GB2082418A

GB2082418A - Multi-way loudspeaker system

Info

Publication number: GB2082418A
Application number: GB8113871A
Authority: GB
Original assignee: ROLA CELESTION Ltd
Current assignee: ROLA CELESTION Ltd
Priority date: 1980-08-15
Filing date: 1981-05-06
Publication date: 1982-03-03
Also published as: EP0046388A1

Abstract

A multi-way loudspeaker system comprising a plurality of electro-acoustic transducers (A, B, C,) wherein any one or more of the said transducers (A) is arranged in such a way that it operates over two separate frequency bands, and wherein an active transducer (B) is arranged to operate at frequencies between the said two separate bands. Preferably, the attenuation between the two separate bands is at least 20 dB. With a three transducer system this creates three crossover frequencies. <IMAGE>

Description

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GB2 082 418A

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SPECIFICATION

Multi-way loudspeaker system

5 DESCRIPTION

* This invention relates to multi-way loudspeaker systems, i.e. systems comprising a

* plurality of electro-acoustic transducers mounted within an enclosure and connected

10 through a dividing filter network or networks to an audio amplifier output as a source of electrical signals.

Various types of multi-way loudspeaker systems are known. Two conventional arrange-15 ments are schematically illustrated in Figs. 1 and 2, each in conjunction with a graphical illustration of the typical sound pressure level frequency response obtainable with such an arrangement. The sound pressure level re-20 sponse of the individual drivers is shown in broken lines, and the sound pressure level response of the combined system is shown by a solid line.

Fig. 1 shows a cabinet 10 fitted with a 25 conventional 3-way system comprising a bass driver unit A, a mid-range unit B, and a treble unit C. Each of these separately enclosed speaker units is an active unit, i.e. it receives its energising power via an electrical connec-30 tion by way of a crossover or dividing filter network 12. This results in the type of sound pressure level frequency response shown in the diagram, with each of the driver units operating within a single limited frequency 35 band, and with two crossover frequencies.

Fig. 2 shows an alternative known arrangement, i.e. a conventional passive radiator or ABR system. This comprises a passive radiator unit A, a bass/mid-range unit B, and a treble 40 unit C. In this arrangement speaker unit B is not separately enclosed within the cabinet and only speaker units B and C are connected electrically to the input source. The passive radiator, speaker unit A, is acting as an auxil-45 iary bass resonator and constituting a passive or "slave" speaker unit by virtue of the air coupling between speaker units A and B. The sound pressure level frequency response diagram indicates that a passive radiator system 50 is similar to the conventional 3-way system (Fig. 1) with each of the drivers operating within a single limited frequency band, and with two crossover frequencies. However, it * should be noted that for a given cabinet J55 volume a passive radiator system will exhibit low frequency extension and steeper cut-off rate at the low frequencies as compared to the conventional 3-way system.

It is an object of the present invention to 60 provide a multi-way loudspeaker system in which one or more of the transducers is arranged to operate in two separate frequency bands.

In accordance with the present invention 65 there is provided a multi-way loudspeaker system comprising a plurality of electro-acoustic transducers, wherein any one or more of the said transducers is arranged in such a way that it operates over two separate frequency 70 bands, and wherein an active transducer is arranged to operate at frequencies between the said two separate bands.

Preferably, the attenuation between the said two separate bands should be at least 20 dB. 75 There are various ways in which one can arrange for the, or each of the double-band transducers to function in this way. This is achieved primarily through the type of filter used in association with the transducers. In 80 one arrangement the filter network for the or each of the double-band transducers is an electrical filter for both frequency bands. In an alternative arrangement the filter network for the or each of the double-band transducers is 85 an electrical filter in respect of the upper frequency band and a predominantly acoustic/mechanical filter for the lower frequency band.

One embodiment of loudspeaker system in 90 accordance with the present invention will now be described by way of example and with reference to Figs. 3, 4 and 5 of the accompanying drawings.

In the drawings:

95 Figure 3 is a schematic representation of a cabinet housing three speaker units in accordance with the invention, together with a graphical representation of a typical sound pressure level frequency response which one 100 obtains with this arrangement;

Figure 4 shows a suitable filter network or crossover for use in this loudspeaker system; and.

Figure 5 shows the voltage frequency re-105 sponse across the individual drive units A, B and C of the filter network shown in Fig. 4.

Referring first to Fig. 3, this shows a multi-way loudspeaker system comprising three drive units A, B and C. Drive unit B is a mid-110 range unit and drive unit C is a treble unit. It is to be noted that, in contrast to the arrangement of Fig. 1, the mid-range unit B is not a separately enclosed unit within the cabinet, and in contrast to Fig. 2 all three drive units 115 are active units. Each of the three drive units A, B and C is connected to a filter or crossover 12. With this arrangement of the speaker units and with an appropriate filter network one can achieve the type of sound pressure 120 level frequency response shown in Fig. 3.

It will be immediately apparent that the sound pressure level frequency response produced by this arrangement differs from those shown in Figs. 1 and 2 in that it is divided 125 into four bands instead of three. The four individual bands are denoted by letters which refer to the speaker units which correspond to them. In other words, speaker unit A operates not only in a band at the lowest frequencies, 130 but also in a separate band within the middle

Claims

2 GB2082418A 2 range. The attenuation between the two bands in which speaker unit A operates should preferably be at least 20 dB, and in practice ought to be somewhat more. This 5 frequency band is filled in by the speaker unit B, which is always an active unit. In contrast to Figs. 1 and 2, this system will have three crossover frequencies, all of which can be adjusted to the desired frequencies by the 10 choice of filter network components and of the acoustic and electrical parameters of the drive units. One appropriate form of filter network, or crossover, is shown in Fig. 4. This shows the 15 connection of the three speaker units A, B, C to the signal source, i.e. to the audio amplifier, via six elements consisting of capacitors C1, C2 and C3 and inductors L1, L2 and L3. Inductors L1 and L2 and capacitor C1 are 20 associated with speaker units A and B, while capacitors C2 and C3 together with inductor L3 are associated with the treble unit C. These two sections are connected in parallel to form the complete filter network. Fig. 5 shows the 25 resulting voltage response as a function of frequency across the individual speaker units. In operation at the lowest frequency band, capacitor C1 blocks the electrical signals which would pass to speaker unit A, thus 30 leaving speaker unit A free to resonate as an auxiliary bass radiator (ABR) by virtue of the air coupling within the cabinet to speaker unit B. Within the next higher frequency band, speaker unit B acts as a normal bass unit and 35 rolls off due to the feeding low pass filter L1, L2, C1. In the next higher frequency band, i.e. the third frequency band shown in Fig. 3, while speaker unit B rolls off, speaker unit A comes back into operation as an active trans-40 ducer by virtue of the band-pass filter L1, C1 and the voice coil inductance of the driver. Finally, at the highest frequency band, as speaker unit A rolls off, the table unit C is brought into operation via its high pass filter 45 C2, C3, L3. Although the embodiment of loudspeaker system described above has just three speaker units A, B and C, the invention is not limited to this number of transducers and is equally 50 applicable to multi-way systems having a larger number of transducers. Moreover, it need not necessarily be the bass unit which is arranged to operate over two separate frequency bands. One could for example arrange 55 for a mid-range unit to operate in this way with appropriate infilling by another active mid-range unit. One could also have more than one transducer arranged to operate in this way over two separate frequency bands 60 within a total multi-way system. Regardless of how one arranges the individual drivers, with the present invention one always has one or more of the transducers arranged to operate over two separate frequency bands with an 65 active transducer operating to cover frequencies between the said two separate bands. CLAIMS

1. A multi-way loudspeaker system comprising a plurality of electro-acoustic transducers, wherein any one or more of the said ? transducers is arranged in such a way that it operates over two separate frequency bands, * and wherein an active transducer is arranged . to operate at frequencies between the said two separate bands.

2. A loudspeaker system as claimed in claim 1, wherein the attentuation between the said two separate bands is at least 20 dB.

3. A loudspeaker system as claimed in claim 1 or 2, comprising three transducers,

each of which is an active transducer, with a first transducer which operates over the lowest frequency band also operating over a second frequency band which is higher than an intermediate frequency band in which a second of said transducers operates, thereby creating three crossover frequencies.

4. A loudspeaker system as claimed in claim 3, in which the transducers are mounted within an enclosure but only the transducer operating over the highest frequency range is separately enclosed within the enclosure.

5. A loudspeaker system as claimed in any preceding claim, which includes one or more filter networks through which the transducers are connected to a source of electrical signals, the filter network for the or each of the double-band transducers being an electrical filter for both frequency bands.

6. A loudspeaker system as claimed in any of claims 1 to 4, which includes one or more filter networks through which the transducers are connected to a source of electrical signals, the filter network for the or each of the double-band transducers being an electrical filter in respect of the higher of the two frequency bands and a predominantly acoustic/mechanical filter in respect of the lower of the two frequency bands.

7. A loudspeaker system as claimed in claim 3 or 4, in which the transducers are connected by way of filter means to a source of electrical signals, the filter means comprising two filter sections connected in parallel, the first filter section being associated with the two lower frequency transducers and the second section being associated with the high-5 est frequency transducer.

8. A loudspeaker system as claimed in claim 7, in which the first filter section blocks ? low frequency signals to said first transducer operating over the lowest frequency band whereby this transducer resonates as an auxiliary bass radiator, acts as a low pass filter to said second transducer, and acts as a band pass filter to said first transducer over the higher frequency bband in which said first transducer is also operative.

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9. A multi-way loudspeaker system substantially as hereinbefore described with reference to Figs. 3 to 5 of the accompanying drawings.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd.—1982.

Published at The Patent. Office, 25 Southampton Buildings,

London, WC2A 1AY, from which copies may be obtained.