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Spatial Hologram M1 Turbo Version 2 Speaker Review

M1 Turbo: $4,000 per pair

by Wayne Myers


The Spatial Hologram M1 Turbo is an open-baffle 2-way dipole speaker. Two 15-inch drivers cover bass and lower-mid frequencies. One compression driver covers upper-mid and high frequencies. The tweeter is concentric with the upper bass/mid driver.

I was introduced to the M1 at the Rocky Mountain Audio Fest in Denver last fall. I was impressed by the transparency and unity of the sound, as well as by the depth of bass coverage and the precise image clarity and natural soundstage. I also enjoyed lively dynamic presentation.

The President of Spatial Audio, Clayton Shaw, explained how high-efficiency speakers like the M1 are able deliver such great dynamic range:
  • Speaker and crossover components are dissipating less power, and so stay cooler and work in their optimum most-linear operating range, keeping distortion low.
  • Power amps do not have to drive them very hard and are less likely to clip.
When we were making plans for the recent Home Theater Shack 2015 High-End Amplifier Evaluation Event, I thought of the M1 as a good speaker for helping us potentially hear differences between different power amps. A couple of emails later, Clayton generously agreed to supply the speakers for our event.


Each M1 comes packed in a two-piece tight-fitting block of spray urethane foam. Once the two halves are separated, the 3-inch thick baffle plate of the M1 is ready to be stood up. The support post fits snugly into an indentation at the bottom rear of the baffle plate, holding the M1 at the proper angle. The compression driver for the tweeter is removed from its own little compartment in the foam, is screwed into place on to the back of the upper driver, its two leads are attached by push-release terminals, and the M1 is ready to go. I was really impressed by the simplicity of the unpacking and assembly process.

The standard Black Satin finish is very attractive and seemed durable. It was fairly resistant to fingerprints. The 3-inch thick composite baffle consists of 5 layers of aluminum and MDF. The passive crossover is integral to the lower portion of the baffle. A pair of spikes was included for each speaker, but we did not use them.

Associated Review Equipment

Measurement Methods

  • Asus G74SX Laptop, Intel I7-2670QM @ 2.2 GHz, 16 GB DDR3 Memory, Windows 7 64-bit, Room EQ Wizard, foobar2000, Reaper DAW
  • Roland Quad-Capture Audio Interface
  • Beyerdynamic MM1 Measurement Microphone
  • miniDSP UMIK-1 Measurement Microphone, Courtesy miniDSP, Home Theater Shack Sponsor
  • American Recorder SPL-8810 Sound Level Meter
  • FiiO X3 Portable DAC/Headphone Amplifier/Media Player
  • ASUS Nexus 7 Tablet (2013 version)
  • Oppo BDP-105D Blu-ray Player
  • Denon AVR-X5200 Network A/V Receiver
  • Parasound HALO A31 Power Amplifier
  • MartinLogan ESL Hybrid Elecrostatic Loudspeakers
  • Bosch DLR130 Laser Distance Measurer
  • Fluke 77 Multimeter

Specifications and Measurements


  • Type: Version 2 - Compact 2-way, point source, open-baffle, dynamic driver, controlled directivity
  • Chassis: 5 layer Aluminum Composite / MDF
  • Driver compliment: Two 15 inch mid/woofers, one wide bandwidth compression driver
  • Crossover: 800Hz - Passive - Hologram Network Technology
  • Frequency Response: 32Hz - 20kHz +/- 3dB
  • Sensitivity: 95dB - averaged across 200Hz to 5kHz at 1M - on axis
  • Impedance: 4O nominal, 3O minimum, low phase angle
  • Dimensions: 36T x 20W x 3D inches (plus magnet depth), 50 lbs.
  • 20 year limited warranty
  • Available in the following finishes:
    • Turbo Black Satin
    • Turbo SE Gloss Black (+ $500)

Frequency Response at 0.5 m, 1/6th octave and 1 octave smoothing. Numerous on-axis responses and averages were taken at various distances, this was deemed most representative.

Frequency Response at Listening Position was just a little "tubby." Better room placement would probably have helped.

Total Harmonic Distortion at 80 dB SPL was very low, even at bass frequencies. Adjusting for noise floor peaks, distortion stays well below 0.5%, peaking to 0.6% at 600 Hz.

Impulse Response indicates some extra energy that might lead to upper-mid "congestion" at higher volumes.

Step Response settles very quickly at LF. Minor MF and HF resonances are indicated.

Impulse Response showing timing match for the front waves from speaker to LP. The match is within 1/8 inch, which can be compensated for with a tiny nudge of the measurement mic. The rear wave arrival time match - thanks to near-perfect room symmetry - is dead on.


An advantage of the dipole speaker type is that placement is supposedly more flexible in many rooms. While this may be true, it does not mean that setup is quick or can be done sloppily. Dipole speakers, especially with a concentric driver design, can give you amazing imaging and sound stage performance, but setup requirements are exacting. The M1 ended up sounding best with the listener's left and right ears directly on the axis of the concentric driver. Using a laser distance measurer butted up against the surface of the baffle above the driver we had a precise aiming mechanism for both horizontal and vertical angle refinements. A microphone positioned at the center-of-head point at the Listening Position (LP) was our target.

The angle at which one speaker leaned back on its support post was slightly different from the other and the imaging did not gel precisely until one speaker had a few layers of cardstock placed under its post to straighten it up. No doubt the spikes would have allowed enough adjustment to accomplish this as well. But even with the angles and distance precisely set, the imaging was still off.

It was not until impulse timing diagrams were used to verify precise acoustical distance from the listening position that we got it set properly. A minor mystery remains in that the physical distance was almost an inch off when the acoustical distance was exactly right. The symmetry of the room construction was excellent, and we found that the arrival times of the rear waves were also extremely close together without having to make adjustments. What luck!

Once set up, we got a monstrous wide sound stage with pinpoint-precise imaging. We had been advised to space them widely, which we did. In fact, they were placed even more widely than I would have dared to because an existing pair of speakers in the room occupied the spot where I probably would have placed them, and those other speakers were so perfectly place that I hated to move them. I would have if necessary, but ended up not having to do so, the M1 performed so well at their super-wide spacing. Even with that extreme spacing, the soundstage and imaging were natural and continuous and precise.

Others at the event commented that the soundstage was wider than ideal, and therefore it had some holes in it. I thought this myself at first, but eventually ended up believing that it was so stretched that we were hearing empty areas in recordings that one would simply not notice with other speakers and their narrower soundstages. The final test for me was the song Default by Atoms for Peace, where the entire soundstage from left to right extremes is filled with reverberation from lead vocals. I listened carefully a number of times to his track on the M1, and that reverberation filled the sound field, leaving no gaps or spaces.

The wide soundstage was useful in helping us evaluate differences between amplifiers. The stretched-out soundstage revealed individual sonic details that would normally have been smashed together with other sounds and missed.

Room Treatment

The side walls of the home theater room were treated with absorptive panels. The front wall underneath the movie screen was not. This worked fine for much of the evaluation but there was one track where we ran into some imaging trouble. The song House of Tom Bombadil by Nickel Creek has guitar on the right side and mandolin on the left. Both instruments were somewhat disembodied, the lower tones of each came from closer to the center of the soundstage, and the higher frequency plucking tones came from closer to the speakers. One particular solo run of the guitar, about 1:20 into the song, starts high and works its way down to lower tones and then back up again. One could hear the position of those notes work their way toward the center of the soundstage and then back out towards the speaker again.

Some portable absorptive panels were placed underneath the movie screen against the front wall, and this took care of the drifting and the disembodiment for both instruments. Front wall reflections were responsible for the effect. Once they were eliminated, the imaging solidified, low and high frequencies coalesced as they should, and the images came from a spot a little further back from the speaker than originally, seeming more naturally located in the soundstage and very stable.

Other Sonic Qualities And Observations

For both the amplifier evaluation exercise and for the evaluation of M1, they were left unequalized. There was a bit of unevenness in the bass and low-mid ranges from room effects. They sounded a bit tubby but remained concise and tight. The M1 could really crank out the bass when called upon. We were running without subwoofers, needing a completely passive speaker presentation for the evaluation. Their extension down to the 40 Hz range in our room was more than adequate for two-channels use, and we could really feel them move the air on deeper sounds.

Mid- to high-frequency clarity was excellent. The dynamic presentation and depth of detail that the M1 were able to deliver for us were very useful and enjoyable. There were a couple of occasions where, at high volume, there was a little grainy congestion on tracks with dense mid- and high-frequency content. I later verified with the less-sensitive electrostatic speakers in the room that those tracks could be delivered cleanly at the same volume and from the same amplifier.

The M1 sound was clean and open and accurate. Under other conditions, a better choice of placement would probably have evened out the low frequencies and given us flatter bass response. The compression tweeter was impressive with its clarity and natural sound, just as I had remembered having heard it 6 months before.

Track Hopping

Fourplay - Chant
The kick drum and the big drum just right of center were both very focused. The M1 can really move some air. We tried this track with and without subs. The focus was so much clearer without the subs.

Radiohead - Weird Fishes--Arpeggi
The four lead-in drumstick clicks were perfectly imaged, very simple and precise.

Radiohead - Packt Like Sardines In A Crushd Tin Box
The electronic kick drum is very focused, and while it seems to extend into low enough frequencies where localization would become broad, it all sounded with the M1 like it comes from a circle about 1 foot in diameter at the wall straight in front of the LP. This only happens on this track when alignment is near-perfect, including timing of rear reflections.

Radiohead - Pyramid Song
The ting of each ride cymbal hit was perfectly clear and focused.

Nickel Creek - Reasons Why
Another particularly revealing imaging track, there were a few "s" sounds where the image did not stay precisely centered, would pull one way or the other for a fraction of a second.

Tower of Power - Fanfare, You Know It
The brass sounded so good on the M1. Their dynamic delivery made this direct-to-master recording sound live.

Scott Davie, Rachmaninoff - Variations on a theme of Corelli
The particularly delicate sound of the Overs grand piano this track was recorded with seemed true with the M1. This is a very dynamic track with close to 30 dB dynamic range, and was fun to hear delivered so dynamically by the M1.

Cincinnati Pops Orchestra - Gayne Ballet - Adagio (From ‘2001’)
In places, the "tubbiness" of the bass stood out a little on this track. First choice would be to optimize speaker placement to even out the LF peaks. Some EQ might also be in order, for those so inclined. No speaker is immune to room effects acting on its bass response.

Porcupine Tree - Arriving Somewhere But Not Here
An all-time favorite track that I only listen to once or twice a year, it covers the range from delicate to sizzling. The M1 seemed comfortable working at both ends of the range.

Michael Hedges - Eleven Small Roaches
This lively acoustic guitar track seems even livelier on a high-efficiency speaker, as I discovered while completing a recent review. There seem to be layers of detail waiting for a speaker like the M1 to pull them apart and put them on display.


The Spatial Audio M1 Turbo Version 2 dipole speaker was a favorite for me at the Rocky Mountain Audio Fest last year, and is a strong contender in their price range. I have become a fan of dipole speakers for the soundstage and imaging possibilities, especially with a concentric design like the M1. Of all the speakers I have evaluated, I have never placed speakers as widely as I did the M1 and still ended up with such a cohesive and natural soundstage with such evenness, such width and depth, and with such precise pinpoint imaging. For the soundstage and image clarity chasers out there, I present the M1 for your consideration as a high efficiency, high clarity, high performance soundstage and imaging monster.

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