MartinLogan Motion Xt B100 gloss black (pack of 2)
Overview
Reaching down to 45 Hz while delivering 93 dB sensitivity in a 37 cm-high cabinet: the specifications are closer to a compact floorstander than an auxiliary bookshelf speaker. MartinLogan brings over the large folded tweeter and Kevlar midwoofer from its Motion XT floorstanders, without changing the materials in the process. The Lawrence, Kansas-based brand presents it as its best bookshelf speaker.
A tweeter that compresses air between its folds
Folded Motion is MartinLogan’s signature outside electrostatic speakers. Its accordion-folded diaphragm does not push air in front of it: it compresses it between its folds, driven by an array of neodymium magnets. The diaphragm’s required movement becomes tiny; the brand cites nearly 90% less excursion than a conventional 25 mm dome, for a much larger radiating surface.
The B100 receives the largest version of this driver, the Gen2 Obsidian Folded Motion XT: 3.2 x 6.1 cm overall, 79.8 cm² of diaphragm, or 40% more than the reference Folded Motion according to MartinLogan, with an enlarged motor that lowers distortion and increases efficiency. The crossover assigns it everything above 2600 Hz. A low crossover point for a tweeter, made viable only by this large surface area.
The waveguide and the height constraint
The driver is recessed into a waveguide molded into the baffle, whose profile was selected after evaluating nearly fifty designs. Two objectives: match its directivity to that of the 16.5 cm driver around the crossover point, and limit early reflections from the side walls and ceiling.
The result is shown in the specifications: 90° in the horizontal plane versus only 45° in the vertical plane. This asymmetry has a practical consequence. Horizontally, the sofa can be wide: tonal balance holds as you move away from the axis. Vertically, the window is narrow and the tweeter must be positioned roughly at ear height when seated, otherwise the upper end of the spectrum fades away. A B100 placed on a low cabinet will not sound like the same speaker on a stand.
Nomex-reinforced Kevlar in 16.5 cm
MartinLogan classifies the second driver as a midrange and leaves the “bass” line blank in its documentation. Yet the 16.5 cm driver handles the entire lower spectrum up to the 2600 Hz crossover point: voices, dialogue, instrument body—all pass through it. Its cone combines rigid Kevlar with Nomex, which damps the fiber’s resonances, with the assembly formed as a single piece with its surround. The basket is made of cast aluminum, whereas the Motion B10 makes do with a polymer basket and a woven fiberglass cone.
The cabinet operates as a rear-ported bass reflex design, with an asymmetrical non-resonant chamber around the driver. Its claimed response extends down to 45 Hz at ±3 dB, an uncommon figure for a 16.5 cm driver in a 20 cm-wide enclosure, paid for with a 4-ohm load and tuning that requires space behind the speaker.
The amplifier to plan for below four ohms
The stated 93 dB are measured at 2.83 V at one meter. Into a 4-ohm load, this voltage corresponds to 2 W rather than 1 W: actual sensitivity is therefore around 90 dB for 1 W, which remains high, but is less spectacular than the raw figure. MartinLogan states compatibility with 4, 6, or 8-ohm outputs, preferably recommends a 4 or 6-ohm output, and places the useful range between 20 and 250 W per channel.
The parameter to watch is less the rated power than current capability. A 4-ohm load tests modest integrated amplifiers and some entry-level audio-video amplifiers, especially at high volume and across several simultaneous channels. The five-way binding posts are doubled and accept both bi-wiring and passive bi-amping. Active bi-amping, however, is not recommended by the brand, as the internal crossover cannot be bypassed.
A stereo pair, a home theater foundation
In stereo, 45 Hz covers almost the entire acoustic repertoire and leaves only the last octaves of synthesized bass or organ out of reach. A subwoofer becomes useful mainly in home theater, where the LFE channel extends significantly lower than what a 16.5 cm driver can deliver in this cabinet volume.
The B100 shares its XT tweeter and Kevlar cone with the C100 center speaker and the F100 and F200 floorstanders, providing tonal continuity from one channel to another when used as a front or surround speaker in a Motion XT system. MartinLogan claims the same consistency with its Motion XT CI in-wall models, for installations combining visible speakers and wall-integrated drivers.
Finishes, grilles and matching stand
Three finishes are listed: gloss black, walnut, and satin white. Secure-Lock grilles are held in place by discreet mounting tabs, without an overhanging frame, and can be removed or reoriented depending on the direction of the fabric grain you prefer to see.
Under the cabinet, a threaded insert accepts the STAND25, slightly over 65 cm high, whose column can be filled with sand and which can be placed either on spikes or rubber pads. Its three interchangeable decorative inserts (black, copper, silver) match the trim of the different Motion finishes. Bolting secures the speaker and stand together, something a universal stand does not do. Otherwise, a 60 to 65 cm stand will be suitable, provided it can support the speaker’s 9.3 kg. The 31.8 cm depth, binding posts included, must still be anticipated on a shelf.
Technical Specifications
Overview
- Ideal for 2-channel stereo or home theater configurations
- Integrated threading allows secure mounting on the matching STAND25 speaker stand (sold separately) for maximum stability
Acoustic Specifications
- Application: bookshelf
- Frequency response: 45 Hz – 25 kHz ± 3 dB
- Dispersion: 45° (vertical) x 90° (horizontal)
- Sensitivity: 93 dB
- Impedance: 4 ohms
- Crossover frequency: 2600 Hz (2-way)
- Recommended amplifier power: 20 – 250 watts
Drivers
- High-frequency driver
- 3.2 cm x 6.1 cm Gen2 Obsidian Folded Motion XT tweeter
- 79.8 cm² diaphragm
- Midrange driver
- 16.5 cm Nomex-reinforced Kevlar cone
- Cast aluminum basket
- Non-resonant asymmetric chamber
- One-piece cone construction
- Low-frequency driver: not applicable
Cabinet and Connectivity
- Cabinet: rear port
- Inputs: custom 5-way binding posts, compatible with bi-amping / bi-wiring
Dimensions and Weight
- Weight: 9.3 kg
- Dimensions (H x W x D): 36.8 cm x 20.3 cm x 31.8 cm
- Product dimensions include feet, binding posts, and grilles
Available Finishes
- Gloss Black, Walnut, Satin White
Audio Technologies
- Controlled Dispersion
- Minimizes early reflections that degrade sound by controlling tweeter sound dispersion in the room
- Improves listening clarity and expands placement options in any room
- Gen2 Obsidian Folded Motion XT Tweeter
- Features a larger motor for higher efficiency and reduced distortion
- 40% greater radiating surface area compared to the reference FMT
- The clearest, most detailed, and most accurate high-frequency reproduction to date, outside the electrostatic range
- Folded Motion Waveguide
- Profile selected from nearly 50 evaluated design options
- Harmonious alignment with midrange driver dispersion for increased efficiency
- Ensures consistent sound quality regardless of listening position
- Minimizes unwanted room reflections and ensures even sound distribution
- Nomex-Reinforced Kevlar Midwoofer
- Durable, lightweight cone
- Absorbs unwanted resonances and vibrations for unmatched midrange clarity
- Paired with the Gen2 Obsidian FMT XT tweeter, it delivers unparalleled precision for vocals, dialogue, and instruments at any volume
- Seamless integration with Motion XT CI products for custom solutions
- McCracken-Vojtko Crossover
- Custom crossover named after our acoustic engineers
- Designed using proprietary measurement and simulation software
- Tuned and validated through double-blind listening tests
- Ensures perfect cohesion between the different driver platforms
Design and Finishes
- Secure-Lock Grilles
- Modern, elegant design with discreet mounting tabs
- Securely holds the grilles in place while allowing customization of the speaker’s appearance
- Grilles can be left in place, removed, or rotated to orient the fabric grain according to your preferences
Frequently Asked Questions
What is the difference compared with the Motion B10?
The B10 is the bookshelf model in the Motion series, one step below the XT series. It features the standard-size Folded Motion (59.4 cm² diaphragm area versus 79.8), a 14 cm woven fiberglass midwoofer on a polymer basket, and its response stops at 56 Hz instead of 45. Its nominal impedance is 5 ohms, its power handling tops out at 200 W, and its single binding post does not allow bi-wiring. At 6.6 kg versus 9.3, it is intended for more modest rooms and listening levels.
How should I set the crossover if I add a subwoofer?
With a stated response down to 45 Hz, a setting around 60 to 80 Hz on a home theater processor is a reasonable starting point: the B100 operates within its comfort zone and its port is relieved. In stereo with a subwoofer, aiming lower (50 to 60 Hz) better preserves mid-bass continuity. Final adjustment depends mainly on the subwoofer’s position and the room modes.
How long should speakers be broken in?
MartinLogan recommends approximately 72 hours of operation at a moderate level, around 90 dB, before any critical listening. The suspension and cone loosen during this period, and the change is heard mainly in the lower end of the spectrum.
Can it really be placed in a bookcase?
Technically, yes, MartinLogan rates it for bookshelf use, but the rear port and 31.8 cm depth require some precautions. A niche enclosed on three sides reinforces the bass in an uncontrolled way and muddies the midrange. If a shelf is the only possible location, leaving around twenty centimetres behind the speaker and avoiding overly close side walls will limit the damage. A stand remains the safest solution, if only because of the tweeter height.
How do I connect the B100 using bi-wiring?
The two pairs of terminals are factory-connected by metal jumpers. They must be removed before connecting two separate pairs of cables; otherwise, the amplifier outputs will be connected together, risking damage. The amplifier must be switched off during this procedure. Depending on the country, regulations prohibit MartinLogan from supplying these jumpers: if they are absent, the connection is made using two pairs of cables or commercially available straps.
Is the B100 suitable for use as a surround speaker in a Motion XT system?
Yes, the drivers are shared across the series, which prevents timbre shifts when panning between channels. Two points to note: the 93 dB sensitivity exceeds that of the F100 and F200 floorstanding speakers (92 dB), so a slight per-channel level adjustment should be expected during calibration, and MartinLogan does not document any wall mounting for this model, as the threaded insert is located underneath the cabinet. A stand or sturdy shelf is required.
How do I maintain the speaker and its tweeter?
A microfiber cloth or a soft brush is sufficient for dusting. MartinLogan advises against spraying cleaning products near the speakers. The pleated diaphragm is delicate and recessed within the waveguide: it is best not to touch it and to leave the grilles in place if children or pets are nearby. Prolonged exposure to direct sunlight should be avoided, both for the finish and the cone materials.
- Eco-contribution of €0.84 included in the sale price.
- GTIN / EAN: 810123026050
