Martin Logan Motion 4i Compact Bookshelf Speakers

Audiophile performance without an audiophile price. Inspired by the clarity and detail of MartinLogan’s ultra-high-end electrostatic loudspeakers, Martin Logan Motion 4i features a Folded Motion tweeter, 4-inch paper cone woofer, and a proprietary Vojtko crossover network in a compact and affordable package. Low-frequencies are enhanced by a rear-firing Cascading Bass Reflex Port, a unique, long-volume port that delivers surprisingly big bass from a remarkably compact loudspeaker. Flexible installation options allow table top or on-wall installation. The Martin Logan Motion 4i can also mount upside down to facilitate placement high on a wall. Available in gloss black.

Engineering, Without Compromises

What makes the Motion Series sound so amazing? MartinLogan’s dedicated in-house engineering and design team started by utilizing and refining the most advanced, compact technologies and combining them with innovative engineering and time-honoured cabinet construction techniques. The result is an emotionally engaging sound that rivals (and most times trounces) traditional loudspeakers of similar size and price. Our ‘no compromise’ philosophy gives Motion Series a unique sound you won’t find anywhere else.

Sound Inspired by Electrostatic Speakers

The success of the Motion Series is directly attributed to its close relation to MartinLogan’s legendary ultra-high-end electrostatic loudspeakers. The desire to transmute that level of performance into a more traditional loudspeaker at a more affordable price drove the initial design imperatives that created the Motion Series.

Folded Motion^® Tweeters

MartinLogan’s signature Folded Motion tweeter utilizes an extremely low mass diaphragm that “squeezes” air, thus demanding significantly less excursion than the typical 1-inch dome tweeter. Its folded design allows for a much larger surface area (compared to that of a regular 1-inch dome tweeter), controlled dispersion characteristics, and vanishingly low distortion. It’s a miracle of audio engineering that’s able to deliver much of the high-frequency detail and speed of a large, dynamic electrostatic panel in a small space.

Proprietary Vojtko ^™ Crossover Networks

Compact Motion Series speakers feature proprietary Vojtko crossover networks using custom air core coil inductors, low DCR steel laminate inductors, and polyester film and low-DF electrolytic capacitors for a seamless sonic presentation.

Vojtko crossovers are named after MartinLogan’s chief audio technologist, Joe Vojtko. His unique approach to crossover design is as big of a part of the “MartinLogan Sound” as are electrostatic and Folded Motion thin-film driver technologies. Vojtko crossovers are designed in such a way that all drivers are kept within their optimal frequency range and balanced with one another. The drivers themselves are as much a part of a Vojtko crossover as are capacitors and resistors. Before the design of any crossover begins, drivers are carefully selected or designed to operate within a very intentional frequency range and with precise and predictable performance parameters.

Vojtko crossovers are always built from high-quality parts, and care is taken to avoid overly complex topologies—a straightforward objective due to the careful selection of woofers and tweeters. The final (and most critical) aspect of a Vojtko Crossover is that final voicing is conducted in a space that is indicative of a real-world environment. This pragmatic approach allows Martin Logan Motion 4i speakers to sound their best in real-world rooms.

Cascading Bass Reflex Port

MartinLogan engineers were faced with a daunting task—create a compact speaker with low-end bass reproduction found in speakers much, much larger. After many sleepless night and a myriad of prototypes, they created the Cascading Bass Reflex Port. This brilliant solution allows a long tuned port, which is folded over itself (think of a trombone’s tuning arm) to be compacted and squeezed into the Martin Logan Motion 4i. The result is amazingly detailed low bass that can play at high volumes with minimum distortion—all thanks to the elegantly simple cascading fold that slows down and controls the air motion of the bass waves.

Specifications – Martin Logan Motion 4i speakers

Frequency Response	70–23,000 Hz ±3dB
Recommended Amplifier Power	20—150 watts per channel
Horizontal Dispersion	80°
Vertical Dispersion	80°
Sensitivity	90 dB/2.83 volts/meter
Impedance	4 Ohms Compatible with 4, 6, or 8 Ohm rated amplifiers.
Crossover Frequency	2,900 Hz
High Frequency Transducer	1″ × 1.4″ (2.6cm × 3.6cm) Folded Motion Transducer with 5.25″ × 1.75″ (13.3cm × 4.4cm) diaphragm
Low Frequency Transducer	4″ (10.2cm) paper cone with stamped steel basket. Non-resonant asymmetrical chamber format. Rigid structured dust cap to reduce cone break-up modes. Folded bass reflex port.
Components	Custom air core coil and low DCR steel laminate inductors. Polyester film capacitors in series and low DF electrolytic capacitors in parallel. Overall system thermal/current protection.
Inputs	Push style with banana jacks
Weight	6 lbs. (2.72 kg)
Dimensions	12.6″ x 5.6″ x 5.7 ” (32cm x 14.3cm x 14.5cm)