MACH 1 Acoustics DM-10 Signature loudspeaker

MACH 1 Acoustics? Cute name. Mach 1 is, of course, the speed of sound—the speed at which a loudspeaker's acoustic output is forever constrained to travel. Quite a fitting choice for Marc McCalmont, Marine and jet pilot turned speaker designer. Marc retired to Wilton, NH together with Melissa. (Oops, that should be MLSSA, the well-known acoustic analysis system—not Marc's girlfriend.)

MACH 1 started off by selling their DM-10 loudspeaker direct to the public with a 30-day return policy, but has now set up a small network of specialist retailers. The company has kept up its profile in the audio press for the past few years, advertising the DM-10 and, more recently, the DM-10 Signature. It was through one of these ads that I learned about the latter.

MACH 1's philosophy of using the best parts they can find is both laudable and reassuring. What caught my attention was MACH 1's use of the Accuton tweeter and midrange. These drivers feature concave "ceramic" domes, the product of vapor-deposition technology developed by Ceratec-Thiel in Germany. The Accuton drivers display smooth frequency response and excellent time-domain behavior, with almost textbook-perfect impulse responses. Naturally, they're very expensive, and as a consequence have seen little commercial application in the US. But no matter how cleverly any designer synthesizes a given driver complement, the resultant sound quality is ultimately dependent on each driver's in-band resonances and colorations. If you start with a lemon, no matter how hard you squeeze, you'll only get lemon juice. It's imperative that one start with the best drivers obtainable at a given price point.

DO's Law of Speaker Design states that the degree of design difficulty increases as the square of the number of drivers. Thus, a three-way is more than twice as difficult to engineer than a two-way. The preponderance of two-way designs in the market is a practical consequence of this law. Computer-aided design techniques are essential tools for synthesizing complex crossover networks for a three-way loudspeaker. Such software eliminates a lot of guesswork, allowing a variety of design options to be investigated before the first plank is sawn. Not only were DM-10's the bass alignment and crossover network computer-generated and -optimized, but McCalmont went one step further, optimizing the enclosure's internal bracing using finite-element structural analysis.

It would be misleading to describe the DM-10 Signature as simply a refined version of the standard DM-10. For one thing, the driver complement is different. While the 1" Accuton tweeter is still used, the Accuton midrange has been replaced by a high-performance Peerless 5.5" polypropylene-cone driver with an inherently very flat (±1dB) response over the 300Hz-3kHz range. The midrange driver has been modified by MACH 1, particularly with regard to damping reflections from the rear chamber. The 10" woofer, also from Peerless, is slightly larger than that in the standard DM-10. However, a similar bass alignment is used: a near critically damped sealed box. On the whole, the Signature qualifies as a new design; similarities with the original have mainly to do with looks and design philosophy.

Technical details
The cabinets, made by a New Hampshire custom furniture craftsman, are beautiful to behold and incredibly well built. The walls are a laminate of 1.25" MDF and a 1/16" A-grade veneer. A loudspeaker's front baffle should be the strongest and best-damped enclosure wall because it acts as a sounding board for the woofer basket: the DM-10's baffle is 2" thick with constrained layer damping. Enclosure rigidity is further enhanced by internal bracing.

The enclosure is "de-coupled" from the floor via rubber isolation feet. McCalmont points out that suspended wood floors are the largest vibrating surfaces in a listening room, and says that the rubber feet improve midrange imaging and bass definition. In my present environment of carpet and ¾" foam over a concrete slab, I've always found spiked feet desirable for improving stability and enhancing lower-octave clarity. MACH 1 offers an optional, spiked, nonresonant platform for their speakers. The platform is intended to slip under the speaker cabinet, thus indirectly allowing you to spike the enclosures to the floor. These large, 17.5" by 19" platforms accommodate a variety of speaker footprints and facilitate tweaking the final speaker position and toe-in angle by allowing you to simply slide the speaker along the top of the platform. This eliminates the frustration of having to move a heavy, spiked enclosure across a carpet. These platforms worked so well for me that they became an integral part of the setup.

The woofer is located close to the floor to minimize frequency-response errors due to floor reflections. It's refreshing to see a sealed-box alignment among the recent horde of bass-reflex designs. This is no accident; driver manufacturers offer few woofers suitable for sealed-box loading, basically because floppy suspensions are very difficult to control in production. Why a closed-box design? Well, for one thing, MACH 1's computer simulations showed significantly less distortion in the 45-80Hz range, where a lot of bass energy resides. Sealed boxes are also much less susceptible to cone pumping due to subsonics—the sub-20Hz garbage analog systems are capable of generating. [The second-order high-pass rollout of a sealed box also gives much better in-room bass extension than an equivalent ported design.—Ed.]

The crossover features computer-generated fourth-order filters, with a Linkwitz-Riley response as an initial target. The lower crossover point is at a rather low 250Hz to prevent acoustic interference resulting from the considerable distance between the midrange and bass drivers. The upper crossover frequency of 3kHz was chosen to ensure good polar response with minimal lobing. Air-core coils are used for the mid and treble networks, while ferrite-cored coils are used for the bass network to minimize DC resistance losses. Only premium capacitors are used; there are no electrolytics anywhere in the DM-10. Solen caps are used in noncritical positions, while proprietary caps are used in all critical circuit positions. All parts are matched to within 1%.

A separate enclosure is provided for the crossover network to isolate the circuitry from the vibrational hell found inside a speaker cabinet. My crossover boxes had three pairs of flying leads for connecting the networks to their respective drivers. Current-production Signatures have binding posts at both inputs and outputs to accommodate a complete run of your favorite speaker cable. The DM-10 is bi-wire-ready, and that's how I used it. TARA Labs RSC speaker cable worked very well with Hovland/Sonic Purity and Mapleshade Electronics' Omega Mikro interconnects.

Sonic impressions
I had the DM-10 Signatures for several months, during which time I had the opportunity to audition them with a flock of power amps, both solid-state and tubed. I believe a great speaker should perform well with either transistors or tubes. A speaker's deficiencies at the frequency extremes are either laid bare or exacerbated by a solid-state amp, while a tube amp tends to be more forgiving. For a speaker to sound much better with tubes than with a good solid-state design implies that there's something wrong with the speaker. The modern trend toward excessive treble energy is hardly well served by bright-sounding amps. For example, a potentially deadly combination is a metal-dome tweeter driven by pure solid-state amplification. Mind you, I'm not anti-metal-dome—in fact, I like their inherent speed and detail. But solid-state typically etches their resonant metallic flavor to the point of sizzle, in my opinion.

The DM-10 sounded good with tubes or transistors. Sonic differences between amps were easily revealed: bad-sounding amps came across sounding bad. However, good tubes and transistors excelled equally in driving the MACH 1. Either way, the treble remained sweet and refined.

Enter the Classé M-700 monoblocks. These solid-state juggernauts in no way clouded the DM-10's sunny, natural top-end disposition. Female voice retained its harmonic sweetness and natural tonality. Even Joni Mitchell's Blue (Reprise MS-2038), whose sound exemplifies early solid-state recording, was well under control. The overall presentation was fast and detailed, with excellent dynamic bloom and a transparent soundstage. Midrange textures, while not as liquid as with tubes, were plenty smooth.

Tommy Flanagan, George Mraz, and Al Foster were fleshed out in a believable space on Nights at the Vanguard (Uptown UP27.29). Bass was so defined and detailed that I could hear bassist Mraz's fingers sliding along his fingerboard. Transient attack and decay were pristine, almost electrostatic in flavor. This enhanced the feel of the original space, as the decay of transients into the hall's background was nurtured with a motherly touch.

Neither was imaging excellence restricted to tube drive. The M-700 was able to portray a large chorus and orchestra with panoramic majesty and convincing spatial resolution. It was left to tubes, however, to flesh out this speaker's full imaging potential. The Jadis JA 200 monoblocks succeeded in erecting a 3D soundstage you could drive a truck through—the front third of my listening room was flooded with sound. Far from being tethered to the speakers, the soundstage appeared to have a life of its own. A "palpable" image focus, together with a transparent view, allowed me to explore the hall's inner recesses.

Too often a three-way design manages to distract my attention from the music by speaking in several voices, this "Tower of Babel" effect occurring in the frequency ranges where two drivers overlap. For a two-way, the overlap occurs once. A three-way has two regions where drivers are asked to join hands, and thus has more opportunity for problems. As the drivers that share the load in the transition band usually have different sonic signatures, and since the crossover networks add their own sounds, there is often some confusion and lack of blending through these regions. The result is typically a split personality that detracts from the presentation's cohesiveness. The organic unity of the DM-10's tightly knit drivers allowed me to focus more clearly on the music.

I was constantly aware of low-level detail surfacing above the noise floor of the recording. With some speakers, such a resonant signature etches detail and exaggerates sonic information. Such analytical transducers hit the listener over the head, shouting, "Notice me! I'm better 'cause you hear more!" This wasn't the case with the DM-10. Detail seemed to flow naturally from the music's fabric, as if I were peering through a microscope and had suddenly increased the magnification. There was absolutely nothing mechanical, electronic, or edgy about the sound. This clarity of presentation allowed me to unravel the harmonic envelope and sample nuances I had missed with lesser speakers.

Tonally, the DM-10's harmonic compass swung only minimally from True Neutral North, thus interfering very little with the music's mood. Harmonic colors were vividly portrayed, with only a slight dulling of soprano voice through the upper midrange. I wished for a tad more weight through the lower midrange, but my taste in reproduced music runs toward a fuller, warmer sound than that of the DM-10. Harmonic textures were smooth, with a softness or hardness dictated by the choice of partnering amp. The lack of grain and glare through the mids and lower treble did wonders for violin overtones and female voice. This whole range could be made to sing with the greatest of ease.

The DM-10s were very low in the "Technicolor" (ie, euphonic coloration) department. Some speakers are capable of "enhancing" musical reproduction with artificial excitement usually attributable to response aberrations in the upper mids or presence regions. A case in point is Western Electric's 755A—a full-range, 1940s-vintage PA driver. The 755A is highly sought after, especially by the Japanese, because of the startling vividness with which it projects voice and harmonic overtones onto the soundstage. Its frequency-response curve clearly indicates that the response from 3-8kHz is boosted relative to the midrange's core. This is nothing more than an implementation of the Academy curve, which prescribes a similar boost or EQ to film soundtracks. The intent is to make dialog not only more intelligible but more exciting—it seems to jump right off the screen into your lap. The same effect can be achieved with an equalizer like the Cello Palette. (It seems that colored speakers often generate strong cult followings, while natural-sounding speakers are often passed over by the audiophile as "not exciting enough.")

The DM-10 had plenty of dynamic flair, most evident in its resolution of the music's microdynamics. Harmonic textures bloomed from soft to loud with great conviction. When called upon to soar from loud to very loud, the speaker's dynamic headroom was quite impressive. Complex musical passages did not congest as the DM-10 scaled the dynamic spectrum. There were limits: When driven very hard, compression set in, most notably through the midband. Although the DM-10 could safely sink a lot of power, its dynamic range was limited, primarily by the midrange driver—perhaps a reflection of its low crossover point to the woofer.

The sensitivity spec is quite decent; even the 50W Air Tight ATM-2 (outfitted with Gold Aero KT99As) made the DM-10 boogie. There was something magical about this combination, which treated the mids to a fresh coat of paint and set my foot tapping along with the beat. Additionally, the lower mids sounded fuller and warmer, the way I like them; a romantic tube amp should nicely complement the DM-10.

Bass lines were consistently quick, tightly defined, and rhythmically precise—this was no doubt a function of the DM-10's critically damped sealed-box alignment and well-damped enclosure. The midbass was tonally convincing, but, as evidenced with cello and double bass, I felt the upper bass to be a bit lean. Still, the definition in the bass octaves was quite remarkable. However, as a tradeoff perhaps to the type of bass alignment used, both deep bass extension and impact were a bit weak. Timpani and bass drum lacked the stentorian response and punch I've come to expect from speakers in this price range. I had a hard time generating much response below 40Hz in my room. The DM-10 Signature doesn't appear to be the ideal speaker for organ-music aficionados.

Final thoughts
The MACH 1 DM-10 Signature is a great dynamic speaker, distinguished first of all by its use of the most natural- and musical-sounding tweeter I've heard to date. That wonderful Accuton unit affords a welcome relief from the monotonous procession of metal-domes presently flooding the market.

The DM-10 Signature's most amiable trait is probably its organic wholeness—a sense of total driver integration which makes it easy to leap forward and embrace the music. This, together with its knack for revealing rhythmic nuances, empowers the DM-10 to touch the soul as only a handful of speakers can.

The MACH 1 excels in preserving the flavor of live music. At the asking price, it becomes sensible to look seriously at a large planar speaker. But if your room and tastes gravitate toward dynamic speakers, be sure to audition the DM-10. It's a breath of sonic fresh air. The DM-10 Signature was a joy to have around; I'll miss its company in my listening room.

COMPANY INFO
MACH 1 Acoustics
RR 2, Box 334A
Wilton, NH 03086
(603) 654-9826
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