Напольная акустика — AudioNec OBi MAX

The OBi MAX is the top model of three open-baffle loudspeakers in the AudioNec OBi line, sitting above the OBi MID and OBi MINI. The design centres on the DuoPole 31 wideband driver first used in the company's Evo loudspeakers, but here the whole speaker works without a conventional box.

Key specs that matter

The band is divided between three kinds of driver. The DuoPole 31, a wideband unit 31 cm tall with the part number 313510, covers 400 Hz to 10 kHz. Below it, two 15-inch woofers in a d'Appolito arrangement handle 20 Hz to 400 Hz, and a horn-loaded dome super tweeter covers 10 kHz to 25 kHz. AudioNec lists a nominal impedance of 4 ohm, a system sensitivity of 86 dB and suggests amplifiers of 150 W to 300 W, while stating that the DuoPole driver on its own reaches an efficiency of 95 dB. Each speaker is 42 cm wide, 155 cm high and 31 cm deep and weighs 37 kg.

Engineering and use context

With an open baffle layout, drivers sit on a flat panel with no sealed or ported enclosure behind them, so the rear wave radiates freely. AudioNec's argument is that removing the cabinet removes the panel resonances that a box can add. The DuoPole 31 suits this layout because it is a dipole by design, with a very light diaphragm, a vertical voice coil and no spider. The 15-inch woofers were developed specifically for open baffle use, where the lack of a box normally costs low-frequency output, and they are placed above and below the wideband driver so that the output converges around its centre. The crossover is a passive high-end network. The same DuoPole 313510 also appears in the smallest OBi MINI, where it is paired with a single 12-inch woofer and the same horn-loaded super tweeter, so the three OBi models differ mainly in the size and count of their bass drivers and in overall height. The MAX uses the biggest woofers and the tallest frame of the three. With its shallow depth the speaker is slim in profile, but its dipole radiation requires free space at the back for the rear radiation to develop.

Pairing

Its efficiency and load point to a solid-state amplifier within the recommended power window instead of a small tube amplifier. Placement well out from the rear wall matters more than with boxed speakers because of the dipole output.

Alternatives

The AudioNec OBi MID is the medium open-baffle model, using two 30 cm woofers in a 127 cm tall frame.