Bookshelf Speakers — Martin Logan Motion Foundation B2

MartinLogan describes the Motion Foundation B2 as the larger bookshelf speaker in its Motion Foundation series. That affordable range, introduced in June 2023, consists of five models - two towers, the F1 and F2, two bookshelf speakers, the B1 and B2, and the C1 centre channel. Every model uses the Gen2 Obsidian Folded Motion Tweeter S, which the brand says carries much of what its larger siblings achieve into a more compact and affordable package, and the aluminium drivers were derived from the more expensive Motion XT and Motion ranges.

Key specs that matter

A 16.5 cm aluminium woofer works with a tweeter of 2.4 x 2.5 cm that has a 22.6 cm2 diaphragm, and the two drivers divide the signal at 3,800 Hz. Tweeter dispersion is 90 by 90 degrees. The rated range is 42 Hz to 23 kHz within plus or minus 3 dB, sensitivity is 90 dB and nominal impedance is 5 ohm. The rear-ported box is 38.1 cm high, 19.7 cm wide and 29.2 cm deep with feet, binding posts and grille counted, for a weight of 6.8 kg. Each finish comes with its own trim colour - Walnut with bronze, Black with gunmetal, or Satin White with silver.

Engineering and use context

In a Folded Motion tweeter, the thin-film diaphragm is folded so that more surface area is packed into a compact frame, which MartinLogan links to fast response. The B2 places this tweeter inside a custom Folded Motion waveguide, which supports the Controlled Dispersion of the tweeter - MartinLogan's method of focusing output into the listening area to limit reflections from surrounding surfaces. The woofer is built as a single-piece unibody cone in a stamped steel frame, and behind the cone sits a non-resonant asymmetrical chamber. MartinLogan developed the McCracken-Vojtko crossover of the series by combining anechoic measurements, in-room measurements and several blind listening tests with the low distortion principles of its Vojtko crossover. Connection is through 5-way binding posts in a single pair, without bi-wire terminals. The grilles lock in place with stealth tabs, and the owner can fit them, remove them or turn them to show the fabric grain in another direction.

Pairing

MartinLogan recommends amplification of 15 to 100 watts. For multichannel use, the C1 centre channel and the F1 and F2 floorstanders from the same series share the tweeter type and finishes.

Alternatives

For a smaller cabinet, MartinLogan offers the Motion Foundation B1, which has a 14 cm aluminium woofer, a crossover at 3,400 Hz and a weight of 5.2 kg.