Patent Application
20130163787
Musical organs have always suffered from lack of expression because the tones produced were simply keyed on and off, could be sustained indefinitely with no attack or decay and were rather pure, unchanging tones. In wind-driven pipe organs, a tremulant varied the wind pressure at a sub-audible rate imparting a vibrato, or pitch variation, to the tones of the pipes, thus adding excitement to the sound. Often multiple tremulants were used for separate ranks of pipes.
In electric organs, the vibrato effect is often imparted electronically; though, this is less than ideal as the sound is too precise and comes from a single speaker. In the case of the pipe organ, the pipes are physically spread; and the sounds comes from multiple directions. To achieve both the vibrato and spatial effect for electric organs, it became common to use an orbiting speaker where the sound sprays in different directions as the sound transducer spins about.
As the transducer orbits; the apparent source of sound, the mouth of the horn, moves toward and away from the listener. As the source moves toward the listener, the pitch would rise; and as the sound moved away, the pitch would fall. This pitch change is due to the Doppler Effect. The sound would reflect from various surfaces in the room, producing the spatial effect. More recently, electric guitar players have used orbiting speakers to add similar excitement to their playing.
While mechanically-orbited speakers have been used very successfully in the past, they suffer from several drawbacks. To produce the vibrato effect over the desired range of musical frequencies, the transducer must spin. The speaker cabinet must be rather large and heavy, making it difficult to move to live shows. The mechanical parts are delicate, requiring frequent maintenance. Attempts have been made to implement mechanically-orbited speakers with rotary joints to conduct sound signals to the orbiting transducers, but noise from the sliding contact and maintenance issues caused this approach to be abandoned.
Synchronizing multiple mechanically-orbited speakers is difficult, and a single physically rotating transducer has limited sound volume output. Venues have grown in size; and audiences have come to expect a full sound, so many performers resort to placing the orbiting speaker in a sound-isolated location, using a microphone and sound amplification system with multiple speakers.
Because the physical size of the orbiting speaker defines the acoustic performance, smaller and less expensive mechanically-orbited speakers do not achieve the desired musical effect, especially losing the desired frequency modulation by only rotating instead of orbiting.
Often mechanically-orbited speakers have only two speeds and no opportunity to vary the effect without physically modifying the speaker; thus, having a very limited expressiveness.
Keyboard players often have two or more instruments, or even one instrument, that can emulate more than one acoustic instrument, such as a synthesizer, that can produce tonewheel organ or piano sounds. Orbiting speakers have difficulty reproducing piano sounds without coloring and cannot reproduce uncolored piano and orbiting organ sound simultaneously.
There is a need in the art for a speaker system to amplify musical instruments that can produce the desired vibrato and spatial effect while being lighter and more rugged for transport, having no moving parts to avoid frequent maintenance, being able to achieve the desired vibrato and spatial effects in a low-cost configuration, or being able to be driven at high power levels and having multiple orbiting speakers ganged for higher sound levels, having the ability to vary the musical effect for increased expressiveness, and producing uncolored sound simultaneously with vibrato and spatial effects.
It is, therefore, the object of the present invention to enable a sound-system design for live performance of music with realistic tremulant and spatial effects in a physical configuration that lends itself to portability, low maintenance and low-cost manufacture. Instead of mechanically-orbited sound transducers, the present invention uses two or more transducers facing in different directions with the sound signal modulated separately for each speaker, as to impart the sense of orbiting as the sound reflects around the room.
The sense of direction of sound in the present invention is increased by using sound transducers or groups of transducers selected and arranged to produce the appropriate sound radiation pattern for the desired effect. The transducer array extends the tremulant effect to lower frequencies than that achieved by existing mechanically-orbited speakers.
Because the orbited effect is imposed electronically, the same set of amplifiers and sound transducers can be simultaneously used to amplify and project sound without the tremulant or other effects or with a different set of effects. This makes it practical for a musician to use a single sound system for organ sound reproduction with strong tremulant at the same time as electric piano having no tremulant, or with a light tremulant appropriate for the desired piano sound. This multiuse can be extended to any combination of instruments, voice or any other sound source.
Embodiments of the present invention lend themselves to addition of other sound effects particular to orbiting speakers, including simulation of horn-throat distortion, overdrive of the amplifier, amplifier- and speaker-cabinet emulation, and spatially diverse reverberation simulation. For various reasons described below, mechanically-orbited speakers have limitations on the amount of sound output a single unit can produce and ganging multiple units may result in the tremulant effect being degraded. The present invention achieves higher sound level from multiple transducers in a single unit and allows for multiple amplifier/transducer units to be ganged for even higher sound levels while maintaining the quality of the synchronized tremulant effect.
FIG. 1—shows the internal mechanism of a currently popular organ sound system.
FIG. 2—shows the outside view of the sound system of Figure.
FIG. 3—depicts a simplistic electronically orbited speaker.
FIG. 4—shows the effect of speaker transducer size on the radiation pattern at various frequencies.
FIG. 5—shows the sound radiation pattern of a horn-type transducer.
FIG. 6—shows a speaker enclosure where two transducers are used on each face forming a line array.
FIG. 7—shows a speaker enclosure where the cone-type transducers have a front-loaded horn.
FIG. 8—shows an electronically orbited speaker pole mounted on top of a subwoofer.
FIG. 9—shows a low-cost electronically orbited speaker with a horn upgrade.
FIG. 10—shows high power electronically-orbited speaker unit ganged for higher sound levels.
FIG. 11—shows the construction details of speaker.
FIG. 12—shows the signal connections of a simple electronically-orbited speaker.
FIG. 13—shows the signal connections of a self-contained, two-channel, electronically-orbited speaker.
FIG. 14—shows a low-cost, electronically-orbited speaker master unit.
FIG. 15—shows the tweeter upgrade unit that functions in conjunction with the master unit depicted in
FIG. 16—shows a high-power master unit intended to be ganged with slave units.
FIG. 17—shows a high-power slave unit with outputs for daisy-chaining.
FIG. 18—shows the block diagram of a very high-power unit with separate rack mount preamplifier/DSP unit and power amplifiers.
FIG. 19—is a plot of the four amplitude envelopes of the four signals intended for the four sets of speakers, one signal for each face of the cabinet, in this case a gentle modulation.
FIG. 20—is a second plot of amplitude envelopes, in this case a medium modulation.
FIG. 21—is a third plot of amplitude envelopes, in this case an aggressive modulation.
FIG. 22—is a fourth plot of amplitude envelopes, in this case including the effect of the two sets of slots on each cabinet face.
FIG. 23—is a fifth plot of amplitude envelopes, in this case including the effect of the two sets of slots on each cabinet face and internal reflections.
FIG. 24—is a signal flow diagram of a basic DSP.
FIG. 25—is a signal flow diagram of a fully featured DSP.
FIG. 26—is a plot of horn-throat distortion over frequency.
The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention can be practiced. The term “exemplary” used throughout this description means “serving as an example, instance or illustration” and should not necessarily be construed as preferred or advantageous over other exemplary embodiments.
This detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments of the invention. It will be apparent to those skilled in the art that the exemplary embodiments of the invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the novelty of the exemplary embodiments presented herein.
In particular, the exemplary embodiment is described in terms of a unit with four faces with associated sound transducers; but this number could be any number from two to some larger number limited by cost and complexity concerns. The faces of the unit may be deployed horizontally, vertically or in any configuration where the sound of two or more transducers is directed in different directions.
In the exemplary embodiment, the signal processing function is described as, but not limited to, a digital signal processor. Some or all of the signal processing may be implemented by other means, such as, but not limited to, analog circuits, standard computing components, or any other electronic or electrical means.
The term “orbiting speaker” is used herein to mean any form of loudspeaker or sound-amplification device or sound-modification device intended to modulate or change the sound of a musical instrument or other sound source in a periodic way, especially to impart a periodic varying of pitch, amplitude or spatial perception. Orbiting speaker is intended to cover speakers that are commonly referred to as rotating or rotary speakers.
The terms “signal processor”, “digital signal processor” or “DSP” may be a purpose designed computing device, a general purpose computing device, a collection of analog or digital electronic circuits, or a combination of any of the above.
Existing orbiting speaker effect units are available in two forms: mechanical or electronic. The mechanism of the mechanical-type orbiting speaker is depicted in
The rotary horn 101 is counter-balanced by a dummy horn 102. Sound is produced by a compression-driver unit 104 and is passed upward through a rotary joint and pulley 103. The horn assembly is rotated by an electric motor and belt 105. In most modern orbiting speakers, there is a second motor, not shown, to rotate the horn at a different speed, providing both a high- and a low-speed modulation effect.
The low-frequency, cone-type speaker 110 fires downward into a rotating drum 111 made of light-weight wood or other material. The drum has a scoop-shaped section that turns the sound toward the side of the cabinet 100 where there are slots to allow the sound to exit the cabinet. The drum 111 is rotated by the electric motor and pulley system 112 Like the horn in modern units, there are two motors, one for high speed and one for low speed. The second motor and clutching system is left out of the diagram for simplicity. The drum 111 is typically rotated in the opposite direction than that of the horn 101. Because of the limitations of the size of the low-frequency transducer and rotary drum, there is little frequency modulation effect; and the amplitude modulation is imparted largely by the mouth of the deflector drum passing by the slots in the cabinet.
As the playing style of many tonewheel organists includes switching often between the high speed and low speed or even stopping rotation of the speakers, the belts and clutching mechanism requires frequent maintenance.
The solution to the needs enumerated above is the electronically-orbited speaker of the present invention described herein. As shown in
In this embodiment, the sound signal from the organ or other musical instrument is taken as input to a digital signal processor, known as a DSP. The DSP would divide the signal into four signal streams. Each stream is modulated to impart an amplitude envelope that corresponds to the sound level that would be experienced by an orbiting sound source as it passed across a face. If the virtual orbiting sound source were pointed toward the listener, the DSP sends the maximum signal to the amplifier driving the transducer 310 on the front face 320 of the box 300. As the virtual sound source orbits to the right, the transducer 311 on the right side 323 of the box 300 is driven at higher levels; and the drive to the front transducer 310 is reduced.
When the virtual orbiting sound source is pointing at the corner of the box, the drive level to both the front and right side transducers 310, 311 is equal and at some typically lower power level, thus sounding like a single transducer pointed toward the corner of the box. This process continues, handing off the audio power from one transducer to the next as the virtual sound source orbits in a complete circle. This is a very simple description of the action of the electronically orbited speaker; and there are many factors that improve the musical effect, which will be described.
Fundamental to the success of the orbiting speaker effect is the radiation patterns of the acoustic transducers. The patterns must be narrow enough to provide the desired effect of the sound spraying out in different directions as the virtual sound source orbits. If the transducers have a very wide radiation pattern, there is little change in the sound no matter which way the speaker is pointed. The ideal transducer pattern for an electronically-orbited speaker with four sides would be a single beam approximately 90° wide. However, as shown in
Sound wavelength formula
wavelength=344/f
f in Hertz
wavelength in meters
In
Classical mechanically-orbited speakers often have a deflector plate attached to the mouth of the horn in an attempt to spread the sound radiation pattern at higher frequencies. In the electronically-orbited speaker system, the DSP may divide a frequency band dedicated for a specific transducer into sub-bands and modulate the signal with different amplitude envelopes for each sub-band to equalize the sound radiation pattern between sub-bands. Alternatively, the amplitude envelopes may be selected to emphasize the difference of radiation pattern between sub-bands. By doing so under player control, the electronically-orbited speaker system can emulate the sound of different models and configurations or modifications of classical orbiting speakers.
Some players prefer to use two classical mechanically-orbited speakers. Each rotor in each speaker rotates at a slightly different rate, making for a very complex variation in the tremulant effect. The DSP of the electronically-orbited speaker system may use a plurality of amplitude envelopes running at different speeds to provide this complex tremulant effect. The delays to impose a reverberation effect may be different for each amplitude envelope to provide the illusion that the virtual rotors are in different physical locations.
Mechanically-orbited speakers often have a feature where the rotor is stopped by a brake with the transducer facing front to provide maximum sound level in the non-orbiting configuration. The DSP of the electronically-orbited, upon receiving a command to stop the virtual orbiting, may continue the current orbit until the virtual transducer reaches front center where it may stop and ramp the amplitude to maximum regardless of the amplitude envelope at that point.
As the virtual orbiting transducer accelerates or decelerates, the amplitude envelope may be changed to emphasize the tremulant effect.
The size of a transducer also affects the efficiency in converting the electrical signal to sound. A smaller transducer works better at higher frequencies while a larger transducer is needed to reproduce lower frequencies. The electrical signals may be divided into bands appropriate for each transducer by a crossover network and each transducer driven with only the signals it can reproduce well. Dividing the musical spectrum up to be reproduced by separate transducers also helps the variation in radiation pattern with frequency. A smaller transducer maintains a narrow radiation pattern only in the upper frequencies. A larger transducer provides a narrow radiation pattern at lower frequencies, though even a very large transducer becomes omnidirectional at the lowest musical frequencies.
This problem of needing to use different sizes of transducers is not unique to electronically-orbited speakers. The best mechanical-orbited speakers use a rotating high frequency transducer and a separate rotating low frequency transducer. To deepen the musical effect, the two transducers are rotated in opposite directions.
The electronically-orbited speaker in another exemplary embodiment uses a high frequency transducer and one or more low frequency transducers on each of the four faces of the box. Each transducer or transducer array has an associated amplifier. The DSP divides the input signal into two frequency bands performing the crossover function, one band for the high frequency transducers and one band for the low frequency transducers. The DSP then divides the signal for each band into four signal streams for each of the transducers on each face of the box. Each of the two sets of four streams is coupled to the associated amplifier. The orbiting is imparted by the same amplitude envelope method as described above. In this case, the high frequency set is orbited in one direction and the low frequency set is optionally orbited in the opposite direction.
In
The following describes three physical configurations of electronically-orbited speakers introduced so that the advantages of the present invention may be appreciated in the subsequent description. The size of the units may vary, with the low-cost units tending to be smaller and the high-power units tending to be larger and heavier.
The electronically-orbited speaker 800 is mounted on a commercially available pole 810 inserted into a socket 811 in the top of the subwoofer 820 and into another socket, not shown, in the bottom of the electronically-orbited speaker cabinet. Mounting the speaker high allows the sound to sweep around the room, unimpeded, for a more vibrant effect. The electronically-orbited speaker 800 may be used without the subwoofer 820 by mounting the electronically-orbited speaker 800 on a commercially available speaker stand (not shown), typically, but not limited to, a tripod type.
In either configuration, a single DSP would drive all units so that they would all virtually rotate in synchrony; and the sound would seem to emanate from a single point in the room. Similarly, the subwoofers 1020 would be stacked together to avoid bass cancellation caused by separation of bass transducers. For self-contained high-powered units, care must be taken to vent heat from the electronics out the sides of the units to allow vertical stacking.
A variation of the above configuration would consist of the DSP having eight channels for eight faces. The channels for the odd-number faces would drive the transducers in the master unit 1010. The even-number channels would drive the transducers in the slave unit 1015 immediately above the master unit 1010. The slave unit would be physically turned 45° to produce, in effect, an eight-face speaker. The remainder of the slave units would be driven alternately by odd and even channels and each turned 45° from the one immediately below. Although this adds complexity to the DSP unit, it provides a smoother transition as the virtual-sound source moves from one face to the next.
Class D power amplifiers can achieve high power with efficiency exceeding 90 percent, which reduces heatsink size and ventilation air requirements. Class D amplifiers of medium-power are available quite economically in a single integrated circuit package, while high-power amplifiers may be constructed with minimal component size and number. A switch-mode power supply eliminates the large and heavy 50/60 Hz power transformer and also operates at high efficiency. This makes it practical to have multiple amplifiers, one for each horn-type transducer and one for each pair of cone-type transducers. For extremely high-power applications, the electronics may be mounted external to the transducer cabinets, driven by cooling considerations.
The control input 1211 may be of one or more types and multiple types may be incorporated into any particular embodiment. One interface may emulate the existing popular mechanically-orbited speaker with discrete signals for fast and slow speeds and a brake to stop rotation. Other control inputs may use the Musical Instrument Digital Interface (MIDI) protocol to control various parameters of operation including, but not limited to, fast and slow speed, stop, variations in speed for each of the high- and mid-frequency channels, acceleration and deceleration of the virtual rotors, crossover frequencies, envelope profile selection (described later), distortion effects thresholds and many other parameters. The MIDI interface may use the MIDI signaling definition or be implemented via Universal Serial Bus (USB) as are many musical instruments. The control interface is assumed to be present in all subsequent drawings and descriptions but not shown for simplicity and clearer understanding of the figures.
The Instrument Input 1310 is divided into nine separate signals. Four signals are bandpass filtered by the DSP for the mid frequencies and four signals highpass filtered for the high frequencies. Pairs of signals, one mid and one high, drive each face. The ninth signal is routed to the subwoofer 1315. The PA Input 1311 is a stereo pair. It is similarly, but separately, split and processed by the DSP and summed at each of the nine outputs to the amplifiers. The right and left channels of the stereo pair are summed into the faces of the speaker with different gains to produce the desired stereo effect.
The Control Input 1312 provides the user the interface to change various parameters and to turn effects on and off. Details of the DSP signal flow are described in support of
The master unit 1400 is comprised of the DSP 1401, four amplifiers 1403 and the associated cone-type transducers for each of the four faces. This comprises the minimum set of components for the sound system to operate and would provide adequate sound reproduction in settings where high sound levels are not necessary. Also included are line-level outputs for four tweeter channels 1402 and a line-level output for an external subwoofer 1404. The number of faces and the number of amplifiers and sets of transducers could be two or more. Four faces are used here as an exemplary embodiment for illustration.
To upgrade the basic system comprised of the master unit 1400, the tweeter slave unit 1500 is added, comprised of line-level inputs 1503 routed from the master unit 1400, four amplifiers 1502 and tweeters 1501. The tweeters may be of the horn type for tight directional control of the high frequency output.
An alternative to the above upgrade configuration may be to include all eight amplifiers in the master unit 1400. When the tweeter slave unit 1500 is not plugged in, each transducer in the master unit 1400 would be driven by an individual amplifier 1403. The mid-range signals would be routed to both transducers on a face to produce the line array configuration. At higher frequencies, this line array would produce a very narrow sound-radiation pattern, which is not desirable. The high frequency signals may be routed to only one of the amplifiers and one transducer for each face, which would produce a radiation pattern appropriate for this frequency range. An eight pole, double-throw mechanical relay may do the switching. With the coil of the relay not energized, the transducers in the master unit 1400 are driven by separate amplifiers. A jumper in the plug for the slave unit 1500 energizes the relay coil and switches one amplifier per face to drive the tweeters in the slave unit 1500.
Another feature illustrated in
The master unit 1600 may include a vacuum tube preamplifier 1602 at the instrument input to provide warmth and soft compression favored by musicians. The vacuum tube amplifier stage may include a variable gain component 1601 before and/or a variable gain component 1603 after the amplifier to adjust the effect of the vacuum tube amplification on the signal. This effect may be simulated by the DSP instead of, or in addition to, the vacuum tube preamplifier.
In the master unit 1600, the power amplifiers 1611 contained in the unit drive the transducers 1610 and 1612. There are four high frequency outputs to drive the four tweeters 1610 and four mid frequency outputs to drive the cone-type transducers 1612. The same signals that drive the internal amplifiers are duplicated and used to drive the slave unit 1700 via the line level outputs 1620, with four signals dedicated for tweeters and four signals for mid-range transducers. The control input 1605 provides external user interface. The external control device may be as simple as the “half-moon switch” commonly mounted on a tonewheel organ, dedicated controls on an musical instrument panel or as complex as a computer with a full complement of parameter controls.
In the slave unit 1700, the line-level inputs 1720 are routed to the appropriate power amplifier 1711, which in turn drives a tweeter 1710 or mid-range transducer 1712. The line-level signals are also routed to an output connector or connectors 1722, which makes the signals available for an additional slave unit 1700 to be driven by a single master unit 1600. In this manner, the line-level signals may be daisy-chained from master to slave to slave and so on. The line-level inputs and outputs may be implemented as analog but are not limited by this exemplary embodiment. The inputs and outputs may be digital in any of a number of configurations, such as but not limited to, Ethernet, SPDIF, optical or coaxial.
The vacuum tube preamplifier 1814 is an optional feature to add warmth and soft compression to the sound. This feature may be implemented in the DSP or with analog circuits other than a vacuum tube. To control the contribution of the tube sound, a pre-gain control 1813 and post gain control 1815 are optionally included.
The rack mount power amplifiers 1820 are standard commercial products typically provided with a stereo pair of channels in one unit. The signal processor 1810 and the power amplifiers 1820 may be mounted in the same rack case for ease of transport. For an exemplary configuration with tweeters and midrange transducers deployed on the four faces of the speaker enclosure 1830, four stereo power amplifiers are required. Typically, short individual cables connect the signal processor 1810 to the inputs of the power amplifiers 1820. A heavier cable or cables 1825 may connect the power amplifier 1820 outputs to the speaker enclosure 1830. The speaker enclosure 1830 may be in the physical configuration shown in
The fundamental orbiting speaker effect is produced by splitting the input signal into one path for each face of the speaker enclosure and amplitude modulating the paths separately to sweep the sound in a complete circle. The sound is physically moved by imposing the appropriate amplitude envelope on the signal paths. The process of physically moving the apparent sound source and direction in a circle imposes both amplitude and frequency modulation on the sound. The amplitude modulation can be depicted as amplitude envelopes as shown in
This process is repeated for each orbit of the sound. The slow-speed effect is called “Chorale” and typically orbits at 45 RPM. The fast-speed effect is called “Tremolo” and orbits at approximately 400 RPM. Some models of mechanically-orbited speakers have multiple pulleys to change the orbiting speed but require disassembly of the cabinet to make the change. In the electronically-orbited speaker several orbital speeds are available, changed via the external control input. Similarly, the external control input provides selection of multiple amplitude envelopes for different orbiting effects.
To orbit in the opposite direction, the count is stepped down instead of up. To produce these amplitude envelopes, a look-up table may be used or the values of the envelope calculated in real time. In the case of the look-up table, the full rotation may be represented by the segment of one of the envelopes from step 0 to 64. The remainder of the circle may be simply produced by modulo arithmetic and incrementing the look-up table pointer up or down for the positive or negative slope of the curve.
The amplitude envelopes of
The Amplitude envelopes of
The physical configuration of sound transducers is key to producing the orbiting speaker sound, but the electronics provide an increased level of control and variation desired for a flexible sound reproduction system. Though the effects described here may be implemented in various technologies, the DSP is powerful and cost effective. This exemplary embodiment will be described in terms of a DSP with embedded software that implements the components of the signal path.
The signal is then split into frequency bands by the highpass 2403, bandpass 2404 and lowpass 2405 filters. The signal from the highpass 2403 filter feeds the tweeters, the bandpass 2404 feeds the mid-range transducers and the lowpass filter 2405 is routed to a line-level output to be connected to the subwoofer. The signal from the PA or alternate instrument input 2406 routed through a similar set of signal function blocks though the parameters, such as distortion models and crossover frequencies may be different from the instrument input 2401 channel.
In this embodiment, the signal from the instrument input is shown as being routed through the amplitude envelope processing 2410, 2411, 2412, 2413, though the PA channel 2406 may optionally be routed through the envelope processing shown or through a separate set of envelope processors.
Envelope processor 2410 imposes an amplitude envelop on the tweeter signal path for the front face. In this example, the amplitude is at maximum at the start of the cycle as the virtual orbiting transducer is facing front. The signal is also at maximum at the start of the cycle for amplitude processor 2411 that is modulating the front face mid-range signal. Envelope processor 2412 and 2413 are modulating the tweeter and mid-range signals for the left face. In this case, we see the tweeter channel becoming maximum in the second quarter of the orbit as the virtual orbiting tweeter moves to the left. On the other hand, the mid-range becomes maximum in the fourth quarter of the orbit as the transducer moves to the right and has to complete three quarters of an orbit to be facing to the left.
The signals output from the envelope processors are then fed to signal mixers and then on to the appropriate amplifiers and sound transducers as shown in
The DSP signal flow diagram 2500 of
The pre-gain adjust 2511, vacuum tube emulator 2512 and post-gain adjust 2513 optionally introduce amplifier distortion emulation to the signal input at 2510. This amplifier emulation takes the form of second-harmonic rich distortion to emulate overdriving the class A preamplifier stage, and third-harmonic rich distortion plus soft compression to emulate the power amplifier stage overdrive. The speaker cabinet emulation may also be introduced at this stage by adding frequency shaping and cabinet induced resonances.
Continuing with the instrument input 2510 signal, it is split into highpass 2515 for the tweeters, mid-range 2516 for the mid-range transducers and lowpass 2517 for the subwoofer. There may be a reverberation emulation block 2530 for each signal path. By splitting the reverberation emulation across the faces of the speaker, a spatial aspect of the reverberation effect is introduced that is lacking the typical front-facing stereo sound system. The signals for the left, right and rear channels have different delays and arrive at the listener from different directions due to room reflections. This better emulates the effect of a larger room. Also, the tweeter and mid-range signal paths are treated differently to add frequency dependent aspects to the effect.
The amplitude envelope processors 2535 operate on each path as described in
Starting at the PA inputs, one for the left 2520 and one for the right 2525 stereo pair, there is a compressor/limiter function 2521 and crossover filters 2522, 2523 and 2524 as described previously. The crossover frequencies for the PA channel may be different from the instrument channel. In particular, the crossover frequencies for the instrument signal path are selected to provide a narrow sound radiation pattern as described in the support for
The lowpass 2524 signals from both the left and right PA channels are routed to the subwoofer mixer 2545, because the lowest frequencies have no apparent directional characteristics. The highpass 2522 and mid-range 2523 signals from both the left and right PA channels are routed separately to the mixers 2540. These channels would have further signal processing blocks (not shown) for amplifier and speaker cabinet effects, reverberation and amplitude envelope.
Before the PA channels are mixed, there may be individual gain adjustments to place the stereo image properly by routing the signals to the appropriate face or faces of the speaker system. In a simple example, the left PA tweeter channel from the highpass filter 2522 would be routed with full gain at gain adjustment 2541 to the left tweeter output mixer; and the right channel highpass signal would be routed with full gain through gain adjustment 2543 to the right tweeter output mixer. The left channel mid-range signal from the crossover filter 2523 would be routed with full gain at the gain adjustment 2542, and the right channel signal routed with full gain at gain adjustment 2544 to the right mid-range output mixer. In this simple example, all other gain adjustments would be set to the lowest setting to block the signals. For situations where a broader coverage was desired, the signals at lower gain may be routed to the front and rear faces. This is especially useful in cases where the audience surrounds the player.
Many rotary speaker simulators add harmonic distortion to simulate overdriving the vacuum tube amplifier used in the classic rotating speaker models. This distortion is caused by large peaks in the lower frequency range; and because the distortion is in the vacuum tube amplifier, the harmonics generated by the distortion are lowpass filtered by the amplifier output transformer. This distortion is emulated in the DSP or other electronic circuits of the present invention.
A second type of distortion is a part of the characteristic sound of these classic speakers and that is horn throat-distortion caused by the nonlinearity of the air in the throat of the horn under high compression of volume peaks. Horns with long narrow throats, such as those used in the classic orbiting speakers, are especially subject to throat distortion. This type of distortion rises with frequency, as shown in
Horn throat-distortion is emulated in the DSP and is particularly valuable for the simple models operated without the horn upgrade. In the DSP, a separate signal path (not shown) is used where the signal is filtered with a 3 dB per octave rise with frequency, peaking at 8 KHz. This signal is modified to produce 2nd harmonic with 3rd harmonic 10 dB lower.
The resulting distortion signal is summed with the primary signal through a variable gain. This variable gain may be player selectable or adjustable to produce the desired amount of horn throat-distortion effect.
The horn throat-distortion effect may be automatically disabled when a horn upgrade unit is associated with the master unit. The user may have the option to override the automatically disabled horn throat-distortion effect when the horn upgrade unit is associated to add the simulated effect with that of the real horns.
One attraction of mechanical-orbiting or rotating speakers is that with the cabinet back or top removed, the listeners can view the spinning horn and drum and associate the change in speed with the changes in sound. Especially for keyboard players where the action of playing is often hidden by the instrument, some physical evidence of live performance is welcome. Therefore, an optional feature is a string or series of lights in the plane of the virtual orbiting transducer. The lights would light in a pattern that indicates the motion of the virtual orbiting transducer under control of the DSP. The string of lights may be duplicated for each set of orbiting transducers and in synchronism with the associated virtual transducer.
As can be seen from the long list of features the electronically-orbited speaker system produces, the sound of classic orbiting speakers while achieving many advantages, such as ease of transport, upgradability, higher sound level output and operation with two or more sound systems with independent characteristics.
Those of skill would appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the exemplary embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps above have been described generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the exemplary embodiments of the invention.
The various illustrative logical blocks, modules, and circuits described in connection with the exemplary embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
The steps of a method or algorithm described in connection with the exemplary embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EEPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD, DVD, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in an electronically orbited speaker. In the alternative, the processor and the storage medium may reside as discrete components in an electronically-orbited speaker.
In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, Flash, CD, DVD or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
The previous description of the disclosed exemplary embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these exemplary embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the sprit or scope of the invention. Thus, the present invention is not intended to be limited to the exemplary embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
