FI76664B - HOEGTALARE. - Google Patents

Description

1 76664

The present invention relates to a loudspeaker comprising a loudspeaker element and a housing on one wall of which a loudspeaker-5 element is mounted.

The most commonly used solution is a dynamic speaker. It has numerous applications. The common features of hi-fi speakers made with dynamic speaker elements can be said to be the use of two or more elements 10 in order to cover a sufficiently wide frequency range with the speaker. The most active product development in recent years has been the uniform frequency response, good efficiency, low harmonic and intermodulation distortion, extensive radiation characteristics and phase error-free operation. These goals have been achieved by improving the quality of speaker components; with more precise manufacturing tolerances, the latest materials (Bextren and Polypropylene cones, Alnico-Samarium cobalt magnets) and by creating better calculation models, especially for the accurate 20 sizing of the subwoofer enclosure. In addition, there has been a shift from traditional 2- and 3-way solutions to even 5-way principles.

Despite these attempts, the quality of the speaker has not been improved enough. On the other hand, based on absolute listening tests performed in good acoustics or even in an anechoic room, it has been concluded that a modern properly made HiFi speaker is a good enough component for an audio chain when the degrading effect of the room is not ruining the end result. This has led to a major improvement in room acoustics, for which several publications and articles have been produced. These present superior methods and attenuation materials for controlling room reverberation time and sound field homogeneity.

Since it is almost impossible to imagine that every buyer of 35 HiFi speakers will start to modify their living room solely to achieve good acoustic properties, 2 76664 is an object of the invention to create a new speaker whose reproduction can be affected as little as possible by room features.

In a conventional rigid-walled speaker solution, the ratio of the 5 power spectra to the frequency response is unfavorable because the directivity of the speaker is affected almost exclusively by the diameter of the radiator. If such a speaker is designed to have a uniform frequency response, its power spectrum will strongly emphasize the bass. This speaker reproduces the sound of a koh-10 in a very soft acoustic room, but in a normal living room the playback is dark and inaccurate due to the bass emphasis.

If a speaker is designed to have a uniform power spectrum, its free-field response may necessarily emphasize high frequencies due to the directional characteristics of the piston radiator. Such a speaker sounds moderately pleasant in a hard room, but in a softly acoustic room it is strenuously flashy with its deficient bass and accentuated mid and treble bases.

The loudspeaker according to the invention is mainly characterized in that at least one wall of the loudspeaker housing is made of a material which transmits the background radiation of the loudspeaker element attenuated in the listening space, such radiation being at least substantially opposite (phase difference 180 °) to the loudspeaker element over a wide frequency range.

Depending on the situation, that wall may be the back wall of the housing, both side walls, or even all the walls.

30 One suitable wall material is styrofoam with a density of about 25-40 kg / m 2, but other so-called lossy materials, such as cardboard or thermoplastic. Sound transmission properties (vibration properties) depend on several factors, such as wall thickness, density, surface area, and internal structure. The right dimensioning can be achieved by experimenting.

3,76664

The invention makes it possible to substantially improve the directivity of the low frequencies of the loudspeaker in the range from 40 to 800 Hz and by means of which the power spectrum can be controlled.

This leads to two points that are important for reproduction.

5 First, because the method significantly increases the directivity of low frequencies, it also dramatically reduces the power radiated by the speaker at these frequencies. This makes it possible to achieve the ideal relationship between sound pressure and power. On the other hand, studies of very recent ai-1o instruments have shown that the most harmful of the room reflections are the so-called early reflections. Early reflections are reflections with delays of approx. 0.1 - 2 ms. These reflections arise from surfaces in the vicinity of the loudspeaker: the rear wall, the floor and the side walls. Studies show that early reflections cause the following reproduction errors: sound colorization, attenuation of transients and dynamics, unstable stereo image, impaired resolution.

In the loudspeaker-20 implemented according to the principle of the invention, the early reflections have been almost completely eliminated. The speaker radiates up and 20 dB more attenuated to the rear and sides than in the direction of the main axis.

The acoustic advantages achieved can be summarized as follows: 25 - uniform free field response uniform power spectrum - spherical and clear reproduction (as is usually the case with electro-static) accurate stereo image 30 - brilliant transient reproduction - accurate and tight bass (no standing waves) - effect of ambient acoustics on reproduction considerably less than usually with speakers.

In addition, structural advantages are achieved: 35 - cheaper materials can be used in the case, which also makes the product cheaper 4 76664 - casting technology can be used for lighter speakers, which means that the design is completely free (a shortcoming that really burdens the current speaker production).

5 As a result of good directivity, the efficiency remains relatively low, which on the other hand is typical of traditional Hi-Fi class speakers. However, in view of the advantages achieved, this disadvantage is very insignificant.

The invention will now be described with reference to the accompanying drawing.

Figures 1 and 2 show situations where the loudspeaker has a wide and a narrow direction beam, respectively.

Fig. 3 shows a dipole radiator, Fig. 4 the radiation pattern generated by it.

Fig. 5 shows an embodiment of a loudspeaker according to the invention, Fig. 6 its radiation pattern.

Fig. 7 shows another embodiment of a loudspeaker according to the invention, Fig. 8 its radiation pattern.

Figure 1 shows a normal situation where the speaker 20 has a wide directional beam. In this case, a lot of early reflections 11 of high intensity can be generated from the walls 10 and the floor. In addition, they come almost directly from the direction of the sound (L, R), making their sound-degrading effect even more pronounced. Figure 2 shows a speaker with a narrow directional beam. In this case, the early reflections 12 are small and their intensity is low.

In a theoretical analysis, a dynamic speaker can be considered as a piston radiator, the directivity characteristics of which depend almost exclusively on the ratio of the diameter of the radiator to the reproducible frequency. Therefore, it is clear that good bass range orientation it. a narrow directional beam requires a large radiator surface. Of course, this is not possible in all constructions.

Another way to achieve good directivity is to utilize a dipole radiator. The dipole radiator is formed, for example, by a loudspeaker element placed on a finite plate. Fig. 3 shows the dipole radiator and Fig. 4 shows the radiation pattern 15 generated by it. The disadvantage of the dipole radiator is the very poor reproducibility of low tones, since at a distance of 1/4 below the corresponding frequency of the speaker 13, playback begins to attenuate at about 12 db / oct. Achieving a sufficient lower limit frequency with a dipole radiator requires an unreasonably large faceplate or, correspondingly, the power supplied to the radiator must be increased considerably at low frequencies to eliminate the effect of an acoustic short circuit.

Figures 5 and 7 schematically show two embodiments of a loudspeaker according to the invention in top sections. Reference numeral 1 denotes a loudspeaker element, 2 denotes a loudspeaker housing in general, 3 denotes the front wall of the housing in which the loudspeaker element is mounted. Reference numerals 4, 5 and 6 denote sound-transmitting walls which transmit (oscillating) the background radiation 9 of the speaker element 1 attenuated to the listening mode so that the background radiation is in opposite phases, phase difference 180 °, with the front radiation of the speaker element 1 in the frequency range. 40 - about 800

Hz. 7 (Fig. 7) shows an additional bass sound attenuation part attached to the middle part of the walls 5 and 6, which may be a piece of wood and which is not in contact with the rigid walls 2 and 3. 8 shows conventional insulation, e.g. mineral wool.

In Fig. 5, the rear wall of the speaker has been replaced by a sound-transmitting wall 4. In Fig. 6, the resulting directional pattern 16 and the corresponding situation shown by the dotted line 17 if the rear wall were conventionally rigid. In Fig. 8, on the other hand, both side walls are replaced by sound-transmitting walls 5 and 6, and in Fig. 8, there is a corresponding directional pattern 18 and a directional pattern of a conventional speaker, a dotted line 19.

The device according to the invention operates as follows: reproducible sound material is fed to the speaker 1. The rear radiation 9 of the loudspeaker 1 enters the listening space partially attenuated via the sound-transmitting wall 4 (or walls 5 and 6). This creates a dipole effect, where the opposite phase background oscillation partially cancels out the front radiation. This results in a radiation pattern according to Fig. 6 (or Fig. 8), where the intensity of the radiation in the lateral direction of the speaker is strongly attenuated. This results in effective attenuation of early reflections from the side walls of the room.

By selecting a sound-transmitting wall such that it attenuates low frequencies more than high frequencies, otherwise detrimental excessive attenuation of lower bass frequencies is prevented. By dimensioning the sound-absorbing wall and selecting the material, the directivity can be influenced in the desired way and thus the so-called control-15 directivity, i.e., independence from directional frequency.

In the following, an implementation of the principle solution according to Figure 7 in practice, which, of course, is not intended to limit the invention.

20 Operating principle: 2 way SWP (Soft Wall Principle)

Power duration: 50 W continuous 60 W music 25 Speaker elements: 215 mm bass (part 1) 25 mm treble (not shown in Figure 7)

Reproduction range: 40 to 20,000 Hz i3 dB

35 Hz - 10 dB

30 Sensitivity: 90 dB / 1 W / 1 m

Impedance: 8 ohms

Net volume: 38 1

Dimensions (W X H x D) 280 x 770 x 285 mm

Connection: Quick connector 35 The front wall 3 and the rear wall are rigid chipboard, thickness eg 18 ram; the side walls 5 and 6 are made of styrox sheet, ti- 3 7 76664 hevs about 40 kg / m and thickness about 25 nm; the damping parts 7 are made of pine wood, length approx. 220-230 mm, height approx. 35-40 mm and thickness approx. 25 mm. The wooden parts 7 can be replaced, for example, with suitably dimensioned aluminum profiles. The walls 5 and 56 are preferably upholstered in a fabric, below the loudspeaker 1 there is a fixed support arranged in a known manner between the front and back wall, which is not shown in Fig. 7.

Claims (10)

A loudspeaker comprising a loudspeaker element (1) and a ledge (2) at one wall (3) of which the loudspeaker element is fixed, characterized in that the edible body of the loudspeaker at least one wall is made of such material which permits the loudspeaker element to pass through. backbone radiation attenuated into the listening space, that the strain in question is exhibited at least substantially opposite phase 10 (phase difference 180 ° C) to the front radiation of the speaker element (1) within a wide frequency range. 2. A loudspeaker as claimed in claim 1, characterized in that the rear wall (4) of the loudspeaker lid (2) is made sound-penetrating in said manner. 15 3. A loudspeaker according to claim 1, characterized in that the two side walls (5, 6) of the loudspeaker lid (2) are made sound-penetrating in said manner. 4. A loudspeaker according to claim 1, characterized in that all the sides of the loudspeaker (2) are made sound penetrating in said manner. Loudspeaker according to any of the preceding claims, characterized in that the wall (4; 5,6) which transmits sound in said manner is made of styrox disc. 25 Loudspeaker according to claim 5, characterized in that the thickness of the styrox disc is young. 3 25 mm and its density is young. 25-40 kg / m, preferably 3 young. 40 kg / m. Loudspeaker according to any one of claims 1-4, characterized in that the wall (4; 5, 6) which permits sound in said manner is made of paff. 8. A loudspeaker according to any one of claims 1-4, characterized in that the wall (4; 5, 6) which transmits sound in said manner is made of thermoplastic.