GB2617375A

GB2617375A - Super tweeter

Info

Publication number: GB2617375A
Application number: GB2205066.0A
Authority: GB
Inventors: Geoffrey Leonard Mills Paul; Michael Sosna Andrzej
Original assignee: Fyne Audio Systems & Tech Ltd
Current assignee: Fyne Audio Systems & Tech Ltd
Priority date: 2022-04-06
Filing date: 2022-04-06
Publication date: 2023-10-11
Anticipated expiration: 2042-04-06
Also published as: GB202205066D0; GB2617375B

Abstract

The super tweeter comprises a dome radiating electromagnetic transducer 13 configured to emit sound energy in a predetermined vertical direction, and an acoustic diffuser or reflector 18 located in the path of the emitted sound energy and shaped to redirect the sound energy omnidirectionally in a horizontal plane generally normal to said predetermined direction. The super tweeter is to be used in conjunction with a main loudspeaker (fig 1), located on top of the cabinet or enclosure of the main loudspeaker and set back so as to be located above the acoustic source of the main loudspeaker. The profile of the diffuser is preferably a Tractrix.

Description

SUPER TWEETER

Field of the invention

The present invention relates to high fidelity loudspeaker system and to an ultra-high frequency loudspeaker, also referred to as a super tweeter, for generating sound energy at frequencies above those normally audible to the human ear.

Background of the invention

Musical instruments produce energy well above the generally considered limit of human hearing (about 20 KHz) . Research has shown that humans are capable of responding to this sound energy, justifying the addition of a super tweeter where wide bandwidth sources are used. Even with conventional CD sources, the addition of a super tweeter, generating sound above 20 KHz and up to 50 KHz, has been found to reduce phase en-or and improve transient performance significantly below 20kHz. This leads to increased tonal accuracy at all frequencies, as the harmonics of instruments are not distorted in time. This benefits any high quality loudspeaker, but especially a point source device, such as the Fyne Audio IsoFlareTM driver.

Over recent years, super tweeters have become available from various manufacturers that are designed to sit on top of the cabinet of a main loudspeaker (producing audible sound) and to radiate energy directionally towards the listener, from a radiating dome, a ribbon transducer or a similar device

Summary of the invention

With a view to achieving further improved performance, there is provided in accordance with a first aspect of the invention a loudspeaker system comprising a main loudspeaker for generating directional sound energy at frequencies that are humanly audible to be directed towards a listener and a super tweeter for generating sound energy at higher frequencies that are not humanly audible, wherein the super tweeter is omnidirectional, being configured to emit sound energy substantially uniformly in all azimuth angles. -2 -

The invention is predicated on the realisation that the relationship in amplitude of a fundamental frequency and its harmonics needs to be preserved accurately both on-axis and at points off-axis. In a normal room, most of the sound perceived by the human ear is derived from reflections generated by the off-axis response of the speaker. The even off-axis response of a point source main loudspeaker means that the reflected energy has the same harmonic structure as the direct on-axis energy, so enhancement by means of a super tweeter is best achieved by an omnidirectional device, rather than a forward facing one, that beams energy directly at the listener.

fo While, in order to provide time alignment, the super tweeter should ideally be located on top of the main loudspeaker at the acoustic source of the transducer that it is designed to enhance, electrical methods may alternatively be used to allow other positioning of the super tweeter.

In accordance with a second aspect, the present invention provides a super tweeter for use in conjunction with a main loudspeaker of a high fidelity loudspeaker system, the super tweeter comprising a dome radiating electromagnetic transducer configured to emit sound energy in a predetermined direction, and an acoustic diffuser located in the path of the emitted sound energy and shaped to redirect the sound energy omnidirectionally in a plane generally normal to said predetermined direction.

In practice, the electromagnetic transducer rests horizontally, preferably directly above the acoustic centre of the main loudspeaker, and emits sound energy vertically. The diffuser then reflects the sound energy to cause it to be emitted substantially omnidirectionally in a generally horizontal plane The diffuser may conveniently be a conically tapering body supported at a predetermined distance from the electromagnetic transducer, with the narrower end of the body nearer the electromagnetic transducer.

The acoustic diffuser may be supported by any suitable means, such as support legs or members, that allow substantially unimpeded acoustic radiation through 360° In some embodiments, the profile of the conically tapering diffuser is a Tractrix.

A Tractrix profile is known to maintain a 900 angle at each intersection of the expanding wavefront -3 -The super tweeter itself may be mounted in any suitable enclosure for practical and aesthetic reasons.

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a schematic representation of a super tweeter of the invention located on the cabinet of a main loudspeaker of which only the upper part is shown in the drawing, and Figure 2 is a section of the super tweeter of Figure 1 drawn to an enlarged scale.

Detailed description of the drawinos

Figure 1 shows a super tweeter 10 mounted on top of a cabinet 11 of a main loudspeaker that comprises a point source transducer 12 covering the accepted range of human hearing. The super tweeter is ideally set back to coincide with the acoustic source of transducer 12.

The super tweeter 10, as shown more clearly in Figure 2, comprises an electromagnetic transducer that incorporates a face plate 13, a radiating dome 14, suspension system 15, a voice coil 16 and a motor system 17. This is an arrangement well known to the person skilled in the art, but embodiments of the invention may employ alternative constructions of dome radiating electromagnetic transducer.

It will be appreciated that to achieve a uniform acoustic output from 20kHz up to ultrasonic frequencies of 50IcHz and above, the dome material 14 needs to be of a high sonic velocity to avoid break up modes and loss of output.

In order to prevent the super tweeter from reproducing unwanted information at lower frequencies, high pass filtering may be required in the signal path. This may be in the form of analogue passive or active networks, or by means of digital signal processing Where, for practical reasons, it is not possible to locate the super tweeter at the acoustic centre of the main transducer and it is instead located too far forward, an electrical delay may be introduced in the signal path to achieve time alignment. This -4 -again may be in the form of analogue passive or active networks, or by means of digital signal processing.

A profiled acoustic diffuser 18 is supported at a predetermined distance from the transducer by any suitable means, such as support legs or members 19, that allow unimpeded acoustic radiation through 360° The plane acoustic wavefront generated by the dome 14 is translated into a spherical wavefront into the room, where it meets the diffuser 18 and is then reflected through substantially 900 to radiate horizontally in all directions In the illustrated example, the diffuser comprises a Tractrix profile. A Tractrix profile maintains a 90° angle at each intersection of the wavefront, as defined by the equation: --x y = a' -+ ln( ) Where:y= distance along axis a= exit radius x= radius at point y While a specific embodiment of the present invention has been described above, by way of example, it will be appreciated by the person skilled in the aet that various modifications may be made without departing from the scope of the invention as set out in the appended claims. For example, it is possible to use a diffuser with a profile that is other than a Tractrix.

Claims

-5 -CLAIMS 1. A loudspeaker system comprising a main loudspeaker for generating directional sound energy at frequencies that are humanly audible to be directed towards a listener and a super tweeter for generating sound energy at higher frequencies that are not humanly audible, wherein the super tweeter is omnidirectional, being configured to emit sound energy substantially uniformly in all azimuth angles 2. A loudspeaker system as claimed in Claim 1, wherein the transducer and the diffuser are mounted within an enclosure resting above a cabinet of the main loudspeaker.3. A loudspeaker system as claimed in claim 2, wherein the super tweeter located directly above the acoustic source of the main loudspeaker.4. A super tweeter for use in loudspeaker system as claimed in any preceding claim, the super tweeter comprising a dome radiating electromagnetic transducer configured to emit sound energy in a predetermined direction, and an acoustic diffuser located in the path of the emitted sound energy and shaped to redirect the sound energy omnidirectionally in a plane generally normal to said predetermined direction.5. A super tweeter as claimed in claim 4, wherein the diffuser is a conically tapering body supported at a predetermined distance from the electromagnetic transducer, with the narrower end of the body nearer the electromagnetic transducer.6 A super tweeter as claimed in claim 5, wherein the acoustic diffuser is supported by members that allow substantially unimpeded acoustic radiation through 360°.7. A super tweeter as claimed in claim 5 or 6, wherein the profile of the conically tapering diffuser is a Tractrix.