100+ Head-Fier
RAAL requiste SR-1a Review - By WaveTheory
Pros: Resolution; spatial presentation; timbre; speaker-like presentation; comfort
Cons: Aggressive subbass roll-off below 60 Hz; incompatible with most headphone amplifiers; slides around on the head
A special thanks to user @sa11297 for loaning me this RAAL gear!



The RAAL Requisite SR1a “True Ribbon Earfield Monitor” is a truly interesting product. It is a pair of ribbon speakers strapped to a headband system that creates a near-field – so near it’s ear-field – listening experience, essentially putting a speaker listening experience in a form factor worn like a headphone. If you wish to own access to such an experience it will set you back a minimum of $3500US new, but there are plenty of accessories that have impact on the experience that will add to that cost. We’ll discuss some of those options through the course of this review. I had the privilege of giving this system, with a handful of those fun accessory options, a spin recently so let’s dig into what I found.


The RAAL seems to accomplish what it sets out to do: bring a high-performance, speaker-like listening experience into a headphone-like form factor. There are some ergonomic quirks that can limit its functionality some, but that doesn’t take away from the fact that its sound is amazing. The spatial performance is unlike anything I’ve ever heard from a head-based systems. The detail retrieval and timbre are also utterly fantastic. The bass and dynamic impact will be a bit too-lean for some but as a whole package and with the right music SR1a can be a phenomenal listening experience.


My preferred genres are rock/metal and classical/orchestral music. I’m getting to know jazz more and enjoying quite a bit. I also listen to some EDM and hip-hop. My hearing quirks include a high sensitivity to midrange frequencies from just under 1KHz to around 3Khz, give or take. My ears are thus quick to perceive “shoutiness” in headphones in particular. I describe “shoutiness” as an emphasis on the ‘ou’ sound of ‘shout.’ It’s a forwardness in the neighborhood of 1KHz and/or on the first one or two harmonics above it (when I make the sound ‘ooooowwwww’ into a spectrum analyzer the dominant frequency on the vowel sound is around 930Hz, which also means harmonic spikes occur again at around 1860Hz and 2790Hz). In the extreme, it can have the tonal effect of sounding like a vocalist is speaking or singing through a toilet paper tube or cupping their hands over their mouth. It can also give instruments like piano, but especially brass instruments, an added ‘honk’ to their sound. I also get distracted by sibilance, or sharp ‘s’ and ‘t’ sounds that can make ssssingers sssssound like they’re forssssssing esssss ssssssounds aggresssssssively. Sibilance does not physically hurt my ears nearly as quickly as shout, though. It’s distracting because it’s annoying and unnatural. Finally, I’m discovering that I have a preference for more subtle detail. I like good detail retrieval and hearing what a recording has to offer, but I prefer what many would consider relaxed and subtle rather than aggressive or detail-forward. To my ear, more subtle detail-retrieval sounds more realistic and natural than aggressive, detail-forwardness. There is a balance here, though, because detail retrieval can get too relaxed and that can sound unnatural, as well, or simply leave out important aspects of the recording. Readers should keep these hearing quirks and preferences in mind as they read my descriptions of sound.


There is a lot to unpack here. This section will be on the long side. I’ll break it up into smaller chanks as best as possible.

Buying Options

The SR1a, essentially being a pair of ribbon speakers held right next to the ears, is basically a low-impedance speaker. That limits the amplifier options available. RAAL offers several packages with the SR1a that take these amplification needs into consideration. The first is a speaker interface that plugs into the output of a speaker amp:


[pictured with my Adcom GFA-555ii speaker amp]

The speaker interface has a female 4-pin XLR headphone output on the front:


and also includes 4 pair of binding posts on the back panel along with a switch to select between using the SR1a or passing the signal through to a pair of speakers:


The speaker interface also comes with a set of 4 speaker jumper cables (2 pair) to go from your speaker amp into the “Amp In” terminals on the interface. Then, your regular speaker cables connect to the “Spk Out” terminals on the back of the interface. The back panel of the interface claims a nominal impedance load of 6Ω for the interface and SR1a together. RAAL offers the SR1a and speaker interface together in a 3500USD package. My review unit came with this speaker interface.

RAAL also offers the current-drive Schiit Jotunheim R headphone amp with the SR1a.


[image taken from RAAL’s website: https://raalrequisite.com/amplifiers/jotunheim-r/]

The package of SR1a and Jotunheim R costs $4000US from RAAL’s website.

RAAL also makes their own high-end speaker & headphone all-in-one amp known as the HSA-1b:


This amp is rated to deliver up to 40 watts per channel from its speaker output into a 2Ω load. It also has both female and male 4-pin XLR outputs on the front panel for headphone outputs. They are designed to drive the SR1a and regular headphones, respectively. This amp lists for $4500US on its own but RAAL offers it with the SR1a in a package that costs $9000US for the two. Add in the speaker interface box and the entire package is $9500US. This amplifier was sent to me be the same person who sent the headset with amp interface. The amp is an impressive product in its own right and will get its own full review in due time. Stay tuned.

RAAL also offers a plethora of headphone cable options to use with the SR1a. I’ll leave it to their website to explain all of the options (https://raalrequisite.com/ribbon-headphone-cables/). I was able to test with the standard 7-foot version and the $1050 “Studio Reference” 7-foot cable. I will comment on the sonic differences between the cables in the last subsection of the Sound section.


As stated in the introduction, the SR1a is pair of ribbon speakers mounted to a set of straps that allows it to be worn like a headphone. The ribbons themselves are well-made and in a machined aluminum housing:


The design does not enclose the ear. It’s a completely open-baffle system. There is a column of soft foam where the speaker rests against the head to cushion the contact point. This column of foam is meant to sit right in front of the ear. The ribbon assemblies are also on a hinged mechanism that allows them to move from being roughly parallel to the ear to essentially 90 degrees to the side of the head:


These angle adjustments have an impact on the sound, too. When completely closed, the bass has the most presence but the soundstage is the most narrow. When all the way open, the soundstage is the biggest/widest but the bass has the least presence. The swivel uses friction to keep its positioning. There is a fair amount of tightness to make the adjustments. Overall, that’s good because they hold their positions well. There were times when I over-adjusted because of that tightness and had to do some futzing to get things into the right positions.

To hold the ribbon assemblies to the head there is suspension-strap headband system that goes over the head, and a second strap the wraps around being the head:


The straps are of a quality leather and quite soft. The headsize adjustment uses a simple peg-and-hole system:


This system is simple and durable but only allows for coarse adjustments. There is roughly a centimeter between the pegs/holes. If your headsize falls between the adjustment levels, you’ll have to pick between it being just a little bit too loose, or just a little bit too tight. This is more problematic for the around-the-head strap. For my head, I either had to have that strap looping around under the curve of my skull in the back (below left), or get it really tight to hug tightly higher up on the back of my head (below right):


In either case I had a problem with headset sliding around my head a bit, particularly forward. If I were to look down at my desktop while working, the whole assembly would slide forward. It never fell off, but needed readjustment, and would often push my glasses forward as well. The fit seems best for sitting in your lounger, kicking back (but not reclining much), and enjoying the music. The sliding around on the head is just a bit too much for anything else. Because the system does not enclose around the ear like a traditional headphone, there is less friction on the sides of the head to take advantage of, which contributes to it sliding around with movement.

Provided you’re still enough to minimize the sliding, the comfort is actually quite good. The clamp isn’t very tight but also not very loose. I never noticed too much pressure on my jaw. I didn’t notice any hotspots either. The headband straps do a good job of distributing weight. It is a set you could take a nap in, so to speak.


The cable entry system is dual-entry with 3.5mm jack on each ribbon. Curiously, the RAAL cables are terminated with 3.5mm TRRS plugs at the headphone end:


Truthfully, I’m not sure why. All the cables have 4-pin XLR connectors on the amp end so there should only be a need for 2 electrical contacts per side. The amp end of each cable is also a female connection. I’m pretty sure that’s done to prevent you from plugging the SR1a into any generic balanced headphone amp and blowing things up.


Test Gear

For all testing the source was local FLAC files ranging from 16-bit/44.1-KHz up to 24-bit/192-KHz, local DSD files, and streamed FLAC (same bit rates) from Qobuz, all using Audirvana 3.5. On my desktop system the PC was connected to a Singxer SU-2 USB bridge then an AES connection to a Berkeley Alpha S2 DAC. The RAAL HSA-1b carried amp duties on this chain. The other chain used the same PC but then streamed all the same filetypes over my local network to an iFi Zen Stream. The Zen Stream was connected via an Audioquest Forest USB cable to a Chord Hugo 2. The RCA outputs of the Hugo 2 fed an original Schiit Saga preamp which in turn connected to an Adcom GFA-555ii speaker amp. RAAL’s speaker amp interface box then connected the amp to the SR1a. I also did some listening by using the Saga’s second pair of RCA outputs and feeding my Polk PSW-505 subwoofer to get a feel for what using the SR1a with a sub would be like. I used the higher quality Studio Reference cable for most of my listening tests, until I set out to see if I could hear differences between the cables.


I’m going to do a subsection just about presentation because of the unique-ness of this product. It really does sound like speakers. The imaging is mostly out-in-front as it is with speakers. However, the room reflections are essentially eliminated so the challenge of speaker placement doesn’t come along for the ride. But, over and over again, listening to the SR1a reminded me of listening to speakers that just happened to be close to my head.

Sound Signature

I ended up landing with the ribbons angled at about 45 degrees to the plane of the side of my head most of the time. Here the signature was somewhat bright with more emphasis on the treble than on the bass. The bass gains a bit more presence the closer the ribbons get to being closed, but these are never going to be bass monsters. In fact, there is a fairly aggressive roll-off in the subbass below 60Hz with very little going on in the deep subbass. This roll-off becomes particularly noticeable in a track like “Mountains” from the Interstellar soundtrack. The descending bass that happens following the large brass swells doesn’t muster much in its lowest reaches. However, above that point the bass presence seems in line with the mid-range presence, with the treble being just a little bit higher yet, although not by much. The brightness in the signature is also quite smooth. So while it’s a brighter sound, it never came across to me as sharp or piercing. There is great balance between being sparkly and being controlled in the top end.


Um, wow. The only other piece of audio gear I’ve heard that challenges the detail retrieval ability of the SR1a is the Abyss Diana Phi. I haven’t had the chance to hear those in direct comparison, but the levels of detail I heard from the 1a reminded me of the Diana Phi…EXCEPT that the 1a was much more relaxed in its detail presentation. Basically, everything is there. Room reverbs, the initial strikes on cymbals followed by the tone, texturing, the zizzy sound of bows on strings…it’s all present and never forced. The way it’s presented is very natural but still easily audible.

Spatial Presentation

Beyond being speaker-like, I flat out haven’t heard soundstaging, imaging, separation, or depth layering of this level before. For me this is the new standard. There is amazing accuracy is where instruments are placed to go with a convincingly realistic since of space between them. The listening space is also rendered well. In live recordings like classical or orchestral works where there is a stage, that sound from that stage is reproduced quite believable with excellent spatial accuracy, but there is also a convincing since of space beyond that stage. In other words, the SR1a is a strong in reproducing room sounds and transporting a listener to a concert hall or arena.


For the most part, voices and instruments sound like excellent reproductions of what they sound like in the real life. In other words, the timbre is excellent. I didn’t notice in shoutiness or honkiness in the mids – which I am prone to hearing. If I had to nitpick I would say that some bass instruments sounded a little thin because the subbass roll-off reduced the presence of some of the lower harmonics, but outside of that the timbre is another true strength of the SR1a.

Macro- and Microdynamics

Let’s first differentiate between these two terms. Macrodynamics refers to the ability to punch, slam, hit, or “slap”. It’s the physicality and impact of the sound. Microdynamics are the small changes in volume and the ability to resolve small changes in sound intensity. Resolving these small changes well help with things like texture. The SR1a is a strong performer in microdynamics. The sound is very textured. This microdynamic prowess also contributes to it sounding very high in resolution as textures are pulled out beautifully. The SR1a is not a particularly macrodynamic piece, though. There is a lot of speed to the sound. The mids and highs reach quickly and clearly. Yet to me, they aren’t impactful. If you’re a listener who enjoys the punch and physicality of brands like Abyss, Fostex, Focal, or to a slightly-lesser-extent Audeze, the SR1a is likely not the headphone for you – or at least not a candidate to be your primary headphone.

Supplementing with a Subwoofer

I mentioned running the SR1a off my speaker amp and using subwoofer with it above. I’ve heard of some people enjoying listening to headphones/earspeakers with a sub, and I’ve long been skeptical of its efficacy. Why? Phasing. It always seemed like it would be really hard to correct for the time misalignment by having transducers for the mids and highs right by the ears and then the bass transducer some number of feet or meters away. What bass the headphone produced would reach the ear earlier, and in situations where a bass tone lasted long enough that both the headphone’s low end and the sub’s delayed wavefront could be heard simultaneously, there would most likely be some wave interference changing the shape of the waveform from what was in the recording. Even with an effective crossover, there are also concerns like the higher pitched sounds of the mallet of a bass drum hitting the skin reaching the ear first and then a delay before the weight of the low tone arrived. So…I put the SR1a on and got as close to my sub driver as I possibly could. Now that became a very macrodynamic experience, hahaha. It took some tweaking to get to a subwoofer volume level that didn’t seem crazy out-of-line with the loudness of the SR1a. Once I got that done, there were a few tracks where I could hear some phasing oddities in the 80ish-100ish Hz range. Mostly, that sounded like a bit of tonal fluttering – not driver fluttering – that was likely the effect of wave interference creating to maxima in and minima in the waveform. They sounded a lot like the beats once listens for when tuning a guitar or piano. The SR1a is still giving noticeable information down at least that low, rolling off mostly below 60 Hz, it seems. I set my sub’s crossover to 60 Hz (its lowest setting) and I didn’t hear that fluttering those phasing issues were producing on the same tracks I had noticed it previously. With all that done, I settled in for some punchier, more dynamic music, and some music that needs crazy subbass reproduction. It was readily apparent that my poor Polk subwoofer (my 2 channel system is nowhere near up to the same caliber as my headphone gear…yet) is not on the same performance level as the SR1a. From high frequencies to low, the experience was like detail detail detail detail BOOM! Even so, it was an overall enjoyable experience and worked well as a proof of concept. “Gypsy” by Fleetwood Mac sounded great. Ditto on “The Less I Know the Better” by Tame Impala. The SR1a with the subwoofer became a much more dynamic, punchy, engaging experience with that kind of music. Grandiose pipe organ music also became fuller and more captivating. Toccata & Fugue in D Minor (AKA the Dracula theme) by Bach and played by Peter Hurford was nothing short of awe inspiring. It sounded enormous and the sub brought the subbass rumble and feeling the SR1a couldn’t provide on its own. Together they created a listening experience that rivaled a huge 2.1 channel system. Now, the Hugo 2 + Saga + GFA-555ii signal chain was not as resolving or spatially coherent as the Alpha S2 + HAS-1b on the desktop chain either, but I’m more comfortable saying now that with enough tweaking and a phase dial on higher quality subwoofer (rather than just a 0 or 180 phase switch) the SR1a and that subwoofer could create an amazing listening experience that many will find truly compelling.

Funny story though…after playing around with the SR1a and sub together and emerging from my basement listening room to see the rest of the family I got lots of strange looks. Eventually one of the kids said “Why just the bass this time? Where was the rest of the music?” Yeah, it needs to be said that using a subwoofer with a head-based listening system does defeat one of the advantages a head-based system brings: more privacy and less interference with the world around you.

Amp Pairings

I touched on this briefly in the preceding section. The SR1a still sounded quite awesome on my signal chain with the GFA-555ii amp. It was not quite as clear or clean and the staging wasn’t quite as cohesive and convincing as the desktop chain with the HSA-1b. Still, it was very impressive and among the best I’ve heard from a head-based system so far. The performance on this amp suggests to me that if you already have a speaker amp that you like and is reasonably powerful, the $3500 option for the headset and speaker adapter box is quite a deal. What I didn’t try as it would require a lot of reshuffling and then waiting for things to warm up again, is using my Berkeley DAC with the Adcom speaker amp. So, some of the performance loss is from the desktop chain is likely due to using the Hugo 2 as the DAC. Still, the Hugo 2 is no slouch as a DAC and it bears repeating that the speaker-amp system still sounded wonderful through the SR1a.

Music Matches

Without a subwoofer the SR1a is at its best when playing music that doesn’t rely much on active dynamics or subbass presence. This includes a lot of classical, chamber music, smooth jazz, some folk music, etc. Where it doesn’t work as well, at least for me, is with the bigger and more bombastic classical works (think Beethoven’s 5th or 1812 Overture here) and rock, metal, hip-hop, EDM, etc. That’s mostly because it just doesn’t have the subbass presence or impact that make a lot of those genres work. It’s not that it sounds bad – the detail retrieval and staging and timbre are all there doing a great job – it’s just a case of not being able to deliver that thick, bass-heavy sound that often defines those genres. Some may still love these genres on the SR1a because the bass isn’t as important to them. I can understand that. I’ll just say that for music of that type, I prefer something else.

Add in a subwoofer and things change quite a bit, though. Even though I don’t have subwoofer that’s anywhere near the quality level of the SR1a nor was I able to get it dialed in perfectly with phasing and crossover and all that, I got enough of a glimpse into it to realize that pairing the SR1a fleshes out the missing parts of the lower regions and adds in that punchy physicality and impact that hard rock, metal, hip-hop, and EDM need.

Cables Matter

OK, venturing into controversial territory here. Does the $1050 silver Studio Reference cable make a difference? Yes. Is that difference worth the $1050? Nice try. I can’t answer that for you. I got the sense that both cables were quite good, although differences and the fact that one was clearly higher performing than the other were detectable. The Studio Reference cable had a darker sonic background, an overall cleaner sound, presented more microdetail, and enhanced the spatial presentation. The separation between sonic images within that spatial presentation was a particular point where the Studio Reference outperformed the stock cable. On the whole, the Studio Reference cable created a more convincing, lifelike sound than the stock cable. The overall sound signatures were also ever-so-slightly different. To the extent the SR1a can reproduce subbass, the Studio Reference cable had more of it and a little bit more treble extension. The stock cable had a slight emphasis on the frequencies in the warmth range which gave it a slightly warmer overall character. Some listeners might prefer that signature, but it’s quite clear, at least to my ears, that the Studio Reference cable is the all-around superior cable on a technical level.


This gets tough because the SR1a is in a very small class of products. The Mysphere 3 is the only other “floating ear-speaker” kind of thing I can think of and I haven’t had the opportunity to hear that yet. I’ve heard a number of headphones in the $3000-4000 range lately, though. Those include HiFiMan HE-1000v2, Focal Stellia, Audeze LCD-24, Abyss Diana Phi, and Meze Empyrean Elite.

The SR1a has a more speaker-like presentation than any of those headphones. The HE-1000v2 and Meze Elite are probably the next most speaker-like, but they don’t catch the SR1a in that regard. The spatial presentation on the SR1a is the most realistic and coherent of the group, to my ear, as well. The HE-1000v2 is probably the next best on this list in this category, but clearly behind SR1a. The HE-1000v2 also brings warmth and subbass presence much more than the SR1a. The Elite can do similarly with its hybrid pads but not as much with its velour pads. The Diana Phi is the only headphone I’ve heard to date that could compete with the SR1a on pure resolution. I can’t say which is more resolving as I didn’t have them at the same time. My guess is they’re very close. The Diana Phi is more detail-forward though, seemingly emphasizing its resolution prowess at times. The SR1a is smoother and more natural in its detail presentation. The SR1a also has far more natural timbre than the Diana Phi, to my ear. All of the headphones named above also have a more macrodynamic presentation than the SR1a. Some of them (Stellia, Diana Phi) are very punchy and physical. Some are more in the middle (LCD-24, HE1000v2, Elite), but they all have more dynamic impact than SR1a by some distance.


I’ve already discussed what kinds of music I think work best with the SR1a above. I’ll add brief comments here about use cases I think make sense for SR1a. If the listening goals are to have a speaker-like experience and remove the effects of the room, it’s a strong option. If you’re primarily a 2-channel listener and a fan of music that isn’t predicated on a lot of bass energy and need a family-friendly late-night listening solution or you’ve moved from a house to an apartment, the SR1a is an excellent option. That it can be driven from a speaker amplifier at the flick of a switch increases the attractiveness of this option. The SR1a is an excellent switch-up to a 2-channel system that brings with it some of the ergonomic and privacy benefits of headphones. In this case, ‘privacy’ means the sound will stay contained within an apartment unit or a room with the door closed – the completely open nature still means anyone in the room with you is going to hear pretty much everything.

The SR1a’s sound is till more speaker-like than headphone-like. Headphones have a spatial presentation that is different and that can be desirable in some situations. Also closed-back headphones offer a level of isolation that is attractive is some situations. Then, there is the lack of subbass presence with the SR1a. The only way to recover that is to use a subwoofer and that removes one of the key advantages to head-based systems. All of these factors should be weighed if you’re considering the SR1a.


Whew! That was a lot of words. But there’s a lot to talk about with a product as unusual as the SR1a. It provides a speaker-like listening experience that’s worn like a headphone. It brings exquisite resolution, excellent timbre, and price-level-leading spatial performance to the table. It’s a bit lean in the subbass and not the most macrodynamic listening experience, which makes it more suited to music genres where heavy bass presence is essential to the experience. However, if the former is the kind of music you enjoy, and you want a speaker-like presentation that removes room limitations, the SR1a is an absolute must-audition for you.

Thanks for reading all! Enjoy the music!

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100+ Head-Fier
Dreams of Electric Space – RAAL-requisite SR1a
Pros: Speaker like experience, second to none soundstage, all-encompassing sensation, tactility, speed, clarity, precision and reference class resolution.
Cons: Not among the best in class in subbass extension. Requires dedicated amping, as no use for normal headamps.

Planar, dynamic, electrostatic drivers. We all attribute various traits to each technology and are biased in our own ways in how we expect them to sound, what technical achievement they are capable of and yet we’re always hoping to be proven differently to get out of our expectation bias zone and while sometimes we are proven wrong and are succinctly happy about it we mourn the fall before perfection yet are also happier than ever. We can really be a bunch of hard to please crazies, but the diversity of today has left us in a better place than ever before. There’s a top of the line headphone for basically every acquired taste.


Over the years, each of these driver technologies spawned contenders who emerged into a superclass and have all qualities that are not easily found in their competitors or even absent. The Utopia for its speed and resolution, the Abyss Phi TC for tactility, slam and the sensation of almost “being there”, the Susvara for timbre, tonality and the pursuit of complete euphony and among them juggernauts like the SR009S and of course the ever so marble stoned HE-1.

From time to time, different driver technologies or ideas of projecting sound into our ears appear like a flash and are gone as fast as they entered the stage, went EOL, into the unknown or simply stayed rare and absent. Piezo electric systems like the Taket H2+ for instance. The AKG K1000 or a few hybrids like the Dharma. Though to be fair, the K1000 wasn’t a flash of an appearance and had a fair run but simply wasn’t pursued as a concept for a long time only making a “comeback” in the form of its lead engineer releasing the MySphere.

Ideas and concepts always come and go, there’s still plenty to innovate and to explore thankfully as understanding and utilising human hearing is a vast, wonderful space of many exciting things to come. Yet after all these years, wouldn’t it be nice to have a technology to enter the headphone game and potentially shake it up quite a bit? Something more radical than just a bit better resolution, slam and imaging?

Well, enter the RAAL-requisite SR1A. A headphone that will surely change the landscape for both its bold design and its excellent and absolutely unique performance.

RAAL-requisite, based in Serbia and California respectively, is very well known for their world-class aluminium based ribbon tweeters and over the course of the last few years they managed to mold a headphone driver out of exactly that renowned design, deep in the fires of their forge. Requisite has been building professional recording equipment for top producers and engineers for over 30 years now.


RAAL-requisite actually calls them earfield monitors and like the AKG or MySphere these immediately do away the usual difficulties of headphone design like reflections, resonances, acoustic impedance of earpads etc etc. Sure, they all come with their own weaknesses, especially shared at one common point, but we will find that out later in this review how these are minimised here more than ever before.

Like the AKG and the MySphere, these earfield monitors are not resting on the sides of your head but instead angled nearby, hanging in the air, and boy, what they do with the air is something really special. No, not special as in being “just” another TOTL that rests among its equal peers to serve a different taste.

No, the SR1A are actually game changers that present and render music in a way that no other headphone does today. Far and away from any post honeymoon period, their initial shock and awe did neither wear out nor did it shake off through brain burnin. Whenever I came back to them from other headphones, their biggest strength: all-encompassing sensation, tactility, speed, clarity, precision and reference class resolution took me immediately over and hooked for hours and hours. Is it this perfect? Yes, and no.

Let’s get the build, looks and ergonomics out of the way so we can go to the meat of this review and find out.

Looks, build, ergonomics:


If the dark side was to build a headphone, it would look and feel like the SR1A. Bold, menacing, durable, sturdy and easy to service if a part would need a replacement. In fact, this quality aspect of the SR1A is a very welcome change in the age of glued pads, headbands attached with far too delicate screws and similar hard to self-service parts. You can even change the drivers themselves in case of blowing one entirely on your own by just replacing the existing cartridge with a newer one. You might even stitch, cut your own material to replace the existing headband by just poking appropriate holes into them. How great is that?

The overall design isn’t hung up on the last artistic detail or the last word in terms of material perfection through employing automobile design craftsmen like certain manufacturers do but it makes up for it through robustness as they don’t feel like breaking easily or falling apart. Something a lot of high end headphones lack.

Not that you should throw them around anyway and even if you wanted to, you would first need to get them off your head, which at the point of running music through them would be quite the herculean feat.

Ergonomics and general fit leave nothing to be desired honestly. You can wear these for hours and hours and not get any hotspots, pressure points or any other banes from the headband world.

Now the fit is a whole different game. These being earspeakers that do not touch your head at all, requires a bit more experimentation than your usual headphone experience taught you so.


The RAAL driver enclosure swivels up to 360° giving you plenty of possibilities to project the sound towards your head. Now:

Carefully choose the angle of each side relative to your head to give the imaging the best space to expand and stretch and try to find the sweet spot between the extremes of blurred, blended imaging when the drivers are to close to your head and the oval, very wide-stretched stage similar to the K7XX AKG headphones, just without the hole in the middle of the image.

Give yourself all the time in the world to find exactly that spot and get rewarded with the best staging and imaging in the business. I just mildly spoiler’d the review a bit, yes, but getting the right fit will make sure you can reap all the benefits this headphone is ready to unleash.



sound impressions:

Do you remember the moment when you put on a great headphone for the first time and what it did to you and all your senses? Remember the smiles, the joy, being impressed, the tapping of toes, the strange sounds you might have made out of sheer happiness? Everybody reading this had such a moment. Sometimes it wore off after a few hours, days, weeks as more or less glaring issues came up like overly excited treble, mid-bass bumps that give you a headache, too thin mids, lower mid dips, strong upper mid dips, etched treble and so on.

Now, if you‘re at a point when you listened or know most of the headphones I mentioned at the beginning, you’re far less likely to impress than compared to your earlier days. No, you’re not getting old. You’re just not easily tricked anymore and time flies faster than ever before, so you are pickier than ever and less likely to impulse buy or follow flavors of the months or general hype. Yet here I am kinda hyping all this up, but it is really worth it, I promise.


First things first:

soundstage, imaging, placement of objects in the space

The SR1A’s soundstage is second to none in size and depth and especially how it is created around your head encompassing you with the music, the instruments, the air, the positioning of every object, the vocalist’s breathe and vibrato and all the tiny stuff that you might want to hear or not but is there in the recording adding to the live quality, the “being there” or presence. Everything is there, stable, not fuzzy, not warbling, solid center image. Compared to usual headphones the “speaker-like” moniker is much more at place here than say the Abyss 1266 Phi TC or similar staging wonders. All are not only dwarfed in terms of sheer size, height but also in how everything is illuminated, placed and rendered in precision and sharpness. It truly is a remarkable achievement and this is thanks to the absolute speed of these headphones due to the ribbons being able to start and stop almost immediately, leaving no trail behind – the advantage of having very low mass and also tight control. Transient speed, transient attacks and decays happen so quick and yet so tactile you get a physical sensation of this experience. It is hard to describe.Think CRTs vs LCDs where the superior stop and start of the CRT is still superior for motion resolution and clarity. Sure, an LCD can pack 4K now but CRT technology has just been discontinued and the speed difference still stands. Now think of the gap being even wider. That’s where the SR1A resides. They kinda make other headphones feel slow and almost sluggish.

It is both extremely fast and yet doesn’t blur the tiniest detail or texture. It‘s all there, drawn as if a lightning bolt would draw into the night sky, sharp and illuminating. It really is impressive how it can be so fast without any blur yet also be tactile and far from any softness or smear.

Now as for how the stage is drawn for the listener, think of a blend of a pair of speakers that is kinda infront of you and the usual headphone experience of top of the line contenders like the HD 800. There is a good amount of frontal projection giving you plenty of believability of having a speaker like experience. The illusion is not quite there yet, but it is closer than ever. There are very few headphones being able to deliver that frontal projection, but they all fall short of the SR1A.


tonality, frequency response, timbre:

In general the RAAL is dead serious in being neutral and flat and consistently so, to the utmost end of the treble especially. Combined with the consistent delivery of energy or should we call it barrage (in a good way) it is not a relaxing headphone at all. The treble while not elevated to the point is ruler flat and can potentially cause issues for listeners who are used to rolled off treble like Audeze LCD-2, Empyreans, HD 650 or generally warmer gear. In any case pairing with amps that are not ruler flat or dead neutral is advised for long term listening and to counter the slightly leaner, whippier character. While not thin or lacking the overall tonality is not an experience full of meat and bones, more athletic, highly agile and especially reactive.


micro and macrodynamics, transients:

Tiny volume variations and gradiations and large variations of the whole musical context are essential in how we perceive and “absorb” music it’s what makes us move and connect with the music or let’s say dig into it as the dynamisms involved there define the emotions the music creates. What sounds like a lot of poetic words is in the end one of the most important traits you should look for in a headphone.

Given the good run the RAAL already has during this review, I’ll just let you know how absolutely great it behaves in this regard. The SR1A never subdues or even suppresses tiny variations into the background and is always up to the task in resolving them fully, giving them space to breathe and fade out. And given the larger picture, it can slam on point and slingshot hard into the space with tactile, snappy transients, like a fiery whip lightening up the darkest of nights with loud cracks, highly dynamic and in high contrast.


Bass quality, quantity and character:

As for the entire frequency spectrum, these ribbons do not lose grip on the technicalities and control they bring and unleash into the sound space on any part of it. Only from around 30Hz on downwards does the bass lose the battle of physics.

Bass goes down to around 28-32hz and rolls off from there, reminiscent of the legendary HD 800. And in similar ways to the Sennheiser, yet superior in every way all bass until that point is marvellous, clean, hard hitting, of high resolve and draws every bass line, every subtlety and corpus without a faint, quick, nimble, lightning fast. Absolutely impressive.


These ribbons simply never stop. Again, plenty of ruthless resolve, texture, speed and cleanliness. The SR1A clearly takes no prisoners and instead hijacks you while simply being impossible to catch for speeding tickets or any arrest. This headphone really needs some adjustment and brain burn-in to realize what’s happening and how it happens.

If you’re a friend of legendary midrange stars like the HE-500, HD 650, HD 600, prepare to potentially get disappointed at first because romanticism and dreamy and honeyed seduction is not the way the SR1A plays. Is it the dreaded “cold and clinical”? Not quite.

It’s just that the stop and starts are happening so fast, the blur and slowliness you are perceiving which gives the aforementioned headphones their romantic vibe is non-existent. The advice of being careful in finding a matching amp naturally especially applies here, where our hearing is the most sensitive.


Gobs of detail, resolve, texture, finesse and, most of all: a natural timbre.

The SR1A’s treble never loses composure in any instance. It will never be brittle, splashy, grainy or even remotely lose focus or fall apart at higher volumes, however it will, as I mentioned a lot by now, be full of energy, speed and attack. An all out attack on the senses in the most neutral way.


Amp pairings:

I’ve been building amps for years, among them the Nelson Pass/First Watt designs are one of my absolute favorites. Back when the HE-6 got released and their (still) legendary power requirements made a few enthusiasts start using power amplifiers it was the defining moment that drove me away from dedicated headphone amps, thus from there on I powered everything through my amps up until the Susvara and now the SR1A.

Unfortunately, lack of space at home makes it hard to keep all the amps I built and own in one place. Making me scatter them around the family to share all the joy and, of course, also all by myself.

Pass Labs XA30.8:


Pass amps are designed with a lot of overhead in mind, it’s why they are able to drive loads beyond what’s on paper while unleashing that special magic Nelson imbues onto the design. The XA30.8 is, despite the mismatch on the spec sheet, a great pairing with the SR1A. Perfectly matched 24 MOSFETS per channel with the right amount of 2nd order harmonics add a slight euphony to the ruthless laser sharp precision and neutrality and enrich the experience effortlessly with both cleanliness, clarity and yet unrestrained bass reproduction. There is zero distortion or limpiness to hear and, of course, given the “physical” nature of the RAAL, to be felt.

Pass Labs XA30.5:

Similar to the XA30.8 but drier, a bit more stoic and technical if there was a word of lesser euphony. Still a great match.

Pass Labs XA25:


Not far from the power of the XA30.8 the XA25, potentially giving out up to 80Ws @ 8 Ohms or 120W @ 4 Ohms did not quite reach the elegance and effortlessness of the bigger brother. I felt there was something lacking and didn’t pursue the combo any further.

DIY F4 Monoblocks:

With 2 F4’s you can achieve around 100 Watts per 8 Ohm load. As the F4s are buffer amplifiers, they take on what the preamp characteristics are. In my case, they currently give more neutrality, a bit more clinical and less euphony overall. While their specs speak of more power and drive, the XA30.8 combo gave out a more holographic and dynamic experience and gave the overall onslaught of energy a good touch of musicality.




This amp, also or especially designed for the Susvara in mind, is a dream to listen to and quite the well engineered effort of HIFIMAN, yet not cheap though, mind you. At 110W @ 8 Ohms, they are officially up to spec. A very clean, neutral sound with an abundance of details and resolution, paired with 6×6922 tubes to enhance the flavor is must-hear experience. Together with the XA30.8 these were the favorite pairings except for the XA30.8 edging the EF1000 out in the delivery of vocals and the more relaxed counter effort. Other than that the holographic stage, the imaging within the space was a common trait both shared. This amp makes switching between the Susvara and the SR1A so easy.

Upgrading the experience: The RAAL Requisite 728 and 1028 silver cable.


Aftermarket headphone cables are always just a matter of time and RAAL fully aware of it took no prisoners with their own take and released the 728 (7 feet) and 1028 (10 feet) full silver cables for those whose mindset is to maximize upon every part of the chain.

A headphone so sensitive and “aware” of changes and competence in the chain absolutely needs a high performing cable.

Where it improves upon the stock cable is is mostly on transparency, micro-dynamics, transient speed and especially in the sharpness of the imaging qualities. It’s quite a good transformation and not just a small step to fill the last gap. Personally, I recommend getting everything else in the chain in place before taking on cable matters. Afterwards, the 728/1028 cable will definitely be the icing on the cake and further reward your efforts.



The SR1A earfield monitors are not the easiest headphone to pair with or integrate into your existing headphone setups or collection. They simply do away with any dedicated amps you might have sitting on your shelf. They require more real estate, overall heat dissipation, and cabling matters. They need more focus, effort and attention to placement and finding the perfect spot to illuminate your aural experience. Once you are deep into their territory though they grab you hard and relentlessly and take you onto a journey that even the most experienced headphone enthusiast hasn’t experienced yet.

Are they an all out assault on your senses? Yes, they are, yet in a good way, in an exciting way, in a way you have never heard before. The RAAL can be everything if you want it to be due to its technical prowess and perfect tonality, but it will never be a warm, smooth and creamy LCD-2 experience or a HD 650 on a top of the line tube amp. They can be cozy, warm, dreamy if the music is, yes, naturally, but the technicalities will always underline the overall picture.

They certainly take getting used to at first. You will find yourself trying to grasp the whole picture and presentation at once since the delivery of information has never been so clean, bare and clear yet so full, dense, packed at such a enormous speed. And you might even find yourself standing on the seat metaphorically but over time you will have found out when to be ready for such a listening session.

The SR1A definitely is the starting point where the headphone experience takes a new and exciting turn and the SR1A is there to collect you, put you into the seat and drive away.

Oh, and if you’re from the UK like me, RAAL-requisite just setup a new camp at Hifonix, right in Birming Rd, Sutton, Coldfield. There you have the chance to listen to the SR1A personally with a few different amplifiers, also RAAL-requisite’s very own.​


396 Birmingham Rd, Wylde Green, Sutton Coldfield B72 1YJ, United Kingdom


+44 121 382 5444


Contact: Aseem

Thanks for reading

Visit RAAL-requisite over at www.raalrequisite.com and don’t hesitate to give them a call (818) 437-0779
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Looking forward to seeing the new RAAL ribbons! - The EVO400 looks like a great combination!
An absolutely superb write up Dill! Well done! Can you have a conversation with these on, like the Abyss?
Yes at lower volumes you can have a conversation with these on :)


500+ Head-Fier
Pros: When properly driven, better resolution and speed than any other headphone
Largest sound stage of any headphone, period
Massive dynamic range with tremendous bass and treble extension
Light and extremely comfortable to wear
Modular design, user-swappable cushions, headband and drivers
Performs surprisingly well on cheap 2-channel equipment.
Cons: Literally requires a 100w speaker amp to drive
No sound isolation at all
Completely neutral signature means treble might be hot to some people
Speed can be a detriment to vocal emotion and lushness
Did I mention that they literally require a 100w speaker amp?
Okay - here's my "feature length" Raal SR1A review. R-r will be at Canjam Singapore (via SLT technologies) and Canjam Socal.

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.


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 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.
Great review. I am using the SR1a's with an SPL s800 power amp (285 watts) at low volume. I have learned from another user to be careful with the volume control, as this is enough power to toast the SR1a's. But the extra power of the s800s allows plenty of grunt to make the SR1a's perform at their best. I have owned the AKG K1000s driven by the First Watt F1, and the STAX SR009s driven by the BHSE. The Raal SR1a's are the best headphones I have ever heard. Period.

Update: Now driving the SR1a's with the Raal Requisite HS1b amplifier and SR728 silver cable- Perfection!
Excellent overview. I'm intrigued and hiding my wallet.
Sajid Amit
Sajid Amit
The EVO 400 is my go-to for the SR1a
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