Pickup system for electrical amplification of acoustic guitars while avoiding sound distortion and feedback

Abstract

Pickup for acoustic percussion and string instruments (especially guitars with sound hole) using a miniature microphone capsule (preferably condenser electreet omnidirectional), distinguished by the fact that the sound-recording microphone capsule is installed flush with the instrument body, whereby the flush surface is made of thin, suitable material (e.g. plywood, plastic, carbon, etc.) with a thickness of approx. 1-3mm and is mounted between the strings and the body in a positionally variable but fixable and removable manner.

Description

1.2 Summary:1.2.1 Technical problem of the invention:

[0001] Amplifying acoustic string instruments is a challenging task. This can be easily accomplished in a studio for productions. Special microphones can be used to capture realistic sound. However, the performers must remain extremely still. Precise microphone positioning is essential.

[0002] Live on stage, the situation is different: Movement, singing, dancing, and even the acoustics on stage cause loud noises and interference. Microphone placement like in a studio is impossible, resulting in feedback, whistling, etc.

[0003] Various solutions have been devised to address this problem in live situations. Electric pickups are used primarily in guitars, but they distort the acoustic sound. The performer can no longer express themselves adequately, and the audience's enjoyment is diminished.

[0004] The invention presented here avoids the danger of live feedback and yet enables a nearly studio-like live stage sound. The instrument itself does not need to be modified, and the artist's freedom of movement is fully preserved. 1.2.2 Solution to the technical task:

[0005] The invention presented aims to solve the problem of feedback (whistling, droning, crosstalk) during live performances with amplified acoustic instruments.

[0006] The aim of the invention is also to achieve the most natural electrical amplification of acoustic instruments possible.

[0007] At the same time, the musician should retain the greatest possible freedom of movement and expression.

[0008] Ultimately, the instrument should not have to be modified by the additional pickup.

[0009] And finally, the pickup system should be inexpensive to produce and purchase.

[0010] These problems are fundamentally solved by enabling the most natural electrical sound pickup - pickup using a (condenser) microphone capsule - through a special suspension system in such a way that the sound guidance of the suspension and attachment eliminates background noise and enables natural instrument sound without generating comb filter effects. 1.2.3 Area of application:

[0011] The field of application of the invention is audio technology, specifically the recording of acoustic instruments for amplification. Specifically, the recording of string vibrations / sounds from acoustic guitars with steel and nylon strings for subsequent amplification, live performance, or recording. 3. Description of the invention3.1 Technical field of the invention:

[0012] The technical field of the invention is sound engineering, the amplification of acoustic instruments and the construction of musical instruments. 3.2 Technical status / presentation of what is known:

[0013] Ever since amplifiers were invented (about 70 years ago or more), musicians and technicians have been working on amplifying traditional and acoustic instruments to achieve higher volumes for live performances on stage or in the studio in front of larger audiences.

[0014] Even for the interplay of traditional acoustic instruments such as guitars, it had become essential to maintain an appropriate live volume with the emerging new electric guitars (Fender, Gibson...).

[0015] There were always three problems to overcome, which have not yet been fully resolved in their basic form: 1. Maintaining their natural sound despite electrical amplification, 2. To avoid a feedback catastrophe during amplification or... to delay it as long as possible and 3. By reducing the tones, the acoustic instrument does not have to be modified or even damaged (drilling, cutting, etc.).

[0016] To date, various approaches have been chosen to address these issues, all of which are still available on the market and in live use. Each has its advantages and disadvantages; no system is capable of combining all desired requirements equally.

[0017] The following is a summary of what is known: 1. Recording with a microphone on a stand. For this, the guitarist must be facing forward or standing and must move very little or not at all. When recording with one microphone, it is aimed at the lower end of the neck; when recording with two microphones, it is also aimed at the body.

[0018] Condenser or dynamic microphones are used.

[0019] Advantage: A particularly natural sound can be achieved, especially in the studio

[0020] Disadvantage: Whistling and feedback occur relatively quickly, other instruments (drums...) are recorded (crosstalk) and the musician has almost no freedom of movement

[0021] 2. Recording with microphones attached to the guitar (internal or external). A (usually small) microphone is attached either to a gooseneck inside the guitar or to a mount outside the guitar (the position can be adjusted).

[0022] There are also systems where a microphone is glued to the guitar (AKG condenser capsule)

[0023] Advantages: The sound is more natural than with piezo systems, you have more flexibility in terms of movement, and the sound doesn't change as much with movement. Crosstalk is also less than with externally mounted microphones.

[0024] Disadvantage: The sound is more altered than with external microphones. It often sounds "muffled" and nasal due to comb filter effects; crosstalk is still an issue; feedback sensitivity is relatively high. 3. Pickup with piezoelectric crystals. Under the bridge or as a glued element (external, internal)

[0025] This process uses the piezoelectric effect, in which a crystal that is set into vibration emits electrical signals that can then be amplified.

[0026] Such crystals are usually placed under the bridge inlay, where they react to the vibration of the strings and the body

[0027] There are also systems in which one or more piezoelectric elements are attached or glued onto the guitar or inside the guitar.

[0028] Advantages: The piezo system is relatively loud and relatively insensitive to feedback

[0029] Disadvantages: The guitar's sound is severely distorted. It takes on a harsher tone, especially in the midrange and upper tones. The attack and decay are perceived as unnatural, and the tone is described as artificial, plasticky, or unpleasant. Nevertheless, the majority of available pickups for acoustic guitars are of this type, as they are inexpensive and easy to handle.

[0030] Another disadvantage: The guitar usually has to be worked on / drilled and cut. 4. Recordings with magnetic pickups.

[0031] Similar to the magnetic pickups on an electric guitar, acoustic guitars with steel strings can also be amplified with magnetic pickups. To do this, a specially tuned magnetic pickup is clamped into the sound hole using a frame.

[0032] Advantages: Simple and cost-effective system, quite loud and very insensitive to feedback and crosstalk

[0033] Disadvantages: The tone is unnaturally altered, sounding rather mid-range, muffled, often with a resonance peak. The character is more like an electric guitar than an acoustic guitar. Brilliance is lost.

[0034] Additionally, this type of pickup can only be used on acoustic guitars with steel strings. Nailon strings (concert guitars) are not possible. 5. Internal microphones using the condenser effect.

[0035] In this case, strips or plates with integrated bubbles and spacers are attached in or on the guitar, which then represent a mechanically deformable capacitor whose currents can then be amplified.

[0036] Advantages: See Piezo electrical pickup

[0037] Disadvantages: See Piezo electrical pickup 6. Internal microphones using the PZM effect (Pressure Zone Microphones)

[0038] This involves attaching or gluing a specially tuned microphone very close to the guitar's body, usually below the bridge. This reduces comb filter effects, creates a high output, and the sound is relatively clear and powerful.

[0039] Advantages: hardly any comb filter effects, clearer and more natural sound than other “attachment” systems

[0040] Disadvantages: Guitar needs to be heavily modified, quite expensive, lots of electronics needed, still less natural than recording with external static microphones 6. Combinations of all the above systems

[0041] The PCM pickup system presented in this document is able to offer the advantages of most of the above-mentioned systems without having to accept their disadvantages

[0042] Furthermore, it is comparatively inexpensive to design, does not alter the guitar, can be combined with all systems if required (although this is not necessary), and does not require a lot of electronics, as the sound can be optimized and modified through mechanical measures (attachment, position, etc.). 3.3 Technical problem to be solved:

[0043] When amplifying acoustic instruments, especially acoustic guitars, the aim is to achieve the most natural transmission of sounds and a high level of protection against feedback.

[0044] Over the past 70 years or so, many technical solutions have been tested and brought to market. However, all of these systems suffer from the fact that they distort the sound or severely restrict the musician's freedom of movement, and are also very susceptible to crosstalk and feedback.

[0045] The invention presented here aims to ensure natural transmission while achieving a high level of feedback immunity. At the same time, the system should be inexpensive, easy to install, and not alter or damage the instrument. 3.4 Means of solving the inventive problem:

[0046] To achieve the goals stated in section 3.3 (natural sound, feedback resistance, affordability, and unaltered performance), a small microphone capsule was chosen as the transmission element. This element (whether condenser or dynamic) remains unchanged in its original function. However, it is mounted on the body of the guitar (acoustic or concert) using special measures to achieve the above goals. For this purpose, the microphone capsule is flush with the guitar. This surface is referred to as a "shadow plate" in the image description because it shades the microphone capsule from the room and protects it from feedback.

[0047] This plate, which is approximately the width of the strings from E to E and slightly longer, is held at a small and constant distance by spacers made of a suitable material (e.g., rubber). This distance is approximately 1 mm. This creates a gap that produces an effect similar to a PZM microphone.

[0048] In this way, sound generated by the strings and radiated by vibrations from the guitar's top can be picked up by the microphone capsule 3-6 decibels more strongly than reflections from the room. This prevents feedback and crosstalk up to high levels.

[0049] Likewise, no reflections are recorded, comb filter effects do not occur and the sound is transmitted naturally.

[0050] A special flexible mounting mechanism is used to securely and slidably attach the shadow plate to the body near the soundhole and beneath the strings. A yoke is inserted into the soundhole. Two clamping screws clamp the shadow plate and yoke (hereafter referred to as the "yoke") together at the edge of the soundhole (toward the bridge) in such a way that both are firmly held while still retaining the ability to vibrate. This ability to vibrate is achieved by hard rubber washers.

[0051] The retaining screws are guided through elongated holes in the shadow plate, allowing the shadow plate to be moved either toward the sound hole or toward the bridge. The starting point for this possible movement is the position of the microphone capsule exactly at the transition from the sound hole to the body, toward the bridge.

[0052] Since this holding and adjustment mechanism would be unstable with just two screws and wouldn't be able to develop sufficient contact pressure on the body, two additional counter-pressure screws are provided on the left and right in the front area of the yoke. These can be manually adjusted to adjust the counter-tension and also the sound character once the capsule's basic position has been found.

[0053] The audio cable for the transformer capsule is routed away from the guitar on the shadow plate below the strings, perhaps to an external power source (battery). It's also conceivable to route it inside the guitar, which would then house a battery and power electronics (attached with Velcro or glued).

[0054] Figure 14 shows how the special sound guide of the PCM system blocks out background noise (shadow plate) and, with the help of the PZM effect (= Pressure Zone Microphone...Pressure Zone Effect / Compression Zone Effect), amplifies the sound of the body and strings by 3-6db louder than the sound of the surroundings.

[0055] Here we also show how the sound can be enriched with bass by shifting the system towards the sound hole and with treble by shifting it towards the bridge.

[0056] The name of the invention Pressure-Cone-Microphen_System is based on two physical principles that were researched during the development of the invention and whose results made this system possible: (1.) The "compression zone effect," also called the PZ(M) effect (Pressure Zone Effect), is a microphone embedded in a flat surface that avoids comb filter effects and amplifies the direct sound by 3-6 dB. This produces a clear and natural sound.

[0057] In the invention presented, this effect is used in the opposite way: The microphone, which is flush with the support plate "Shadowplate", looks downwards towards the body and is (2.) shaded upwards by the same plate against noise in the (effective) shape of a cone / funnel (=English: "Cone"), thus protected from noise and resonances.

[0058] The gap created between the top and shadow plate by the spacers determines the strength and tone of the PZ(M) effect. Both together enable a natural sound with minimal feedback, with the added possibility of shaping the sound (bass / treble) by linearly shifting the system (elongated holes / position closer to the sound hole / closer to the bridge, etc.). 3.4.1 Achievable improvements:

[0059] The pickup system presented here is capable of ensuring a particularly natural transmission of the instrument when electrically amplifying acoustic string instruments (live on stage or in the studio), similar to what would be heard acoustically without amplification.

[0060] It is also able to avoid noise and feedback up to a high level.

[0061] By using few and inexpensive parts, it has a low manufacturing cost and can also be purchased cheaply.

[0062] In addition, the instrument does not necessarily have to be modified or altered when installing this pickup system. 3.5 Example of implementation

[0063] To build a functional prototype, 2mm thick multi-layer propeller wood is used as the starting material for the support plate (called the "shadow plate"). The dimensions are approximately the width of the strings from low E to high E (approximately 6cm) and a length of approximately 8cm. A recess is made in the upper part of the support plate, leaving approximately 3cm of the sound hole free in the center. This creates two ear-like objects to the left and right of the recess, which later serve as supports for the counterforce screws.

[0064] A hole (approximately 4 mm) is drilled approximately in the center of the shadow plate for the microphone capsule (condenser) used, and this condenser is then glued to the bottom. Two elongated holes are milled to the left and right of the microphone capsule. These holes accommodate the screws for the main clamp at the sound hole and also allow for longitudinal adjustment toward the neck or bridge (more neck position = more bass, more bridge position = more treble. The optimal mix must be achieved by playing).

[0065] The lower end of the shadow plate takes the form of a curved bend towards the striking plate, which later serves to guide the microphone capsule's transmission cable away from the strings towards the lower sides.

[0066] The named transmission cable is glued flat onto the shadow plate and exits freely at the end of the curved bend.

[0067] Here it can be connected via a longer cable to a mixer with phantom power, to an on-board wireless transmitter, or to a battery-powered phantom adapter that is attached to the guitar strap or otherwise flexibly mounted on the guitar.

[0068] It is also conceivable to route the cable not towards the sides, but towards the sound hole, into it and to an internally mounted power and control electronics (e.g. with Velcro).

[0069] To keep the shadow plate at the optimal distance for creating a PZ(M) effect, spacers made of a suitable material are glued to its underside (the side facing the guitar top) in several places. In this example, these are 1mm thick rubber buffers. The thinner the resulting gap, the greater the PZ(M) effect (this prevents indirect sound and only amplifies instrument sound coming through the gap). To attach the shadow plate with the microphone capsule and rubber spacers in a stable yet adjustable way (length adjustment...sound...), a bracket shaped like a yoke (hereinafter referred to as the "joke") is inserted into the sound hole.

[0070] The "joke" (=yoke) brace rests against the guitar's top at three points from the inside, with the tip of the joke positioned near the intersection of the guitar's inner ribbing (bracing). The two outer points then provide support and counterpressure on the left and right sides of the soundhole.

[0071] In the lower part of the joke there are threaded holes on the left and right, which hold clamping screws coming from above through the elongated holes.

[0072] These clamping screws (2 in total) represent the stable connection between the body (top), shadow plate and yoke.

[0073] To prevent scratching the top and ensure a secure fit, hard rubber washers are placed between the top and the joke / shadow plate. To ensure the joke and shadow plate fit easily into the guitar during initial installation, a spring is placed on the left and right of the clamping screws to push the joke and shadow plate apart.

[0074] The clamping screws not only provide a secure connection between the elements and the guitar, but can also alter the sound by tightening them more or less. This occurs by influencing the vibration mode of the elements. This is because the shadow plate not only shields external noise (shadow...) and creates a PZ(M) effect through the micro-gap (approx. 1 mm...), but also because it is itself a vibrating element, thereby transmitting "structure-borne noise" to the microphone capsule.

[0075] While the connection of the slotted screws secures the PCM system's basic position, it cannot guarantee that the shadow plate rests securely and evenly on the ceiling along its entire length. If only these screws were present, the shadow plate would continue to lift toward the bridge, the gap would widen, and the entire element would begin to vibrate, thus preventing the desired effect from being achieved.

[0076] To prevent this, there are two "counterpressure screws" that come from below, on the left and right sides of the yoke, which push the "ears" of the shadow plate upward, thus stretching the shadow plate back toward the bridge and onto the body. How tightly they are tightened determines the contact pressure and, ultimately, the sound produced.

[0077] In practice, this has to be tested live, but this can be done quite quickly.

[0078] Since the counterpressure screws of the Joke have to be tightened from below, they each have a large and easy-to-grip "knurled wheel" that can be easily adjusted with the fingers from above, reaching through the strings.

[0079] To adjust the slotted screws, you will need a small screwdriver, as they should be as flat as possible in the shadow plate to avoid disturbing the musician while playing (finger contact, noise, etc.).

[0080] In its basic shape, the shadow plate, viewed from above, resembles a cat with large ears in profile and a tail angled to the right. The ears serve as the contact surfaces for the counterpressure screws, and the space between them is the area from which bass tones are fed from the body to the microphone capsule. (Proportion = depends on the position of the capsule found by shifting it using the slots)

[0081] The starting position for the tonal variations of the pickup is a position of the microphone capsule exactly above the area between the lower end of the sound hole towards the bridge and the transition into the guitar top.

[0082] As mentioned, moving the shadow plate toward the bridge produces a bass-poor, high-frequency sound, while moving it toward the soundhole produces the opposite. The shadow plate's "ears" channel additional sound from within the guitar to the PZ(M)-effect area of the shadow plate. 3.6 Possibilities of commercial applicability

[0083] The PCM system offers musicians and musical instrument manufacturers the opportunity to combine capabilities previously thought impossible in a cost-effective and flexible manner.

[0084] It can be sold as a separate upgrade kit that any musician with an acoustic guitar (steel strings and nylon strings) can upgrade permanently or as needed for live performances.

[0085] It's also possible for manufacturers to equip their instruments with the PCM system from the start. This would allow for the integration of the electronics into the guitar.

[0086] The system can be offered as a cable-based system with phantom power without additional electronics. In this case, the guitar must be connected via an audio cable to a mixer with phantom power.

[0087] A retrofit with a wireless microphone is also conceivable. Here, the manufacturer could offer the PSM system combined with a small wireless transmitter (battery-powered), which can be easily attached below the sound hole with Velcro or hooked onto a guitar strap.

[0088] It is also possible to combine existing guitars with existing pickups (e.g. piezo), where the additional installation of the PCM system provides an extension of the natural and tonal possibilities.

[0089] Even smaller companies would be able to market a PCM system, for example, using 3D printing as a simple retrofit kit for existing guitars. The manufacturing costs are low and the potential profit margins are high. The selling price should also be attractive, because the raw materials (e.g., plastic, wood, small microphone capsule) are inexpensive to procure and process. 5. Figure naming and part labeling: Fig. : PCM system built into a western guitar Fig. : PCM system installed in a western guitar - enlargement Fig. PCM system_installed in test plate_view obliquely from above Fig. PCM system_installed in test plate_view from below Fig. PCM system_installed in test plate_view obliquely from above_v.2 Fig. PCM system_installed in test plate_view obliquely from below_v.2 Fig. PCM system_removed_view from above Fig. PCM system_removed_view from below Fig. PCM system_removed_view from above_details a knurled wheel_counterpressure screw b Recess for low tones c rubber buffer d yoke / counterholder e Fixing screw Shadowplate f slot g Audio cable microphone capsule h Shadowplate i Microphone capsule Fig. PCM system_removed_view from below_details a yoke / counterholder b Counterpressure screw c Shadowplate d Knurled wheel counterpressure screw e rubber washer decoupling f microphone capsule g spacer Fig. PCM system_installed_view from sound hole to bridge a spacer b Connecting and adjusting screw c Microphone capsule d Shadowplate the sound hole f ceiling / body g Knurled wheel Counterpressure screw h Rubber disc fixation i Counter pressure spring j Counterpressure screw k yoke / counterholder I Rubber buffer / anti-slip pad Fig. PCM system_installed_view from sound hole top to sound hole bottom a Shadowplate b Retaining screw / fixing screw c Microphone capsule d audio cable e spacer (rubber) f corpus g yoke / counterholder h Counter pressure spring i Counterpressure screw j Knurled wheel counterpressure screw Fig. PSM system_solo installed_view from above a microphone capsule b Shadowplate c slot d spreading spring e knurled wheel counterpressure screw f counterpressure screw g yoke / counterholder h Rubber pad anti-slip i Fixing screw / adjustment screw j spacer k Audio cable Fig. Sound guidance, explanation: “Pressure - Cone - Effect” (= compression zone and shadowing cone effect) a external noise / reflections / background noise b Interior sound / bass component PCM c Shading by shadow plate d Bass level + / - for microphone capsule e Bass level + / - for microphone capsule f sound proportion of top / body / strings (in PZ column) g Shift to neck = more bass h Shift to bridge = more heights i strings j Ceiling / Body k Vibrations / sound in the body I Bridge m floor guitar n guitar neck Fig. PCM system_clip-on variant_without screws with elastomers a anti-slip pad b “Joke” counterholder (connected to shadow plate via elastomers) c Elastomers (for counterpressure, replaceable, adaptable) d retaining clip steel (replacement clamping screws / on ceiling sound hole) e shading plate IPZ effect plate / shadow plate f Spacer Shadowplate (variable) g sound hole h Microphone capsule i Shift direction neck position j Displacement direction web Fig. PCM system_clip-on variant_simplest + cheapest design a spacer - as long strips b Shadowplate c Spacer - regular d spacers - as long strips e retaining clip complete system (steel) f displacement direction neck g Displacement direction web

Claims

[1] Pickup for acoustic percussion and string instruments (especially guitars with sound hole) using a miniature microphone capsule (preferably condenser electreet omnidirectional), distinguished by the fact that the sound-receiving microphone capsule is installed flush with the instrument body, whereby the flush surface is made of thin, suitable material (e.g. plywood, plastic, carbon, etc.) with a thickness of approx. 1-3mm and is mounted between the strings and the body in a positionally variable but fixable and removable manner. [2] Pickup system according to claim 1, characterized in that the microphone capsule carrying surface is held at a defined distance from the sound body of the instrument (instrument top) by spacers of suitable and damping material (e.g. rubber, felt or similar) (e.g. 0.5mm- 1.5mm or other), whereby a defined gap is created between the microphone carrier plate and the body, which enables a PZM (Pressure Zone Microphone) similar effect with miniaturization of comb filter effects, increase of the sound pressure of 3-6 dB and simultaneous recording of the strings and body sound while masking out disturbing room components (by shading the capsule) and avoiding feedback effects. [3] Pickup system according to claim 1-2, characterized in that the described microphone capsule carrier plate is clamped by 3 or multi-point fastening to the sound hole (or other part of the instrument) in such a way that it can be quickly attached, quickly removed, continuously variable in contact pressure (the spacer made of rubber...) and can be changed in the length position of the microphone capsule (position more towards the sound hole and or more towards the bridge), whereby the proportion of bass from the sound hole with treble and mid-range from the body and the strings can be continuously mixed and modified by pressure and change in position. [4] Pickup system according to claims 1-3, characterized in that the fastening system in the sound hole / instrument body consists of a V- or yoke-like shape / construction, which is supported from the inside left and right below the sound hole, supports the tip of the V (yoke) inside the instrument (just before the "bracing" / inner stiffening cross in the middle) and has 2 (or more) clamps at the height of approximately the strings EAD and GHE, which firmly but variably connects the construction (V / yoke...) located below the sound hole with the microphone capsule carrier plate (between the instrument top and the strings), whereby all clamping points are provided with anti-slip and vibration-inhibiting discs and points. [5] Pickup system according to claims 1-4, characterized in that contact pressure and counter pressure screws and springs are dispensed with and instead the existing elements are converted into a flexibly attachable and detachable system via elastomers, expanding spring elements and the like, which can be assembled and varied without tools, whereby the elements (shadow plate, joke...) can be made / cast more or less from one piece and can therefore be manufactured cost-effectively. [6] Pickup system according to claims 1-5, characterized in that a variable clamping and holding construction as described is dispensed with, but instead the microphone capsule holding plate is connected to the instrument ceiling by flexibly attachable holding clips (similar to clipboards / clothespins), which also allow a variation of the position. [7] Pickup according to claims 1-6, characterized in that the system of capsule and shadow plate with spacers is positioned on the instrument body with removable but durable adhesive pads. [8] Pickup according to claims 1-7, characterized in that other microphone capsules are used than the miniature Electreet capsule with omnidirectional characteristic shown here [9] Pickup according to claims 1-8, characterized in that, using the pressure-cone combination effect investigated here, other suspensions of a microphone capsule can be realized with the same result as with the pressure-cone system [10] Pickup system according to claims 1-9, characterized in that, for the purpose of complete simplification and cost reduction, only a shadow plate + microphone with spacers and, instead of elongated holes, elongated rubber pads (displaceability) at the height of the spacers with the aid of one or more spring clips flexibly and displaceably press the shadow plate onto the guitar top.

Images