Beginning at the end
Plenty of audio reviews praise some flavor-of-the-month product with the threadbare phrase, “these are game changers.” But, trite phraseology or not, that’s what the Spatial Audio M4’s are. After living with them for nearly 6 weeks, they have re-calibrated my expectations for the level of musical pleasure that an audiophile with the proverbial kids, mortgage and restricted budget can enjoy. In one online interview, the M4’s designer said, “I don’t want to just make toys for rich guys.” In this, Spatial has succeeded.
Game changers, indeed.
Put plainly, the Spatial Audio Hologram M4’s are the most musically captivating speakers ever to occupy my listening room. I’d be impressed by the M4’s at any price, but that they cost under $1300 [see below for pricing updates] makes them even more remarkable.
If you have an aversion to rave reviews of audio gear, read no further. If not, come along and I’ll tell you just what makes the M4 so remarkable.
Spatial Audio is the brainchild of Clayton Shaw. Before founding Spatial, Shaw was the Designer at Emerald Physics, and before that, he was employed as Director of R&D and Engineering at a large pro sound speaker manufacturer. He has been researching the ins and outs of open baffle speaker design for quite a few years, and made a splash in the audio press with his Emerald Physics designs that utilized outboard DSP (digital signal processing) to achieve the best possible performance in real world listening rooms like yours and mine.
Clayton formed Spatial after leaving Emerald Physics in order to keep pushing open baffle tech forward. Spatial now offers two levels of models. The top end Lumina, with an active subwoofer system and a beryllium diaphragm compression driver sells for $20,000 and up, depending on the finish. The upper end of the Hologram line, the M1 and M2, which use a complex, multilayer construction technique for the baffle, were selling for around $4000 when last available. They are currently not for sale on the Spatial web site. Clayton tells me that they are in revision, with a Mk. II version of each due out sometime later this year.
The entry level models are the Hologram M4 and M3. They both use a very dense, 3 inch thick, two-layer sandwich of HDF (high density fiber board) for the baffle. All crossover parts are internally mounted. Cabling, too, is largely internal, giving the rear side of the Hologram an unusually orderly appearance for a speaker with its drivers mounted in the open on the back. And unlike much of the Emerald Physics line, the Holograms require no DSP, bi-amping or active, outboard crossovers. Shaw (in an online interview) identified DSP and bi-amping as a layer of complexity and expense that created an impediment to wider adoption of his designs. So, the Holograms are entirely passive.
Both M3 and M4 utilize three drivers per channel. On top, we have a coaxially mounted compression driver and a larger mid-bass unit from American OEM driver supplier Eminence. The physical alignment of the compression driver at the center of the larger transducer of the Hologram series presents a point-source for more coherent sound. Also working toward greater coherence, compression driver handles all frequencies from 800 Hz and up.
The larger driver is 12″ in diameter for the M4 but 15″ for the M3. One result of this difference is that the M3 digs lower than the M4: down to 32 Hz (± 3 db) for the M3 and down to 45 Hz for the M4. The larger Eminence driver also affects the overall size of the speaker. The M4 is 36 inches tall and 14 inches wide – surprisingly petite when you see it in person. The M3 adds 6 inches to the height and 3 inches to the width.
This seems a good time to mention that the M4’s, which are available in a satin black, white or red finish, create a clean and handsome appearance. My wife, who has an Art History degree and a strong aesthetic sense, saw the M4’s for the first time and said, “Hey, those speakers are snazzy looking!” If you have a significant other who must approve of the appearance of your rig, this is worthy of note.
Depth of the M4 is minimal, around 9 inches from the front of the baffle to the back of the compression driver. In fact, Clayton mentioned that some customers who cannot leave their speakers at an optimal distance from the wall behind them simply push them up against the wall when not in use, taking advantage of their very minimal depth.
Do check out this YouTube video by New Record Day, where Shaw talks about the several-years-long process of co-developing the Hologram drivers with Eminence, as well as his vision of driving down costs and selling direct to the customer so as to create an affordable, “mass produced” [by high end audio standards] loudspeaker. There’s also a very cool video on Spatial Audio’s Facebook page, showing a fully automated CNC machine producing M4 baffles, yet another element to creating a high quality yet lower cost product.
When I purchased my M4, Clayton was offering 3 iterations of each model: entry level, Turbo (featuring better crossover parts and fancy WBT binding posts) and Turbo S (which adds an upgraded compression driver with a specially treated driver material). Clayton confirmed in an email that the base model has recently been discontinued since few customers ordered it, so you now have a choice of Turbo ($1495) or Turbo S ($1995). My particular set, ordered when the entry level model was still available, might be described as an “M4 Plus.” I saved some money by getting a pair with the upgraded crossover parts but sporting the very nice standard (but not-WBT) binding posts.
Why Open Baffle?
How many speaker reviews have you read in which the review either raves about “a total lack of boxy colorations” or complains of “a hint of boxy resonances”? What this boils down to is that conventional speaker boxes vibrate to some degree, so that the listener is hearing the cabinet as well as the driver – generally thought to be A Bad Thing. In fact, the “back wave” of the speaker driver goes crashing all over the inside of that box and even pushes back against the driver itself, unless the designer finds some way of taming it.
How should a designer deal with this? The more common approach is to make the box as acoustically dead as possible with internal bracing, damping materials and, in some cases, exotic materials like synthetic marble and aluminum. The other approach, taken most famously by some British brands like Audio Note and Harbeth, is to deliberately create a “lossy,” thin walled cabinet, designed in such a way that the vibrating frequencies of the cabinet walls are kept out of the crucial midband. Thus, says the theory, the part of the audio band where most of the music lives is kept pristine.
But what if you could get rid of the boxy resonances by… well… getting rid of the box itself? That’s the reasoning behind open baffle speakers. No box, no boxy colorations. In addition, open baffle designs are prized for having a wide open, spacious, dynamically uncompressed way with music that makes them sound more like the real thing. Finally, while your generic open baffle design may not, on paper, play quite as deep as a box speaker of the same height and width, open baffle bass is said to load the room differently than bass from a box speaker. Specifically (and this is one of Clayton’s claims for the Hologram series) the bass is immune from the muddy, boomy quality that too often afflicts box speakers, especially ported cabinet designs placed in smaller rooms.
As Clayton explained it to me, the bass from a given open baffle speaker rolls off more gradually than does the bass from a comparably sized box speaker, lending more tonal character and refinement to the low end. Additionally, the bass of a controlled directivity speaker does not trigger room mode excitations in the vertical and horizontal planes, thus – according to the owner’s manual – reducing room excitation problems by 2/3. Finally, with a box speaker, moving the speaker closer to the wall generally reinforces the bass response. With an open baffle design, moving the speaker closer to the wall may actually diminish bass response, since the rear wave from the driver may cancel out the bass tones.
A key design goal of the Hologram design is controlled directivity. The Hologram is designed to restrict the frontal radiation pattern of sound to a total of about 80 degrees from side to side. The result is that room interactions are minimized and the listener hears much more direct sound than sound bouncing off the walls and floor, effectively “taking most of the room out of the equation.”
Jumping the gun, I think this technique is a smashing success. As documented in the photo below, my listening room ain’t exactly “HP’s big room at Sea Cliff” (if you get my drift). It is, like many of yours, I’d suppose, a severely compromised (from the acoustic perspective), medium-small space that doubles as a guest bedroom, whose layout must pass the approval of a non-audiophile significant other.
That the M4 sounds so glorious in this acoustically untreated, multipurpose space (that also has restrictions on speaker placement) is a testament to its design brilliance.
The Buying Decision
Followers of this blog may remember that I had procured a pair of Omega Speaker Systems “Super Alnico” monitors, as mentioned in my review of the superb Skylan 4-post speaker stands. The Omega’s were/are fantastic in many ways and they are very much worth checking out if the single-driver route appeals to you, but they weren’t at their best in my room and system. So it was back to the drawing board.
I’d actually been thinking about the Spatial’s for the better part of a year. On paper, with their 93 dB sensitivity rating, they seemed a good match for a low-power SET like the Kit 1. I exchanged a few emails with Clayton Shaw once the Hologram M3 was released. The price was within my budget and Spatial was offering a 45 day home trial. The hitch was that the original version of the M3 used a (viewed from the top down) T-shaped configuration, with a thick, HDF floor support perpendicular to and behind the front baffle. As a result, they were much heavier than the current M3/M4 design which (see below) uses two metal support feet and packs relatively flat. Because the original design would have cost nearly $300 in return shipping if I chose not to keep them, the original M3 was a nonstarter.
Speaking of home trial, by the way, Clayton has recently extended the trial period to a very generous 60 days, although you cannot return the speakers for a refund prior to 45 days, to ensure that they have a chance at being reasonably well broken in before you make that judgment.
Once the lower-cost and physically streamlined M4 hit the market, I took the plunge. I’ll note that I had also seriously considered several of the very reasonably priced speakers from Tekton design but was intrigued enough with the open baffle concept to give the Spatials a go.
Prelude: Prepping The Audio Note Kits “Kit 1” amplifier for a 4 ohm speaker
The Kit 1 SET amp can be wired for either an 8 ohm or 4 ohm speaker load. The difference is just a matter of swapping two wires that go from the output transformers to the speaker binding posts. I’d wired my Kit 1 for an 8 ohm speaker (appropriate to the Reference 3A De Capo’s which I’d owned when I built the amp) but left the 4 ohm leads intact (but insulated!) in case I ever decided to try a 4 ohm speaker. Good move!
The Hologram M4
Alas, unlike John Atkinson of Stereophile, I don’t own a plastic tape accelerometer and am thus unable to regale you with pulse-pounding adventures in measuring cabinet resonances. So what can I give you to compensate, dear reader?
When you order your Holograms, Clayton does a smart thing: he emails you a PDF of the owner’s manual, which includes unboxing instructions. At 44 pounds per speaker (not counting the box and packing materials) it takes a little care and finesse to unpack the Hologram M4’s, but if you’re taller than, say, 5 feet and have decent upper body strength, you can do it all by yourself.
The owner’s manual for the M4 recommends getting at least 24 hours of warm up time on them before expending any serious effort trying to optimize their position. Once you begin to dial them in, you can install the carpet piercing spikes. My M4’s shipped with spikes only, but Clayton was happy to send me some feet with a non-abrasive, hard plastic base for my wood floors.
At this point, I have the speakers toed in around 22 degrees toward the listening position, with the outside (i.e., further out) corner of each speaker about 30 inches from the wall behind them. The M4’s sit at about 9 feet from my listening position. This set up is probably less than ideal – the owner’s manual recommends either a near-field or far-field placement as shown in the diagram below, with the speaker between 18 and 36 inches from the wall behind them. The M4’s response in the 200 to 800 Hz range can also be adjusted by changing the distance between the speaker and the side wall.
A Digression: “Musical vs. Accurate”
A perennial debate on audio discussion forums swirls around whether a speaker should be “accurate” or “musical.” “Accurate” typically means “it measures flat in an anechoic chamber and delivers nothing but the unaltered, unadorned input signal.” “Musical” means “It sounds good to me, in my room, regardless of how it measures.” Devotees of accuracy tend to sneer at the musicality crowd: “You just prefer certain euphonic colorations!” Card-carrying members of the musicality camp respond, “We’ve heard too many speakers that measure ruler flat but sound sterile and uninvolving.”
The fact that this debate even exists, let alone rages on, tells you something that folks who have been on the speaker merry-go-round will confirm: A speaker that measures really poorly will probably sound like it, but a speaker that measures well may sound “impressive”(“What highs! What imaging! What bass!”) yet lack the ability to move the listener the way that real music should.
I would like to offer this “gut” definition of what makes a speaker musical: If the speaker (and, of course, its associated gear) make me think, “What a great speaker,” it’s not providing the magic. But if the speaker makes me think, “Wow, what a great performance,” then it’s providing genuine musicality.
Can a speaker sound both accurate and musical? Yes, it can, because the Spatial Hologram M4 is both. As difficult as this is to put into words, I’ll try to break it down as follows.
I now understand what posters on speaker forums mean when they say things like, “Tone is everything. What good are imaging and bass extension if the instruments don’t sound like what they are?”
This is one way in which the Hologram M4’s truly excel. They are masters of tone. Trumpets, saxophones and other wind instruments sound very real. Orchestral strings sound sweet and woody, with the shimmer of the real thing. Voices are as palpable, expressive and human as the best single driver designs that I’ve heard, and that’s really saying something.
To offer a well-known example of the latter, on the 20th anniversary CD reissue of Jennifer Warnes’ Famous Blue Raincoat, there are a couple of moments on the title track where Warnes speaks the word “Yes,” hesitating ever so slightly before launching into the chorus. It’s a moment of great interpretive artistry and expressiveness, a kind of thinking aloud as the narrator of the song pauses and gathers her thoughts. (She is, as we learn at the very end of the Leonard Cohen’s song, composing a letter to a former lover.) And because of the way the M4 communicates her breath, timing and emotion, that word, “yes,” is just devastatingly beautiful.
Additionally, I played my music loving, non-audiophile wife a cut from James Taylors’ Other Covers CD – a gorgeous remake of Oh, What A Beautiful Morning, and she remarked, “Wow, it’s like he’s in the room!”
Ease and Fun
When I say “ease,” I mean that music flows unimpeded. There’s no sense that the music is constricted, forced or miniaturized. And this open, free-flowing quality contributes to a feeling of ease (and delight) in the listener.
Remember that great LA band, War, from the 1970’s, that produced radio hits like Why Can’t We Be Friends and The World Is A Ghetto? Their music was full of gorgeous vocal harmonies, loose, loping Latin rhythms – funky yet precise – and at times borderline out of tune (but never quite!) horn parts. I have a cheap WAR: The Hits compilation CD that sounds mesmerizing on the Spatial M4’s precisely due to that relaxed, open presentation. Low Rider makes you want to get up and dance because the musicians who cut that tune are clearly having such a ball playing it, and that all comes through on the M4’s.
The M4’s have a midrange clarity and upper register sweetness that, combined, manage to be very revealing of inner detail and yet never etched, fatiguing or harsh. In other words, the detail is there if you choose to attend to it, yet it somehow never calls attention to itself.
For example, I recently picked up the 25th anniversary, remastered pressing of Bonnie Raitt’s 1989 comeback LP, Nick Of Time. There’s a lot of wonderful music on this disc, but my favorite track has long been Cry On My Shoulder, a song about true friendship and love. The chorus, “Cry on my shoulder / I’ll help you rise above / Cry on my shoulder / My love,” is sung in tight harmony by a group of excellent background singers. And the rendering of those voices on the M4’s is positively luminous. You can follow each and every separate voice in the chorus if you choose to make that your focus, but the overall impression is revelatory: “It’s not background vocals, it’s a choir!” Amazing.
The same can be said for James Taylor’s cover of R&B group The Spinners’ classic Sadie, a tribute to (as the opening monologue says) “the young mothers who were around when we were growing up,” from his Covers CD. Again, on the chorus, we have harmonized background singers crooning, “Sadie / Don’t you know we love you / Sweet Sadie…” Not only are the vocals clear as a bell, but there’s a low bass vocal part that some speakers will totally miss, but that the M4’s capture perfectly.
Dynamics and Scale
One advantage of having a speaker as sensitive as the M4 when you have a low powered tube amp, particularly a single ended design like the Kit 1, is that it enables even a small amplifier to sound big, gutsy and dynamic, all while operating within its lowest-distortion “1st Watt of power.” This means that even large-scale orchestral music, such as the final sections of the Ravel orchestration of Mussorgsky’s Pictures at an Exhibition – with its blaring brass, pounding drums and crashing gongs – sounds shockingly uncompressed and convincing.
One of my very favorite orchestral CD’s is the magnificent soundtrack to the classic anime film, Princess Mononoke. Full of exotic Japanese drums and flutes, unexpected synthesizer lines, great orchestral crescendos and crashing percussion, this beautifully recorded CD presents a dynamics-and-scale challenge to any stereo rig. Play the first track on the CD through the M4’s, and there is no sense at all (even with an 8 watt tube amp!) of compression or strain on the crescendos – just clarity and musical expressiveness. Similarly, on track 20… the pounding drums are jump-out-of-your-seat powerful.
As for “scale,” sometimes planar speakers have a reputation for presenting music with an impressively expansive soundstage yet with unrealistically sized images, as in the 4 foot high guitar or the singer with the three-foot wide mouth. But I haven’t found this to be at all a problem with the Spatial Hologram M4. The soundstage is, indeed, impressively wide and deep (more on that in a moment) but images within the soundstage are appropriately sized.
For example, on one of my favorite live recordings, Steely Dan’s Alive in America, one hears the band as if from about midway back in a large, outdoor concert venue. The background singers, horn section and percussion are all cleanly localized and realistically sized. It’s very impressive! In general, well recorded live performances are a special treat on the M4’s.
Naming a line of speakers “Hologram” sets up some pretty steep expectations around the imaging and soundstaging capabilities of those products. Does the M4 deliver? Yes, indeed, it does. I’ve never heard the reverberant field of Joe Jackson’s Body And Soul LP (recorded in an old church with minimalist miking) reproduced so convincingly. With the tracks Happy Ending (a great tune, by the way) and Be My Number Two (ditto) the M4’s take you right to the large, echoing space in which they were recorded.
And what about the old, audiophile war horse we know as Pink Floyd’s The Dark Side Of The Moon? The M4’s render all of engineer Alan Parsons’ funhouse spatial effects with a dimensionality that is at times frightening, as befits the band’s alienation-and-madess theme on that LP, filling the room with screams, alarm clocks and guitar riffs coming at you from every direction.
One unquestioned tenet in the orthodoxy of “speaker accuracy” is that a speaker should be revealing, even ruthlessly so. That means that if the mastering or recording technique on an album is really bad, then, alas, the album should sound really bad. The speaker should be true to the source material.
While I understand this line of reasoning, I have recently figured out that some speakers, because of the way they are voiced or because of an inherently tipped up or emphasized upper midrange, have a tendency to make harsh, bad sounding recordings sound even worse through their own high-end emphasis.
To give you one example, on Steely Dan’s Everything Must Go CD, there is some nasty sibilance on the chorus of Slang Of Ages when Walter Becker and the background vocalists sing “Drop me off in groove time / Soothe me with the slang of ages…” On speakers with a tipped up treble (which is often marketed as “speed” or “transparency” or “detail”) the “s” in both “soothe” and “slang” will sound like an icepick to the eardrum. On the M4’s, you hear the harsh moments, but they don’t take over the rest of the mix and the track is still eminently listenable.
The same thing is true in the case of Let’s Face The Music And Dance from Diana Krall’s When I Look In Your Eyes CD. The production values of this album are very high and things sound quite glorious most of the time. But Krall is very closely miked throughout much of the album so that, again, sibilance can be an issue on less than evenly balanced speakers, so that the “s” in “Soon we’ll be without the moon / Humming a different tune…” will be painfully emphasized. With the lovely upper midrange of the M4’s, it’s clear that Krall has her mouth right up against that microphone, but there’s no added harshness, only a sense of intimacy.
I think that the M4’s may be the most honestly spec’ed speakers I’ve ever owned. They play with a dynamic ease that leads me to believe that their 93 db sensitivity rating is both useful and accurate.
Furthermore, their rating down to 45 Hz also sounds about right to me… but that’s worthy of comment because I don’t think that the frequency number tells the entire story.
What Clayton says about the quality of open baffle bass mirrors my experience with the M4’s. Bass is clean and clear (like every other part of the presentation), making it easy to follow moving bass lines. Additionally, the lack of boom and bloat makes it effortless to hear the tone and texture of bass notes. Rather than being presented with an impactful but amorphous bass “thud,” the M4 makes it easy to hear what kind of instrument – electric bass guitar, upright string bass, synth bass, and so on – is producing those notes. So the bass has – I’ll say it again – texture and tone, and thus a musical quality that I’ve never experienced in my home before.
To return briefly to this theme, I’d be remiss if I didn’t mention that the coherence, tone and dynamic swing of the Spatial Hologram M4’s have a way with mediocre recordings that I find very intriguing. I’ve played numerous CD’s and LP’s with music that I like but that I’d always thought of as indifferently recorded and produced, and have been repeatedly surprised at how the M4 seems able to sort out the music in a way that makes the music pleasurable on a much higher level. Billy Joel’s The Stranger, for example, which I hadn’t listened to for years and which is hardly on the Stereophile “Records To Die For” list, sounded compelling and entertaining in a way that totally took me by surprise. Ditto for Michael Franks’ Burchfield Nines LP, which the M4’s laid out with a kind of slinky, jazzy joy that was quite beguiling. And on Steely Dan’s great album Pretzel Logic, the wall-to-wall sound stage of the electric pianos in Any Major Dude (Will Tell You) was an unexpected treat.
So… What’s not to like?
No speaker is perfect; all have their strengths and shortcomings. But at their asking price, or even far beyond it, I find it nearly impossible to find fault with the Spatial Hologram M4’s. Even in my less than stellar listening room, they make beautiful, emotionally engaging music and have proven to be a great match with my Audio Note Kits Kit 1, SET amp.
The only criticism I can produce would be that they don’t (nor does Spatial claim that they do) plumb the lowest depths of the bottom octave. I’ll qualify that statement in three ways.
- As mentioned above, what the M4’s may lack in ultimate bass extension, they more than make up for in low end tone, texture and musicality.
- I have only missed that ultimate extension on a few albums, especially music that features some types of hip-hop style synth bass, like some tracks from Lorde’s Pure Heroine CD. On the other hand, in my medium small, 16 x 13 x 8 room, orchestral music sounds wonderful and not at all lean or miniaturized.
- Clayton suggests that the M4’s need about 100 hours of play time at healthy volume levels to loosen up the cloth surround (and other parts) of the drivers. I lost exact count of the playing time on my M4’s a few days ago (drat!) but I’m guessing they have about 50-60 hours on them. During that time, the soundstage has bloomed tremendously, tonality has become more vivid and, yes, the low end has become more relaxed and palpable. So it is entirely possible that the low end of the M4’s will flesh out even more over the next 40 or so hours of play time. But might I consider moving up to the larger M3’s to grab that last octave? Yeah… maybe. 😉
Back To The Beginning
I hope I’ve been able to convey what makes the Spatial Hologram M4 such an impressive achievement. If you value the emotional uplift that comes from listening to music that you love, they may be the speaker for you.
Until next time, be kind, and enjoy your music!