US3402371A - Delay device for producing artificial reverberation - Google Patents

Delay device for producing artificial reverberation Download PDF

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Publication number
US3402371A
US3402371A US335969A US33596964A US3402371A US 3402371 A US3402371 A US 3402371A US 335969 A US335969 A US 335969A US 33596964 A US33596964 A US 33596964A US 3402371 A US3402371 A US 3402371A
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Prior art keywords
springs
delay
coil
magnet
spring
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Expired - Lifetime
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US335969A
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English (en)
Inventor
Weingartner Bernhard
Marschall Otto
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AKG Acoustics GmbH
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AKG Akustische und Kino Geraete GmbH
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K15/00—Acoustics not otherwise provided for
    • G10K15/08—Arrangements for producing a reverberation or echo sound
    • G10K15/10—Arrangements for producing a reverberation or echo sound using time-delay networks comprising electromechanical or electro-acoustic devices

Definitions

  • a delay device for producing artificial reverbera-tions, is disclosed as of the type including a driving magnetic system connected to one end of relatively elongated coil spring means for converting electromagnetic oscillations into mechanical vibrations of the coil spring means, and a driven electromagnetic system connected to the opposite end of the coil spring means for converting vibrations of the coil spring means into electromagnetic oscillations to produce an output voltage.
  • the coil spring means comprises two or more concentric coil springs disposed one within the other. Corresponding ends of all of the springs are connected to each other, and one commn end of all of the springs is connected to the electromagnetic driving system and the other common end of all of the springs is connected to the electromagnetic driven system.
  • the ratio of the respective delay times of the springs is preferably an irrational number, and damping means may be provided for modifying the apparent reverberation time and the frequency response.
  • torsional vibrations to the helical springs is preferred because of the freedom of dispersion, the ease of excitation and the simple damping.
  • the ends of the springs are suspended from a frame, which is resistant to vibrations and reflects the mechanical waves.
  • each spring has associated with it a separate small permanent magnet at each of the drive and pick-up ends.
  • Each magnet is disposed in an air gap associated with a common drive or pick-up coil.
  • the invention relates to a delay device of the type described hereinbefore, which serves for the production of artificial reverberations. It is an object of the invention to simplify this device, and to reduce its cost and increase its reliability in operation.
  • the invention provides a delay device which comprises delay elements in the form of coil springs, a preferably electromagnetic drive unit for imparting mechanical vibrations to said springs at one end, and an analogous unit for converting said vibrations into electrical oscillations at the other end of the springs.
  • the invention uses coil springs having different diameters and concentrically arranged one inside the other. All the springs are interconnected to each other at both ends and the opposite interconnected ends are connected to drive and pick-up units, respectively, which are comomn to all springs.
  • the ratio of the delay times associated with each of the springs is preferably an irrational number.
  • damping means may be provided for modifying the apparent reverberation time and the frequency response of the arrangement.
  • damping is effected by damping material, such as felt or the like, which is provided in the air gap of the drive and/or pick-up unit, in which air gap the permanent magnet is movable.
  • the transmission line may be provided with a plurality of delay devices according to the invention, in a series rand/or parallel connection with each other.
  • FIG. 1 is a diagrammatic view showing a delay device according to the invention, in which longitudinal flexural vibrations are imparted to the springs.
  • FIG. 2 is .a view showing such a device in which the springs are subjected to transverse vibrations.
  • FIG. 3 shows a device in which torsional vibrations are imparted to the springs.
  • FIG. 3a is a sectional view taken on line 8-5 of FIG. 3 and shows a drive unit.
  • FIG. 4 shows a series connection of a plurality of delay devices according to the invention.
  • FIG. 5 is an enlarged view showing two coil springs arranged one in the other, for an explanation of the advantages of the arrangement with respect to its vibration behavior.
  • FIG. 6 is an equivalent circuit diagram of FIG. 5 on a four-terminal network basis.
  • the drive unit is indicated at A. It comprises an exciter coil 1, which produces lines of force in the magnetic circuit 2 when an audio-frequency voltage U is applied to the coil.
  • the circular air gap accommodates a 'bar magnet 3, one end of which is connected by a stiff spring 4 to the housing of the drive unit, whereas the other end of the magnet is secured to the interconnected ends of three coil springs.
  • the vibration performed by the magnet is propagated in the form of compressional Waves in the delay springs and transmitted to the permanent magnet 3' of the pick-up unit B, which has basically the same design as the drive unit A.
  • the stiff spring 4' holds the permanent magnet bar 3 in the housing of the pick-up unit.
  • the mechanical vibration of the magnet 3', and the resulting movements of its field of force, induce, in the pick-up coil 1; a voltage which is available as an output voltage U
  • the support of the bar magnets 3 and 3' in their housings is relatively resistant with respect to vibrations, the vibrations imparted to the concentrically arranged springs are reflected repeatedly between the ends of the springs until they decay.
  • a reverberation voltage is obtained, which simulates the acoustic conditions of a room.
  • the ratio of the delay times associated with the respective springs should be an irrational number.
  • FIG. 2 shows a delay device according to the invention, in which concentrically arranged coil springs are caused to perform fiexural vibration (transverse waves).
  • the reference characters have the same meanings as in FIG. 1.
  • a difference from the embodiment described hereinbefore resides in that the springs 4 and 4, holding the permanent magnet bars 3 and 3' in the housing, are leaf springs.
  • FIG. 3 A particularly desirable embodiment is shown in FIG. 3, and provides for application of torsional vibrations to the concentrically arranged coil springs.
  • Torsional vibration has the advantage of being free from dispension so that it provides for a delay or transit time which is independent of frequency.
  • a and B are again the drive and pick-up units, respectively.
  • An audio-frequency alternating voltage U applied to the exciting coil 1 of the drive unit produces, in the air gap of the magnetic yoke 2, an alternating magnetic field, which imparts torsional vibrations to the diametrically magnetized permanent magnet 3, the magnetic axis of which is inclined by approximately 45 from the vertical.
  • FIG. 3a is a sectional view taken on line S-S through the front part of the pick-up unit, and indicates the arrangement of the diametrically magnetized permanent magnet 3 in the air gap.
  • the rotary vibration or oscillation of this magnet bar 3 is propagated in the coil springs 5 as torsional vibrations, the velocity of propagation of each of which varies with the square of the diameter of the helix of the respective spring.
  • the vibrations are transmitted to the magnet 3' of the pick-up unit B.
  • the movement of this magnet induces a voltage in the pick-up coil 1'. A part of each vibration is reflected and decays slowly, depending on the inherent damping of the system.
  • the springs 4 and 4' which hold the magnets 3 and 3 may consist either of leaf springs or of coil springs.
  • the entire system may be submerged into a viscous liquid, such as oil.
  • frictional damping material such as felt, may be used, e.g., in the air gap between the magnet bar and the magnet yoke, as is indicated in FIG. 3 at 6 and 6. This material may alternatively extend across only a part of the width of the air gap.
  • a plurality of delay devices according to the invention may be arranged in series in the transmission line, as is shown in FIG. 4, and/ or in parallel in the transmission line.
  • the drive or repelling unit for producing torsional waves may comprise a fixed magnet and a movable rotating coil in the field of the magnet yoke, as in a rotating coil instrument.
  • FIG. 5 is an enlarged view showing an arrangement of the type illustrated in FIG. 3, comprising two concentric springs 5 and 7.
  • the masses of the magnets 3, 3 are represented by the inductances L, L.
  • the compliance of the suspension springs or strips 4, 4' is represented by the capacitances C, C.
  • the damping resistances 6, 6' are represented by the ohmic resistances R, R.
  • the two springs 5 and 7 are represented by the series-connected four-terminal networks having the resistance matrix Z or Z7 and the characteristic impedance of each spring Z or Z
  • each four-terminal network (each spring) is terminated at each end by the total of the input impedance of the other spring in series with the impedance of the drive or pick-up units.
  • the reflection of a wave propagated in one spring decreases as the difference between the characteristics impedance and the terminating impedance increases.
  • the characteristic impedance of the springs being proportional to their diameter for the same thickness of wire, and proportional to the third power of the thickness of the wire for the same diameter, an optimum approach to the characteristics of a natural reverberation can be achieved by the selection of springs having appropriate dimensions in relation to the impedance of the drive and pick-up units without need for additional, individual damping means which can be adjusted only with difficulty.
  • the characteristic resistance Z of the drive and pick up system is derived from the square root of the ratio of the moment of inertia of the magnet to the compliance of the support wire, and this is expressed as follows:
  • torsion waves which are generally used, have a velocity of propagation of:
  • a delay device as shown in FIG. 5 has actually been constructed with the following dimensions:
  • the friction in the air gap of each of the drive and pick-up units was equivalent to approximately ohms.
  • the large spring 5 had a mean turn diameter of 10 mm.
  • the small spring 7 had a mean turn diameter of 3.4 mm.
  • the wire of both springs 5 and 7 had a diameter of 0.3
  • the characteristic impedance Z was equivalent to r 10.5 ohms.
  • the characteristic impedance Z-; was equivalent to 3.5 ohms.
  • the large spring had 220 turns and a delay time of approximately 90 milliseconds.
  • the small spring had 260 turns and a delay time of about 12.4 milliseconds.
  • a delay system for producing artificial reverberations of the type including at least one delay device having helical spring means as a delay element, an electromagnetic drive system connected to one end of the spring means to convert electrical oscillations into mechanical vibrations of the spring means, and an electromagnetic driven system connected to the opposite end of the spring means to convert vibrations of the spring means into electrical oscillations: the improvement in which said spring means comprises relatively elongated helical springs, of different respective diameters, arranged coaxially one inside the other; corresponding first ends of all of the springs being connected in common to said electromagnetic drive system, and corresponding opposite ends of all of the springs being connected in common to said electromagnetic driven system; whereby all of said springs are connected in parallel with each other between said electromagnetic drive and driven systems.
  • a delay system for producing artificial reverberations of the type including at least one delay device having helical spring means as a delay element, an electromagnetic drive system connected to one end of the spring means to convert electrical oscillation into mechanical vibrations of the spring means, and an electromagnetic driven system connected to the opposite end of the spring means to convert vibrations of the spring means into electrical oscillations;
  • said spring means comprises relatively elongated helical springs, of different respective diameters, arranged coaxially one inside the other; corresponding ends of all of the springs being connected to each other; one common interconnection of all of the springs being connected to said electromagnetic drive system, and the opposite common interconnection of all of the springs being connected to said electromagnetic driven system; each of said electromag netic systems including an air gap and at least one of said electromagnetic systems including damping means disposed in the air gap thereof and damping vibrations of said springs.
  • each of said electromagnetic systems includes said damping means in the air gap thereof.
  • the improvement claimed in claim 4 in which at least one of said electromagnetic systems comprises a stationary magnetic field means and a moving coil system operatively associated with said magnetic field means.
  • a delay system for producing artificial reverberations of the type including at least one delay device having helical spring means as a delay element, an electromagnetic drive system connected to one end of the spring means to convert electrical oscillations into mechanical vibrations of the spring means, and an electromagnetic driven system connected to the opposite end of the spring means to convert vibrations of the spring means into electrical oscillations: the improvement in which said spring means comprises relatively elongated helical springs, of different respective diameters, arranged coaxially one inside the other; corresponding ends of all of the springs being connected to each other; one common interconnection of all of the springs being connected to said electromagnetic drive system, and the opposite common interconnection of all of the springs being connected to said electromagnetic driven system; at least one of said electromagnetic systems including a movable permanent magnet connected to a common interconnection of all of the springs.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)
US335969A 1963-01-18 1964-01-06 Delay device for producing artificial reverberation Expired - Lifetime US3402371A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT41263A AT242973B (de) 1963-01-18 1963-01-18 Einrichtung zur Erzeugung künstlichen Nachhalls

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US3402371A true US3402371A (en) 1968-09-17

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US335969A Expired - Lifetime US3402371A (en) 1963-01-18 1964-01-06 Delay device for producing artificial reverberation

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US (1) US3402371A (xx)
AT (1) AT242973B (xx)
CH (1) CH428858A (xx)
DK (1) DK109111C (xx)
GB (1) GB1072411A (xx)
SE (1) SE306184B (xx)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3517344A (en) * 1966-12-06 1970-06-23 Akg Akustische Kino Geraete Delay device particularly for the production of artificial reverberation
US3526793A (en) * 1968-11-25 1970-09-01 Akg Akustische Kino Geraete Transducer for converting electrical oscillations into torsional vibration and vice versa
US3611202A (en) * 1969-02-24 1971-10-05 Johan Van Leer Variable decay reverberation unit
US4112396A (en) * 1975-02-17 1978-09-05 Chuzo Honda Echo annexation device

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1852795A (en) * 1928-10-24 1932-04-05 Bell Telephone Labor Inc Wave transmission device
US2230836A (en) * 1939-07-15 1941-02-04 Hammond Laurens Electrical musical instrument
US2375004A (en) * 1943-05-12 1945-05-01 Josephine Knotts Knowles Training apparatus
US2480131A (en) * 1943-11-26 1949-08-30 Hammond Instr Co Electrical musical instrument
US2853145A (en) * 1953-09-09 1958-09-23 Baldwin Piano Co Reverberation loud-speaker assembly
US3092792A (en) * 1961-07-03 1963-06-04 Nathan I Daniel Electro-acoustical delay line useful for producing reverberation in electrical musical instruments
US3150335A (en) * 1962-04-26 1964-09-22 Hammond Organ Co Reverberation unit assembly

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1852795A (en) * 1928-10-24 1932-04-05 Bell Telephone Labor Inc Wave transmission device
US2230836A (en) * 1939-07-15 1941-02-04 Hammond Laurens Electrical musical instrument
US2375004A (en) * 1943-05-12 1945-05-01 Josephine Knotts Knowles Training apparatus
US2480131A (en) * 1943-11-26 1949-08-30 Hammond Instr Co Electrical musical instrument
US2853145A (en) * 1953-09-09 1958-09-23 Baldwin Piano Co Reverberation loud-speaker assembly
US3092792A (en) * 1961-07-03 1963-06-04 Nathan I Daniel Electro-acoustical delay line useful for producing reverberation in electrical musical instruments
US3150335A (en) * 1962-04-26 1964-09-22 Hammond Organ Co Reverberation unit assembly

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3517344A (en) * 1966-12-06 1970-06-23 Akg Akustische Kino Geraete Delay device particularly for the production of artificial reverberation
US3526793A (en) * 1968-11-25 1970-09-01 Akg Akustische Kino Geraete Transducer for converting electrical oscillations into torsional vibration and vice versa
US3611202A (en) * 1969-02-24 1971-10-05 Johan Van Leer Variable decay reverberation unit
US4112396A (en) * 1975-02-17 1978-09-05 Chuzo Honda Echo annexation device

Also Published As

Publication number Publication date
CH428858A (de) 1967-01-31
AT242973B (de) 1965-10-11
DK109111C (da) 1968-03-18
SE306184B (xx) 1968-11-18
GB1072411A (en) 1967-06-14

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