It should be made clear at the outset of this portion of the Cautionary Tale that the fabrication considerations herein will refer to the trials and tribulations that I endured in the course of evolving and fabricating my true ribbon design. At left is a representation of the horizontal cross-section of the poles, magnetic structure, acoustic aperture and ribbon electrical return which comprise the structure of the design.
The design is currently operated magnetically open-circuit, which evolved from a previous consideration of using a form of horseshoe configuration. Lister's 1982 U.S. Patent was the direct source of my inspiration, and embodies the concept of cladding a central iron/steel pole piece with ceramic blocks [1]. Gerard's U.S. Patent gave inspiration to add (very many of) the small neodymium high-energy magnets on the outer spine of the pole pieces [2].
There is interesting, but flawed, data available on the growth of the magnetic field
during the course of assembly of this design; and also, some data on the increase of flux
density in the air gap by using
common steel wool to 'close' the magnetic circuit at the rear of the assembly. I hope to present that data next in
this series.
John R. Whittaker
[1]. C.R.B. Lister, "Vibratory Ribbon Speaker," U.S. Patent No. 4,317,966, (1982 May).
[2]. W.A. Gerard, "Open-Circuit Magnet Structure for Cross-Field Tubes and the Like,"
U.S. Patent No. 4,187,444, (1980, February).
Considerations on the
Optimal Design of True Ribbon Loudspeakers - Index.
Acoustic Line Source Research - Table of Contents.
