VIAWAVE GRT-145-4

Viawave GRT-145-4: sealed ribbon tweeter with 98 dB at 4 Ω for high-efficiency designs

The Viawave GRT-145-4 is the 4 Ω version of the GRT-145 – a ribbon tweeter using the patented SRT technique (Sealed Ribbon Tweeter). In a conventional ribbon the air gap between foil and magnet poles is open; Viawave seals it with a U-shaped, heat-resistant polymer film. That cuts distortion at the lower end of the operating range noticeably and raises sensitivity by 2 to 3 dB.

The ribbon itself measures 14 × 50 × 0.009 mm, weighs 0.018 g and has 7 cm² of area – for that size, 98 dB at 2.83 V/1 m (measured 4 to 18 kHz) is a remarkable figure. A word on context: at 4 Ω the driver draws twice the power at 2.83 V compared with the higher-impedance sister version, so the 3 dB advantage is a voltage gain, not an efficiency gain. That becomes interesting where the amplifier supplies the voltage anyway and you need less attenuation in a passive crossover. Operating range 1,800 to 30,000 Hz, aluminium faceplate, NdFeB magnets, 1.32 kg.

Use and enclosure

Viawave recommends a high-pass from 3,000 Hz at 12 dB/octave; with that filter the 150 W program rating applies. Crossing lower is possible – the range starts at 1,800 Hz – but demands a steeper slope, since the rear chamber resonates at 900 Hz and the RMS rating is only 17 W (40 W peak). Without a high-pass a ribbon is destroyed instantly – that is not a footnote, it is everyday experience.

The 4 Ω winding has consequences for the crossover: the nominal impedance comes from the matching transformer, while the ribbon itself has 0.06 Ω DC resistance. With 3.5 mH low-frequency and 0.017 mH high-frequency inductance, a passive filter sees a load you should take from the measured impedance curve in simulation, not from the nominal figure. Dispersion: wide horizontally, tightly focused vertically because of the 50 mm ribbon height – mount it at ear level.

What to look out for

• 4 Ω nominal – the amplifier must be stable into 4 Ω; watch parallel branches in the crossover
• High-pass mandatory: 3,000 Hz, 12 dB/oct as the manufacturer's spec, 150 W program only with it
• 17 W RMS, 40 W peak – the ribbon sets the limit, not the amplifier
• 1.32 kg, aluminium faceplate, rear chamber damped with natural wool
• Ribbon 14 × 50 mm – narrow vertical dispersion, mount at ear height

Frequently asked questions

Viawave GRT-145-4: manufacturer, spellings and classification

Viawave (Viawave Audio) is the maker of the patented SRT ribbon tweeters with sealed air gap. The GRT-145-4 is a ribbon tweeter, available from 42.audio, Viawave dealer in Germany, with datasheet and full specifications in the driver database.

At 42.audio you get the VIAWAVE GRT-145-4 with all key data in the driver database. More drivers from this manufacturer: Atlas Viawave.