Loudspeakers

At the top of this cone-filled tower sits MartinLogan's 2nd-generation Folded Motion Tweeter (FMT), the Obsidian 'XT' version featured here boasting a 40% increase in radiation area to 80cm2. The folded thin-film diaphragm is an AMT (air-motion transformer) transducer, bathed in a magnetic field, that stretches and squeezes in response to the audio signal fed across its surface. FMTs or AMTs are hi-fi's equivalent of the accordion!

The component parts of ML's FMT driver are illustrated here [inset picture], revealing the robust metal frame, thin film diaphragm [centre] and high intensity neodymium iron boron (NIB) magnets arranged in bars [behind]. Aligning the acoustical output of this AMT-style tweeter with the dispersion of the 165mm Nomex/Kevlar midrange unit at the 2.6kHz crossover is the job of the partnering 'Folding Motion Waveguide' – the grille and flared aperture that blends the FMT into the baffle. The waveguide for the larger XT FMT unit used in the F200 acts over 45° vertical and 90° horizontal, and allows MartinLogan's designers some measure of control over floor and ceiling bounce. PM