ACOUSTICS :: THEMA :: ALTRA :: VARIATION ::

:: CONCEPTION :: by Christian Yvon

THEMA was the first loudspeaker to appear in the new range - and with it the characteristic shape known as " ARCH " (Anti Resonance CHap). This design confers great rigidity and allows unwanted vibration to be rapidly dissipated viathe central cone. It also favours a non-resonant sound and allows for a precise placement at the correct angle.
The THEMA uses a 17 cm medium-bass driver designed by AperturA and built by ATD following a strict design brief. It is a polymethyl-pentene con which combines fast response with excellent damping properties whilst remaining rigid and light. Because of this, there are very few distortions in the cone and the few that remain are towards the top of the frequency range, well beyond the roll-off poin. The suspension rests on an ultra-rigid chassis with a totally decompressed spider cavity.
The crossover is elliptical on one of its branches, with three different slopes : 6 dB, 12 dB and 24 dB per octave. This three pronged attack allows an overall intrsection at +6 dB and therefore a minimal intermodulation zone.
Following the same logic as the bass drivers, a new ribbon-tweeter has been developed - the NFB6. This " zero leakage " technology uses a powerful and stable magnetic circuit which gives perfct control of the ribbon over all its length.
The result is minimum distortion - to a level never before achieved with this kind of transducer.
Musically speaking, the THEMA is typically AperturA ; disciplined and limpid, energetic and delicate, with a geuine three dimensional image, but above all willing to give precedence to the music by respecting rhythm, tempo, nuance and colour.
The THEMA can give of its best with a wide range of amplifiers. It can also be associated with electronics at price pointsseveral times greater than its own.

:: TECHNICAL SPECIFICATIONS THEMA

• 2 way system. Crossover point 2.8 kHz.
• Phase optimised.
• Bass/mid-range : 17 cm polymethyl-pentene specially developed for AperturA.
• Selected ribbon tweeter with lossless Neodymium agnet.
• Ribbon mass : 0.011 g.
• Crossover assembly using " wrapping " technique - the best but most expensive solution.
• Stereo pairs rigourously matched.
• Sensitivity : 89 dB.
• Impedance : 4 Ohms.
• Dimensions : W 200 mm x D 325 mm x H 1035 mm.