A structural support for a bolt collar in an automotive vehicle main structural support is provided and includes a rear wall having a rounded portion, a pair of side walls extending substantially perpendicular from the rear wall and a base extending from a lower portion of the rear wall and from a lower portion of the rounded portion in a direction opposite to that of the pair of side walls. The mounting mechanism includes a shaft connected to the loudspeaker housing. The multi-layered wiring substrate includes: a via conductor arranged at a position of the one capacitor electrode for electrically connecting among a plurality of power-supply patterns in a thickness direction; and a via conductor arranged at a position of the other capacitor electrode for electrically connecting among a plurality of ground patterns in a thickness direction. Permeable material slugs are pressed into the receivers to control the form factor of the flux density.