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Spatial Audio factory tour, Hologram M4 review

  • The tyranny of choice. The number one challenge for the audiophile looking to level up from sub-$500 loudspeakers: overcome the options or be overwhelmed by them. With some Internet research under his/her belt, our ladder-stepper might not lean quite so hard on his high street dealer as with the first loudspeaker purchase. Forums spill with suggestions but the end result of advice sought is akin to having three watches (instead of one). What time is it?

    Would Sir/Ma’am prefer the laser-guided image specificity and disappearing act of KEF LS50’s coaxial driver array? The low volume dynamic twitch and twinkle and heavy tone of Zu Audio’s high-efficiency Omen? Or how about going outside the box with Magnepan’s flat-panel MMG? Extended experience with the MMG in three different rooms tells me their narrow dispersion means they are less prone to ceiling and wall reflections. They work nicely in smaller spaces.

    These three are some of the best loudspeakers to be had for US$2000 or less. However, each comes with its own compromise. No one loudspeaker gets everything right.

    Their boxiness more evident, the Omen (US$1500/pair) don’t disappear as readily as the identically priced LS50. Standmounts demand stands but with the KEFs hooked up one might miss the seemingly more realistic tonal qualities of the Zu floorstander or the six-foot high soundstaging of the Magnepans. With the latter in play, amplifier options narrow quickly. So too does sweet spot seating. The Zus are the pick of the three for late-night listening where a lid must be kept on SPLs.


    The KEF clock in at 85db (in)efficiency (a full 13db lower than the Zu). In ensuring fleshed-out tonal mass and decent dynamics, serious consideration must be given to LS50’s partnering amplifier’s ability to step up to the plate with current delivery.

    Mind you, the LS50’s need for power is wholeheartedly usurped by the thirstier 4 Ohm (flat) mini Maggies. Their need for current is just to get ’em out of bed in the morning. A real wake-up call! Don’t pick up the phone though. On the line, it’s the 1970s – they want their monoliths back.

    For the apartment dweller, loudspeakers exist as pieces of audio furniture. The room is often shared with others and doubles as TV watching and entertainment space. Aesthetic appeal is crucial to any long-term commitment. Bye-bye MMG, hello red KEF LS50.

    On bass response, the KEF brochure informs us of the LS50’s lower limit: 79Hz ±3 dB. The MMG? 50Hz ±3 dB. The crossover-free Zu Omen are rated down to 34Hz – direct experience reminds me that they are probably the most likely to satisfy in a subwoofer-free setup.

    Clayton Shaw poses with the Hologram M3, M4 loudspeakers at his Utah workshop.

    Enter Clayton Shaw of Utah’s Spatial Audio whose Hologram M4 floorstanders is a more affordable, smaller version of the previous Hologram M3.

    The elephant in the room is the Hologram M4 is an open baffle design. Shaw is no stranger to thinking (literally) outside of the box. He helmed Emerald Physics before selling up and moving to Spatial’s first project: loudspeaker and room correction software. That was 2011.

    In the intervening years, Shaw has gradually returned to designing more affordable open-baffle loudspeakers with the Hologram M1 and M2. Last year he introduced the M3 at T.H.E. Show Newport, then the M4 at RMAF.

    Unlike the Emerald Physics designs of yore, the Hologram series are completely passive. Dispensing with external crossover units is central to Shaw’s aim at the more mainstream buyer.

    When I visited Shaw at his Utah HQ at the very end of 2015 (NYE!), he talked of the need to re-invent the open-baffle loudspeaker’s public image, one that is by and large defined by hobbyists and DIYers; folk who are more inclined to accommodate the additional physical intrusion and complexity of external crossovers and DSP EQ settings.

    Shaw talks M3/M4 philosophy and tech here:

    According to our host, more expensive open baffle loudspeakers are largely attributable to higher-margin required to compensate for lower sales volumes.

    Under the Spatial Audio banner, Shaw is driving down costs through higher production volumes. Lower costs translate to sharper pricing. Sharper pricing will hopefully lead to broader adoption. That’s the plan.

    The M4 is Spatial Audio’s most affordable loudspeaker to date. The Turbo version (US$1599) adds WBT terminals and superior crossover capacitors to the recently discontinued M4 Standard. Doing time at DAR HQ is the Turbo S version which adds a ‘higher-end M25 compression driver’ and sells for US$1995.

    The M4 Turbo S is also the only version to be made available through Spatial Audio’s international dealer network. In the USA and territories where local representation doesn’t yet exist, both M4 Turbo and M4 Turbo S ship factory-direct from Spatial’s HQ in Kaysville, UT. Under the same roof sit mainman Shaw’s contracted woodshop and paint booth. Upstairs, assembly, testing and office space.

    Shaw walks us ’round:

    Lending a helping hand to the M4’s intended everyman appeal is their sharp appearance: 42”/106cm tall. Shaw hears my friendly jibes about similarities to IKEA furniture as compliments; he’s a big fan of Scandinavian design. Shaw’s office is peppered with the Swedish giant’s wares…

    …and so too is this reviewer’s 5.5m x 8m listening space. The rear wall hosts three KALLAX towers full of vinyl. Colour? Red. Just like my review pair of M4 which, positioned 1.5m from the opposing wall, aesthetically jive with a red Rega RP6 turntable and red AURALiC Gemini headphone stand. The point? Modern homes are no longer beholden to the muted visual tones of leather and wood grain. Besides, M4 buyers looking to strike the conservative middle-ground have the option of white or black satin finishes. I’d urge Shaw to consider yellow, blue, and green as per Crystal Cables’ Arabesque Minissimo.

    On weight, however, the M4 bear zero resemblance to the one-hand lift of IKEA’s cheaper LACK coffee tables. Each loudspeaker tips the scales at a healthy 75lbs/34kg. Pulled clear of Zu Audio-esque foam cheeks one only need to screw on the legs before hooking up loudspeaker cable, in my case AudioQuest’s Rocket 88, to an amplifier. I alternated between running the Vinnie Ross LIO solo and having the Red Dragon monos intercede at the business end of loudspeaker drive whilst the LIO handled pre-amp, DAC and phono stage duties.


    The M4 is a loudspeaker that sports the sharpest of haircuts: no back, no sides and all front. With three sides MIA, open baffle speakers show a ‘Figure 8’ radiation pattern, largely caused by the interaction of the front and rear waves as they wrap around the baffle edge. This interaction between front- and rear-firing waves also has implications for an open-baffle loudspeaker’s low-frequency output.

    Shaw explains: “Low-frequency wavelengths are long and are therefore able to wrap around the baffle. With front and rear outputs out of phase (high and low-pressure zones) and both seeking equilibrium, low-frequency cancellation can occur. Wavelengths that are shorter than the width of the baffle are projected in a normal fashion perpendicular to the baffle.”

    One solution is to deploy a larger baffle. That’d blow out shipping costs. Another is to correct via DSP in an external crossover – greater complexity. Neither fit with Shaw’s KISS (keep it simple, stupid) modus operandi. His Spatial fronted solution was to co-develop a 12” driver with Eminence and then attach two to a 3”/7.6cm-thick multi-layered HDF slab.

    “I don’t attempt to mitigate the [bass cancellation] effect, just overwhelm it with more woofer area to compensate for the lost output caused by cancellation. Hence, the two 12-inch woofers,” says Shaw. In other words, the target response curve is built into the driver and its suspension for low frequency handling down to 45Hz.


    A compression driver – initially specified by Shaw as from Italy’s B&C but later referred to as co-developed with an unnamed manufacturer – is fitted to the rear of the upper drive for a coaxial (i.e. point source) arrangement. That takes us up to 20Khz. In between, a second-order crossover works with the compression driver’s natural 800Hz roll-off. That’s considerably lower than your average box loudspeaker. The mid/bass drivers are more bass than mid. The upshot is that vocals are reproduced with spectacular clarity, particularly for the price point. There’s quite a bit more all-round transparency on offer than that served up by the warmer Magnepan MMG.

    Time to pull from Wikipedia: “A compression driver is a small specialized diaphragm loudspeaker which generates the sound in a horn loudspeaker. It is attached to an acoustic horn, a widening duct that serves to radiate the sound efficiently into the air. It works in a “compression” mode; the area of the loudspeaker diaphragm is significantly larger than the throat aperture of the horn so that it provides high sound pressures. Horn-loaded compression drivers can achieve very high efficiencies, around 10 times the efficiency of direct-radiating cone loudspeakers.”

    The Hologram M4’s high efficiency means they wake up as early on the amplifier’s volume dial as the aforementioned Zu. Shaw rates the M4 at 93db and reckons as little as 5wpc is sufficient for realistic get-up-and-go.

    At audio shows, however, our man from Utah chooses to partner with neighbour Ryan Tew of Red Dragon Audio. Tew’s S500 Class D amplifiers are built around Pascal modules and pack some serious power, especially when bridged to mono where a whopping 1000wpc drops into 8 and 4 Ohm loads.


    Central to Shaw’s preference for open baffle loudspeakers is a box speaker’s increasingly omnidirectional radiation pattern as frequency decreases. Although box size-dependent, low bass moves in all directions. The result is an uneven off-axis response, exacerbated by room reflections. The listening position nets a combination of (presumably even) on-axis response and the time delayed, uneven off-axis response.

    According to Shaw, an open baffle’s intrinsic lack of side and upward dispersion means we hear less reflected audio. Not only is internal box colouration sent packing, so too is a large chunk of the room’s interference.

    The Eminence drivers might be a giveaway but Shaw has drawn on his long-time experience in the pro audio sector. Say hello to ‘Controlled Directivity’ where, according to the Spatial Audio website, “The dispersion angle is limited to around 80 degrees and held constant across the spectrum, allowing less interaction with the room and much more even response in reflected field energy.” In other words, less but higher quality reflected information reaching the listening position.

    How does Shaw achieve this? The open baffle design itself controls bass directivity, the large surface area of the Eminence driver directs the midrange whilst doubling up as a waveguide to the coaxially-mounted compression driver.

    And so it goes. Whilst this loudspeaker’s soundstage is nothing short of enormous compared to the KEF LS50 or (my recollections of) the Zu Omen, less sound spills to the right and off the balcony and to the left towards the reflective nightmare of the kitchen’s hard surfaces.


    The promises of lower room interaction become reality when spinning Radiohead’s King Of Limbs. Played through the KEF LS50 with Vinnie Rossi LIO + Red Dragon S500 on respective pre/power duties, the album’s mid-bass dominant cuts are more likely to agitate room modes as SPLs head north. This is less evident with the M4 in play. A win for those who can’t – or won’t – add room treatments.

    On stage height, the M4 almost rival (my recollection of the) Magnepan MMG. Both cast the LS50 into the shade. On stage width, the nod goes to the M4 – an easy call.

    I like to sink in the immensely satisfying tonal saturation of Neil Young & Crazy Horse’s guitar work on Everybody Knows This Is Nowhere. Here the Spatial match (my recollection of the) Zu Omen and Soul MKII. Pulling up in third place on this qualitative call are the KEFs. The fourth spot goes to the MMG.

    Perhaps it’s in the Eminence driver’s DNA but the M4 also bring Zu levels of dynamics to the table – a win for low-level, late-night listening, especially with the LIO’s 25wpc MOSFET module.

    Herein lies the rub for Ryan Tew’s monos: the KEF standmounts benefit more from Red Dragon’s serious power injection than do the Spatials. Even then, the M4 ace the LS50 on low-end thrust and, most notably, micro-dynamic flicker. When I cue up L.S.G.’s The Black Album I expect to be taken on the musical equivalent of a lightspeed spaceflight through an asteroid field. Coming on as slightly faster than the KEF, the M4 deliver the bigger thrill ride.


    Only on central image specificity and overall detail retrieval do the KEF match the Spatial open-baffles. A floorstander that disappears as readily as a standmount is something to write home about. You’ll have to work for it though. Ensure more than one meter’s front wall clearance and be prepared to have your patience tested with the tiniest of toe-in adjustments.

    The conclusion comes easy.

    Spatial’s Hologram M4 is a loudspeaker that matches the striking visual appeal, imaging and detail dig of the (red) KEF LS50 but then piles on the high-efficiency pop-and-shove dynamics and more natural tone of Zu Audio before adding the midrange eloquence and soundstage height of the Magnepan MMG. A bigger sound that’ll work in smaller rooms but without the need to pull on megawatts.

    With pricing ballparked in Zu Omen floorstander or KEF standmount territory, the package sums to quite the result! A loudspeaker to make an entry-leveller’s upgrade choice a whole lot easier. DAR-KO award for sure.


    Further information: Spatial Audio



    Written by John

    John currently lives in Berlin where he creates videos and podcasts for Darko.Audio. He has previously contributed to 6moons, TONEAudio, AudioStream and Stereophile.

    Darko.Audio is a member of EISA.

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