Test Bench: The 27TFC/T 1" Soft Dome Tweeter from the SEAS Prestige Titan Line

The 27TFC/T is a new 1" (25mm) tweeter featuring a one-piece centenary profile dome and wide surround fabricated from SEAS pre-coated lightweight Sonolex material, both integrated into an injection molded faceplate. The voice coil consists of a non-magnetically conducting titanium former wound with round copper wire. Driving the removable dome assembly is a ferrite magnet with a damped vented pole piece that is coupled to an injection molded rear cavity. This article was originally published in Voice Coil, May 2025.

RS Speakers is a new Italian brand recently introduced by SICA Altoparlanti, to enter the high-end home transducer market. The driver on this Test Bench is a 28mm soft dome tweeter that features a treated silk dome directly bonded to the voice coil, with a wide roll surround and an unusual wire screen to keep the damping in place beneath the dome.

Having stumbled upon some reports on the loss of micro details due to a collapse of permeability in output transformers, and being of an inquiring nature, Hans Polak decided to have a detailed look. This supposed phenomenon would be detected with push-pull (PP) tube amplifiers with output transformers at low levels, near our auditory threshold. For this investigation he focused on the output transformer (OPT) in isolation.

The original Mu Stage project, published in Glass Audio in 1993, remains a popular build, serving the author's purpose to "combat listener fatigue." His Type 2 Mu Stage, published by audioXpress in 2019, introduced a streamlined version with added capabilities. Now, the new Type 3 Mu Stage resulted in what the author believes to be a breakthrough, improving the realistic reproduction of music. This latest iteration of the circuit was prototyped by Kim Bond, an enthusiastic builder of the previous Mu Stages.

Voice Coil May 2025 is now available and in this issue, Vance Dickason explores the popular miniDSP Flex HTx processor, while Mike Klasco dives into the world of microspeakers. For this issue's Test Bench, Vance Dickason characterizes his first driver from the new Italian brand RS Speakers, a new TW 104.28 N/Ag 1.1” tweeter, and next measures the 27TFC/T 1” Soft Dome Tweeter from the SEAS Prestige Titan Line.

This year’s special Glass Audio issue of audioXpress includes interesting explorations such as the Ultra-Linear Power Amplifier by Rudolf Moers, Micro Details in Push-Pull Output Transformers by Hans Polak, Getting Less Gain From Tubes by Merlin Blencowe, and the Type 3 Mu Stage Breakthrough by Alan Kimmel. This issue also includes two speaker designs from Ben (Wolf) Shaffer and Ken Bird, an article about the intriguing return of 78 rpm records, and Paul Marchese’s Part 2 of his insightful Primer on Class-D Amplifiers. Richard Honeycutt shares how he learned to DIY with Tubes.