Напольная акустика — Raidho Acoustics D3.1

The D3.1 is a floor-standing three-way model in the Diamond, or D, Series of Raidho Acoustics, designed by Michael Borresen. The D range was introduced after the ceramic-cone C Series as an extension of that driver technology, adding a diamond layer to the cones. Raidho today places the D3.1 in its archive of earlier products that cannot be brought up to the current generation. The maker describes it as a speaker for listeners prepared to spend time on system setup and component matching.

Key specs that matter

A sealed ribbon tweeter, one 100 mm diamond midrange and three 115 mm diamond bass drivers make up the five-unit array. Second-order filters split the signal at 150 Hz and 3 kHz. Raidho specifies a range of 30 Hz to 50 kHz, a sensitivity of 90 dB at 2.83 V and 1 m, and a nominal impedance above 5 ohm, with an amplifier of more than 50 W. The cabinet measures 200 x 1,235 x 500 mm, or 320 x 1,320 x 540 mm with its feet, and weighs 53 kg. It comes in black piano, walnut burl veneer or a custom paint colour.

Engineering and use context

Borresen chose several small cones over one large diaphragm and housed them in a slim, deep and rigid enclosure to keep moving mass down. Each cone carries a coating about 10 microns thick, half diamond-type sp3 carbon and half graphite-type sp2 carbon, equal to roughly 1.5 carats of diamond. Raidho and its ceramic coating partner worked out a way to vaporise diamond that is stable and has a very low failure rate. According to the maker's tests the result is 140 times harder than the plain aluminium ceramic diaphragm, and the first resonance of the mid and bass cones sits above 20 kHz. The neodymium magnets are arranged as strips in a ring pattern rather than as a solid ring, and the rear of each motor is open, which limits reflections from the back of the cone and air compression behind it. The ribbon tweeter moves a membrane of only 0.02 g. The MDF cabinet has non-parallel sides in a teardrop plan and a tilted front, the drivers are fixed to aluminium faceplates, and the box is braced and vented to the rear.

Pairing

The high sensitivity lets smaller tube amplifiers drive the D3.1, and solid-state designs above the stated minimum are equally suitable. The recessed binding posts take banana plugs only, and the connection panel offers no provision for bi-wiring.

Alternatives

The Raidho C3.2 shares the five-driver three-way format with Ceramix cones in place of the diamond units, a shallower cabinet and lower sensitivity.