very, very good. The headphones are reasonably light at 450 grams, and they feel even lighter because most of the weight is closer to your head rather than in the ear cups. They don’t have any “clamping” effect on your head, and pressure from the headband is distributed perfectly. I can wear them for hours with zero physical fatigue - the same can’t be said for just about every one of the SR1A’s major competitors.
However, two ergonomic issues stand out to me. First, the headphones simply cannot be used while lying down. This is a problem shared with the Mysphere 3.2, but while the Mysphere 3.2 is merely uncomfortable because of the position of the cable exit, the SR1A’s will fall straight off your head. I love listening to music right before bed, and the SR1A’s are just not suited for this task. Second, the fit is just loose enough that, if you walk around with them or tilt your head too far forward or back, they can slide out of alignment and have to be pushed back into place. This is mostly an issue for me because I like to have headphones on while soldering or making cables and need to bend over or reach around for stuff.
The SR1A’s are a pretty great option to wear while working at a desk, but the lack of any noise isolation whatsoever is something to keep in mind. The SR1A’s have less isolation than most open-back cans, and if you have a computer (or an actual, fully stocked server rack like me) in your bedroom you will hear the fans and drives over quiet music. They are also
loud - the lack of isolation goes both ways, and the driver design puts them further away from your ear canals than most other headphones. You may need to be mindful about noise if you live with a roommate/spouse.
General Sound Impressions:
The first thing that stands out when you listen to the SR1A’s is the blistering speed of the cans. Ribbon drivers have so little mass that their movements are much faster and more precise than traditional driver technology. Energy delivery has no perceptible lag across the entire frequency range
whatsoever - the cans go from 0 to 10 and then 11 immediately, without hesitation. The speed and the dynamic range lends to a refreshing “crispness” that I simply have not heard in any other headphone system. Transitions on the Abyss 1266 Phi or Stax 009 sound downright indecisive and plodding in comparison. When you first put them on, music almost seems sped up because everything is being attacked so rapidly. My mind went from “is my music at 1.1x” to “hot damn that’s fast” to “should music even be this fast” to “I guess this is my speed now” in the first hour I had them on.
The second thing that stands out is the soundstage. The size of the soundstage is extremely large, substantially bigger than just about every other pair of headphones that I have tried, with the Mysphere 3.2 being a not particularly close second. More impressively, when you get the SR1A’s in the right spot, you feel as if much of the soundstage is actually outside of your head. The staging not quite similar to that of a real pair of desktop speakers, but similar enough that you can
almost believe that sound is coming from drivers mounted in front of your face, and not to the side of it. The best way I can described the SR1A’s soundstage is that it’s about 30% speaker mixed with 70% headphone.
The treble and midrange speed is striking on the SR1A but nowhere near as striking as the
bass speed. You won’t truly appreciate how much energy delivery lag cans like the Abyss and LCD4 have in their lower register until you’ve tried the SR1A. Bass is on the lean side on the SR1A and technically speaking, the drivers bottom out at around 30hz as opposed to the single-digit extensions on summit-fi planars. But when the SR1A’s go to 30,
all of the energy is there in the blink of an eye. The superb delivery lends itself to class-leading "perceived" bass extension, and I never felt that the 30hz floor was a limit factor in any way.
The SR1A’s have arguably the most technically impressive and resolving treble range in any headphone - the ribbons pull out an abundance of detail, and treble structure is impressively solid in spite of the amount of energy being thrown around. While speed lends the perception of detail in the treble range, the actual amount information is also superb. The treble response is highly linear though, and if you are sensitive to sibilance, they do have the potential to be sibilant with neutral amps. If you want to listen to the SR1A’s as if they are a pair of traditional headphones, a strong KT88 or KT150 amp will introduce some treble rolloff and shave off the perceived “hotness” that people often associate with linear treble. However, strong solid states will also produce perfectly smooth treble, albeit quite a good amount of it.
That said, there is no getting over the point that the SR1A’s are
energetic, highly analytical, literally neutral cans. Just about every headphone and most headphone amps on the market very subtlety roll off the treble range to aid in perceived smoothness, and people vary in their ability to handle lots of treble energy. If you're someone who likes to pair something like the LCD4 with 300b amps and enjoy that kind of euphoric, darker signature, you probably won't find an amp that will darken the SR1A’s enough for them to sound pleasing to your ears. But for people who like metal, electronic, or treble-heavy synthetic music - the treble performance on the SR1A alone is worth the price of admission.
The midrange on the SR1A is an interesting discussion, something on which my views have evolved as I’ve had these for longer. When I received them, my immediate reaction was that midrange imaging was a little soft and recessed. In retrospect, the midrange is actually so resolving that it exposes the flaws in your files and pushes them right into your face - the vocals felt slightly soft because the cans put a spotlight on the softness in a way that the Abyss and the Mysphere didn’t. Switching to masterfully recorded and processed vocals completely got rid of the softness problem. The SR1A’s midrange is also not recessed
per se - if the mastering doesn’t do a great job of positioning the vocals, the SR1A’s won’t emphasize or embellish the imaging of the vocals for you.
However, the midrange is still quite lean by headphone standards, and the speed takes away some of the “emotion” in vocal performances. Conventional wisdom on headphone midrange performance values clarity of imaging and "lushness" which is often associated with slightly warmer tuning. And even if midrange frequencies are not emphasized, the slower response speed of dynamic and planar drivers is what we are generally comfortable with as headphone enthusiasts. And the fact that response speed slows with lower frequencies helps with perceived clarity of vocals relative to the bass range.
The SR1A's are not even in the same post code as that comfort zone. Is a lean, accurate, hyper-fast, and almost too revealing midrange worse than a slower, thicker, lush, more "emotional" midrange? I can see convincing arguments for both positions and ultimately, whether you’ll like these headphones for vocals comes down to this question. That said, for someone more receptive toward a neutral signature and leaner imaging, the SR1A's with the right amp does have the capacity to be a vocal powerhouse, especially with extraordinary well-mastered files.
Assuming that everything is being driven exceedingly well, the Mysphere 3.2 - a free-floating dynamic driver design that’s about as perfectly optimized for human voice frequencies as drivers can be - is still my choice for the strongest midrange imaging and doesn't trade off much midrange resolution against the SR1A's on any system. The Abyss 1266 Phi's midrange is arguably a tiny bit more pleasing in its imaging, thicker and more full-bodied but isn't quite as revealing as the SR1A. And while the LCD4 is the least resolving, thickest and most "lush" of the bunch, I don't think that resolution or imaging is a substantive concern with any of these headphones, if you can drive them to their full potential.
Performance wise, what Raal and Requisite has accomplished is not just technically impressive but
unprecedented. You will not have heard a pair of headphones with more resolution, a bigger soundstage, or with faster transitions. The faults I perceive can mostly be chalked down to deliberate design decisions - at the end of the day, Raal will sell more of these things to high-end recording studios and high-power sound engineers than they do to audiophiles, and those people will prioritize clarity, resolution and a truly neutral response. If you believe that the perfect headphone should be a neutral “pipe” of music from the amp to your ears, the SR1A’s come meaningfully closer to that goal than anything else that’s currently on the market.
Amp parings:
Raal made extensive use the Benchmark AHB2 during their development of the SR1A, and while I have not experienced this particular combination, the AHB2 is an excellent power amp and I have no doubt that it will work well with the SR1A. Here’s a list of the amps that I have tried the SR1A’s on, in no particular order:
Nagra Classic INT Just barely powerful enough for the SR1A’s, the Nagra has amazing midrange density and is superbly clean with the SR1A’s. I think I would have went for a more powerful amp with more power reserve if I were shopping a new high-end integrated unit right now, but the INT driven with the Nagra Classic DAC is still my go-to system for the SR1A’s with most types of music.
Simaudio Moon 600i Exceedingly neutral and polite, one of the better value propositions for driving the SR1A. Among the amps listed here, this one is probably the least flavored. It does sound a tiny bit boring with the SR1A, although if you really like an uncolored and transparent signature this amp could be a great choice.
Octave V80SE One of the three tube amps that I’ve tried with the SR1A. Also slightly underpowered but not as much as the Hegel Rost. The tubes slow down the SR1A just a bit and adds warmth to the mid-lower midrange. Feels like a more “tube” amp than the REF 75 but I didn’t get a chance to listen to them side by side. Treble is rolled off but still very fast, much faster than the 1266 phi with a fast solid state amp. The KT88 tubes do add a slight bit of “graininess” to the midrange that I didn’t like as much.
Audio Research REF-75 On the more neutral side of the V80SE, and also slightly underpowered. I ran this directly from the the Berkeley Audio Alpha DAC 2 and the combination worked reasonably well. I want to say that this amp is also slightly more detailed and refined than the V80SE, but I’m not sure how much this has to do with the V80SE being used as an integrated, and the REF75 being driven straight from the DAC.
NAD C368 This is the cheapest amp I’ve tried the SR1A’s with. The build-in DAC on the C368 is awful and borderline unusable. However, moving to a Berkeley Alpha DAC series 2 resulted in a surprisingly listenable system. The pairing compared not unfavorably in resolution and has superior dynamics to driving the Abyss 1266 phi's through a WA7 or nx03 with a similarly strong DAC. A sample size of one is not quite representative but I would expect the SR1A to be very listenable on most power amps in this price range.
Hegel H190 The built-in DAC seems to punch at or above its weight, and the amp has a light, clean and smooth signature, if a tiny bit lean and indecisive compared to stronger stand-alone power amps. The headphone jack is actually driven by the same circuitry as the taps and does fairly well with both the Ether C Flow and LCD3. The SR1A is pretty good on this amp - transparent, clean, with pretty good resolution for the price of the system. If you're looking for a simple, no-fuss solution for the SR1A that also works with normal headphones, the H190 seems like a solid value proposition.
Hegel Rost shares the H190's signature but has less grunt. On only 75 watts of output at 8 ohms you can feel that the SR1A is struggling a little with bass extension, although loudness was not an issue for me. For the price difference I think that the H190 is clearly the better option, but I wouldn't mind using the Rost with the SR1A's on a day-to-day basis.
Spectral DMA 150s2 + DMC 30ss This is the Spectral setup that I run at home. The 30ss is much quieter than the DMC 30 and with the SR1A the combination is sharp, clean, bright and, above all, insanely fast. Composure is somewhat impacted by response speed, though, and the combo is not quite as composed as the Nagra INT or even the 600i.
Older Spectral setups seem to have a “minmax” effect on the SR1A. Speed, dynamics, and clarity of imaging are pushed to the extreme but at the cost of coming across as brittle and somewhat shouty. I don’t like this combination for anything except electronic and synthetic music, but with those music types performance is absolutely extraordinary.
Spectral DMA 240 + DMC 30sc This is the Spectral setup that I
want to run at home, and will probably eventually upgrade to. You’re still getting the lightning quick response, the punchy bass and the clarity, but the new-generation Spectral’s stay dignified and smooth where the older systems get harsh. Resolution is absolutely superb on this system, and I love how the treble stays composed and non-fatiguing in spite of being the absolute fastest treble I have ever heard. The system is whisper quite on even the Mysphere 3.2.
Thrax Spartacus 300 I did, in fact, manage to find a
300b amp that has enough wattage to drive the SR1A. The Thrax uses 6 300b tubes per side to go up to more than 60 wpc. Nominally underpowered, the amount of current from the Thrax is such that it seems to overcome deficiencies that typically arise from driving the SR1A’s with underpowered amps: bass is surprisingly good with the SR1A’s and the midrange is sweet and lush in a way that I have not heard on any other amp. For better or worse, the “ribbon-ness” of the SR1A’s are substantially mitigated by the amp, they slow down, the bass loosens up, and they simply sound like an overwhelmingly good pair of headphones, incredibly resolving and with accurate imaging.
The combination is wildly impractical, and I didn’t feel that the system added anything to technical performance over the “merely” $25,000 Spectral monoblocks. However, it is a testament to Raal’s engineering that you could drive the SR1A’s with amps at this level of performance, and they still allow the amp’s highlights - the composed speed of the Spectral, the sweetness of a pure 300b design - to shine through in a meaningful way.
To SR1A or not to SR1A?
The more I listen to the SR1A’s, the less things I find to criticize it. It’s not that they are perfect headphones - but instead of flaws coming from engineering limitations or oversights, their design trade-offs are a necessary aspect of making these headphones work, in the sense that they are uncompromising tools for professional recording and mastering. The bottom line is that they aren’t trying to cater to audiophiles. However, in spite of all that and other, not insignificant caveats, the SR1A’s are
amazing audiophile headphones
if you can live with its limitations.
For people who run sufficiently strong speaker setups and who are looking into a headphone system, the SR1A’s appeal is self-evident. You get to keep everything you like about the speaker setup, right down to literally running it on the same taps, and with headphones that sound more similar to a pair of speakers than any other pair of headphones. For people who want a single headphone system for both personal listening and professional audio, the SR1A’s are arguably the single best double-duty option on the market: they’re simply too good of a production-level tool to pass up.
Otherwise, you need to be willing to invest in a strong, probably quite hot, large and power-hungry amp that may not work well with your other headphones, and be okay with a realistic amount of treble energy, and give up any notion of noise isolation
and deal with a non-enhanced amount of emotion in vocals and the mid-to-bass range. Then, with the SR1A’s you are rewarded with incredible, class-leading resolution, staging, speed, and just about the most dynamic music representation attainable in the headphone world. These are, as a matter of fact, higher-performing headphones than the Susvara, Abyss 1266 Phi, LCD4, Stax 009 and the Mysphere 3.2. But they are also a more constraining and demanding system than any of the other options.
And while I am perfectly fine with the SR1A’s in their current form, I would like to see Raal and Requisite make a more concentrated push toward the head-fi market as opposed to the professional - the modularity of the headphones means that they could sell a speaker adapter box with treble rolloff and a bit of midrange coloring, and all owners of the SR1A’s would be able to enjoy that option at a relatively small extra cost. Commenting from a marketing standpoint - a slightly more “hi-fi” tuning would go a long way in terms of making these sound less alien to audiophiles, especially those who grew up with tube amps and vinyl.
However, that departure from conventional head-fi equipment is also what makes the SR1A’s truly special. It’s probably the case that most people who are reading this review, and who are actually in the market for a $3,500 pair of headphones are not entirely unreceptive toward crazy ideas. And as crazy ideas go, Raal and Requisite have accomplished something remarkable: going from scratch, up against headphone designs and technology that’s been iterated on and perfected for the better part of a century, and still managing to be in the same conversation as - if not outright besting - the biggest players in the market. If you’re not wholeheartedly against a lean, fast, and relatively bright signature, the SR1A’s offer the rare opportunity of owning something unapologetically, fundamentally different, that somehow managed to also be great.
