Gramophone Dreams 32: RAAL-Requisite SR1a headphones Page 2

"Since the amplifier damping factor plays no role and the cables need to be terminated with more than 2 ohms, then we can use a resistor of any convenient value connected in series to the headphones and their cable. As far as the ribbon is concerned, this is a current-source operation mode.

"The RAAL specs say: Impedance: 0.018 ohms; Sensitivity: 85dB/1mW; Power Handling With Bass-Heavy Tracks: 450mW RMS; Max SPL at 450mW RMS (limited by ribbon excursion at LF): 111dB.

"To develop 450mW of power at 0.018 ohms load, we need 5 amps RMS."

Listening with the Schiit Aegir
Schiit's new $799 Aegir amplifier generates 10Wpc in class-A and 20Wpc in Schiit's proprietary Continuity bias. It is lower-powered than the RAAL-Requisite headphones require, but it is my current reference for high-quality solid-state power at a low price. It is also my current favorite headphone amp. Not surprisingly then, it is the first amp I used with the SR1a's.

With moderate musical program at moderate volume levels, I did not notice any power limitations—only clear, liquid, elegant sound. The sound of Vladimir Horowitz's piano on Horowitz the Poet (44.1/16 FLAC, Deutsche Grammophon/Qobuz) flowed naturally and emitted all the coded data my brain needed to forget hi-fi, headphones, and audio journalism. Vlad's piano sounded true of tone—like it should always sound. Enjoyability level was high.


Listening to this record was the first time I felt I had the SR1a's positioned perfectly relative to my pinna. Because the RAALs sit away from my skull, and because the carbon fiber "baffles" are adjustable, it took me a couple of days to get the bass vs space ratio dialed in. As always, when Horowitz sounds right, I know my system is right.

With the Schiit Aegir, the RAAL-Requisite headphones' greatest virtue became obvious: They did not sound like any circumaural headphone or in-ear monitor I know of. With their extreme purity and resolution, the SR1a's deposited Vladimir Horowitz, his piano, and the room he was playing in right there, in the space in front of me. Not inside my skull.

Everyone knows I'm a devotee of small, monitor-type speakers listened to in the extreme nearfield—wherein they play big. And the RAALs are just that: They are, unquestionably, small monitor-like speakers that play big when listened to from about 0.75" from my ear. What more could I want?

The words "whole" and "resolved" acquired new meaning as I listened to my favorite test track: "Buddy & Maria Elena Talking in Apartment" from Buddy Holly's Down the Line: Rarities (CD, Decca B001 1675-02). More than ever before, I felt like I was in a real apartment (not in my head) hearing two people sound like themselves, saying real-life things. Think high resolution and natural at the same time—not hi-fi.


That being said, when I turned the volume up on "Love Is Strange," the Aegir made a few crunchy clipping sounds. The RAALs were demanding more current than the Schiit could deliver.

Listening with the Pass Labs XA25
If you want to hear what your amp really sounds like, or everything your expensive phono cartridge is recovering, or how different all your DAC's filters sound, you need a head-mounted transducer that resolves at the level of the RAAL SR1a, coupled to the class-A Pass Labs XA25 stereo amplifier, which is definitely more powerful than its modest 25Wpc into 8 ohms and 50Wpc into 4 ohms ratings suggest. No matter what hi-fi you have, it's unlikely to dig deeper and find more beauty in your recordings than the RAAL-Requisite SR1a's connected to this extraordinary design. I experienced no current shortages, and Vladimir Horowitz's piano sounded richer and more solid than ever.

The Nelson Pass–designed amp made the Aleksandar Radisavljević–designed ribbons sound absolutely pure and relaxed with not even a hint of glare on sopranos or massed strings.

On viola da gamba virtuoso Hille Perl's Loves Alchymie (44.1/16 FLAC, Deutsche Harmonia Mundi/Tidal), when soprano Dorothee Mields speaks these words from John Donne's poem The Bait—"Come live with me and be my love / And we will some new pleasures prove"—I could hear each word bounce off the church walls. Her voice was framed in seductive pulsing reverberation. The experience made me grateful to be an audiophile and to have discovered this beautiful, enchanting album.


Best of all, on this recording, the RAALs showcased their most engaging virtue: material presence. Hille Perl's viola da gamba appeared in full, tangible materiality. Her instrument had bite and weight and emitted the sounds of ancient wood. Perl's bow strings felt more like horsehair than they had with any other headphones in my possession.

Listening with the Benchmark AHB2
The Schiit Aegir demonstrated that the RAAL ribbons were highly resolving. The Pass Labs amp took said resolution and transparency to the next higher level, and added more physical weight to the presentation. But both amplifiers are under 100Wpc. So I decided to try a more powerful amplifier, one that many people recommend for the SR1a headphones: Benchmark's AHB2 stereo amp. The AHB2 is famous for its low measured distortion, low output impedance, and high damping factor.

According to the Benchmark manual, the AHB2 combines a class-H power supply and class-AB amplifier technologies with feed-forward error correction. Most important, the Benchmark amp is specified to deliver greater than 29A into 1 ohm (!) and 80V peak-to-peak into any load. The manual says it can put 130Wpc into 6 ohm loads such as the RAAL SR1a.

The AHB2 drove the RAAL ribbons with authoritative clarity. Playing "Cet Enfant-là" from Alexandre Tharaud's Barbara (44.1/24 FLAC, Erato Warner Classic/Qobuz), I experienced an avalanche of previously unheard inner detail. The AHB2 made the SR1a's feel like an aural microscope. The sound was unabashedly clear and well-sorted, but it was also brittle and bright on the Horowitz and Hille Perl recordings.

During parts of Jean-Louis Aubert's vocals (on Barbara), this brightness would sporadically flash my ears with a distracting glare (between 1kHz–3kHz). This reoccurring glare compelled me to turn the volume down. Tharaud's piano appeared enjoyably percussive, but its normally saturated tone was now lightly and evenly bleached. The spit and wet throat were missing from Aubert's vocals. The sensual pleasures of "Poème Vivant" were abridged.

Nevertheless, I understood why so many engineering types would choose the AHB2 with the SR1a's: It played superclear, dug deep, and recovered much.

Listening with the Rogue Audio Stereo 100
I tried the RAAL SR1a's with only one tube amp: Rogue Audio's 100Wpc Stereo 100. It sounded okay, but the amp clipped easily and often. That discouraged me from trying any other tube amplifiers.

Important comparisons
Q: Are the $3500 SR1a's better than the $4999 Abyss AB-1266 Phi's?

A: No.

But they are not inferior.

The Abyss AB-1266 Phi's remain my reference headphones. When powered by the Pass Labs XA25 amplifier, the Abyss 'phones deliver the most natural, lifelike audio reproduction I have experienced. The Abyss headphones are also quieter and more transparent than the SR1a's.

Like the SR1a's, the AB-1266 Phi's sit off the ear, but only far enough to not cup or chamber. The SR1a's sit farther off the ear and, consequently, let in more room sound. This added openness is a pleasure to experience—especially the imaging. But said openness automatically reduces quietude and transparency.

The sonic landscape of the Abyss AB-1266 Phi's is liquid and silent, like its namesake. Like the ocean's depths, the Abyss 'phones showcase a shadowy transparency. In stark contrast, the SR1a's exhibit a hazy, bright-sun transparency. The RAAL-Requisites are more conspicuously open and dynamic than the Abyss 'phones. But . . .

Please understand . . . the Abyss and RAAL headphones sound more alike than they sound like any other headphones out there. Both headphones exist on the leading edge of transducer science. Their only competition (in my limited experience) is the HiFiMan Susvara headphones.

Q: Are the RAAL SR1a ribbons better than the HiFiMan Susvaras?

A: Maybe a little.

As I switch from the completely open SR1a's to the merely open AB-1266 Phi's to the not-very-open (circumaural) HiFiMan Susvaras, the sonic landscape becomes more closed in. With the Susvaras, I can definitely hear that cupping-induced seashell reverb I described at the beginning.

Three types of audiophiles will appreciate the RAAL-Requisite SR1a's:

The first are seasoned headphone connoisseurs who have been in the game a while and already own a collection of venerable exotics like Sony's MDR-R10 and Qualia 010, AKG's K1000, and Grado's original RS1. These listeners are confirmed aficionados seeking to experience recordings with the greatest amount of verity . . . and (!) that extra special lightning-in-a-bottle something that raises a headphone above the herd of its time. For these audiophiles, the RAAL-Requisite SR1a's will be a must-have addition to their collection.

The second are crotchety audiophiles who detest headphone listening, declaring it "unnatural!" These headphone holdouts will love and embrace the RAAL-Requisite SR1a. They will be astonished (and feel validated) by how much the SR1a's sound like regular sit-on-the-floor loudspeakers.

The third are mastering engineers. My friend Frank Schröder, the renowned German tonearm designer, was the person who turned me on to the RAAL-Requisite ribbons. He loaned me his pair while he visited NYC. Frank said he used the SR1a's to master recordings, and sure enough, I discovered that Aleksandar Radisavljević designed them with that use in mind. No question, they are revealing enough for the job.

In my view: The RAAL-Requisite SR1a's are both revelatory and revolutionary. Class A+.


Anton's picture

It seems that would offer easily achieved upgrades and even a low cost way for people to experiment with aftermarket mods.

It's out of my budget but seems reasonable and loads of fun to be had with it.

I hope you get to keep it around and we can see its evolution.

Thanks for a killer 'turn on' to a fascinating product!

Bogolu Haranath's picture

Another nominee for Stereophile 2020 product of the year award, RAAL SR1a ribbon headphones :-) .......

Anton's picture

It went on my "Lotto" list.

Bogolu Haranath's picture

May be HR could also review the MYSPHERE 3.1/3.2 headphones ($4,000) ........ HR mentioned about them favorably in his CanJam NY 2019 report for Inner/Fidelity :-) ........

JRT's picture

One advantage of the Mysphere 3.2 is that it does not need as much amplifier to work well.

Bogolu Haranath's picture

Both MYSPHERE 3.1 and 3.2 models should work well with conventional headphone amplifiers ........ Like the RAAL, they don't need amplifiers/integrated amps, that can drive loudspeakers :-) ........

JRT's picture
Bogolu_Haranath wrote:

"Another nominee for Stereophile 2020 product of the year award, RAAL SR1a ribbon headphone"

Seems so.

jeffhenning's picture

...the Benchmark AHB-2 to drive these things. At least, that's what he said last year.

In any event, man, the whole package is a lot to spend on headphone listening and a lot in general, mastering engineer or not. This is not an insignificant amount of kit for headphone listening.

Possibly, if I could write the system off as a business expense as an audio engineer at a ridiculously successful studio. Even if I won the Powerball, these would be really, really low on my list.

Would love to hear them, though.

Glotz's picture

Perhaps that was the reason why he heard them 'brittle and bright' on some recordings?

I wish I could read JA2's follow-up, as I can't find the issue nor remember all of the findings, outside of the RC blurb.

More to the point, $3k is pretty inexpensive for the company is competes with. It's not easy to compete with 5-figure amps at this price point.

That being said, I did purchase the Benchmark HPA-4 (LA4 with headphone amp), and it is fantastic and my feelings very much echo the thoughts in several pubs.

Straight wire with gain, baby!

partain's picture

Just a quick comment on the natives not recognizing the chief.

Ortofan's picture

...a seasoned headphone connoisseur who has been in the game for a long, long while, is a confirmed music aficionado and already owns the venerable Stax Lambda Pro earspeakers.

As a replacement, and with a budget of about $3,500, he is considering the Stax SR-L700 MKII paired with either the SRM-007 TII (tube) or SRM-727II (solid-state) driver units.

Would such an individual be likely to find the sound quality of the RAAL-Requisite SR1a to be astonishing, revealing, revelatory, revolutionary - and, above all, a must-have?

Anton's picture

Perhaps, maybe, yes, to quote Kraftwerk.

It's up to the audiophile you mention.

Bogolu Haranath's picture

Yes ..... If that audiophile is also rich :-) .......

Bogolu Haranath's picture

BTW ..... Why not that audiophile get both tube and transistor drive units with those Stax headphones? ...... He/she can have both flavors :-) ........

Bogolu Haranath's picture

Or .... That audiophile could go for the new Stax flagship SR-009S electrostatic headphones with the matching SRM-007T tube amplifier and SRM-007S transistor amplifier :-) ........

Herb Reichert's picture

I am listening to the SR-009S right this minute


Bogolu Haranath's picture

Great ... Looking forward to reading that review ........ Try them also with the matching Stax amplifiers, if you aren't already doing so :-) .......

Ortofan's picture

... the finest headphones (or earspeakers) on Earth, you can then use them as a reference transducer with which to conduct listening evaluations for your upcoming survey of cables.

Note that the cable for the SR-009S is silver-coated 6N copper. You should inquire as to whether or not the conductors are twisted - judging by the flat cable, it would appear that they are not. But don't do it while you're harbor-side in Cannes, lest it disturb your reverie.

Bogolu Haranath's picture

Wait .... We want HR to review the Warwick Acoustics Aperio electrostatic headphones with matching DAC/headphone amplifier ($24,000, reviewed by Hi-Fi News) ....... Then, HR can tell us which headphones are the world's best :-) .......

Herb Reichert's picture

the SR-L700s just arrived


Bogolu Haranath's picture

I'm trying to guess which amp HR is gonna like ...... Tube or transistor? :-) ........

Ortofan's picture

... of my seat.

Bogolu Haranath's picture

'Watchin' the tide roll away'? :-) .......

Bogolu Haranath's picture

Schiit Audio just came up with an integrated amp to specifically drive the RAAL ribbon headphones, Jotunheim R ($799) ......... May be HR could review that integrated amp? :-) ........

Herb Reichert's picture

of course (it is on its way)

Bogolu Haranath's picture

Looking forward to reading that review, including comparison with other amplifiers :-) ......

JRT's picture

Thanks for the well written review.

Bogolu Haranath's picture

The 'Cupping and Chambering' problem HR describes above in his review, gets even worse with 'closed-back' versions of headphones ...... That is one of the reasons why, most of the headphone listeners prefer 'open-back' headphones :-) .........

dcrowe's picture

I have the immense pleasure of owning the SR1a and using it with a Schiit Vidar which has adequate power and current for my listening. I do look forward to obtaining the AHB2 with DAC3 though.

agb's picture

Has no cupping problems, none, nada, and even though it fits into the ear (lightly for me), no bass pressure build up. OK, I recognize it is a "different" type of earphone. In my experience, two years or more after its release, it still trounces many other would-be's I have here. Lastly, I don't miss the weight like a brick on top of my balding head. There's a lot to be said for small and light, the great sound - and portable. It being what it is, it's magic.

Incidentally, worked with Julius Futterman for a while who also built me two ESL headphone amps for the two Staxes I had back then. One didn't sound like the other.

Whatever headphones do wrong, speakers always had a tough time catching up to them. And regardless the cost and expense, they still do.

Let's face it, with few exceptions, the room screws up the sound, one way or another. If not the room, it'll be your wife.

Earphones are hardly perfect...rooms far less so.

jww1's picture

Your favorite headphone amp? May be a silly question but By what means do you accomplish this?