CIMERA® for Acoustic Membranes
Created to address a problem with no existing solution in 2004
In 2004, acoustic component manufacturer NXP Knowles approached 4a engineering with a development brief: a stiffening element for a new generation of compact, rectangular microspeakers. The goal was to enable full audio reproduction, music, not just ringtones, through a driver small enough to fit inside a mobile device.
The requirement was a non-magnetic material with high bending stiffness at very low weight and very low thickness. No commercially available material met all three constraints simultaneously.
The answer was a foam-core microsandwich: thin aluminum skin layers laminated onto a precision-cut polymer foam core. The concept worked. The material was new, no existing supplier produced it. 4a manufacturing was founded in 2005 to manufacture it at scale.
That original sandwich architecture, refined through twenty years of serial production, is CIMERA®.
Why standard membrane materials hit a wall
Speaker membranes in mobile devices operate under competing constraints. The membrane must be light enough to move efficiently at low drive levels, stiff enough to maintain pistonic motion at high frequencies, and thin enough to fit within a device geometry that shrinks with every product generation.
Monolithic materials, aluminum foil, polymer films, standard CFRP, force a direct tradeoff between these properties. Increasing stiffness means adding thickness or switching to a denser material, both of which increase mass. A heavier membrane requires more magnet force to achieve the same sensitivity, which adds cost and volume. And a less stiff membrane breaks up at lower frequencies, producing resonance peaks in the audible range.
Structural efficiency at sub-millimeter scale
CIMERA® places two thin skin layers, metal, polymer, or fiber, on either side of a MILLIFOAM® foam core. The core separates the load-bearing surfaces, converting bending stress into tension and compression distributed across the section depth. This is the same structural logic as a bridge girder or an aircraft floor panel, scaled down to membrane thicknesses starting at 0.1 mm.
The practical effect: a CIMERA® membrane achieves the bending stiffness of a much thicker monolithic part, at a fraction of the mass, while also benefiting from the damping properties inherent to the foam core.
| Parameter | Value |
|---|---|
| Total thickness | from 0.10 mm (acoustic grades) |
| Skin layer thickness | from 8 µm |
| Available skin materials | aluminum, fiber-reinforced polymer |
| Core material | MILLIFOAM® (40+ grades available) |
| Lightest production grade | under 90 g/m² |
| Thickness tolerance | +/- 15 µm |
| Max. operating temperature | 150°C |
| Construction | 5 layers: skin / adhesive / core / adhesive / skin |
Higher break-up frequency. Less magnet. Lower Energy consumption.
A stiffer membrane per unit mass means the first break-up mode occurs at a higher frequency, outside or at the edge of the audible range rather than within it.
Lower membrane mass reduces the moving mass of the driver system. For a given sensitivity target, this means a smaller, lighter magnet system, relevant in devices where every milligram and cubic millimeter is budgeted. Tight thickness tolerances across production runs mean consistent acoustic behavior unit to unit, which matters in high-volume consumer electronics manufacturing where variance in acoustic output is tested and rejected.
Production and supply
CIMERA® acoustic membranes are manufactured at 4a manufacturing’s facility in Traboch, Austria. Material is supplied to membrane fabricators and speaker manufacturers as flat stock or pre-formed membranes, depending on process requirements.
CIMERA® acoustic membrane materials are used in products sold by manufacturers in the global consumer electronics market.
