RAVAUD, Romain, Guy LEMARQUAND, Valérie LEMARQUAND, and Claude DEPOLLIER. “Ironless Loudspeakers With Ferrofluid Seals”. Archives of Acoustics 33, no. 4(S) (January 31, 2008): 53–58. Accessed March 4, 2026. https://acoustics.ippt.gov.pl/index.php/aa/article/view/835.