Abstract: Sound reproduction systems are described that have superior response to pure bass frequency signals from musical instruments such as electric bass guitar and string bass. A first amplifier drives a low frequency woofer and a second amplifier drives a full range speaker system. The bass component of the audio signal handled by the second amplifier is monitored and progressively compressed as the bass energy approaches a critical level that may damage one or more elements of the full range speaker. Speaker protection devices are also described that passively limit damaging pulses into speakers typically caused by plugging in equipment.

Abstract: Marching band string instruments and wearable string instruments are described that include a stiff waist band to prevent excessive side to side movement during use, while providing easy doff and don of the string instrument. String instruments also are provided with adjustable chest braces to allow accommodation for different player sizes and for minimization of back strain when playing the electric string instrument for extended time periods. Electric string instruments optionally have soft material interposed between bridge feet and a string instrument body, to allow a more resonant sound detection from a pickup located between the bridge feet and the body. Other advances include generation of a stereo signal from bridge vibrations, and electronic processing of sound that enhances the electric string instrument playing and learning experience.

Abstract: Rapid shaft stop devices and transmissions are described that utilize permanent magnets for coupling and/or braking and are useful for electronic propeller guards and other equipment. In an embodiment, one or more capacitive discharge pulses are used to rapidly stop a shaft. A magnetic transmission is provided having axially oriented magnets on each side of an air space junction that transmit torque across the junction with a torque/speed profile that particularly suits boat propellers. The junction may include a bearing and allows slippage when the propeller resistance exceeds a given value. This slippage acts as a variable gear reduction. One or more electromagnets may be energized and thereby add to or subtract from one or more magnetic fields and provide electronic control of torque and of gear reduction ratio for devices such as watercraft drive systems.

Abstract: High speed electric watercraft of various configurations are provided that utilize at least one submerged enclosed hull containing an electric motor and at least one other parallel float positioned higher that the enclosed hull to provide buoyancy for a platform that can carry one or more individuals above a water surface. The watercraft optionally include features of (1) a rounded front end on the platform, (2) a platform length that is shorter than the float for stability against tipping, (3) entryways that do not require stepping over a vessel hull, (4) dimensions fore and aft that minimize spray onto the rear of the platform, (5) shock absorbers to provide a smoother ride, and (6) adjustable struts that connect floats with the platform to allow control of the platform height above the water surface. These and other features are made possible by a fast electric design that avoids certain problems of vessel type watercraft.

Abstract: High speed electric watercraft of various configurations are provided that utilize at least one submerged enclosed hull containing an electric motor and at least one other parallel float positioned higher that the enclosed hull to provide buoyancy for a platform that can carry one or more individuals above a water surface. The watercraft optionally include features of (1) a rounded front end on the platform, (2) a platform length that is shorter than the float for stability against tipping, (3) entryways that do not require stepping over a vessel hull, (4) dimensions fore and aft that minimize spray onto the rear of the platform, (5) shock absorbers to provide a smoother ride, and (6) adjustable struts that connect floats with the platform to allow control of the platform height above the water surface. These and other features are made possible by a fast electric design that avoids certain problems of vessel type watercraft.