Abstract: Differential flow vents allow airflow within a vent to be preferential. A flange disposed within a vent introduces non-linearities and causes a preferred direction of airflow into an expanding volume. The differential flow vents are used in conjunction with the natural motion of the loudspeaker cone acting as a pump to cool the loudspeaker cabinet enclosure without having to directly cool the woofer magnet structure. In one embodiment, at least one pair of opposed differential flow vents within the cabinet enclosure provide fresh air to be preferentially circulated to cool the interior of a loudspeaker system. In another embodiment, by providing an odd number of opposed differential flow vents within the cabinet enclosure, positive air circulation also results. By making either the pairs or odd number of differential flow vents to be asymmetrical, dynamic woofer offset is compensated.

Abstract: A drum having improved acoustic characteristics comprises a rigid annular bridge at one or both ends of a thin resonant annular shell attached to the bridges. A drum head is mounted on the bridge by a tension mechanism attached only to the bridge, and the drum is mounted on a drum stand by mounting hardware attached only to the bridge, leaving the shell free of load bearing and tensive and compressive forces and making the shell resonate more effectively. The bridge is machined from a solid block of wood formed of horizontal laminations. A microphone can be mounted on the inside of the bridge, with electrical leads exiting the drum through the mounting hardware. A snare drum having a thick body instead of a resonant shell is machined in the same way and has internal head tension members that make it possible to have a thicker body.

Abstract: A digital delay system employs a phase-locked loop to control a recall address generator. The phase-locked loop comprises a subtractor for determining the difference between the store address and the recall address and for producing a phase signal corresponding to this difference. The phase signal is directed to a voltage controlled oscillator for controlling the rate at which the recall address generator recalls data from a memory. A delay length is introduced as a phase error into the phase-locked loop. Input data is stored in a memory at a fixed rate, and recalled from the memory at a rate determined by the phase-locked loop. When the error signal is zero, the recall address rate will equal the store address rate and the respective addresses will be equal.

Abstract: A loudspeaker is provided which has a novel integrally formed back plate and pole-piece. The back plate and pole-piece has an annular portion and a toroidal portion. The result is a marked reduction in magnetic leakage caused by reluctance due to interfaces and corners.

Abstract: A mounting ring-thumbrest is provided for an electric guitar. The article provides a mounting ring for securing a pickup to the guitar and a thumbrest. The thumbrest is located to provide the optimum position of a player's hand.A method of mounting a pickup uses only two screws to secure the mounting ring-thumbrest and pickup to the guitar and allows the space between the strings and the pickup to be adjustable.

Abstract: A speaker system comprises a main cabinet and two auxiliary speakers. The main cabinet encloses a bass speaker and includes a slot for slot-loading of the bass speaker. The auxiliary speakers have a frequency range higher than that of the bass speaker, and are in enclosures which fit within slots in the main cabinet.The system provides a high-quality speaker system which is easily transported by placing of the auxiliary speaker in a slot.

Abstract: Circuitry is provided for simulating a combination of vacuum tube clipping and soft cross-over characteristics in a transistor power amplifier circuit. A first circuit includes a biasing network for assuring that the transistor amplifier saturates in response to high level input signals. A second circuit includes a biasing network for providing sufficient bias current to maintain the transistor in an active, rather than cutoff, operating region when the first circuit fails to provide the needed bias at times when the instantaneous input signal level is low but average or peak input levels are high. A combining circuit provides the higher of the bias values to the amplifier, to assure that the amplifier saturates for particular high level inputs yet operates at a modified, linear mode for low level inputs, thus simulating a compression characteristic of vacuum tube amplifiers.

Abstract: A bridge for a stringed musical instrument, particularly a guitar, is disclosed. The bridge is economical to manufacture, and may be made with simple punching and pressing operations. The bridge comprises a base which is secured to the instrument, and a saddle which is adjustably secured to the base. The saddle includes a lip which provides individual nodal points for the instrument's strings.

Abstract: A loudspeaker is provided which has a novel integrally formed back plate and pole-piece. The back plate and pole-piece has an annular portion and a toroidal portion. The result is a marked reduction in magnetic leakage caused by reluctance due to interfaces and corners.

Abstract: Circuitry is provided for distorting an audio signal, useful in providing a "dirty" sound to an electric guitar simulating a vacuum tube amplification thereof. The circuit includes components for simultaneously changing the amount of distortion introduced by a clipping circuit and the amount of gain boost provided at a preselected narrow bandwidth. Addition of such gain boost leads both to increased clipping of the audio signal and to reduced frequency response, at both low and high frequencies. A separate volume control is provided for broad band gain adjustment. Independently operable control switches permit insertion or elimination of the distortion, and insertion or elimination of a brightness circuit boosting high frequency response of the circuit.