CN1108857A

CN1108857A - Loudspeakers

Info

Publication number: CN1108857A
Application number: CN 94115423
Authority: CN
Inventors: 格雷汉姆·怀特海德
Original assignee: British Broadcasting Corp
Current assignee: British Broadcasting Corp
Priority date: 1993-08-27
Filing date: 1994-08-18
Publication date: 1995-09-20
Also published as: GB9412099D0; GB2281469A; GB2281469B; TW231394B; GB9317850D0; JPH07154885A; EP0641142A1

Abstract

A loudspeaker assembly comprises a cabinet having top, bottom and side walls, a rear wall and a front baffle. A tweeter (10) and woofer (12) are mounted on the front baffle and connected to a crossover and filter unit. A flared vent pipe (64) is mounted in a port (62) in the rear wall extending into the cabinet. The vent pipe is coaxial with the tweeter and spaced from the tweeter such that the air gap (68) between the pipe and tweeter behaves as if it were a part of the vent pipe, increasing the acoustic length of the pipe, improving the low-frequency response of the assembly and reducing port noise.

Description

Loudspeakers

The present invention relates to loudspeaker, particularly relate to the ventilation sealing loudspeaker that ventilation duct is housed.

The sealing loudspeaker that ventilates is known.It is with loudspeaker sound panel sound insulation basically, takes place to interfere nocuously with acoustic energy by surface radiation before the loudspeaker to stop acoustic energy surface radiation behind the loudspeaker, particularly under the situation of low frequency.Except loudspeaker, sound panel also provides a kind of passive radiation surface.In airtight fully obturator many loudspeakers have been installed, this obturator attempt provides countless sound panels and limited volume of air is provided after loudspeaker.As basxs reflex or the known ventilation sealing loudspeaker of Helmholtz resonator, a port is housed in obturator.In conjunction with the size and the micropkonic resonance of obturator, select the size and the interval of port, to postpone the wavefront of loudspeaker back, make it and front wavefront recurring structure interference, widen and strengthen LF-response.

As everyone knows, would rather use a ventilation duct also not use a simple ventilation hole to increase LF-response.The ventilation duct that extends in the obturator act as an inductance coil, and it has the inductance more much bigger than the ventilation orifice of same diameter.This situation can make the volume of obturator or casing reduce, and keeps LF-response simultaneously.

When the loudspeaker casing with good LF-response was key subjects, concerning high fidelity industry, the size that reduces casing was a particular importance.As most of loudspeaker that uses in home environment, when buying loudspeaker, the size of casing is important consideration usually.

So, need to produce a kind of loudspeaker that has little casing and don't sacrifice LF-response.

We understand that the performance that a kind of in some cases ventilation duct shows is just as longer than its actual physics length.The present invention is based on above-mentioned understanding and it is incorporated in the loudspeaker.

Loudspeaker assembly of the present invention, comprise a tweeter and a woofer of being installed in the ventilation casing, and a port in the casing extends into a ventilation duct of casing, with respect to the back of tweeter this ventilation duct is installed, is made effective acoustic length of ventilation duct greater than its physical length.

Implementing the advantage that loudspeaker of the present invention has is, can getable LF-response to given casing size, and be the LF-response that can only just can obtain from bigger casing size so far.

Secondly, the present invention provides a kind of grid for high frequency loudspeaker or tweeter.We understand that such grid has played the physical function of protection tweeter, and have worked the acoustic function that spreads high-frequency sound and improved the purpose that acoustics distributes to reach.

Now, most preferred embodiment of the present invention is described with reference to the accompanying drawings, wherein

Fig. 1 implements micropkonic sectional view of the present invention;

Fig. 2 is the sound panel assembly of Fig. 1 and the sectional view of casing;

Fig. 3 is the rear board sectional view of Fig. 1 when ventilation duct being housed in position;

Fig. 4 is the front view of rear panel outer surface;

Fig. 5 is the front view of preceding sound panel;

Fig. 6 is the front view of first kind of tweeter grid;

Fig. 6 a is the front view of second kind of best tweeter grid;

Fig. 7 is illustrated in the connector on the rear board of Fig. 4; And

Fig. 8 a and 8b are respectively high and low frequency cross-over connection element circuit figure.

The loudspeaker assembly of Fig. 1 is one, and a high frequency loudspeaker is housed is tweeter 10 and the Helmholtz's bass-reflection resonator that the low frequency loudspeaker is a woofer 12.Tweeter and woofer can be commercially available standard cells, for example by the DYN AUDIO 260 and the 15W75-08 type of Denmark Dynaudio A/S manufacturing.Tweeter 10 and bass are raised device 12, are installed in to represent among Fig. 5 on the more clearly preceding sound panel 14.Protect tweeter by a grid 16, as Fig. 6 finding, this grid 16 is equipped with a solid annular external component 15 and the dome-type middle body 17 of many apertures is arranged.In Fig. 6 a, represented second kind of best tweeter grid.It is circular that the edge in middle body hole is done.Grid 16 protection tweeters exempt from the infringement of contingent, and the high-frequency sound that tweeter is sent is to outdiffusion.When the wavelength of sound of the radiation ratio for the diameter of tweeter, the low-frequency sound contrast that is produced with woofer 12 is for low the time, and tweeter produces very directed radiation mode.Grid 16 produces the acoustic pattern of diffusion more.

18 lanes, edge of preceding sound panel 14 are circular, to reduce by the caused diffraction effect in sharp-pointed edge.Although can only see top and bottom portion edge in the drawings, but that the edge of side is similarly done is circular.

By couple of conductor 20,22, each of tweeter 10 and woofer 12 is connected on cross-over connection and the filter cell 24.In Fig. 8 a, illustrate cross-over connection and filter high frequency unit and for tweeter 10, it is equipped with positive and negative input 26,28 and output 30,32.The the 1st, the 2 and the 3rd capacitor C1, C2 and C3 in series has been installed on positive conductor.Typical capacitor is C1:2.2 μ f; C2:8.2 μ f and C3:2.2 μ f.Between the positive and negative lead, an inductance coil L1 has been installed, it has typical inductance L 1=250 μ H.Be installed in parallel the 1st resistance R 1=10 Ω with capacitor C3, and on the output cross-over connection positive and negative lead of R1/C3, the 2nd resistance R 2=10 Ω be installed.The resistance of R2 depends on that balance and its representative value between woofer and the tweeter is between 8 Ω and 18 Ω.

Low frequency cell is equipped with one the 2nd inductance coil L2, and it is installed between input 34 on the positive conductor and the output 36 on the position in parallel with the 3rd resistor R 3.Inductance coil L2 has typical inductance value 2.7mH, and resistor R 3 has resistance 12 Ω.2.2 the capacitor C3 of μ f is connected across to the output of woofer 12.Cross-over connection and filter cell are the conventional parts of the present invention that do not constitute.On the outside of cabinet rear panel 40, the input of two unit has been installed, with short swing link 42 anode is connected to anode, negative terminal is connected to negative terminal.

Inside, top 43, side (not shown) and the ends 44 at casing serve as a contrast with three layers of silencing pad 46.In noise reduction bed course the inside one deck acoustic foam 48 is housed, and between woofer 12 and tweeter 10, thereby second layer sculpture foam 50 is housed defines two

chambers

52,54, and it sees the most clearly by Fig. 2.

Rear board 40 on the surface, is equipped with two-layer silencing pad 58 within it, and with the gummed location and installation on afterframe assembly 60, see the most clearly from Fig. 2.Rear board has the port 62 of the garden shape opening of the approximate 60mm of a diameter.With the open ventilation duct 64 in end, be contained in the port, extend internally as shown in the figure.Ventilation duct is cylindrical tube normally, opens in its outer end, and a series of fin 66 is arranged on the outer surface of its outer end.When the location, fill suitable inertia filter in the space between fin, for example ISOPONP38.

Ventilation duct itself is known, and available as parts NO:ARG255019 by Dynaudio A/S.Ventilation duct prolongs its length and is tapered and opens in the outer end, and has typical length 145mm and diameter 60mm.Illustrated casing has the external dimensions of approximate 300 * 200 * 180mm, is significantly less than the casing external dimensions for ventilation duct.

For the quality of loudspeaker assembly performance, the arrangement of ventilation duct is very crucial.Ventilation duct is as one " inductance ", be tuned to and the casing that driven of woofer diaphragm in air " electric capacity " resonate.The acoustic length of ventilation duct is taken as actual length of tube usually and adds a correction that is proportional to the radius of pipe at every end.

Usually,, wish to use ventilation duct a kind of length or narrow, with the high inductance that obtains and the generation of low casing electric capacity is resonated for the casing ventilation that makes such size is low frequency.This ventilation duct has high impedance for air stream, and will be easy to generation sound under high-power and disturb effect.Embodiment for so large diameter ventilation duct of casing size use can produce less undesirable effect.

As shown in Figure 1, ventilation duct 64 and tweeter 10 are coaxial, and the Air Coupling make between tweeter and tube end are installed to pipe with respect to tweeter.Pipe is had resemble it on sound performance is the effect of longer pipe.

The increase of the effective length of pipe is because due to the aerodynamic effects between pipe and tweeter body.Reorientate ventilation duct, depart from or misaligned, do not produce extra effectively port length with tweeter.The relative spacing of the back of ventilation duct and tweeter body is such, makes when tweeter is crossed in circulation of air the end of air flow line ground turnover ventilation duct.In an illustrated embodiment, the volume of air between the physics end of tweeter and ventilation duct is identical with the normal end correction volume of being done approx.The end that is added to actual ventilation duct length is revised, and not only resembles the volume of air part that has prolonged the normal conditions around the ventilation duct end, but also has prolonged the volume of air part around tweeter body back.In this way, the end that is added to ventilation duct the inner is revised, and approximately is the twice with the added correction of other method.

The natural effect of linearisation air stream is further to reduce near the sound of ventilation duct inner end to disturb noise.

Be appreciated that this size and be experience at interval.Yet, given tweeter and ventilation duct can be mounted to like this, make ventilation duct have a effective length, and increased the LF-response of this assembly, and do not increase the adverse effect that sound is disturbed noise greater than its physical length.

" part pipe resonance " or standing wave also may take place and suffer damage in a long ventilation duct in a ventilation casing in tube length.Noise elimination sculpture foam 50 is installed in casing, can be made and before they reach ventilation duct, be decayed the frequency that can excite these wave modes.Make the thickness and the density of foam not influence low helmholtz frequency.

Claims

1, a kind of loudspeaker assembly, comprise a tweeter and a woofer of being installed in the ventilation casing, and a port in the casing extends into a ventilation duct of casing, with respect to the back of tweeter this ventilation duct is installed, is made effective acoustic length of ventilation duct greater than its physical length.

2, according to the described loudspeaker assembly of claim 1, wherein ventilation duct and tweeter are in line.

3, according to the described loudspeaker assembly of claim 1, wherein ventilation duct is coaxial with tweeter.

4, according to claim 1,2 or 3 described loudspeaker assemblies, wherein the distance between the back of the inner terminal of ventilation duct and tweeter is the sub-fraction of ventilation duct diameter.

5, according to each the described loudspeaker assembly in the claim 1 to 4, the area of section of ventilation duct inner terminal wherein, approximate is half of area of section of tweeter back.

6, according to the described loudspeaker assembly of each aforementioned claim, wherein port is in the face of the casing back that faces toward tweeter.

7,, a grid that many apertures are arranged is housed on the front of tweeter wherein according to the described loudspeaker assembly of each aforementioned claim.

8, according to the described loudspeaker assembly of claim 6, wherein grid comprises that a solid outer shroud and one have the dome-type middle body of many apertures.

9,, acoustic foam wherein is installed in casing to reduce the standing wave in ventilation duct according to the described loudspeaker assembly of each aforementioned claim.