Полочная акустика — Martin Logan Motion 4i

The Motion 4i is a compact two-way speaker from MartinLogan and one of the smallest boxes in the Motion family, a range the company first introduced in 2010 to bring its Folded Motion tweeter to lower prices. MartinLogan designed it to work as a stereo pair on a shelf or desk, as a surround channel or as the centre speaker in a home cinema, and it ships only in gloss black.

Key specs that matter

A Folded Motion tweeter with a 1 x 1.4 inch (2.6 x 3.6 cm) opening and a pleated diaphragm of 5.25 x 1.75 inch (13.3 x 4.4 cm) covers the treble, and a 4-inch (10.2 cm) paper cone in a stamped steel basket handles the rest of the band. The two drivers hand over at 2,900 Hz. MartinLogan rates the response at 70 Hz to 23 kHz within 3 dB, sensitivity at 90 dB for 2.83 V at 1 m, and nominal impedance at 4 ohm, while stating that amplifiers rated for 4, 6 or 8 ohm are compatible. Recommended amplifier power runs from 20 to 150 W per channel. Horizontal and vertical dispersion are both given as 80 degrees. The cabinet stands 32 cm tall, 14.3 cm wide and 14.5 cm deep and weighs 2.72 kg.

Engineering and use context

The Folded Motion principle folds an extremely low-mass diaphragm to give it far more surface than a regular 1-inch dome tweeter offers, with controlled dispersion. The woofer sits in its own asymmetrical, non-resonant chamber and carries a rigid structured dust cap. Low-frequency output comes from a Cascading Bass Reflex Port, a long folded port tuned inside the slim enclosure so that a small cabinet still gets a usable port length. The Vojtko crossover network uses custom air-core coils, low-DCR steel laminate inductors, polyester film capacitors and low-DF electrolytic capacitors, and a system-wide thermal and current protection circuit guards the drivers against overload. Mounting options include tabletop or shelf placement, speaker stands and a supplied wall bracket that sets the cabinet at one of two angles, and the speaker can also hang upside-down high on a wall. Push-type binding posts accept banana plugs, and the front carries the perforated grille used across MartinLogan speakers.

Pairing

With its limited bass extension, most cinema systems built on this model add a subwoofer, with the crossover in the AV receiver set so the small woofer is spared the deepest bass. In stereo use on a desk or shelf, a compact integrated amplifier or AV receiver within the recommended power window is enough for the 4-inch driver.

Alternatives

The MartinLogan Motion 15i steps up within the same Motion family to a bookshelf cabinet with a 5.25-inch aluminium cone woofer and a rear-firing bass port.