US3241631A

US3241631A - High-fidelity column-type stereomonophonic diffuser with regulated sound deflection

Info

Publication number: US3241631A
Application number: US416798A
Authority: US
Inventors: Manieri Domenico
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-01-31
Filing date: 1964-12-08
Publication date: 1966-03-22
Anticipated expiration: 1983-03-22
Also published as: GB1083467A

Description

United States Patent 3,241,631 HIGH-FIDELITY COLUMN-TYPE STEREOMONO- PHONIC DIFFUSER WITH REGULATED SOUND DEFLECTION The normal arrangement used to achieve stereophonic listening consists of two sound sources, either placed respectively at a certain distance to the left and to the right of the listener, or else assembled in a single unit, being fitted into the sides of such a unit and directed towards the side walls of the room so as to take advantage of sound reflections. However, as is well known, methods such as these do not give good results in rooms which are of modest size (such as ordinary living-rooms in modern houses) because of the multiplication of cross-reflections from the walls, which create an acoustic chaos and limit true stereophonic listening to a small area of the room. Furthermore such methods lead to the creation of a socalled acoustic vacuum, that is to say the sounds seem to come only from the side and never from the centre; this in turn requires the setting-up of a third sound channel.

With the diffuser which is the subject of the present discovery, these inconvenience are avoided; it is suitable for stereo listening in small rooms because it does not make use of reflection from the side walls (in fact such reflections are a disturbance and are avoided), but uses reflection from the wall in front of the listener, he having the diffuser at his back, and thus brings about a displacement of the frontal sound axis which is diverted sideways by the very high lateral buildup of sound pressure.

Even though the invention is linked to a normal (left and right channel) amplifier, the acoustic vacuum is avoided by means of the front-facing loudspeakers. Furthermore, having a double vertical alignment of loudspeakers one obtains the benefits of a column of sound" which has more or less cylindrical radiations and is therefore free from the pronounced initial drop in sound intensity found in the passage from the sound-source to the ear and, in addition, allows-for there is an alignment of loudspeakers in continuous operation-the employment of common, low-cost loudspeakers giving nevertheless extremely good reproduction of low notes; with dual cone loudspeakers of 16 cm. diameter a range of 20 to 18,000 cycles/sec. was obtained.

Sound deflection, that is to say the displacement, towards the left and right sides, of the sound axis from the front loudspeakers, is obtained by a mixture of the acoustic pressures set up by the lateral loudspeakers with that set up by the front loudspeakers. The resultant effect of such acoustic pressures varies in direction according to the variations in sound pressure ratios. With the present system it is possible to regulate this sound deflection so as to obtain a stereophonic listening-area of any predetermined amplitude and therefore the diffuser is suitable for use even in rooms of small dimensions. Thus, for example, with a sound pressure ratio of 4 to l (i.e. lateral sound pressure 4, front sound pressure-1), the resultant sound beam is found to be at about 37.5 degrees from the mean frontal axis, giving a stereophonic listening area of 75% which, in practical terms, for a room of 4 x 4 yards, means a stereo listening-area of 11 sq. yards if the diffuser is placed in the centre of the wall.

Since, furthermore, it is possible to make use of loudspeakers of small diameter, the unit can be of modest dimensions (the prototype, shown in the attached drawing, measures 11.8 x 11.8 x 27.559 inches, employing loudspeakers of 6.299 inches diameter).

The results, therefore, are a unit of modest size, excellent low-range frequency response even when cheap loudspeakers are used, and stereophonic listening even in small rooms.

The attached drawing shows, by way of example, one practical form of the diffuser according to the present invention, in which:

FIG. 1 shows the invention in tranverse section.

FIG. 2 shows the front view.

FIG. 3 shows a right side view, the left side view being a mirror image of this figure.

FIGS. 4 and 5 are two longitudinal section, frontal and lateral respectively.

FIG. 6 is a view in perspective, reduced.

In normal use the holes in which the loudspeakers are mounted are in vertical extending position.

The diffuser according to the present invention is mounted in a cabinet 10 of wood or other material (plywood being recommended) with walls thick enough to avoid vibrations, and is paralleloid in form (in practice, a cylindrical form would also be satisfactory) having three vertical volumns of holes, one column in the front designated F in the figures and a column on each of the two sides designated L and R for left and right sides respectively. This cabinet is hermetically sealed on three sides. Internally it may be packed to a thickness of 1 or 2 cm. with a sound-absorbing material such as glass Wool, or the equivalent, especially at the rear and at the angles, to avoid echoes.

For aesthetic reason the cabinet may be covered externally with normal loudspeaker cloth and, for functional reasons, it may be provided with feet so that it may stand, or with hooks for attaching it to the wall.

The number of holes, which must always be even, can vary, as can their surface area, according to the number and the size of the loudspeakers which are to be used. The centre of the front and of the side holes must always be on the same horizontal line (FIGS. 4 and 5) and, respectively, on the same vertical line. In practice, on the front section, instead of a column of loudspeakers (FIG. 2) a double column of paired holes could be used.

The loudspeakers 25-28 of the left-hand sound channel are placed in the holes 21-24 of the left-hand lateral column and similarly loudspeakers 35-38 of the righthand channel are placed in the holes 31-34 of the righthand .lateral column; in the front column are inserted loudspeakers 15-18, alternatively for each channel, (e.g. loudspeakers 15 in hole 11 of FIG. 2 for the right-hand channel, loudspeaker 16 in hole 12 for the left-hand channel, loudspeaker 17 in hole 13 for the right-hand channel and so on); when a double frontal column is used, in the left-hand column the loudspeakers for the left-hand channel are placed, linked to those of the left-hand lateral column; and similarly on the other side.

The loudspeakers can be of any type (normal or high-fidelity) of any diameter, impedance, etc. However they must be linked so as to operate in phase and remain so through the whole frequency range; also,

besides the necessity of maintaining their polarity, it is essential that the distance between each of them is never greater than the diameter of the smallest of them; that is to say, less than D (FIG. 2). For example, if there are two loudspeakers with a diameter of 3 .9 and 6.3 inches respectively, they must be set up so that the distance between them is not greater than 3.9 inches.

To prevent the frames of the frontal loudspeakers from interfering with the sound-wave exchanges which occur inside the cabinet between the lateral loudspeakers (increasing or decreasing the intensity of the sound waves produced), the holes for the lateral loudspeakers must be off-centred towards the back of the cabinet (FIGS. 3 and 5 Variations in the number of the cones of the loudspeakers and in their diameter will depend upon the low-frequency response required. For example, where dual cone loudspeakers are used with a single range from 80 to 18,000 cycles/see, it will be sufficient to use four loudspeakers for each lateral assembly. This will give a double range alignment (80:4:20) from to 18,000 cycles/sec. It is advisable to use loudspeakers of different diameters so as to realise a more linear response to the frequencies reproduced; provided they are in corresponding pairs, one for the left-hand channel and one for the right. For example; if in the right-hand lateral assembly there is a loudspeaker of a given type, there must be a loudspeaker of identical type both in the other lateral and in the frontal assembly; again, to a certain type of loudspeaker in the right-hand channel there must be linked one of identical type in the lefthand channel; thus, if at 11 in FIG. 2 there is placed a loudspeaker 7.874 inches in diameter linked to the righthand channel, one of similar diameters linked to the lefthand channel must be placed at 12. It is obvious that the loudspeakers are set up in two groups, one for the lefthand channel and the other for the right. Such groupings may be made in series, in parallel, or mixed, this depending on the overall impedance which may be required for each channel.

To achieve stereophonic effects in small rooms it is essential to bring about a correct deflection of sound, that is to say an accurate displacement of the sound axis which results from the combination of both frontal and lateral sound pressures. The frontal loudspeakers contribute the monophonic elements of the stereo programme and these go directly to the listener, while the lateral loudspeakers displace to the right side and to the left the stereo elementsi.e. those contributed on the right and left side respectively by the frontal loudspeakers-according to the rules governing the action of component forces.

To achieve such displacement, the acoustic pressure exercised by the lateral loudspeakers must be greater than those exercised by the frontal loudspeakers. In practical tests a sufliciently large area of stereophonic listing was obtained by Working with a lateral acoustic pressure four times greater than the frontal (with such a 4:1 ratio the actual area of stereophonic listing can be calculated from the angle 75 degrees approximately, which has as its point of origin the centre of the diffuser). This difference of acoustic pressure can be obtained in various ways: thus one may vary the ratio between the surface area of the frontal and that of the lateral cones, or the ratio between the intensity of the magnetic fields (Gauss), or the ratio between the input potential of the frontal loudspeakers and that of the lateral ones. Of these ways, the last two are to be preferred to the first one. In practice, using loudspeakers which are all of the same type, the last way is preferable, having, for example, the lateral loudspeakers fed in series and connecting, in series with them, the frontal loudspeakers arranged in parallel. In such a sace the input current will pass right through the mixing coils of the lateral loudspeakers and will then divide so as to pass through the moving coils of the frontal loudspeakers.

In monophonic listing, all the loudspeakers work in base.

p To achieve efiicient results from the diffuser, that is to say to obtain a good stereophonic effect, it must be mounted so as to have behind it a reflecting surface (i.e. a normal wall); it is not necessary to place it in the centre of the surface, though it must never be placed in a corner. With a unit 27.5-31.4 inches high having feet 2.773.9 inches long, one can obtain a good compromise between the spreading of the low notes, by means of the floor, and of the high notes which follow set directions. As has been said, reverberations from the side walls of the room cause interference and acoustic chaos; they are, therefore, to be avoided, whenever possible, by the hanging of curtains or similar material, even if this is only done on a level with the diffuser.

What I claim is:

1. A high-fidelity stereo-monophonic sound diffuser comprising a cabinet having openings in its front and on each side,

a loudspeaker attached at each opening,

said loudspeakers positioned in columnar alignment in the front and at each side,

a right-hand channel electrically connected to said loudspeakers positioned at openings on one side of said cabinet and at alternate openings in the front of said cabinet,

at left-hand channel electrically connected to said loudspeakers positioned at openings on the opposite side of said cabinet and at remaining alternate openings in the front of said cabinet,

and acoustic pressure between loudspeakers at openings on the sides of said cabinet in comparison to loudspeakers at openings at the front of said cabinet regulated so as to maintain a greater acoustic pressure from said loudspeakers at the openings in the sides of said cabinet whereby said loudspeakers at the front openings are monophonic elements and the stereophonic effects are the resultant of the acoustic pressures from said loudspeakers at the side openings relative to the acoustic pressures of said loudspeakers at the front openings.

2. The high-fidelity stereo-monophonic sound diffuser of claim 1, further characterized by a difference in the intensity of the magnetic fields of said loudspeakers to regulate the acoustic pressure.

3. The high-fidelity stereo-monophonic sound diffuser of claim 1, further characterized by a difference in the input potential of said loudspeakers to regulate the acoustic pressure.

4. A high-fidelity stereo-monophonic sound diffuser comprising a cabinet having openings in its front and on each side,

a loudspeaker attached at each opening,

and a left-hand channel electrically connected to said loudspeakers positioned at openings on the opposite side of said cabinet and at remaining alternate openings in the front of said cabinet,

said loudspeakers at openings at said one side connected in series and said loudspeakers at alternate front openings connected in parallel with each other in a series connected with said loudspeakers at said one side,

said loudspeakers at openings at said opposite side connected in series and said loudspeakers at remaining alternate front openings connected in parallel with each other in a series connection with said loudspeakers at said opposite side,

and acoustic pressure between loudspeakers at openings on the sides of said cabinet in comparison to loudspeakers at openings at the front of said cabi net regulated so as to maintain a greater acoustic pressure from said loudspeakers at the opening in the sides of said cabinet,

whereby said loudspeakers at the front openings are monophonic elements and the stereophonic effects are the resultant of the acoustic pressures from said loudspeakers at the side openings relative to the acoustic pressures of said loudspeakers at the front openings.

References Cited by the Examiner UNITED STATES PATENTS 2,710,662 6/1955 Camras 181-31 5 3,104,729 9/1963 Olson 181-31 FOREIGN PATENTS 1,130,856 6/196-2 Germany.

272,869 1/ 1951 Switzerland.

LOUIS J. CAPOZI, Primary Examiner.

LEO SMILOW, Examiner.

S. J. TOMSKY, Assistant Examiner.

Claims

1. A HIGH-FIDELITY STEREO-MONOPHONIC SOUND DIFFUSER COMPRISING A CABINET HAVING OPENINGS IN ITS FRONT AND ON EACH SIDE, A LOUDSPEAKER ATTACHED AT EACH OPENING, SAID LOUDSPEAKERS POSITIONED IN COLUMNAR ALIGNMENT IN THE FRONT AND AT EACH SIDE, A RIGHT-HAND CHANNEL ELECTRICALLY CONNECTED TO SAID SAID CABINET AND AT ALTERNATE OPENINGS IN THE FRONT OF SAID CABINET, A LEFT-HAND CHANNEL ELECTRICALLY CONNECTED TO SAID LOUDSPEAKERS POSITIONED AT OPENINGS ON THE OPPOSITE SIDE OF SAID CABINET AND AT REMAINING ALTERNATE OPENINGS IN THE FRONT OF SAID CABINET, AND ACOUSTIC PRESSURE BETWEEN LOUDSPEAKERS AT OPENINGS ON THE SIDES OF SAID CABINET IN COMPARISON TO LOUDSPEAKERS AT OPENINGS AT THE FRONT OF SAID CABINET REGULATED SO AS TO MAINTAIN A GREATER ACOUSTIC PRESSURE FROM SAID LOUDSPEAKERS AT THE OPENINGS IN THE SIDES OF SAID CABINET WHEREBY SAID LOUDSPEAKERS AT THE FRONT OPENINGS ARE MONOPHONIC ELEMENTS AND THE STEREOPHONIC EFFECTS ARE THE RESULTANT OF THE ACOUSTIC PRESSURES FROM SAID LOUDSPEAKERS AT THE SIDE OPENINGS RELATIVE TO THE ACOUSTIC PRESSURES OF SAID LOUDSPEAKERS AT THE FRONT OPENINGS.