Jump to content
  • austinpop
    austinpop

    Part 1: RAAL-requisite SR1a Earfield Headphone Monitor &  HSA-1b Headphone & Speaker Amplifier Review

    SR1A-HSA-1b.jpg


     

     

    RAAL-requisite SR1a Earfield Headphone Monitor & 

    HSA-1b Headphone & Speaker Amplifier Review

     

    Part 1 of 2: Introduction, Setup, and Initial Impressions

     

    Rajiv Arora

     

     

    • Part 2: Optimizations, Competitive Comparisons, and Conclusions (link)

     

     

    Introduction

     

    My interest in the RAAL-requisite SR1a was first piqued at CanJam RMAF 2018, where I noticed a booth with perennially long lines, demoing what looked from afar like an electrotherapy device. We headphone nuts know that looks are deceiving, and what look like medieval instruments of torture can in fact be world-class headphones! I never did get a chance to have a listen to the SR1a, so it went on the mental list of “things to check out in the future.” 

     

    I didn’t run into the SR1a at any of the shows I went to in 2019, so it wasn’t until early last year, when Chris @The Computer Audiophile published his review, that my attention was revived. After Chris’ review, I was determined to get my hands on them and hear them for myself. But since I didn’t have high-end speaker amps lying about — I am, after all, a headphone guy — I decided I would do a combined review of the SR1a with the then-forthcoming RAAL-requisite HSA-1b amplifier. Arrangements were made, but with pandemic disruptions, delays were inevitable. Finally, earlier this spring, a handsome Pelican case containing the SR1a and HSA-1b showed up at my doorstep.

     

     

    About the SR1a Headphones

     

    sr1a-titled-scaled-2048x1490.jpg

     

     

    There are several attributes that make the SR1a “earfield monitors” ($3500 MSRP) interesting, even unique, in the headphone space. Unlike the more common dynamic, planar magnetic, or electrostatic drivers, these drivers are true ribbons that are claimed to reproduce 30Hz to 30kHz.  The ribbons are engineered to fit in a cartridge that easily slides into (and out of) baffles that are mounted like wings on a headband. The baffles are designed to pivot, so their angle and position relative to the ears can be changed, allowing one to tune the sound. The modular ribbons are  easy to replace, making for excellent serviceability.

     

    Another interesting attribute of the ribbon drivers is their extraordinarily low impedance of 0.2Ω (ohms), which means they cannot be driven directly by conventional headphone amps. RAAL-requisite offers two paths to achieve this. The first is to use a so-called direct-drive amp, like the Schiit Jotunheim-R (MSRP $799 amp only, $999 with internal Multibit DAC), or RAAL-requisite’s own HSA-1b ($4500 MSRP, reviewed here). These amps are designed to deliver high current with extremely low output impedance via the headphone output directly to the SR1a. 

     

    raal-requisite interface box.png

     

     

     

    The second path is to use RAAL-requisite’s amp/ribbon interface, driven by a conventional speaker power amp rated at 100Wpc or above. This interface box presents an impedance of 5.6Ω to the power amp, while supplying high current/low impedance output to the SR1a. Using this interface box opens up a universe of possibilities, and I know of audiophiles who have experimented with truly TOTL boutique power amps. I’m sure these sound wonderful, but this is a rabbit hole I was not equipped to explore!

     

     

    About the HSA-1b Headphone & Speaker Amplifier

     

    HSA-1b-front.jpg   HSA-1b-rear.jpg

     

     

    The RAAL-requisite HSA-1b ($4500 MSRP) is a real Swiss Army knife of an amp because of all the things it can do! Direct-drive the SR1a? Check. Drive conventional dynamic and planar magnetic headphones? Check. Drive speakers? Check. It even has a gorgeous red (though not Swiss Army red!) precision stepped volume attenuator. Both single-ended and balanced inputs are provided. 

     

    I found the fascia design and red accents very attractive. At 8.58” wide, this amp is narrower than it is deep, but it has a substantial heft to it, and looks and feels like it means business. It weighs in at 11.6 lbs, almost the same as my reference Cavalli Liquid Gold amp (at 12.1 lbs).

     

    Much is demanded of headphone amps at this price point, and ultimately,  the proof of its quality will be in the listening. 

     

    You can read the full specifications at this link

     

     

    My Listening Setup

     

    The RAAL-requisite combo arrived at a very serendipitous time as, after many years of intense tweaking, I had reached a fairly stable system topology that was sounding as good as it has ever done. When this happens, the itchy audiophile often turns to transducers for the next leap forward, so this was a dangerous time for my wallet to bring a highly acclaimed, and potentially game-changing, set of headphones into my system! Of course, from the review perspective, it meant the RAAL-requisite combo would be driven by a high-quality chain that would fully showcase what they were all about.

     

    Rajiv Topology RAAL.jpg

     

     

     

    Hardware

     

    My system hardware is shown in the picture above. It consists of a chain of audiophile switches, feeding my music server, the Taiko SGM Extreme, equipped with the Taiko USB card upgrade. Audio data is output over USB to an Audiowise SRC-DX bridge, which presents it to the Chord DAVE DAC via its dual BNC S/PDIF inputs. My reference headphones are the Meze Empyrean, the Abyss AB-1266 Phi CC, and a modded Sennheiser HD-800 (SD mod). The switches are powered by independent DC rails supplied by a Paul Hynes SR7MR3DRXLFC10 power supply. AC power is delivered via a 6AWG dedicated circuit to a Sound Application TT-7 Reference power conditioner, to which the amps, the Extreme, and the Paul Hynes PSU are directly connected. 

     

    The bulk of my listening is through the Empyrean, driven directly from the single-ended 6.3mm jack on the DAVE. Those who know the DAVE know that the sheer transparency of this direct path is incredible, and hard to beat using conventional amps. Not pictured, but included in my system, is a Cavalli Liquid Gold headphone amp. These days, its primary role is to drive the Abyss headphones, as these relatively insensitive ‘phones really benefit from more power than the DAVE can directly provide.

     

     

    Software

     

    The software stack plays a vital role in maximizing the sound quality delivered by the hardware. The foundation is the highly optimized Windows 10 LTSC OS in the Taiko SGM Extreme. Second is the music player. Taiko addressed growing concerns about Roon’s lagging sound quality (SQ) by developing their own player, Taiko Audio Server (TAS), and its SQ is head and shoulders above Roon’s. Finally, I used PGGB, a remastering tool, to upsample my music files offline, so the DAVE only ever sees 24-bit, 16FS (705.6/768kHz) music streams.

     

     

    Review Playlist

     

    RAAL-requisite SR1a/HSA-1b Review Playlist on Qobuz (US)

     

    To enable you to listen to the same tracks that I did, I have created a public playlist on Qobuz USA. This playlist includes the tracks mentioned in this review, as well as some of the others I listened to in the course of this evaluation. Please note that in some cases, the Qobuz track will not match the mastering I listened to, especially since all my listening was with PGGB-upsampled files. Still, this gives you a sense for the music I listened to for evaluation.

     

     

    Listening Setup

     

    Since PGGB remastering only applies to local files, and since the resulting SQ of a native file PGGBed offline is head and shoulders greater than the SQ of the same native file streamed from Qobuz and real-time upsampled with something like HQPlayer, all my critical listening for this review was done with remastered PGGB files stored locally on the Extreme.

     

     

    SR1a Listening Impressions (with HSA-1b Amp)

     

    Before any serious listening, I followed my usual practice of letting both the headphones and the amp burn in for a couple of weeks of continuous music. How much burn-in is actually necessary I couldn’t say; certainly, by the time I started listening, there were no further changes in the sonic characteristics that I could discern.

     

    My initial reaction to the SR1a was somewhat mixed. I quickly realized these sound very different from the other headphones in my stable, and I couldn’t just do quick A/B’s between them and the SR1a. I found I had to wean myself off of my existing headphones’ sound signatures, and allow myself time to acclimate to the SR1a. This isn’t particularly unusual, as I’ve done this with other headphones, but in the case of the SR1a, it proved absolutely vital. It took a few days of exclusively listening on the SR1a, and strictly abstaining from the others, before I felt my brain was truly dialed-in to these headphones!

     

    The SR1a are fast. As in blazingly fast. The transient response and accuracy is just off the charts compared to anything else I’ve heard. Leading edges of percussive notes, like plucked strings, piano, cymbals and drums are perfectly rendered, and the resolution and detail impart a sense of realism that just takes your breath away. Consistent with this speed, music seems to flow effortlessly, and the level of rhythmic articulation, especially in the upper bass is simply superb. 

     

    mahler.jpgAnother attribute that grabs you immediately is the soundstage. It is vast and holographic.  Instruments are placed with pinpoint precision in three-dimensional space. This becomes even more impressive in dense passages in large orchestral pieces like Mahler’s 8th symphony. Rather than sounding congested and muddy, the SR1a takes these passages in its stride and maintains a coherent soundstage.

     

    Tonality is where things get a little interesting. Let’s start with the excellent. The upper-mids and highs are just exemplary, with no harshness or edge to speak of. The mids provide what I would characterize as a front-row presentation. Relaxed, these headphones are not! I’m sure some of this perception just comes from the extreme speed and resolution of the transducers, but the SR1a is not forgiving of subpar recordings or upstream electronics. That said, the only time I heard grunge was when I played it! Which was almost never. Luckily my tastes run to more refined genres.

     

    Which brings us to bass. I’ve already waxed lyrical about the articulation of the upper bass. However, there is no getting around the fact that the SR1a is light in the lower and sub-bass. I’ll explore to what extent this can be mitigated with cables, EQ, etc, but as shipped, the SR1a are definitely bass-light. Obviously, the degree to which this matters depends on your sensitivity to this frequency region and personal preference. It’s tempting to say this affects some genres more than others, but I disagree. Accurate bass response is vital to all music genres, whether it is a capella, solo piano, or a massive orchestra.

     

    Coming soon in Part 2 (link) of this review, the rubber finally meets the road. I’ll describe various adjustments and tweaks I made to see how much more the SQ of the SR-1a and HSA-1b could be improved. Following that, we get to the part I love most: comparisons with the competition! Finally, I’ll wrap up with my conclusions and overall assessment of the SR1a and HSA-1b.

     

    Stay tuned!

     

    Link to Part 2

     

     

     

    Product Information:

     

     

     

    Associated Equipment

     

     Primary System

     

    Music Computer:          Taiko Audio SGM Extreme Music Server, Taiko USB upgrade

    Headphone Amplifier:  Cavalli Liquid Gold

    Headphones:                Meze Empyrean, Abyss AB-1266 CC

    DAC:                             Chord DAVE

    USB to dual-SPDIF:       Audiowise SRC-DX bridge

    Ethernet Switches:        SOtM sNH-10G, Uptone EtherREGEN, 

                                         Buffalo BS-GS2016 (modded for LPS)

    Power supplies:            Paul Hynes SR7 MR 3DSXL (dual regulation, 3-rail)  for switches 

                                         Sean Jacobs DC-3 for DAVE

    Power Details:               Dedicated 30A 6 AWG AC circuit, 

                                         Sound Application TT-7 Reference Power Conditioner

    Power Cables:               Sablon King (wall to TT-7), Sablon Prince (Extreme),

                                         Cardas Clear Beyond (DC-3, SR-7), 

                                         Cardas Clear for all other components

    USB cables:                   Sablon Reserva 2020 USB

    BNC cables:                  High Fidelity Cables CT-2

    Ethernet cables:            Sablon 2020, SOtM dCBL-Cat7, Supra Cat 8

    DC cables:                     Neotech OCC (DC-3), Paul Hynes fine silver (SR-7)

    Interconnects:               Cardas Clear XLR balanced

    Headphone cables:       Transparent Ultra cable system

    Accessories:                  Synergistic Research Tranquility Base XL UEF with Galileo MPC

                                         Synergistic Research MiG 2.0 footers

                                         Taiko Audio Daiza Isolation Platforms

     

     

    Acknowledgments

     

    Many thanks to the following companies for supplying cables and accessories to aid in this evaluation: 

    • Cardas Audio, for a full loom of Cardas Clear cables.

    • Transparent Audio, for the Transparent Ultra headphone cable with a full complement of headphones leads and source terminators.

     

     

    About the Author

     

    Rajiv Arora — a.k.a. @austinpop — is both a computer geek and a lifelong audiophile. He doesn’t work much, but when he does, it’s as a consultant in the computer industry. Having retired from a corporate career as a researcher, technologist and executive, he now combines his passion for music and audio gear with his computer skills and his love of writing to author reviews and articles about high-end audio.

     

    He  has "a special set of skills" that help him bring technical perspective to the audio hobby. No, they do not involve kicking criminal ass in exotic foreign locales! Starting with his Ph.D. research on computer networks, and extending over his professional career, his area of expertise is the performance and scalability of distributed computing systems. Tuning and optimization are in his blood. He is guided by the scientific method and robust experimental design. That said, he trusts his ears, and how a system or component sounds is always the final determinant in his findings. He does not need every audio effect to be measurable, as long as it is consistently audible.

     

    Finally, he believes in integrity, honesty, civility and community, and this is what he strives to bring to every interaction, both as an author and as a forum contributor.


     



    User Feedback

    Recommended Comments

    While I disagree with Chris on a few things, this setup is not one of them.

     

    As I sold my primary house in July, pretty hastily at that and moved to my other home in MT, I had to put my main system into storage. My speakers are Gobel Aeons which for a multitude of reasons just push all the right buttons for me. True holographic and non-distorted soundstage with incredible accuracy. All of the qualities of great ribbons (although a bending wave driver) and then some.

     

    Unfortunately my MT house is too small for my main system and the Mrs. isn't ready for it to take over the main room. In the past I have tried different headphones but when I saw Chris's review and the return policy from RAAL I gave it a shot. I purchased the amp in this review with headphones and RAAL's 10 foot cable. Until I get my new DAC out here I am using my Chord Mojo. Lastly, I purchased Mitch's convolution filters.

     

    I was more than surprised at how much I enjoy this system. I can't say they replace my Gobels, but, I have yet to hear any headphones I enjoy more than the Gobels and while I have not heard them all, nothing comes as close to a ribbon type speaker than these, IMO.  I agree with the reviewer that they take some time to get used to because they are so different and positioning on the head takes some time to get right, not just right for the music but right for one's preference. A remarkable difference in fact. I have them "dialed in" for my preference and while different than just about any headphone, to me they really are the closest thing to my reference system especially when considering I am wearing them on my head. 

     

    Kudos to all that have reviewed these things, kudos to Mitch for making an amazing headphone system much better (although he claimed it would a "minor improvement) and Kudos for RAAL raising the bar for "head speakers" for those of us looking for such a product. 

     

    Yes without Mitch's filters, the bass is shy however, with them I don't miss the lower most octave that it may be missing and the lower mid-bass is very taut and excellent. 

     

     

    Share this comment


    Link to comment
    Share on other sites
    9 minutes ago, Priaptor said:

    While I disagree with Chris on a few things, this setup is not one of them.

     

    As I sold my primary house in July, pretty hastily at that and moved to my other home in MT, I had to put my main system into storage. My speakers are Gobel Aeons which for a multitude of reasons just push all the right buttons for me. True holographic and non-distorted soundstage with incredible accuracy. All of the qualities of great ribbons (although a bending wave driver) and then some.

     

    Unfortunately my MT house is too small for my main system and the Mrs. isn't ready for it to take over the main room. In the past I have tried different headphones but when I saw Chris's review and the return policy from RAAL I gave it a shot. I purchased the amp in this review with headphones and RAAL's 10 foot cable. Until I get my new DAC out here I am using my Chord Mojo. Lastly, I purchased Mitch's convolution filters.

     

    I was more than surprised at how much I enjoy this system. I can't say they replace my Gobels, but, I have yet to hear any headphones I enjoy more than the Gobels and while I have not heard them all, nothing comes as close to a ribbon type speaker than these, IMO.  I agree with the reviewer that they take some time to get used to because they are so different and positioning on the head takes some time to get right, not just right for the music but right for one's preference. A remarkable difference in fact. I have them "dialed in" for my preference and while different than just about any headphone, to me they really are the closest thing to my reference system especially when considering I am wearing them on my head. 

     

    Kudos to all that have reviewed these things, kudos to Mitch for making an amazing headphone system much better (although he claimed it would a "minor improvement) and Kudos for RAAL raising the bar for "head speakers" for those of us looking for such a product. 

     

    Yes without Mitch's filters, the bass is shy however, with them I don't miss the lower most octave that it may be missing and the lower mid-bass is very taut and excellent. 

     

     

    Great to hear. I’m totally with you on the dialed in part. Once you get comfy in the driver’s seat with these, it’s game on. Hard to beat, unless it’s with a full size system. 
     

    Mitch and minor improvements don’t go well together :~) Everything he does has a major impact for the better. 
     

    I’m glad Rajiv liked them in his system for this review because it’s quite different from my system. And, he’s a “headphone guy” with much more experience in this area than me. It’s always good to have 2nd and 3rd opinions, whether they jibe or not. 
     

     

    Share this comment


    Link to comment
    Share on other sites
    11 minutes ago, The Computer Audiophile said:

    Great to hear. I’m totally with you on the dialed in part. Once you get comfy in the driver’s seat with these, it’s game on. Hard to beat, unless it’s with a full size system. 
     

    Mitch and minor improvements don’t go well together :~) Everything he does has a major impact for the better. 
     

    I’m glad Rajiv liked them in his system for this review because it’s quite different from my system. And, he’s a “headphone guy” with much more experience in this area than me. It’s always good to have 2nd and 3rd opinions, whether they jibe or not. 
     

     

    I am ever indebted to you. After reading your take on these I said to myself, if they are as good as he says, it may just be the perfect match for my needs and I have to say they are and them some. 

     

    Just waiting on my Esoteric N-05XD to top it off. Meanwhile I am enjoying what I have.

     

    AND YES Mitch greatly understated the difference his filters made. 

    Share this comment


    Link to comment
    Share on other sites

    I've been waiting for this review for what seems like ages - Rajiv (with Taiko Extreme and PGGB) vs. the most hyped headphone system yet.

    Share this comment


    Link to comment
    Share on other sites

    I heard the HSA-1b again today after about a 10 month hiatus. I have also heard the SR1a on lots of 2 channel amps I have owned, CODA #8, KRELL K-300i integrated, D-Sonic M3a 800s, Benchmark AHB2 mono, and LSA Voyager 350 GAN. So I have gained perspective on what great sound is with the SR1a. The HSA-1b today belongs in that great amp class, in line with the best amp setups I have had. I will likely get a HSA-1b for a bedroom.

     

    I currently use the KRELL K-300i integrated amp with the Benchmark DAC3B. The KRELL integrated has tremendous bass and really fills in the sound of the SR1a. The neutral DAC3B compliments the smooth and warm KRELL which are Class A on the first 90 watts.

     

    My CODA #8 has power meters. Those meters were very instructive when I used that amp with the SR1a. The SR1a was drawing more power out of the amps than my floorstanders, Thiel CS3.7 (also power hungry). I noticed that amps with a lot of power make the SR1a sound the best. The CODA #8's meters proved that to me.

     

    Mitch's filter made the Benchmark AHB2's + CODA 07x preamp sound great with the SR1a`. Otherwise, the AHB2 is not tolerable with the SR1a, even though the designer in Serbia is supposed to favor it. I am now debating whether to use the SR1a Convolution filter with the KRELL K-300i. I am leaning towards not using it.

     

    BTW - the KRELL K-300i and CODA 07x | #8 separates and CODA CSiB integrated are the great SR1a setups for me. The AHB2 is also there but it requires the Convolution filter so I do not consider it at the top.

     

    BTW2 - the CODA 07x is a perfect preamp for the SR1a. The sound is phenomenal with the SR1a and it also has 2 sets of XLR outputs for 2 sets of amps. I use 1 amp set for my floorstanders and another amp for the SR1a. Just turn the amp that is not needed OFF. This way I do not have to use the SPEAKER selection on the RAAL Amp Interface box (just HEADPHONES). I have 2 Amp Interface boxes so I have the KRELL with 1 box and the other box with a variety of amps.

     

    BTW3 - I sold my Meze Empy and Benchmark HPA4 headphone amp recently. After, the SR1a, I did not listen to the Empy. 

    Share this comment


    Link to comment
    Share on other sites

    Thanks Rajiv.

     

    Great work.

    Especially like the way you link your evaluation playlist.

    Looking forward to part 2 and your take on eq.

     

    @PriaptorDoes RAAL offer a "better amp" than the HSA-1b?

     

    "Of course, the "while I'm at it attitude" crept in and I decided, a system like this needs a "better" DAC as well as the better amp that RAAL sells and on and on."

    Share this comment


    Link to comment
    Share on other sites
    2 hours ago, HeeBroG said:

    Thanks Rajiv.

     

    Great work.

    Especially like the way you link your evaluation playlist.

    Looking forward to part 2 and your take on eq.

     

    @PriaptorDoes RAAL offer a "better amp" than the HSA-1b?

     

    "Of course, the "while I'm at it attitude" crept in and I decided, a system like this needs a "better" DAC as well as the better amp that RAAL sells and on and on."

    Sorry, I didn't mean in my post to imply that there is a "better" amp than the 1b. That was the amp I chose to get with my "while I'm at it attitude". 

    Share this comment


    Link to comment
    Share on other sites

    Thanks Rajiv,

    If I remember correctly from another review, you had a clock that synchronized the SOTM and Uptone Audio network switches and a USB interface. Did you remove it after adding the Taiko server?

     

    Share this comment


    Link to comment
    Share on other sites
    1 hour ago, Sagittarius said:

    Thanks Rajiv,

    If I remember correctly from another review, you had a clock that synchronized the SOTM and Uptone Audio network switches and a USB interface. Did you remove it after adding the Taiko server?

     

     

    Yes, there has been a sea change in my approach after I bought the Extreme, and more recently, due to my use of PGGB. I used to have a Mutec REF10 SE120 reference clock supplying a 10 MHz reference to the eR, the sNH-10G, and a tX-USBultra. The tX turned out to be unnecessary, and in fact an impediment, in the Extreme's USB chain. As for the network, I now live by the credo "no network is better than the best network." Since all my critical listening is with local PGGBed files, I just hit play and power down the switch chain. The only time my 3 switches as shown are active during playback is for non-critical discovery listening with Roon/Qobuz/HQPlayer. A reference clock is overkill for this use case.

     

    For more discussion, see the section "Dispensing with the network" in my post from earlier this summer: 

     

    Share this comment


    Link to comment
    Share on other sites


    Create an account or sign in to comment

    You need to be a member in order to leave a comment

    Create an account

    Sign up for a new account in our community. It's easy!

    Register a new account

    Sign in

    Already have an account? Sign in here.

    Sign In Now



×
×
  • Create New...