Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R1/00—Details of transducers, loudspeakers or microphones
  • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
  • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
  • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
  • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
  • H04R1/2815—Enclosures comprising vibrating or resonating arrangements of the bass reflex type
  • H04R1/2823—Vents, i.e. ports, e.g. shape thereof or tuning thereof with damping material
  • H04R1/2826—Vents, i.e. ports, e.g. shape thereof or tuning thereof with damping material for loudspeaker transducers

Definitions

• the present invention relates to loudspeakers and audiovisual devices comprising such a speaker.
• a vent with an acoustic enclosure comprising at least one electro-acoustic transducer, such as a loudspeaker, mounted in a box.
• an enclosure is generally called a bass-reflex enclosure or a ventilated enclosure.
• the assembly formed by the volume of the box and the vent reacts to the vibratory excitations of the loudspeaker like an oscillating system (Helmholtz resonator), with a resonance frequency F 0 called the resonance frequency of the bass-reflex.
• the frequency response of the bass-reflex speaker can thus be adapted to the desired use.
• the use of a bass-reflex enclosure is notably known in audiovisual devices, such as televisions, as described for example in the utility model JP 63-183 788.
• FIG. 1 An example of frequency responses in the case of an enclosure without vent (dotted line) and with vent (solid line) is given in FIG. 1 where the resonance peak F 0 clearly appears in the case of the enclosure with vent.
• the vent comprises means of attenuation at the resonance frequency of the bass-reflex.
• the vent comprises at least one flexible plate
• the vent comprises at least one plate whose mechanical resonance frequency is close to the resonance of the bass reflex;
• the vent comprises at least one plate whose mechanical resonance frequency is practically equal to the resonance of the bass reflex; -
• the vent comprises two flexible plates which define a vent volume opening into an opening of the box; - the electro-acoustic transducer is a hard suspension speaker.
• the invention also provides an audiovisual device which includes a display device and such an enclosure.
• FIG. 2 shows an acoustic enclosure produced in accordance with the teachings of the invention
• FIG. 3 represents the frequency response of the acoustic enclosure of FIG. 2 compared to the frequency responses of FIG. 1.
• the enclosure 2 shown in FIG. 2 comprises four speakers 4 mounted on the front face 6 of a parallelepipedal box 8, the walls of which are made of wood.
• the speakers 4 are aligned on the front face 6 of the box 8 in a general direction Y.
• the box has an upper face 10 and a lower face 12 parallel to each other and each perpendicular to the direction Y.
• the box also has a face rear 7 parallel to the front face and two lateral faces 14.
• the speakers are of the Odyssey 1 type with foam suspension.
• the dimensions of the box 8 in the example studied are as follows: height 250 mm (between upper face 10 and lower face 12); width 43 mm (between side faces 14); depth 55 mm (between front face 6 and rear face 7).
• the enclosure 2 also includes a vent 16 consisting of a rectangular opening 18 in the front face 6 as well as an upper plate 20 and a lower plate 22 parallel to the upper 10 and lower faces 12.
• the opening 18 n ' is not necessarily rectangular; it could alternatively be oblong.
• the lower 22 and upper 20 plates do not extend over the entire depth of the box 8 (that is to say that their surface is less than that of the lower 12 and upper 10 faces). In the example, they extend over 40 mm.
• the plates can have different lengths from one another. They are not necessarily rectangular or perfectly flat.
• the bottom plates
• the lower 22 and upper 20 are spaced 5 mm apart and thus define between them a vent volume which opens on the one hand to the outside of the box 8 through the opening 18 and on the other hand to the inside of the caisson.
• the lower 22 and upper 20 plates extend over the entire width of the front face so that the vent volume is also delimited by the lateral faces 14.
• Such an assembly constitutes a bass-reflex enclosure 2 having a resonance frequency F 0 of 155 Hz.
• the lower 22 and upper 20 plates each have a rigidity less than the walls of the box 8. In the example studied, the plates
• PS - Hl impact polystyrene
• These plates 20, 22 behave like flexible vibrating plates and are designed so that their mechanical resonance frequency F M is close to the resonance frequency F 0 of the bass-reflex enclosure 2.
• the plates 20, 22 have a mechanical resonance frequency F M of 153 Hz.
• D is the stiffness factor of the plate defined as follows
• the plates 20, 22 achieve an attenuation and limit the influence of the vent around the resonance frequency of the bass -reflex F 0 , without changing its value, by partially absorbing vibrations whose frequency is close to the mechanical resonance frequency F M.
• the bass-reflex 2 speaker therefore has an acoustic response (bold solid line) improved at low frequency compared to a ventless box (dotted line), without however presenting the peak of resonance too sharp a classic bass-reflex enclosure (thin solid line).
• only one of the plates can be produced with a rigidity lower than the walls of the box 8, the other plate being for example produced in an identical manner to the walls of the box.
• the dimensioning of the lower rigidity plate will then be designed so that the vent constitutes a mechanical system having a mechanical resonance frequency F M close to the resonance frequency of the bass reflex F 0 and thus achieves a means of attenuation around the resonance frequency of the bass reflex, and therefore in particular the resonance frequency of the bass reflex.
• the mechanical resonant frequency is very close to (substantially equal to) the resonant frequency of the bass reflex. It is important to note, however, that the invention is not limited to this specific case but consists in providing attenuation means which notably cover the resonance frequency of the bass-reflex.
• the cut-off frequency at -3 dB can be considered as close to the resonant frequency.

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• Health & Medical Sciences (AREA)
• Otolaryngology (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Details Of Audible-Bandwidth Transducers (AREA)
• Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2001
  • 2001-01-24 FR FR0100906A patent/FR2819974A1/fr active Pending
• 2002
  • 2002-01-21 EP EP02700340A patent/EP1368987B1/de not_active Expired - Lifetime
  • 2002-01-21 ES ES02700340T patent/ES2254640T3/es not_active Expired - Lifetime
  • 2002-01-21 DE DE60208000T patent/DE60208000T2/de not_active Expired - Lifetime
  • 2002-01-21 US US10/470,146 patent/US7111706B2/en not_active Expired - Lifetime
  • 2002-01-21 WO PCT/FR2002/000223 patent/WO2002060217A1/fr active IP Right Grant
  • 2002-01-21 CN CNB028040333A patent/CN100518383C/zh not_active Expired - Lifetime
  • 2002-01-21 JP JP2002560422A patent/JP3965120B2/ja not_active Expired - Lifetime

Non-Patent Citations (1)

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