DE3542872A1 - Loudspeaker enclosure having bent acoustic pipes - Google Patents

Abstract

The invention consists of a number of symmetrically arranged acoustic pipes which are bent away to the rear and which increase the sound pressure in the low-frequency range and widen the frequency range. These are installed in an enclosure which is open at the rear and, due to their arrangement, result in equalised pressure conditions at the rear of the diaphragm and in little generation of standing waves. This prevents distortion and ensures accurate reproduction quality in accordance with the hi-fi standard. <IMAGE>

Description

I I

I ■

■ »

■ »

• 111

• · · I

UM Ii,,

Loudspeaker.qehause with c: ebo <-en acoustic tubes

The invention is through an arrangement of irebo'-enes acoustic Tubes marked in a backside · :. (, opened Housing are installed and the low-frequency component radiated into the housing by a dipolar sound transducer is in phase coupled to the chewing sound.

There are several found in conventional loudspeaker enclosures Shapes of acoustic tubes that have a constant cross section. The phase reversal channel or the are known Propagation line, v / elche the sound pressure through phase rotation amplify in the low frequency range.

Also the one described in the German Auslegeschrift 2437538 acoustic tube shows a special form of delay line.

Research has found that the bass gain causes standing waves through conventional acoustic tubes and uneven pressure conditions on the membrane leads.

These influences are particularly pronounced in the low frequency range, whereby the natural sound reproduction clearly audibly deteriorates will. For a strong bass boost, v / ie them in particular is necessary for small diaphragm diameters and small housing volumes, these tubes are acoustically unsuitable because they either need too much volume or too much distortion which can only be partially suppressed by acoustic damping.

The object of the invention is to exclude standing waves and uneven pressure conditions on the back of the diaphragm, as well as dampening inertia-induced natural vibrations of the diaphragm while improving the impulse fidelity and to obtain the possibility of ^{amplifying frequencies below the 1} sound transducer natural resonance. This enables reproduction of the low-frequency area in hi-fi quality.

The invention solves this problem by adding the acoustic tubes are bent in a small radius so that no standing waves can form, the installation of sound transducers and acoustic Tubing is done so that the Schallwaiidler on an approximate square initial volume acts, date creates uniform pressure ratios.

When the pressure changes generated by the sound transducer, there is a pressure change in the acoustic tubes that are open to the rear. coupled to the ambient atmosphere, a low-frequency amplification and through the angle of the acoustic tubes

- P -

ti ■

«Ι

C (

35A2872

is resonance-free and an indirect damping of the diaphragm vibration results. Due to the absence of resonance of the acoustic Tubes can also have frequencies below the transducer natural resonance be reinforced.

The opening on the back reduces the resonances inherent in the housing and those to be overcome by the sound converter Back pressure, which results in a faster response of the membrane and thus a higher impulse fidelity. A closer one Explanation follows on the basis of graphic representations.

Fig. 1 shows a schematic plan view showing the symmetrical Structure and the square initial volume clarified.

Fig. 2 shows an embodiment with anti-parallel side walls, which leads to a reduction in the housing's own resonances.

Fig. 3 shows the dampening and bass-amplifying effect the acoustic tubes in connection with the rear. Housing opening.

Fig. 4 shows an embodiment with two sound transducers and 3 pairs of Aksutian tubes.

The mode of operation of the housing arrangement is described below.

Investigations have shown that standing waves are only formed between parallel surfaces and membrane resonances can be influenced by pressures acting on the membrane. Therefore the acoustic tubes with a radius r equal to the does not exceed twice the tube diameter, bent at an angle of approx. 70 - 90 °. The total cross-sectional area of the tubes is to be chosen smaller than twice the total membrane area.

To further prevent standing waves, the rear of the housing is open, which at the same time improves the impulse fidelity will. Minimum membrane resonances achieved when the sound propagates within the housing in each, from the sound transducer off, direction is the same. This is optimally achieved in a spherical housing. For manufacturing reasons however, a cube-shaped housing is preferred, which shows approximately the same properties.

As shown in Fig. 2, there is also an anti-parallel housing Walls suitable for the further prevention of standing waves.

The dimensions of the housing opening and acoustic tubes can be changed as required within wide limits, resulting in a large Flexibility in the selection of the transducer to be used results.

Furthermore, it has been found that a, as shown in Fig. 2, HiFi-like playback quality even without acoustic damping achieved that particularly insane. Bass range clearly will.

Claims (1)

• III
> t ι • · 1 ι. Claims |> 1. Acoustic tubes that are vertically and horizontally in pairs
I or point-symmetrically in even or odd number in I the housing is installed. The tubes are built into the side walls and sloped backwards at a small radius r. \ l 2. Loudspeaker housing with acoustic tubes according to claim 1, ^Y l characterized in that the rear is a rectangular one I Opening 2 is present, the height of which corresponds to that of the housing I speaks, the width of which varies until it is at most that of the K housing.