A flexible planar inductive coil configured for producing an acoustical sound, the flexible planar inductive coil being suitable for embedding in a product, the flexible planar inductive coil comprising: at least one flexible substrate, the substrate being conformable; a matched function ink set, comprising matched additively printed matched function inks, matched to at least: a receptivity of the flexible substrate onto which the matched function inks are printed; and a chemical reactivity between the substrate and the matched function inks; the additively printed matched function inks forming a plurality of successive conductive traces, additively printed as as least one layer on the at least one flexible substrate; wherein successive conductive traces have a line height in a range of 4.58 μm +/- 0.6μm printed onto a substantially planar face (106a, 106b) of the at least one flexible substrate; wherein the successive conductive traces are configured to receive a current flow from at least one source; and wherein the flexible planar conductive coil is provided by the successive conductive traces separated by gaps between successive conductive traces around a central axis through the plane of the at least one flexible substrate, the successive conductive traces having line widths and the gaps in a range of 180 μm - 260 μm; wherein the successive conductive traces are of high density, and wherein the high density provides a series resistance in a range of 16 Ohms to 1 kOhms. at least one flexible substrate, the substrate being conformable; a matched function ink set, comprising matched additively printed matched function inks, matched to at least: a receptivity of the flexible substrate onto which the matched function inks are printed; and a chemical reactivity between the substrate and the matched function inks; the additively printed matched function inks forming a plurality of successive conductive traces, additively printed as as least one layer on the at least one flexible substrate; wherein successive conductive traces have a line height in a range of 4.58 μm +/- 0.6μm printed onto a substantially planar face (106a, 106b) of the at least one flexible substrate; wherein the successive conductive traces are configured to receive a current flow from at least one source; and wherein the flexible planar conductive coil is provided by the successive conductive traces separated by gaps between successive conductive traces around a central axis through the plane of the at least one flexible substrate, the successive conductive traces having line widths and the gaps in a range of 180 μm - 260 μm; wherein the successive conductive traces are of high density, and wherein the high density provides a series resistance in a range of 16 Ohms to 1 kOhms. a receptivity of the flexible substrate onto which the matched function inks are printed; and a chemical reactivity between the substrate and the matched function inks; the additively printed matched function inks forming a plurality of successive conductive traces, additively printed as as least one layer on the at least one flexible substrate; wherein successive conductive traces have a line height in a range of 4.58 μm +/- 0.6μm printed onto a substantially planar face (106a, 106b) of the at least one flexible substrate; wherein the successive conductive traces are configured to receive a current flow from at least one source; and wherein the flexible planar conductive coil is provided by the successive conductive traces separated by gaps between successive conductive traces around a central axis through the plane of the at least one flexible substrate, the successive conductive traces having line widths and the gaps in a range of 180 μm - 260 μm; wherein the successive conductive traces are of high density, and wherein the high density provides a series resistance in a range of 16 Ohms to 1 kOhms.