Gramophone Dreams: Heretic AD614 Loudspeaker
Herb at the HiFi Loft. (Photo: Jason Tavares)
I remember a Saturday morning around 30 years ago, when I just happened to be at Sound by Singer, the New York City audio salon, watching this wizardy German fella named Joachim Gerhard unbox the newest speaker in his line, Audio Physic. I remember how bright the sun was as it streamed in through the windows, forming a wall of light behind him and silhouetting two implausibly thin box speakers. Their silhouetted forms displayed proportions similar to the World Trade Center.
I was taken aback by how Gerhard set up these thin twin towers in Andy Singer's biggest listening room. He positioned both speakers at least 6' from the wall behind them and maybe 5' from the walls beside them, with at least 10, maybe even 12 or 13' between them, radically toed-in. Andy's listening chair had been moved into the middle of the room—closer to the speakers than to the wall behind it. I had never seen small speakers set up in a way that so dominated an entire room.
Speaking in the serious tones of a German scientist, Gerhard explained how, with "conventional speakers," front-baffle–instigated response anomalies (diffraction) obscure detail and remind listeners constantly of the speaker box's presence, and how "applied physics" has allowed his "baffle-less" designs to eliminate that problem and reproduce the "fine details" and "intricate soundstaging" that conventional speakers could not.
Everyone in the room agreed: Joachim Gerhard's speakers disappeared more completely than any we had ever heard. When I sat alone in the sweet-spot chair, I watched the well-drawn outlines of musicians performing in the space between the speakers, without directly noticing the speaker boxes themselves.
This was my dramatic introduction to a new type of carefully conceived audio holography, where the projected soundspaces were clearer, wider, and more conspicuously arranged than I ever thought possible. Unfortunately, the musical part of the program came through affectless and low on corporeality.
Since that Saturday at Sound by Singer, such narrow-baffled speakers have become de rigueur in high-quality audio. This design orthodoxy dominates the marketplace so strongly that it has incentivized conformity and marginalized competing engineering strategies. How many newly designed horns, omnidirectional, electrostatic, planar-magnetic, or full-range open-baffle speakers do you see advertised these days? The hegemony of the skinny-box orthodoxy had me worrying about our collective music-listening future—until a day in September 2022 at Jason Tavares's elegantly appointed HiFi Loft in Hell's Kitchen, NYC, where, after auditioning Klipsch's new, spectacularly dynamic, precise-imaging Jubilee horns (which have front baffles 52" wide) and Harbeth's latest not-skinny-but-consummately-coherent SHL5plus XD, I auditioned these stout, unpainted, unveneered-plywood box speakers. Their 19"-wide baffles looked ever so much like the baffles on Altec's 612 utility enclosures, which I once used with my 15" Altec 604B coaxial speakers.
Jason played Frank Sinatra Sings for Only the Lonely (Capital LP W-1053) on Luxman's upgraded PD-151 MARK II turntable (see Michael Trei's review in the March 2023 Stereophile) with a Dynavector XX2 moving coil cartridge (covered in the March 2023 Gramophone Dreams). For the first time since I can't remember when, Sinatra seemed to be standing intensely there in front of me, sounding like his warm-blooded, coolness-emitting self and not a ghostly hologram.
Heresy
The speakers I was listening to were the smallest of Heretic Loudspeaker Company's three models, the $7290/pair AD614 (footnote 1); they placed Frank between the speakers more physically than I'd ever heard in an audio store. While I smirked with pleasure, I began wondering if this might be the loudspeaker—or at least the type of loudspeaker—I'd been searching for.
These Heretic speakers, Jason said, were manufactured in Montreal, Canada. Their coaxial drivers were made in Italy by a company called Faital Pro. From one look at their raw-looking cabinets, it was obvious that Heretic's founder and chief engineer, Robert Gaboury, created the AD614 in willful contradiction of every protocol of today's speaker-design orthodoxy. The AD614 was not designed to look or sound or sit in your room like any speaker currently listed in Stereophile's Recommended Components.
The AD614 uses a 12" coaxial driver rated at 97dB/2.83V/m into 8 ohms. This pro-quality driver features a cast basket, which supports a treated-paper cone with a "triple-rolled" surround, a glass-fiber voice-coil former, and a ferrite magnet. Partially visible behind its open-weave dustcap sits a compression-driver tweeter with a neodymium magnet, which pressurizes a short, thick aluminum horn with a dome made of polyether ether ketone (PEEK) plastic.
According to Gaboury, "One very important aspect is the tuning of the AD614's box. I started out by back-engineering the Altec 612 Utility cabinet, which was designed 20 or 30 years before Thiele/Small parameters were commonly used to calculate air volume and tuning, so Altec's box was probably tuned by ear.
"The first aspect I found puzzling was the ductless vent, with no 'tube' to tune the port. Altec's 'port' works in the same manner as any other bass-reflex design, except the loading is not centered on a single, precise frequency but rather over almost a whole octave, because—my hypothesis—it does not work radially. Air pressure can escape naturally, from all angles, thereby extending loading a bit. "It also has an effect on impedance by reducing the common saddle curve, so electrically the AD614 looks more like an infinite baffle design."
According to Gaboury, the AD614's drivers are connected through a series-wired second-order Linkwitz-Riley crossover terminated at the solid copper binding posts (footnote 2). "Recommended amplifier power: 3–300W, unclipped." These boxes can play LOUD!
According to Heretic's website, "Most of today's loudspeakers have a circuit called a Baffle Step Compensation (BSC) filter, which boosts low frequencies to compensate for the acoustic effects created by narrow enclosures. Heretic speakers do not have this circuit and therefore rely on the 'broad shoulders' of the enclosure, acting as a launch pad for low frequencies.
Therefore, it is advisable to place Heretic speakers against the wall and benefit from the natural reinforcement offered by your room boundaries." How's that for heresy?
Guess what the "AD" in AD614 stands for? Like me and all my pals, Robert is a dedicated fan of the eager, aw-shucks sincerity, snarky-but-light-hearted humor, and timeless audio wisdom dispensed by the late Art Dudley. Robert explains: "I met Mr. Dudley a few times at shows, and I was always torn between telling him how much I liked his writings and bias toward a certain type of sound—emotions, really—and just keeping to myself, which I did.
"When he passed away, I thought that maybe, maybe I should have told him, but then again, who am I?
"I think Mr. Dudley was the ultimate heretic, and the ultimate gentleman. I felt he didn't care much for the business side of hi-fi and was absolutely solid and true to his convictions."
In my mind, Art was the high priest of an audiophile cult that believed that listening was a true path to the Divine.
The design
During my years, I've noticed that concentric drivers seem to project singers into the room with a greater presence than domes and cones mounted separately. And that big-coned concentric drivers, like 15" Altec and Tannoy coaxials, project voices and instruments with greater ease and presence than smaller ones. You tell me, how can any speaker effectively imitate a chesty baritone, a grand piano, or a close-miked cello with a 5" driver?
Gaboury says: "In the frequency domain, coaxial (point source) drivers are everything but linear. In the time domain, they are excellent. But large paper woofers do not act like the theoretical ideal piston. Paper has too much flexibility, and by the time higher frequencies reach the outside perimeter of the cone, they are already out of phase and damped by the cone's compliance. Yet, we must question whether pistonic behavior is musically relevant or not. Or could controlled cone breakup become desirable musically? I think it can." That's pretty heretical. Right?
My friend David Chesky and I believe that humans are way more sensitive to distortion and timing than frequency response, and that the majority of today's box speakers create their own "signature" time smear that we can hear but don't notice—except when it's not there. Like when listening with headphones.
According to Gaboury, the main speaker-design question is always "Should speaker designers focus on the frequency domain or the time domain?" He thinks the time domain should be prioritized. And I agree.
I queried Gaboury about the AD614's crossover.
"Why Linkwitz-Riley? Because it sums to zero. Because the woofer and tweeter are connected in series, the network logic is inverted. If you want to fix something in the high frequencies, you must act on the LF section. It's like writing with your left hand in front of a mirror.
"Why second-order? Because I cross at 1.7kHz, which is a bit under the point where the tweeter starts to feel uncomfortable. I also chose that frequency because this is where the dispersion of both drivers overlaps nicely, while steering away from the woofer cone's breakup."
I asked J.C. Morrison, me ol' runnin' buddy and audio-engineering mentor, if he had any thoughts about a two-way coaxial driver with a series-implemented Linkwitz-Riley crossover. His response:
"Parallel crossovers store energy and release it in a different way than series crossovers do. Because all the current goes through both drivers and the filter components shunt current 'sideways,' the drivers are forced to act more as one. In parallel, the drivers act alone. If the source is current drive, then a series 2-way crossover is the 'constant voltage' model and much less affected by motional impedance than a parallel crossover. This is why series crossovers favor the higher output impedance of no-feedback tube amps and/or current drive."
Gaboury: "Another aspect that tickled my mind was that serial crossovers are almost impossible to model in software, which is probably the reason nobody is crazy enough to dig into them. Designing a second-order serial crossover is something that, to do right, requires a lot of time spent doing trial-and-error listening. That amount of time, plus the uncertainties involved, cannot be justified in a mainstream corporate environment."
According to Heretic's published specs, the AD614 comes in a 3ft3, 12-ply, FSC-certified birch plywood box that weighs 43lb and measures 25.5" high, 18.75" wide, and 14.5" deep. That's the same size and weight as Altec's classic 614 speaker enclosure, which was used with Altec's own 12" coaxials. Finishes for Heretic speakers are specified as a choice of water-based acrylic Black or a semitransparent mixture of linseed oil and bee's wax in either White or Clear. Heretic's warranty lasts 10 years.
Setup
In my room, Heretic importer and Fidelis Audio principal Walter Swanbon set the AD614s on custom 12" Fidelis stands about 20" from the wall. In that position, they played big soundstage-wise but were a little lean through the midrange. After he left, I experimented by moving them first forward some, which made them leaner and brighter. So then I tried moving them backward, ending up with the two boxes no more than 6" from the wall behind.
Sitting on the Fidelis stands, the 614's tweeters were 27" from the floor. My normal listening position places my ears 33" to 36" above the floor.
Because all the photos on Heretic's website show their speakers sitting directly on the floor aimed straight ahead, I tried that position for a while. The sound was overtly rich and smooth, not boomy, and quite listenable. I put ¾" wood blocks under the front feet, which allowed me to aim the 614's tweeters directly at my nose. In the new configuration, the sound was more transparent, deep-spaced, and sharply focused than it was with the speakers aiming straight ahead. Fidelis's Swanbon tells me that Heretic is finalizing the design of matching wood stands that will deliver the type of sonics I experienced with the arrangement described above.
Listening with Elekit's new TU-8900
The AD614 is so far outside today's mainstream design and marketing paradigms that whenever I listened, I couldn't stop my left brain from scanning for all those terrible faults the knowers told me I should find. But all I discovered was a Santa's bag of new pleasures—pleasures not offered by my Falcon Gold Badges or any other box speaker in my collection.
The first new pleasure the Heretics delivered was reproducing Sinatra's Only the Lonely LP, in my studio, with touchable textures similar to but less intense than those I experienced in the demo at HiFi Loft. Consider, though, that at my house, the Heretics were playing Frank with just two or three single-ended 2A3-tube watts. How many narrow-baffle speakers can do that?
The second new pleasure was even more exciting: The AD614s displayed an oceans-wide, minutely drawn, evenly lit soundspace that felt natural and relaxed, not exaggerated or contrived. A few days before Christmas, I was listening to the Medieval Players playing a bagpipe and a little bowl-shaped drum called a naker, performing a Christmas song from the Moosburg Gradual of 1360 entitled "Anni Novi Novitas" (Cum infulatus et vestitus Presul intronisator), from their album Al Manere Minstrelsy (LP, Planet Life PLR 052). The experience was striking to the point of being hypnotic. I watched drumbeat transients bouncing off stone walls with identifiable trajectories. The bagpipes, nakers, and the stone walls felt physical and visible, and the music felt timeless and universal.
Playing Sigismondo d'India: Lamenti & sospiri (24/96 FLAC, Ricercar/Qobuz) with Cossor 2A3 tubes in the Elekit TU-8900, the way-back part of the soundspace was clearer than ever, vibrant, and micro-focused. In contrast with my long-term budget-reference 300B amp, the TU-8600, which uses high-nickel cores in its output transformers, Elekit's TU-8900 features amorphous core outputs, which I think tend to juice up the recorded sound in an overly spectacular fashion. When you're old and alone in the dark, "overtly spectacular" feels like kinky sex.
When I switched from 2A3s to Cossor WE300Bs, opera sounded larger, smoother, and more electrifying through the Heretics than through my Falcon Gold Badges, so I kept playing opera recordings—from Italy and Kentucky—and staring at the AD614's treble. All I saw were beautifully textured, minutely articulated soprano harmonics.
With the WE300Bs, the Heretics' upper octaves sounded creamy, extra-dynamic, and clear. The 614's treble sounded uncompressed, wide open, and low-distortion, making sopranos, trumpets, and the upper octaves of the piano sound more intense than they did through my tiny Falcons or DeVore Fidelity's broad-baffled Orangutan O/93 floorstanders.
With the Elekit amp, the Heretics sounded more vivid and high-energy than the easygoing, rich-toned DeVore speakers. On the other hand, the comparison led me to notice how the O/93s played consistently quieter, with a more laid-back energy, most likely the result of a soft-dome tweeter, contrasting the Heretics' compression-driver horn.
The AD614s showed me how much my Falcons' compression was limiting my enjoyment of several of the world's louder, funner, and less intimate music genres. Most especially ska, dub, and reggae: genres for which large woofers on broad baffles are necessary to get out the message. With the Heretics, Scotty and Lorna Bennett's "Skank In Bed" from This Is Reggae Music Vol. 2 (1975 Island Records LP ILPS 9327) sounded more like I am sure it was intended to sound than it has sounded here since I gave my Altec 604Es to Art Dudley.
I used only three amplifiers for this report, and I ended up amazed by how the Heretics' amp-friendly load allowed each amplifier to sound more awake and vigorous than it usually does driving other speakers.
With the Parasound A 21+
I doubt any amp-swapping on any speaker could render a more dramatic change in sonics than exchanging the 3-watt 2A3 tubed Elekit TU-8900 for Parasound's 300W Halo A 21+ amplifier. The 21+ injected steroids into the AD614's monitor-like clarity. Every tiny bit of sonic data seemed perfectly clear and fully charged.
When I played my beloved Skip James LP, Devil Got My Woman (Vangard VSD-79273), my first thought was "Wow! I've got to tell J.C. how much this series-crossovered speaker likes solid state amps." The Heretics really lit up with Parasound's mighty class-A/AB watts. Skip and his guitar and piano never sounded more present or exposed by the microphone.
I doubt the AD614s ever dragged more than a few watts out of the Parasound, but the watts they pulled were smart, good-looking watts. The sound I experienced was probably the result of the A 21+'s heavy transformer and high-current power supply effortlessly streaming tiny details into the Heretic's resistive load.
Keep in mind that, throughout these Heretic auditions, I was listening constantly for those faults the knowers told me I would find. You know the ones: bloat, boom, uneven frequency response, and diffuse, unfocused imaging. But I didn't hear those faults. The A 21+ amp driving the AD614 speakers played dense, difficult-to-play piano and violin concertos with better-sorted, more tightly rendered, quicker-moving bass than any of my other speakers. The Parasound emphasized the Heretics' propensity for sharply focused details and rhythmic drive.
With the First Watt SIT-3
The first thing I noticed when I switched from the John Curl–designed Parasound A 21+ to the Nelson Pass–designed First Watt SIT-3 was the huge reduction in gain, from 29dB with the Parasound to only 11.5dB with the SIT-3. The thing I didn't notice, at all, was the reduction in potential output power, from 300W (into 8 ohms) to 18W. What I noticed most was the SIT-3's denser, more colorful and relaxed presentation, which I attribute to the absence of feedback in the First Watt amp. Beyond that, the sonic differences were subtle, with the A 21+ winning the Leica-focused deep-imaging contest and the SIT-3 taking gold medals for Best Tone and Longest Reverb Tail. Powering the Heretics, both amps showcased free-swinging dynamics and Webb Telescope vividosity.
Most importantly, the Heretics proved they could play comfortably and enjoyably with a wide range of amplifier types. That's rare.
Dear Reader,
That day at Sound by Singer, I was alienated by the disembodied clarity of those early Audio Physic speakers.
As I stared between those thin towers, my attention wandered. I looked around distractedly, noticing how everything in the room—including my chair—had been arranged for no other purpose than to facilitate what I felt was an excessively cerebral form of man-machine interaction. All feng shui lines pointed at that lonely Le Corbusier chair. No sofa, no scantily clad lovers, no pets, no cluttered coffee table.
My taste in listening environs leans toward plush, Bohemian-style couches with silk-embroidered pillows, candles, colored lights, and various forms of temple incense. Heretics feel at home in that environment.
There's another side of me that seeks pro-quality studio monitor sound, something I'd feel confident mastering a recording on. The Heretics scratch that itch, too. And then there's the Jazz Kissa and hip coffeeshops with speakers hanging from the ceiling. I suspect the Heretics would feel right at home.
One last point
As much as these speakers look like vintage Altecs, they do not sound like vintage Altecs. Compared to the various Altecs I've owned, or to Alex Halberstadt's Valencias, which used to belong to Art Dudley, the AD614 is dramatically smoother, more precisely focused, and more evenly balanced across its bandwidth. Art thought speaker imaging was overrated, but I loudly disagreed. For me, if tone, texture, and tempo are properly recovered, then vivid imaging is added proof that a majority of small-signal info is getting through.
In my room, with my sources and amplification, the broad-chested Heretics project the widest, most intricately focused and evenly lit soundspace I have encountered, and they did it while sitting only inches from the wall.
The Heretic AD614s played larger, louder, and more electrifying than my Falcons, Magnepans, or DeVores. They sounded more like studio monitors than Harbeth's 30.2 speakers. But I doubt they sound much like any contemporary speakers you are familiar with. I could always hear the paper in the Heretics' cones, and I was never not aware of the location, mass, and volume of their thin-walled boxes. But for me, those things were more of a comfort than a distraction.
You know how I'm always saying that I can't find what I'm not looking for. Well, the Heretic AD614 seems to be the kind of loudspeaker I've been searching for.
It works well with all types of amplifiers, suits my taste in sound, and is sized perfectly for my room. I am happy I discovered them.
Give them a listen. These Heretics might be the speakers you've been wishing for, too.
By Herb Reichert | Mar 21, 2023 | stereophile.com