Abstract: A mechanical spring with negative spring stiffness adapted for use in an electroacoustic transducer unit for reducing the transducer resonant frequency. The mechanical spring with negative spring stiffness comprises two blade springs having both ends coupled to each other and which, under the influence of a compressive force F which acts in a direction along an imaginary line through both ends of the mechanical spring, are each bent in one of two opposite directions.

Abstract: An electroacoustic transducer unit comprises an electroacoustic transducer with a diaphragm (1), a magnet system (2) with an air gap (3), and a voice-coil former (4) with a voice coil (5) arranged in the air gap (3) of the magnet system. The transducer unit comprises means for reducing the transducer resonant frequency including mechanical springs with negative spring stiffness each coupled between a stationary part of the transducer unit and a movable part, for example the voice-coil former or the diaphragm of the transducer (FIG. 1b). The transducer unit further comprises a control device (42) which generates a control signal for correcting the position of the diaphragm. The mechanical spring with negative spring stiffness comprises two blade springs with both ends coupled to each other and which, under the influence of a compressive force F which acts in a direction along an imaginary line through both ends of the mechanical spring, are each bent in one of two opposite directions.

Abstract: A device, and method of using such a device, for measuring tension in a thin flexible tape by guiding the tape along a curved path between two parallel curved guides, supplying pressurized gaseous medium to each side of the tape, and measuring the difference in gas pressure between the two sides of the tape. Measuring ducts, terminating substantially opposite each other in the curved guide surfaces are connected to at least one pressure transducer which in turn is connected to an electrical measuring circuit.

Abstract: A tape recorder having a tape guide member with a guide edge against which the tape is loaded or biased by pressure members. To press the tape against the supporting edge with a transverse force approximately constant per unit of length, pressure members are arranged beyond the ends of the tape-supporting edge, and the tape supporting edge has a curvature convex toward the tape, with a peak substantially midway between tape-support entry and exit points having a smaller radius of curvature than that of the remainder of the tape-supporting edge.

Abstract: The invention provides a carrier foil for magnetic recording tapes composed of a thermoplastic synthetic resin, which foils have been manufactured so that the stiffness (elasticity modulus) E.sub.1 in the longitudinal direction of the foil is at least 4000 N/mm.sup.2 and the stiffness (elasticity modulus) in the transverse direction of the foil is at least 1.3 E.sub.1. These carrier foils are more suitable for very thin magnetic tapes and are more resistant against defects such as buckling, folding, wrinkling and cupping than known carrier foils for record carriers having a comparable stiffness, but in which the stiffness distribution is different.

Abstract: A transversely scanning magnetic tape recorder having a concave tape guide member which shapes and aligns the tape at a location by the rotating magnetic heads and between two cylindrical tape guides. The magnetic tape is deformed in cross-section from straight to curved and then back from curved to straight. To prevent kinks and folds in the magnetic tape as a result of this deformation, tape curving means exert pressure on the magnetic tape to increase the local degree of curvature of the magnetic tape. As a result, differences in local membrane stress in the tape cross-section at the location of the rotary magnetic head paths are reduced.