The Acarian Systems Alón I Loudspeaker
FLYING CLOSE TO THE SUN
COMMON WISDOM SUGGESTS that in an ideal reviewing world, the audio critic should be uncontaminated by biases derived from familiarity with a designer's prior work, or from judgments offered by others- some of whom may have a vested interest in shaping the reviewer's conclusions. Opinions about a component ought to emerge from actual experience, rather than from the auditioner's own prejudices about a particular design philosophy; or from influences provided by advertising literature, friendship with the manufacturer, a sales rep's largesse, or outside opinions.
Now none of us lives in such isolation that we are immune from contacts of one sort or another that can influence our judgments. But never have I been asked to review a product whose arrival was preceded by more conflicting opinion (of which I was aware) than the Alón loudspeakers from Acarian Systems.1Well over a year prior to Scot Markwell's offer of a pair of Alón I's, I had read a comparative speaker review in Stereophile in which a panel of listeners ranked the design dead last among eight competing systems. When Acarian's founder and president, Carl Marchisotto, protested that the samples that fared so poorly had been damaged in transit, Stereophile performed a follow up review of a second set of speakers several months later (which I read only once I knew I would be receiving a pair of I's) in which the primary flaw detected several months earlier was absent. Nevertheless, the reviewer, John Atkinson, still refrained from offering enthusiastic accolades. Simultaneously, however, Ken Kessler published a positive assessment in HFN& RR, which I also read. What every critic noted was that the Alón I's make a lot of bass, and image well. Some perceived, among other flaws, a recessed midrange. Was the midrange really diminished, I wondered, or did it only seem so because the bass was overblown? I also had to digest Scot Markwell's opinions, for his offer of the Alóns came in direct response to a comment I made about the Paragon Acoustics Jubilees' lack of hefty, fulfilling bass. "You want bass?" Markwell shot back, "I'll send you a pair of speakers that make bass!" A week later the Alóns arrived in Lancaster.
Carl Marchisotto offered his own opinions before my listening began, noting, if not quite complaining, that all the critics seemed so entranced (my word, not his) by the bass performance of the Alón I's that they ignored, or glossed over, the speakers' other attributes. After a series of conversations, he asked if he could replace the much-traveled units that Markwell had sent with a pair fresh from the factory, which he and his wife and daughter hand-delivered in the midst of last winters arctic onslaught. They spent a half-day here. I was elated when, after a morning of setup (while I was at my office), the speakers' designer left the units positioned precisely where I had placed the first set (32 inches from the side walls, 60 inches from the rear wall, 47 inches apart, measured center-to-center, pointed straight ahead), thereby confirming my own judgment as to where they performed best.
Thus, before I ever began listening to the Alón Is with note pad in hand, I had a whole set of opinions about the speakers that, even if they did not shape my own thoughts, might work to establish the questions I would ask- might, in other words, create a review agenda for me. Needless to say, among the primary advantages of the "innocent" approach is that one can respond exclusively to the experience itself. I feared that as I listened, at some level I might be influenced by what others had said or written. I was/am also sensitive to my predicament in reviewing a product that has stirred considerable controversy. If I rave about the Alóns, all the naysayers and skeptics will simply attribute my words to some ulterior motive that impels us (TAS) to disagree with them (Stereophile). If I debunk the Alóns, the same folk will whisper that I do not possess an independent mind (or pair of ears).
My opening comments: The second, hand-delivered pair of Alóns sound virtually identical to the first set. I am fairly certain I could not identify differences, though I did not conduct a direct A/B comparison. As I began to listen seriously, I had to overcome two prejudices of my own. First, the Alóns do not present a particularly impressive visual aspect with the grille work in place- they look quite ordinary. While there is nothing wrong with their appearance, it strikes me as sort of generic. With the upper cover removed, however, the innovative "open baffle" (on which reside the 4 1/2" cone midrange and 3/4" aluminum alloy dome tweeter) is visible, and when thus "half-covered," the Alóns look anything but typical, for the design screams high-tech, out-of-the-ordinary, this-didn't-come-from-K-Mart at the observer. Second, I was struck by the speakers' light weight (40 lbs. each). When UPS delivered the first set, I was shocked that the speakers could be lifted with virtually no effort. My very first independent impressions, therefore, were responses to lightweight- were these flimsy, cheaply-constructed, resonant, or prone to vibration, I wondered? Our experience predisposes us to associate heavy enclosures with serious design and high-quality sound. The Alóns defy that premise.
Marchisotto arranged for VTL to loan me a set of MB150 amps, which I used extensively prior to the Alóns' arrival. He also provided a set of Orpheus speaker cable configured to take full advantage of the speakers' bi-wiring capability. I used these cables exclusively with the Alóns.
Trained as an electrical engineer (MSEE from NYU), Marchisotto spent 15 years with Dahlquist prior to starting Acarian at the end of 1991. He and his wife Marilyn, the company's vice president, coined the name Acarian from the mythological Icarus- the name's origin has been (until now) their private joke, for they intend their products to fly high, but assert that unlike the wax that secured the ambitious Icarus's wing feathers, their glue will not melt (their cabinets will not fall apart). I asked Carl why he is wedded to the baffle-less dipole design that marks all his speakers. The answer was simple: by eliminating the enclosure, one simultaneously eliminates the colorations cabinets impose. In theory, such designs ought to be free of internal standing waves, air column resonances, cabinet wall resonances, delayed resonances, etc. These, he argues, are impossible to control completely in any enclosed system. Hence, the midrange and tweeter drivers sit atop a cabinet that houses the 8" woofer (a traditional sealed system), on an MDF panel so nicely finished that I thought it was plastic or some exotic creation of the petrochemical industry. The drivers are all proprietary, that is, manufactured to Marchisotto's own design criteria, and are sourced from different producers, He would not divulge the manufacturers' identities, only saying that the midrange and tweeter are made in Europe, while the long fiber wool cone woofer is US made. Earlier Marchisotto designs specified soft dome tweeters, but the high frequency demands imposed by CD cause many soft domes to break up. Unhappy with the sometimes harsh sound and tendency to resonate of most hard domes, Marchisotto designed an aluminum alloy tweeter that he claims does not break up until 25 kHz. The small version fitted to the speakers displays its first breakup mode at 35 kHz. "What's great about this tweeter," he says, is that "it doesn't do anything wacky."
So for a little over $1,000, the Alón I's purport to be a down-sized version of the speakers that some critics have raved about. The larger and pricier models make deeper bass and play louder. But the sonic character, if the Is fulfill their design goal, ought to be similar. And in my small (11' x 14') room, the I's should, in theory, actually perform better than their larger siblings.
Having discoursed at such length before describing my listening sessions, allow me to generalize: The Acarian Systems Alón I's are not good speakers. They are great speakers. I have no way of knowing how they will perform in other venues, using ancillary components different from what they encountered here. But in my home, using high quality (and expensive) electronics, the Alón I's not only gave continuous pleasure, but simply astonished me with performance that made their price seem ridiculously low. They strike me as an absolute best buy in High End audio, with virtues that make them comparable with speaker systems costing thousands of dollars more. May I elaborate?
In my room, with LP and CD, driven by the VTL MB 150 amps in tetrode and in triode configuration, and by the Beard M70 amps, the Alón I's did nothing badly. In fact, they did nothing less than very well. But they did several specific things so remarkably that my listening notes time and again refer to these aspects of the Alóns' performance. These traits therefore, in my judgment, define the speakers.
First, the Alóns image spectacularly, producing sounds that have the spatial specificity, the three dimensionality, and the physical size that until now I have experienced only in much larger systems, Second, the Alóns create a soundstage whose size is, if not the very largest I have encountered, certainly a contender for that honor; but what is more riveting, a soundstage that is light and open and full of air- a stage rivaled in my experience only by the B&W 801 s which I loved for this single trait. Third, the Alóns provide bass that fully lives up to the reputation the speakers earned prior to their arrival here in Lancaster- bass whose appeal to me derives more from its quality than its quantity. Fourth, the Alóns have an endearing nature that I will attempt to describe in more detail, but that relates to what I see as the way they honor music both as sound and as performance. It is a quality that provokes feelings and emotions in the listener that only partly relate to dynamic range, or bass extension, or glare-free highs, or tonal balance, or soundstage width and depth, or to any of the other parameters of performance I can identify and describe with some confidence that a reader will understand exactly what I heard. What I am talking about here is different. It is the kind of characteristic that led me to jot in my notepad on five different occasions, "I am not sending these speakers back."
Imaging: This aspect of the Alóns' performance occupies more space in my notes than does any other characteristic. Hence, it was what attracted my attention as most noteworthy, and, therefore, strikes me as critical to a description of what makes the Alón I speakers distinctive.
Examples: I used Yaz Don't Go [Sire 29886-OA] as a test for bass performance. Yet what I wrote about as I listened to that recording was how "surprised" I was to find myself focusing not on the bass, but on what I described as "the precision of the images- each instrument and voice is absolutely clear and focused as if seen through a lens." Stupefied (a word I used in my notes), I was stunned when the series of sonic "splashes" that enliven the performance "had, for the first time, a shape as opposed to merely a sound- this is incredible," I wrote, "their location varies as does their form- they occupy both vertical and horizontal space, and still more incredible, they have depth!" Listening to Slatkin and the St. Louis Symphony Orchestra perform the Brahms Academic Festival Overture [RCA CD 099026-61715-2] (it was commencement weekend- I could not help myself), I was struck by the "jocular bandying back and forth among the winds," that I described as "eerily precise, i.e., the interplay takes place in the center of a much larger fabric of sound but each instrument has its own distinct and clearly perceptible location- this is wonderful," Dorati and the LSO performing the Dvorak Seventh [Mercury CD 434-3112-2] provided delight after delight for the imaging aficionado. I loved the way the Alóns placed the strings in front of the orchestra, part of the whole, but at the same time separate and distinct from it. During the third movement I became fascinated by the exchanges between string sections seated left and right; what I called "a dialogue that rivets one's attention [because] the images are so clear, so precise." The Eighth on the same disc elicited this comment: "The first violins and the basses have a kind of body, of corpulence that I cannot recall sensing to this degree on any system. I'm not sure if it is the Alóns or the VTLs or both, but it is striking and immensely enjoyable." Among my standard tests for imaging is the "San Francisco Bay" cut from the Weavers at Carnegie Hall [Vanguard VSD 2150] 2. Frank Hamilton and Eric Darling have never been separated more clearly, side-to-side, and front-to-back, or with greater precision. Another old standard, the persuasions We Came to Play [Capitol 791] led me to remark, "the clapping and tapping is precise- laser-like imaging, wonderful." Belafonte at Carnegie Hall [RCA CD 6006-2-R] yielded similar results. "The supporting players," I wrote in my notes, "both left and right are riveted and focused and so clear- this is like seeing through a just cleaned window." Or a bit later, "the bass to Belafonte's right, then the guitar in front, then the drum- each entry seizes my attention, each player is visible in a specific space- just splendid. There is not a hint of enclosure, of a box. The speakers just disappear. All that is here is the music and the players. I'm not returning these speakers." A final note about imaging. With recording after recording I sensed that the size of the images was convincing- at least as large as what I have heard from such planar speakers as Magnepans, Acoustats, and Martin-Logans. Some months ago the little Paragon Acoustics Jubilees really impressed me with the believable size of the images they crafted, a revelation from such diminutive speakers. Well, the Alóns do an even better job at crafting full-scale credible images- they are what my notes refer to as "convincing." What is telling is that the Alóns are far from large. In fact, their footprint, at only 9"x 13.5", is in the mini-monitor league. And they are only 38" tall. That such small units, designed to mesh perfectly with small rooms, create images so lifelike that one thinks he or she is hearing real musicians in real space, alone would justify an audition, Taken in the context of the Alóns' other virtues, one is left in amazement at the value offered for the purchase price.
Soundspace: Closely related to imaging, of course, is the space the speaker creates for the images to occupy. The Alóns craft a stage whose dimensions, though huge, are not unnaturally huge. Especially attractive, there is an overarching sense of openness, of light, of palpable clarity with these speakers that makes other systems seem veiled, muffled, dark, cloudy by comparison. I suppose this is a consequence of the enclosure-less baffle that supports the tweeter and midrange, and of the true dipole design. Whatever the reason, the size and the clarity of the soundspace the Alóns create is simply stunning. In a different room the I's might well behave differently. In my room the match seems perfect. You want examples? Hear these comments as I listened. My very first reaction upon auditioning the very first disk at my very first "serious" session with the Alóns was: "The room is full of sound! Left to right, front to rear. Great. The proportions are just right. No dead spots, no blind spots. The images float free of the speakers. There is a superb sense of openness, a complete freedom from boxiness. This is exactly what a High End component should do." A bit later in the session I noted, "The imaging is so good at the edges that I find myself questioning my setup and the ability of the Alóns to provide centerfill information. Then, all of a sudden, a perfectly placed horn, or flute, or wind will pop out from dead center, or left center, or right center, disabusing me of such concerns" [Dvorak Seventh Mercury CD 434-3112-2]. The Alón soundstage is not only wide, it is also deep. Better still, it is not truncated in any way-there is not even a hint of trapezoid-ness. From front to rear the soundspace maintains a consistent width, when (and only when) the source specifies a need for it. In my experience, reproduced sound typically falls short of that ideal, diminishing the size of part of the stage by shrinking the rear in relation to the front or vice versa. The Alóns are wholly free of this defect. Listening to Dorati's Dvorak Eighth I instinctively strained forward in my seat as I would at a live concert in an attempt to get closer to the "hall sounds" that were "so lucid, the rear wall is right there, way to the rear of the speakers," The Brahms Academic Festival Overture led the Alóns to create a stage I found "sooo deep" with precise images from the left rear right across to the right rear. Perhaps best was the chorus in the Fauré Requiem [Collegium Col 101], which literally occupied all 11 feet of the wall behind the speakers, and yielded sounds of otherworldly beauty. I wrote, as I listened, that there was "no congestion during exclamations. As the sound level increases every voice is clear- a bunch of individuals as opposed to an undifferentiated indistinct mass-this is sensational performance under a very demanding load." The Alóns placed Ronnie Gilbert "really deep" to the rear, and Pete Seeger in his customary location far to my right as the Weavers performed "Guantanamera." And I cannot tell you how thrilled I was when, at last in my "new" small listening room, I heard Jimmy Hayes well to the left of the left speaker as the Persuasions sang "Chain Gang," a position he used to occupy in my former much larger rooms, but which no speaker until the Alóns had been able to achieve in my current listening room. If I had needed any further evidence that the Alóns make a terrific soundspace, Gilbert Kaplan's Mahler Second with the LSO [MCA 2-11011] would have decided a verdict in favor of Marchisotto's creation. "The LSO," I jotted excitedly, "is spread all across my room. I have the hall floor, the walls, everything... my eyes dart all over the room to find the sounds I can see with my ears- the depth, the imaging, is state-of-the-art- the Alóns are perfect in my room. I'm never sending them back." Moments later I wrote, "what is great is that the Alóns make a far right, far left, far center," that is as wide as the front of the stage, "a wonderful feat, totally convincing." Listening to Hogwood and the AAM perform the Water Music [L'Oiseau Lyre DSLO SAS], I simply remarked, "The stage is spectacular." Enough said, I think.
Bass: As I listened to the Alóns, seldom did I note their bass performance. I was far more struck by their other qualities. I certainly did not find their low-end performance excessive, or bloated. Rather, I considered the bass satisfying, fulfilling, and, most important, supportive of the music rather than attention-grabbing in a self-indulgent, vulgar fashion. Thus the bass lends "body and corpulence" to some instruments (Dvorak Eighth), and provides a rock-solid foundation for large-scale orchestral works. This is certainly not to imply the Alóns are bass shy, or that I ever found myself unsatisfied by what I once described as the bass' "shockingly powerful, overwhelming weight and impact" [Power of Love, Chrysalis 4V9 42889]. Rock recordings allowed the Alóns to demonstrate what so many commentators have noted, an ability to produce levels of low frequency sound that belie the speakers' size or price, bass that seemed "stunning." But when listening to Yaz's Don't Go, a recording chosen specifically to allow the Alón bass to strut its stuff, I failed to hear what former TAS technical director Jeff Goggin used to describe as "a rhino rumbling around in the basement." Instead, my attention was diverted from focusing on the bass by the Alóns' virtuoso display of its imaging capabilities. Similarly, Don't Look Down [Chrysalis GOW 3], which on a system with overblown bass might have caused one to remark on the lower frequencies, led me instead to note the spectacular "wall-to-wall images" and the "stunning articulation of the synthesized highs." I found the bass nicely integrated with the other drivers, and most impressive not on rock recordings, but rather on large-scale orchestral works such as the Mahler Second, whose opening bars allowed the Alóns to "stun with impact." The bass capabilities of the Alóns endow the speakers with the capacity to reproduce such massive works in a truly convincing fashion, at a level bass-shy systems never can. Thus, when appropriate, the Alóns can indeed produce "a cataclysm of sound, just what Mahler (or Dvorak, or Beethoven, or Brahms, etc.) must have intended," but what, in our homes, we so seldom hear.
Are the Alón Is "perfect"? Hardly, They certainly would not perform as well as they did in my room were they asked to fill a far larger space with sound. And the bass, while satisfying to a level that belies the speakers' size and price, does not reach into those subterranean regions where earth tremors lie dormant waiting for a subwoofer to stir them. As I have noted, perhaps the biggest surprise of my sessions with these speakers has been that I was not overwhelmed by levels of bass that obscured other facets of the Alóns' performance- an expectation I brought to my listening from all that I had heard and read about the speakers before they arrived. The bass is great. It is not out of balance, overblown, or life-changing. Were I pressed to note a flaw in the design, or an aspect of its presentation that left me wanting something more, or different, I might cite the Alón I's high end. I was far more "aware" of the highs, as I listened, than I was of the speakers' fabled bass. Why did the highs attract my attention? Sometimes (repeat, sometimes) strings sounded "a tad dry" (Dvorak Eighth) or "antiseptic as opposed to rich." On the other hand, the tweeter created synthesized highs I found "stunning-clear and clean- a virtuoso performance" (Don't Look Down). The violin solo I found so "fragile" so "delicate" in the Fauré Requiem still seemed "a touch dry, not sweet." It was, nevertheless, beautiful and lifelike. "The violin and Caroline Ashton's voice," I wrote, "do not have the ethereal otherworldly sweetness they can take on when heard via ribbons, but there is such delicacy and fragility, it is so moving and so beautiful." Using the Beard M70s, the Fauré became "just heavenly- the solo violin in 'Sanctus' is not dry at all, and the voices ascend to heaven as in a dream... is the violin a touch wiry?... no, this is great... Ashton's voice is unreal, angelic, she floats in space." Under severe load, as when Jody Karin Appelbaum performs "Galathea" or "Gigerlette" from Schoenberg's Brettl-Lieder [Music & Arts CD-729], the tweeter displays "terrific micro-dynamics" but also jars with its sharp presentation. Now Appelbaum heard live also jars with high notes that, were they heard on a recording, might cause an audiophile to ask if perhaps the highs might be a bit harsh. The Alón tweeter is not reticent or shy. And the Alón I's highs can be prominent (when the source calls for prominence). But I never found them harsh or strident.
An endearing nature that honors both the music and the performance, or, why I love the Alón l's: I am of two minds about whether I should be writing this final part of my Alón I review, for I want to relate responses to the speakers that are not verifiable or repeatable by others-that are essentially personal and subjective. When I tell you that the Alóns make great bass, a huge soundstage, or image deftly, I am certain that if you were to visit my home you would hear pretty much what I have described hearing. But now I must try to relate something quite different- not what I heard, but rather what I felt. I say all this so that you know that I know that what follows is something other than a dispassionate attempt to report accurately exactly what I heard.
Having offered the caveat above, I would like to say a final few words about the powerful emotional response I had to the Alóns. Repeatedly these speakers made me aware of aspects of the performance that had been hidden by the system or ignored by the listener (me) previously. "The speakers," I mused as Dorati conducted the LSO, "allow me to appreciate just how flawless the execution is."During another session I wrote, "I cut my teeth on Giulini's lyrical, gentle Dvorak Eighth, but this performance (Dorati) is a rocket ship by comparison." Again and again my notes contain comments about what I supposed was the performer's mood- adjectives or adverbs that suggest I was hearing more than just the music- that I was gaining a deeper sense of the performance than is customary. Caroline Ashton seemed so "vulnerable," so "innocent," so "naive," and the accompanying violin so "fragile" as she sang the "Pie Jesu" of the Fauré Requiem, that I noted I "was feeling what I should be feeling but almost never do. These speakers convey emotion. Why," I asked rhetorically, "do I not feel this way with other speakers?" "For the first time." I jotted, as Kaplan conducted the Mahler Second, "I appreciate the way he nurtures, cuddles, certain passages, giving a nuanced performance whose subtleties I have missed before. I am engaged by these speakers." Listening to the Beard M70s drive the Alóns in the Water Music I wrote: "This is music for the heart and the soul, not the head- I don't want to analyze or dissect, I only want to feel." This past year Jody Karin Appelbaum and her husband Marc-Andre Hamelin performed cabaret songs on campus, which I heard from a table very near the piano. Their CD Masterpieces of Cabaret contains much of that program, and as I auditioned it through the Alóns, I felt the emotional impact of Appelbaum's live performance. Would other speakers, I wondered, have conveyed so clearly the wit of her singing? Listening to Harry Belafonte's classic Carnegie Hall performance I could not bring myself to shut the system down, even though I was already late for an appointment. "The Alóns are too involving," I noted, as I decided to choose art over business. Another session, this with the CD version, caused me to note that "I'm ready to try another disk, but I can't stop, this is so seductive, not just the music, but the quality of the experience- it is so enjoyable, everything is so right... the Alóns provide treat after treat, beauty after beauty- myriad subtle accompanying sounds in "Jamaica Farewell"- little tidbits are somehow so revealed that I can't wait to see/hear what will come next. And this in a performance I've heard countless times. But it's like the first time all over again. A return to innocence when everything was fresh, new, exciting. I love this. To make a hackneyed disk seem as fresh as if heard for the first time. It's as if I had never heard a High End system before. And this after three months with the Alóns."
I think that is why I am so enamored of Marchisotto's design. The Alón I's returned me to a state of innocence in which I rediscovered so many of the pleasures associated with music. I found myself returned to a long-past (and I had feared long-lost) time when I approached reproduced music with enthusiasm born of a childlike innocence.
How can I predict if any other person will have a similar response to the Alón Is? I cannot even be certain that it was the Alóns as opposed to some unidentified cosmic force acting on me that provoked such feelings. I can tell you that again and again music via these small speakers engaged me at a level that truly reminded me of a time when my musical world was fresh and new. These are wonderful speakers. Heard in a supportive setting (a room of the appropriate size), connected to amplifiers of sufficient quality, the Alóns can reward a listener with a level of pleasure I thought impossible to achieve at this price. If you love music and have limited space to dedicate to a music room, hear the Alón I's. I'm not sending my pair back.
-Aaron M. Shatzman
Many thanks to Aaron Shatzman and The Absolute Sound for [the] review of the Alón I loudspeaker.
Thanks also to Humberto Adrian of Adrian Cabinet Arts for his fine cabinetry... providing... "an MDF panel so nicely finished that I thought it was plastic or some exotic creation of the petrochemical industry."
The thrust of the design philosophy behind the Alón loudspeakers is in capturing the intent and emotional content of a musical work-not just notes displayed in three-dimensional space... [as AMS wrote].
"These speakers convey emotion. 'Why,' I asked rhetorically, 'Do I not feel this way with other speakers?"'
We are delighted that this review illuminates the differences which [we feel] separate Alón from other loudspeakers. Mr. Shatzman's final comment tells it all, "I'm not sending these speakers back." *
--Carl J. Marchisotto, President
* And the bill will be forthcoming - FD
1 When I wrote about the Audio Research SP-9. I knew Stereophile had reviewed the product, and published negative criticisms. But I did not read that review until after I had submitted my own essay to Sea Cliff. David Manley hand-delivered the VTL AMPS I wrote about six years ago.
2 A number of readers over the years have criticized some of us for referring again and again to specific recordings, noting that they "couldn't care less how such-and-such sounds, and faulting us for ignoring "more relevant and interesting music 'These unhappy audiophiles I fear miss the point. I do not audition The Weavers or other LPs that appear regularly in my essays because I am enamored with the music per se (In fact often I wish I could listen to something I found more relevant or interesting.) Rather, I listen to these discs because I know how they sound, and how they have behaved in any number of systems and rooms. They are a reference point, a standard. that give me insight into the performance of components that are visiting my home. I thought that was obvious, but given recent comments from readers. I suppose it was not.
This review has been reprinted in its entirety from The Absolute Sound, with not one word censored or deleted. The Absolute Sound is the journal of High End audio and reports its findings on audio components and recordings without fear of or favor from any commercial interests. Its literate evaluations and tests take place in real space, hence, music (the absolute sound) is the measure of reference.