Eighteen Sound’s Tetracoil technology combines four mobile voice coils used into a dual-gap magnetic motor. Such configuration, in addition to increasing the applicable power, linearizes speaker behavior by significantly reducing the distortion and significantly increases the power vs. weight ratio.
As the company explains, loudspeaker nonlinearities are synonymous with sound distortion, which especially at the high levels that can be reached during live concerts can reach values well above 10%. “Over time, various techniques have emerged to limit this problem; the main limit is that each of these techniques operates in a limited frequency range and this introduces additional side effects. In the particular case of subwoofers, one or more aluminum rings positioned in the magnetic gap are used resulting in a partial reduction of the distortion rate. The side effect is the introduction of a sensitive magnetic field asymmetry in the gap, where the moving coil is to operate.”
Tetracoil technology corrects most of those non-linearities, while making the speaker lighter and easier to build. As Eighteen Sound notes, “In fact, this particular type of realization allows optimizing the amount of magnetic material needed and increases the heating exchange of the voice coil by at least 50%, consequently improving significantly the power handling.”
The new Tetracoil subwoofers
During Prolight+Sound 2017 in Frankfurt, Eighteen Sound showcased its two new Tetracoil subwoofers, starting with the 15TLW3000, a 15-inch diameter version of the 18TLW3000 model, successfully adopted by several reference manufacturers in their top-of-the-range subwoofer cabinets. The 15TLW3000, characterized by its rear die-cast aluminum heat sink, and its 4-inch - 100mm - ISV Tetracoil engine is now shipping from the company’s Reggio Emilia factory. The 15TLW3000 uses a straight ribbed, water repellent composite cone, and achieves a 35mm peak to peak excursion with a symmetric flux density and inductance behavior. The driver is rated for 3000W program power handling, with a 95 dB sensitivity.
Following this presentation in Frankfurt, Eighteen Sound is now also announcing the introduction of the new 21NTLWL5000, 21” – 540 mm – neodymium Tetracoil subwoofer. For the company, this is also the introduction of the 5000 Tetracoil subwoofer family, equipped with a new generation 4.5 inch - 115mm - Neodymium magnet engine. The 21NTLW5000 is able to reproduce frequencies down to 20 Hz at very high-pressure levels (130dB). Preliminary specs indicate a 96,5 dB SPL average sensitivity (1W / 1m) and an astonishing 4000 W program power handling.
Commenting on this new 21” design, the Italian company explains that the most renowned professional audio manufacturers are always looking to increase linear excursion of the membrane in its subwoofers designs. “To do so you need to control significant moving masses at very low frequencies for membrane excursions of several centimeters. To achieve this goal, in the new 21-inch a lot of effort was spent using simulation techniques for defining the suspension geometry, which was designed and produced specifically for this model.”
The 21NTLW5000 is currently under test by several manufacturers and the first production run is scheduled for the fourth quarter of 2017. Next up, reveals the company, a new Tetracoil 18-inch version is also in the works and already in an advanced development phase. “The benefits of Tetracoil technology will be then applied to smaller speaker diameters. A 3.5-inch motor to be followed by a 2.5-inch engine is already in the pipeline,” Eighteen Sound reveals.