Напольная акустика — Cessaro Horn Acoustics BETA 0.5 II

BETA 0.5 II is a Cessaro Horn Acoustics speaker from Germany using a 4-way horn layout. Each channel combines a main horn cabinet with an external active backloaded bass horn, so the low end is powered separately while the upper bands run from the main amplifier.

Key specs that matter

Efficiency is 100 dB at 1 W/1 m with a nominal impedance of 8 ohm, and the rated frequency range spans 30 Hz to 45,000 Hz. Power handling is 60 W and maximum output exceeds 122 dB. The main unit measures 176 x 58 x 84 cm, and the active bass horn is 102 cm high, 53 cm wide and 84 cm deep. Total weight per channel is 310 kg in plywood or 480 kg in composite construction.

Engineering and use context

Founder Ralph Krebs had the horn contour worked out over 2.5 years in custom simulation software, and the edge of each horn mouth is reshaped to soften the wavefront there. A 16 inch alnico bass driver works in a backloaded horn built from plywood or a material mix. The low-mid band uses an 11 inch alnico bass unit in a sealed box, a layout not found in the 3-way ALPHA II. A 2 inch alnico compression unit using a beryllium membrane serves the midrange in a composite spherical horn 58 cm across, while the top octaves come from a 0.5 inch cobalt-magnet compression tweeter, also beryllium, set in a 9 cm spherical horn milled from brass. The brand advises a room bigger than 20 m2 with at least 2.5 m between seat and speakers. Horns are formed as a double shell with a dense polymer core for damping, and each throat is a one inch solid aluminium ring coupled straight to the driver. Cabinets are finished by hand by German craftsmen, drive units are largely custom TAD types, with in-house and co-developed units added because of sourcing difficulties, and the internal cabling is pure silver. Crossover networks are built with high value pure silver MICAS capacitors and designed around psychoacoustic properties of hearing.

Pairing

The maker sets the minimum amplifier power at more than 1.5 W for the passive section and calls for fast amplifiers of high quality. Once the bass horns are active, the chosen amplifier only drives the low-mid, mid and treble bands, which suits single-ended tube designs of a few watts. Mains power has to reach both bass horn units.

Alternatives

Cessaro BETA II is a larger floorstanding model from this maker with four alnico bass drivers per channel and 105 dB efficiency.