Electrical audio signal processing systems and devices – Including frequency control
Patent
1987-11-16
1989-06-27
Isen, Forester W.
Electrical audio signal processing systems and devices
Including frequency control
H03G 500
Patent
active
048436259
DESCRIPTION:
BRIEF SUMMARY
This invention relates to sound reproducing systems and, more particularly, to a bypass for a loudspeaker.
According to the invention, there is provided a sound reproducing system comprising an amplifier and a loudspeaker unit and a bypass modifying the signal passed from the amplifier to the loudspeaker unit. The bypass is a circuit or circuits consisting of resistance, capacitance and inductance. The essential unit of resistance is within about 5% of 6600 ohms and this may be divided by N.sub.1, an integer of, say 1 to 12. The essential unit of capacitance is within about 5% of 0.152 Microfarad and this may be multiplied by N.sub.2, an integer of 1 to, say, 8, though one-half units or one-third units are sometimes needed. The essential unit of inductance is within about 5% of 24 Microhenrys and this may be divided by N.sub.3, an integer of, say, 1 to 15. The capacitance may be used in series with resistance and inductance or in parallel with resistance, in which case both capacitance and resistance should be in series with inductance (or the inherent inductance of wire-wound resistors should be present).
The invention also provides a bypass as defined in the preceding paragraph.
Advantageously the amplifier is a multi-channel amplifier having a multi-channel output and a loudspeaker unit for each channel and the said sound modifying bypasses are provided in parallel with the loudspeaker units.
In carrying out the invention, capacitors complying with British Standard BS 9000 and resistors complying with the BS CECC 40 201-002 are preferably used. Avoidance of the introduction of unacceptable levels of harmonic distortion has been found possible only by using high quality wire-wound resistors. Such resistors may be obtained from Welwyn Wirewound Resistors Limited of Bedlington, Northumbria, England. For similar reasons polystrene capacitors are preferably used. Other types of capacitors and resistors may alternatively be used but provide an inferior substitute, albeit one which may be acceptable on some sound-reproducing systems.
Component nominal values for optimum results will depend on the source of the components used. Fine-tuning can be carried out by adding small-value capacitors and resistors, of the same type as the main components, in parallel and/or series.
The total circuit or circuits may be used entirely on one of a pair of channels A and B or divided into separate unequal circuits for the two channels. Circuits may be used in parallel with each other, either consisting of the same numbers of units of resistance, capacitance and inductance or of different numbers. There are many useful ways of combining the units, some more satifactory than others in achieving a linear spectrum of sound and the closest approach to a three-dimensional effect. The preferred design is a circuit only on channel A where N.sub.1 is 3 and the number of units of capacitance, N.sub.2, is 7, though the numbers and proportions between the channels may be varied, albeit with somewhat inferior results. For the inductance N.sub.3 equals 11. This is the resultant of separate inductances. In some variations of the design, N.sub.2 may be an integer plus 1/2, and for digitally-processed sound, in all cases an extra 11/2 units of capacitance should be added, with an inductance of 3 Microhenries in series, to compensate for the difference in high frequencies. For a single loudspeaker system, the circuit may be used on the one speaker. In some variations of the design, several similar circuits may be used in parallel on one channel or unequally on both channels.
I have found that the use of a bypass comprising one or more resistors and capacitors of particular values with inductance as described can modify the sound emitted by a loudspeaker unit in a beneficial manner. The power is distributed more evenly over the spectrum than it is in the absence of the bypass. The bass and treble range and power is increased (and the middle ranges controlled) the dynamic range is increased.
I have determined that the bypasses in accordance with
REFERENCES:
patent: 4198540 (1980-04-01), Cizek
patent: 4237340 (1980-12-01), Klipsch
patent: 4593405 (1986-06-01), Frye et al.
patent: 4597100 (1986-06-01), Grodinsky et al.
patent: 4606071 (1986-08-01), White, Jr.
International Search Report dated Jun. 15, 1987, from the European Patent Office.
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