GB2435207A

GB2435207A - Vibration absorbing support feet

Info

Publication number: GB2435207A
Application number: GB0611196A
Authority: GB
Inventors: John Kalli
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-02-15
Filing date: 2006-06-07
Publication date: 2007-08-22
Also published as: GB2435206A; GB0602998D0; GB0611196D0

Abstract

A vibration absorbing foot for electrical equipment and electrical equipment stands, such as loudspeaker cabinets and stands, comprises two distinct parts: a first upper resilient damping element 16 and a second lower structural foot element 17. The cylindrically shaped resilient upper part 16 is preferably made from a relatively soft rubber whilst the conical or hemispherical lower part 17 is made from metal or relatively hard rubber. The feet are height adjustable allowing for easy set-up and levelling. Each foot may be attached to a supported item, e.g. a speaker cabinet, by an adhesive tape 20 or by a threaded bolt 14. The materials of the upper and lower parts can be matched to the desired application, e.g. speaker requirements, support surfaces, room environments. Three feet may be used together to provide stable support and suppress speaker cabinet vibration. The feet may take various forms.

Description

I

A Patent Specification

Loudspeaker feet and loudspeaker support equipment feet This invention relates to feet that provide stability and suppress speaker cabinet vibration for improved sound reproduction. Also this invention provides ease in use for levelling and positioning a speaker without fixing to the supporting surface and with less need to re-level should they be relocated, and are simple to fit and suitable for any surface.

Back2round There are three principle sources of vibration and noise energy that degrade the speakers' performance. The first is the vibration from the operation of the speaker itself, such as the action of the driver's diaphragm and the drivers frame, that cause mechanical vibration of the cabinet and its contents. These vibrations affect both the original audio source mechanism and the electrical circuitry, both of which result in a loss of quality to the reproduced sound. Also the connecting feet and supports also form pathways for vibration energy to the support structure and affect the amount of energy that remains in the speaker. Second is caused by the audio energy from the speaker causing vibration of the room environment that will enter the speaker body via its supports. The third is room, furniture or external noise in the environment, such as footfall, that enter the speaker body via its supports.

The performance of a speaker is compromised by its support arrangement, one part of the support arrangement is the type of support feet. There are known steel spike and cone speaker feet manufactured with various profiles and sizes. These, however, offer a poor barrier to noise and vibration. Such spikes and cone feet are of rigid construction with a honed point to minimise the contact surface for isolation; however, they offer no additional damping other than that provided by the body of the spike or cone. Such spike and cone feet rely upon penetration of the floor or furniture surfaces to effect stability seen in Figures 1 and 2, thereby forming a rigid structure with no brake or discontinuity to the vibration and noise energy that are able to propagate feely. In a trial (reference -Articles on vibration by Keith Howard in the July and August 2002 issues of Hi Fi News), measurements of vibration energy of a speaker stand, when playing a speaker fitted with cones, produced vibration in the stand of over one hundred times greater than if the cones were replaced with small rubber feet. The aim of the proposed speaker feet is to attenuate noise and vibration energy to and from the speaker and the support structure.

The practicalities of speaker set-up with spike and cone feet require the user to lift the whole speaker and force the tips of the feet into the support surface. This however may leave some feet unattached to the support or an uneven degree of fixing between the feet and support. Also required for set-up of the speaker with spikes and cones is levelling, being rigid structures, however, the support height is critical to stability; too tall and the speaker raises against some or all the other feet producing gaps, or too short and gaps appear. In practice they are difficult to use and rely on the tips penetrating the contact surface to affect stability and if the floor or surface is impenetrable the speaker will remain unstable. Also there are dimpled discs to sit under the spikes/cones and protect the finished surfaces; these however, are without improvements to stability or little additional isolation. Under dynamic operating conditions, microscopic rocking will occur and reduce the speaker's performance. The aim of the speaker feet is to provide stability, with the weight equally distributed on each foot and without any gaps between the feet and support structure.

The second part of the support arrangement to affect performance of a speaker is the room and furniture support itself. First, there is the type of support surface that affects the degree of coupling with the foot; this in turn affects the interface and degree of vibration energy transmitted to and from the speaker. It follows that the nature of the support surface, such as compliance, hardness, and surface friction will change the interface or couple and change the spectrum and level of noise transfer to the foot and in turn to the operating speaker. Floor and furniture surfaces include timber, laminates, timber with veneers, composite woods (such as fibrous boards), linoleum, ceramic tiles, and woven products such as carpets, mats and foam underlay. The aim of the speaker feet is to provide an optimum couple or interface with the support surface to maximise the transfer of noise energy to the surroundings and lower the level of external environment noise entering the support and the body of the speaker.

Together with the support surface, there is the effect of the support structure and its interaction with the vibration energy from the speaker. It follows that the performance of the speaker is affected by the support structure. The structure may be constructed in a variety of types, such as a timber joists and floorboards, reinforced concrete floor, and metal frames, and with a variety of fabrication materials used in its construction. Finally the size of the support structure, its dimensions, volume and slenderness etc. all change the degree of vibration energy transmitted to and from the speaker.

For example two identical sized rooms with a carpet floor finish, one having a timber floor the other a concrete slab; both will have a particular sonic register for the same speaker and support arrangement. Also it may not be possible to form holes or anchors into floors or furniture and it may be necessary to protect their finishes. The aim of the speaker feet is to provide an optimum couple with the support structure, such that the support structure may contribute to, and attenuate noise energy from the speaker. Also the speaker feet need to be used without fixings or anchors to the structure and be easy to install on any surface without damaging them.

Finally the type of foot support depends upon the requirements of the speaker itselfi Individual speakers may weigh anything from a few hundred grams up to 100kg or more each, be of any shape, size and have a centre of gravity that exerts uneven pressure. Also speakers are manufactured to different specifications and produce sound waves by diverse means such as dynamic cones, electrostatic, horn, planer-magnetic, and sub-woofer speaker. Consequently, each speaker will operate having a cabinet response of a specific dominant range of fundamental peaks and resonant frequencies and will to a greater or less degree "colour" and reduce the clarity of reproduced sound.

The aim of the speaker feet is to provide a stable support for all speaker type, size and shape and to minimise cabinet vibration and be easily fitted.

Some speakers project sound waves in a primary direction whilst others radiate the sound in all directions; both however require their cabinets to be angled or levelled to balance the sound to a particular room by means of adjustable feet height. The aim of the speaker feet is to have adjustable height for ease of set-up and performance.

Vibration isolation of a mass and forces transmitted to supports are described by Fl Fahy and JG Walker in Fundamentals of Noise & Vibration, 1998, Chapter 5 as follows; a vibration isolation system model is represented by a concentrated mass mounted on a linear elastic spring or vibration isolator and the compliance of a support structure modelled by a second mass-spring system. The effectiveness of the isolator is greatly reduced at frequencies close to the foundation resonance. The foundation response is proportional to the stifThess of the isolator spring, which therefore must be sufficiently low to compensate for the effect of foundation resonance. Further, reference to FJ Fahy and JG Walker, detail that resilient elements exhibit modes and resonances like every other structure, but well below their fundamental frequencies it is reasonable to model them as lumped, massless elements consisting of a combination of an elastic spring and a viscous dashpot. Also analysis of a high frequency vibration isolator model under dynamic load demonstrates that low damping is beneficial, however, in practice sufficient damping is necessary at high frequencies to suppress the adverse effects of standing wave resonances within the isolator element; a compromise is necessary. What is more for the high frequency mobility isolator model the analysis demonstrates that, to be effective, the differential mobility of the isolator must greatly exceed the mobilities of both the source and the receiver.

Also N. ,Jalili and E. Esmailzadeh, reference Adaptive-passive structural vibration attenuation using distributed absorbers (Proceedings of the institution of Mechanical Engineers, Part K: ,Journal of Multibody Dynamics 7SSN. 1464-4193 issue: Volume 216, Number 3/2002 Pages: 223-235) published in 2002) demonstrate the use of a doubled-ended cantilever beam to act as the absorber subsection.

The invention detailed in this application is speaker feet formed of two distinct parts, see figures 7- 22; an upper resilient damping element (16) the lower a structural foot element (17). The resilient damping element (16) separates the rigid parts of the speaker and support structure for vibration isolation. The structural foot element (17) defines the contact surface area and in turn the degree of coupling of the foot structure to the support structure by its compliance, size and shape and surface friction. The structural foot element (17) also contributes to the feet damping and siifThess.

In addition to the vibration attenuation of the foot itself, there is a further mechanism that suppresses vibration that is the action of the coupled mass of the structure. An operating speaker, its feet and support structure are modelled in Figures 30 and 32 for the purpose of applying the above to demonstrate this mechanism for vibration attenuation.

Shown in Figure 29 is a floor-standing speaker and building structure, with Figure 30 the model described in the preceding paragraphs to represent the mechanism for vibration attenuation. The speaker (1) and invented feet (33) is the primary system, with a speaker mass Ms, and total feet dampening Cs, total feet stiffness Ks, and vibration disturbance of the loudspeaker F(t). The floor structure, is the secondary system, and represented by a beam of length L, of lumped mass in, at distance a, and spring/damper Cf and Kf. Here the feet elements (16) and (17) of the invented feet (33) are selected with damping and stiffness to optimise the vibration suppression of the system.

Figure 31 is the speaker, speaker stand and floor, and Figure 32 the model having three mass spring systems. The first is the speaker and support feet, the second the speaker stand (35) and support feet, and last represents the floor support (34). Here the feet elements (16) and (17) of the invented feet (33) are selected with damping and stiffliess to optimise the vibration suppression of the system.

Considerable vibration suppression is achieved by matching the damping element (16) and the structural foot element (17) to form an optimum absorber foot for the specified speaker requirements and support conditions i.e. the secondary system.

The invention detailed in this application, speaker feet shown in Figure 7 -28, are compliant and distribute the weight of the speaker evenly to all supports and improve stability and the performance of the speaker with the advantage of ease of use and less need to re-level should they be relocated.

The invented feet have a wider application to provide support to electronic equipment and support equipment for stability and suppression of vibration of both the on-board sources of noise such as electric fans, transformer hum, compact disc transports, electric motors etc. and isolation from external noise to enhance performance For example, in the case of a heavy speaker with vertical sides that tilt to the rear, shown in Figure 4; the centre of gravity will be off-centre causing a concentration of compressive forces on the rear set of feet and a stability problem. The invented feet have a structural foot element (17) with a contact profile shown in Figure 23 made of either wood or hard rubber to affect a degree of coupling, improve stability for the speaker and enable the user to move the speaker without lifling it or damage or the need to create holes to the fmish surfaces. A set of feet with hard rubber resilient damping element (16) at the rear feet and a medium hardness set at the front will improve stability of the speaker. Since the sections are interchangeable to suit the finish surface and speaker type the optimum solution will be subjective to the listener as much as to the other considerations and offers the user the ability to "fine-tune" or match the supports to suit their circumstances and changing requirements, for example set-up in a different room or moving home.

There are also known feet made of rubber or polymer formed in a hemisphere, Figure 3 shows these feet to support a floor-standing speaker. This illustrates stability requirements that compromise speaker performance with the weight distributed unevenly leaving the speaker out of alignment. For this speaker the feet will compress differently with the need for re-levelling.

When using a stand mount speaker and support, shown in Figure 1; typically such a speaker is of low weight and has a small footprint. These cannot rely upon their weight to affect stability and anchoring the feet may not be an option on furniture leaving them vulnerable to micro-movement and a reduction of sound reproduction. The invented feet, see figure 7, cross-section 15, have a structural foot element (17) with a contact profile shown on Figure 24 of medium hardness rubber to offer a degree of coupling and improved stability, without damage to the fmishes. Also, the resilient damping element (16) will be soft rubber to increase compliance and stability.

If a floor-standing speaker or speaker stand or sub-woofer is used in a room with heavy carpet and underlay, it is difficult to form a good fixing to the sub-structure introducing the possibility of an unstable speaker, particularly where the sub-structure is hard. Additionally, a fixing to the sub-structure will introduce increased levels of noise energy to the speaker; with spikes, for example, the user is required to lift the speaker to position or set-up. The invented feet, shown in figure 9 &l7, 14 & 22, have a structural foot (17) of a metal and conical shape that will substantially compress the floor coverings and form a contact profile as shown in figure 25 to provide coupling to the floor structure. The feet are stable and enable the user to slide the speaker without lifting it. Also the resilient damping element (16) is compliant and the speaker will require less re-levelling and set-up.

To obtain the best results, speakers need careful set-up and in room sound trials to find the best location in that particular room as shown in Figure 5. The ease of positioning and set-up is therefore critical with the least amount of physical lifting of the speaker and re-levelling plus the need to avoid damage to the finish floors that may otherwise be laborious, awkward and time consuming.

The invention detailed in this application is not directly secured to the finish surfaces and offers contact profiles that may be pushed across the surface without damaging them when re-locating the speaker and has compliance to accommodate uneven support surfaces and requires little or no re-levelling to secure stability.

Even a speaker manufactured with specific set-up guidelines such as the dynamic floor speaker shown in Figure 4 designed on time-alignment or phase alignment theory to project the sound waves in a coherent manner to form a "soundstage" or "sweet point" for the listener will require the face orientation to be adjusted for the listening position by control of the height of the supports. This speaker type is a three way type with drivers operating in fixed frequency ranges (e.g. high, middle and low driver units) such that the drivers are set back from the face of the speaker to form a coherent sound wave at listening distance to the user based upon assumptions of typical room sizes.

Subjective sound trials to position the speaker including the height of the feet are required to ensure the best sound performance, the invention detailed in this application enables the height to be adjusted for this purpose.

Also, speakers are directional depending to a greater or lesser degree upon the type of speaker and the design used, for example they may concentrate sound in a conical form like the light beam seen in Figure 6. A further requirement to adjust the feet height and playing angle depends upon the directional characteristics of the speaker, the users personal preferences, the main listening location and the effect of the rooms' acoustics to get the best performance from the speaker. This invention has height adjustment screws to control of the angle of the speakers vertical playing field and enable the user to set-up the speaker to its optimum performance.

This invention also has a choice of either connecting threaded rod (14) to fit directly to the speaker's nut fixings, or semi-permanent adhesive system (20) both of which are easy to install.

Another prior art support device couples the equipment to the support surface and has the principle interface at a treated ceramic ball between the metal structural base-plate and another detached upper plate. Its function is to transfer and control the resonance energy between the speaker and the supporting surface. There is no damping element and height adjustment.

A prior art technique (reference United States Patent No. 5,681,023 dated Oct. 28, 1997) describes support of the speaker on a floor with coverings, such as carpet using a metal pin to directly fix the speaker enclosure to the massive substructure of the support surface. Also there is a resilient damper element to achieve controlled additional damping in the critical bass frequencies.

Another prior art technique (reference United States Patent No. 4,880,077 dated Nov.14, 1989) details a foot support comprising of two disc shaped elements. The support disc is formed of sound-insulating material and arranged to form an inner hollow space, within which the structure-borne sound can die out freely.

The following patents are researched and found in the search -United States Patent No. US 2002/0 162937 Al dated Nov.7,2002 German Patent No. 2 259729 dated 7th June 1973 Spanish Patent No. 2 129 360 dated I June 1999 European Patent No. EP 1 347 198 Al dated 24th September 2003 United States Patent US 6,283,437 Bi dated Sep.4, 2001 United States Patent 6,155,530 dated Dec.5, 2000 United States Patent 5,942,735 dated Aug.24,1999

Statement of invention

The essential features of this invention are feet for all types of loudspeaker and loudspeaker furniture or support equipment that has: i) An optimum absorber loudspeaker foot used in sets of three or more to provide considerable vibration suppression and improvement of loudspeaker performance by matching both or either of the two principle parts, the upper resilient damping element (16) and the lower structural foot element (17), to the speaker type/requirements and support surface and structure requirements.

ii) A resilient damping element (16) of low damping, however with sufficient damping to suppress the adverse affects of standing waves resonances within the isolator element to reduce speaker cabinet excitation and enhance sound reproduction.

iii) A resilient damping element (16) with differential mobility far in excess of that of the loudspeaker cabinet and the support structure.

iv) Feet with stiffness sufficiently low not to cause resonance of the support structure and having a structural foot element (17) with a contact surface area to the support surface to form an optimum couple to that support structure whereby the mass of the structure contributes to the control of the vibration energy of the loudspeaker and offer isolation from the enviromnent.

v) A structural foot element (17) with damping and structural stitThess contribution to the foot.

vi) A structural foot element (17) with a conical or hemispherical shape.

vii) Overall compliance to distribute the speaker weight more evenly to each foot, improve stability and minimise the need for height adjustment when setting up or positioning the speaker.

viii) A resilient damping element (16) that is a solid cylinder rubber element which separate the rigid parts of the structure.

ix) Height adjustment screws to control of the angle of the speaker's vertical playing field and stability to allow the user to set- up the speaker to its optimum performance.

x) Connecting threaded rod to fit directly to the speaker's nut fixings, or adhesive fixing surfaces uppermost to fix directly to the body of the speaker.

Reference is made to item numbers 1 to 15, 17 to 20 and 28 of the Claim as essential features of the invention.

Advantages The advantaged offered by this invention are speaker feet and speaker furniture feet with: i) Flexibility to fme tune and match the feet to suit the system to optimise performance.

ii) The ability to be adapted to match changes of use or circumstances, such as moving equipment to different locations i.e. different support surfaces or when upgrading or changing equipment.

iii) Less of a requirement to manually lift the speaker as it has hemispherical and conical structural feet elements that are smoother and allow the speaker to slide when positioning and set-up.

iv) Compliance of the foot and smooth contact profile minimise damage to floor or furniture support surfaces.

Introduction to drawinis

Figure 1: Shows known spike and cone supports used with a speaker and speaker stand that with instability and isolation problems.

Figure 2: Is a section view of a spike foot forced through carpet and underlay and into the timber floor beneath that compromise isolation of the speaker.

Figure 3: Shows a known rubber hemisphere support with a floor standing speaker to illustrate the stability requirements that compromise the performance of the speaker.

Figure 4: Shows a floor standing speaker to illustrate the playing angle and its importance to produce time-alignment of the speaker and coherence of the sound received by the listener.

Figure 5: Shows how subjective auditioning is used to locate the speakers for the best sound for a type of speaker, the room acoustics and personnel preferences.

Figure 6: Illustrates how a speaker with strong directional characteristics will concentrate the sound in a conical beam, and how the playing angle is crucial for optimum sound balance for the user.

Figure 7: Shows an embodiment of this invention in perspective view with Figure 15 a cross-section view of the same.

Figure 8: Is an alternate embodiment of this invention in perspective view with Figure 16 a cross-section view of the same.

Figure 9: Is a further alternate embodiment of this invention in perspective view with Figure 17 a cross-section view of the same.

Figure 10: Is a further alternate embodiment of this invention in perspective view with Figure 18 a cross-section view of the same.

Figure 11: Is a further alternate embodiment of this invention in perspective view with Figure 19 a cross-section view of the same.

Figure 12: Is a further alternate embodiment of this invention in perspective view with Figure a cross-section view of the same.

Figure 13: Is a further alternate embodiment of this invention in perspective view with Figure 21 a cross-section view of the same.

Figure 14: Is a further alternate embodiment of this invention in perspective view with Figure 22 a cross-section view of the same.

Figure 23: Shows a contact profile of 2nun diameter formed by a structural foot element made of wood or a hard rubber on a hard floor surface.

Figure 24: Shows a contact profile of 4mm diameter formed by a structural foot element made of a soft or medium hardness rubber on a hard floor surface.

Figure 25: Shows a contact profile of 4mm diameter formed by a structural foot element made of metal on a heavily carpeted and underlay floor surface.

Figure 26: Are the type of resilient damping element to demonstrate the nature of the connecting arrangements.

Figure 27: Are the type of structural foot element to demonstrate the nature of the connecting arrangements.

Figure 28: Shows the type of structural foot element shapes.

Figure 29: Is a cross section of a floor-standing speaker and building structure, with Figure 30 the model to represent the mechanism for suppressing vibration.

Figure 31: Is a cross section of a speaker/speaker stand and building structure, with Figure 32 the model to represent the mechanism for suppressing vibration.

Description of drawings

Figure 1 Shows spike and cone feet (3,4) used with a speaker/speaker stand (1,2) to illustrate instability problems and require precise adjustment of their heights leading to micro-movement.

They also rely on penetration of the surface to affect stability and such a direct fixing to the stand is seen to increase vibration and noise energy. The height of the foot is critical; any shorter than the distance between the speaker and the support surface or if larger will result in unequal distributed pressure between the feet and instability will allow movement such as rocking when the speaker operates with increase in noise and vibration and a lose in accuracy of the speaker.

Fi2ure 2 is a cross-section of a spiked foot (3), shown forced through the floor coverings of carpet and underlay (5) and into the timber floorboards (6) below to secure stability of the speaker (1). A rigid link will couple the speaker to the floor and introduce noise and vibration energy into the speaker system, a deteriorative effect to sound reproduction.

Fi!ure 3 Shows another type of known speaker foot made from a rubber material in a hemisphere shape (7) supporting a floor standing speaker (1) with a body shape that slants at the back and with weight greater at the back feet causing the supports to deform and illustrates instability and compromise to the speaker performance. Also these feet (7) are not height adjustable for improved stability and for carrying-out sound trials to optimise the speakers performance.

Fi2ure 4 Shows a floor standing speaker (1) manufactured with time-alignment of the three drivers (9) set in a terrace in the front face of the speaker each is set back from the vertical (11) by a distance (12) to ensure the sound waves (10) from each driver (that operate over a specific frequency range) to form a coherent "soundstage" or "sweet spot" for the listener based upon assumptions about typical room sizes and the listening distance. A requirement is for the user to adjust the playing angle of the speaker by means of secure and effective adjustment of the height of the feet.

FiEure S Shows how subjective auditioning (verified by in-room sound measurements) is used to locate the speakers (1) and in practice require listening in different positions to achieve the best sound, for example relative to walls -shown by arrowed dimensions. The ease of handling andset- up of the speaker depends upon support arrangements and feet that are easy to use, with minimal re-levelling of the feet, lifting of the speaker, and damage to the floor finishes.

Figure 6 Illustrates a speaker with strong directional characteristics; here the speaker and stand (1,2) are set up with the principal direction of sound (11) from tweeter (9) above the listening area.

The focus of sound from the tweeter driver (9) forms a conical shape (13) above the listening area that would otherwise appear too prominent or "bright" had the speaker been directed at the listener and illustrates the need for height adjustment and auditioning.

Figure 7 Is a perspective view of an embodiment of this invention with Fi2ure 15 a cross-section view of the same. The foot has a connecting threaded rod (14) size M8 of length 25mm to fix the foot easily and securely to the speaker cabinet feet nuts. A locking nut (15) together with (14), enable control of the foot height. A thrust plate (21) is a circular steel plate diameter 38mm and thickness 2mm to distribute the speaker load over the resilient damping layer (16) without piercing or damage of this material. The resilient damping layer (16) is a cylinder of solid rubber with diameter 40mm and thickness 20mm and of hardness index soft. This part (16) is compliant and separates the rigid parts, that is, the thrust plate (21) from the structural support feet (17). The structural support feet (17), is fixed to (16) by a semi-permanent double-sided adhesive tape (20) that enables the interchange of parts (16) and (17) to meet specific support surfaces and loading requirements. The conical shape of(17) is formed of medium hardness rubber and has depth 15mm and diameter 40mm to form an optimum contact surface area to the support surface and reduce the interface of noise and vibration energy between the speaker and the support surface. The element, (17) increases damping and compliance of the foot support. This foot is suitable for a small speaker on a speaker support and a small floor standing speaker on a wooden floor without damage to their surfaces.

Figure 8 Is a perspective view of the same embodiment of this invention with Figure 16 a cross-section view of the same. Here the resilient damping layer (16) has a I Onmi thickness and 50mm diameter and made of a medium hardness rubber. The structural support feet (17) are of hard conical shaped rubber of 15mm depth and diameter of 50mm. This foot is suitable for a heavy and medium speaker on hard floor surfaces.

Figure 9 Is a perspective view of an alternate embodiment of this invention with Figure 17 a cross-section view of the same. The threaded rod (14) size M8 and length 15mm tightens the foot to the speaker cabinet nut fixing to make direct contact between opposing faces of the foot and the speaker cabinet. The thrust plate (21) made of steel has a diameter of 38mm and 2mm thickness and fixed to (14) to distribute the weight and pressure to the resilient damping layer (16). The layer (16) is a solid cylinder of hard rubber and has a 40mm diameter and 20mm thickness. A lower thrust plate (21) attaches the threaded rod (18) size M8 length 25mm with locking nut screw (15) to adjust the feet height within the T-nut fixing (26) that has a surface mount to the structural foot (17). The structural foot (17) is a metal conical of 40mm diameter and 25mm depth and suitable for use of a medium speaker or sub-woofer on a carpeted floor.

Figure 10 Is a perspective view of an alternate embodiment of this invention with Figure 18 a cross-section view of the same. This has the same fixing arrangement as that used in the foot in figure 9 and a solid mass resilient damping layer (16) with thrust plate (21) uppennost to lock the foot to the speaker cabinet using screw (14). On the lower side of the section (16) is a thrust plate (21) that is fixed to a threaded steel tube (22) with diameter 22mm and length 15mm that inserts to a female threaded steel cap (23) with outside diameter of 28mm Here the structural foot element (17) is a wooden hemisphere with diameter 28mm and 15mm depth. The foot has significant increase in structural strength to side forces and sheer forces and has advantages of stability over the feet illustrated in figures 7,8 and 9, whilst retaining the ability to adjust the foot height and is suitable for large speakers and equipment stands, Figure 11 Is a perspective view of an alternate embodiment of this invention with Figure 19 a cross-section view of the same. This has the same fixing arrangement of the foot to the speaker as feet described in figure 9,10. Here resilient damping layer (16) with diameter 40mm and thickness 20mm is recessed in a steel threaded cap (24) with diameter 46mm and 25mm depth that inserts the female steel cap (25) of 52mm diameter and height 25mm for adjusting the height of the foot. The structural foot element (17) has a wood conical form diameter 40mm and thickness 20mm. Also a locking nut fits on the screw (24) but the locking nut is not shown here. The foot has significant increase in structural strength to side forces and sheer forces and would offer the advantages of stability, isolation, compliance and suitable for use with large speaker and equipment stands.

Figure 12 Is a perspective view of an alternate embodiment of this invention with Figure 20 a cross-section view of the same. This has the same configuration of parts as the feet described in figure 7, 8 however here there is no height adjustment available and the M8 threaded rod (14) has a length of 15mm to screw the foot directly into the speaker cabinet nut fitting. This offers a rudimentary means of creating a foot of greater structural strength as the body that locks directly to the speaker without any other connecting rods such as that used in the feet described in figure 9, and the added advantage of offering a smaller overall foot height. This may be important to some applications where clearance is limited between furniture but retains the advantages of isolation, stability, compliance described to the invention. The part (16) is of soft rubber and diameter 50mm and depth 20mm. The part (17) is a hard rubber hemisphere of 50mm diameter and 20mm depth.

This foot is suitable for a small speaker on a stand or a small floor stand speaker on timber and hard floors.

Figure 13 Is a perspective view of an alternate embodiment of this invention with Figure 21 a cross-section view of the same. This has the same configuration of parts as the feet described in figure 12, however the fixing is achieved by a semi-permanent double-sided adhesive system (20) with removable characteristics to enable its use on other speakers and speaker equipment supports.

This offers a rudimentary means of creating a foot of greater structural strength having a body that contacts direct with the speaker without any other connecting rods such as that used in the feet described in figure 9, and the added advantage of offering a smaller overall foot height this may be important to some applications where clearance is limited between furniture but retains the advantages of isolation, stability, compliance described to the invention. The part (16) is of medium hardness rubber and diameter 50mm and depth 10mm. The part (17) is a hard rubber hemisphere of 50mm diameter and 25mm depth. This foot is suitable for a medium speaker on a stand and a mediumllarge floor stand speaker on timber and hard floors.

Figure 14 Is a perspective view of an alternate embodiment of this invention with Figure 22 a cross-section view of the same. This has the same configuration of parts as the feet described in figure 9, but enables fixing to speakers without foot fixing nuts by using a semi-permanent double-sided adhesive system (20) with removable characteristics to enable its use on other speakers and speaker equipment supports and with the advantages described to this invention. The part (16) is a soft hardness rubber of 40mm diameter and 20mm depth, and (17) is a metal conical of 40mm diameter and 25mm depth. This will be suitable for small and medium speakers on carpeted floors.

Figure 23 Is a representation of the structural foot element (17) made of wood under a load (27) and subsequent contact profile (28) of 2mm diameter and is suitable for a hard floor surfaces supporting medium to heavy loads. A similar profile would be obtained using hard rubber and would offer greater damping and protection to support surfaces.

Figure 24 Is a representation of the structural foot element (17) made of medium hardness rubber under a load (27) and subsequent contact profile (28) of 4mm diameter and is suitable for light to medium weight speaker with protection to veneered furniture or floors finishes.

Figure 25 Is a representation of the structural foot element (17) made of metal under a load (27) on a heavily carpeted and underplayed floor. This point force produces the effect of a contact profile (28) of 4mm diameter to effect stability for the speaker. A similar profile would be obtained using wood or hard rubber and with greater damping and protection to support surfaces.

Figure 26 Are the type of resilient damping element (16) to demonstrate the connecting arrangements offered by each, either by connecting threaded rod and thrust plate (31), adhesive membrane (20) and recessed t-nut (32) to enable interchange with different speakers and structural feet element (17).

Figure 27 Are the type of structural foot element (17) to demonstrate the connecting arrangements offered by each, either by connecting threaded rod and thrust plate (31), adhesive membrane (20) and recessed t-nut (32) to enable interchange with different resilient damping element (16) and to match support surface.

Figure 28 Shows the type of structural foot element shapes: pointed conical, hemispherical and flat conical.

Figure 29 Is a cross section of a floor-standing speaker and building structure, with FiEure 30 the model to represent the mechanism for suppressing vibration. The speaker (1) and invented feet (33) is the primary system, of speaker mass Ms, and combined feet dampening Cs, combined feet stiffness Ks, and vibration disturbance of the loudspeaker F(t). The floor stnicture, is the secondary system, and represented by a beam of length L, of lumped mass m, at distance a, and spring/damper Cf and Kf. Here the feet damping and stiffness are varied to optimise the system vibration suppression.

Figure 31: Is a cross section of a speaker/speaker stand and building structure, with Figure 32 the model to represent the mechanism for suppressing vibration. This is a three mass spring system, the first is the speaker (1) and support feet (33), the second the speaker stand (2) and the invented feet (33) with the speaker stand represented by a beam (35) of mass Mst. The last represents the foundation (34). Here the feet damping and stiffness are varied to optimise the system vibration suppression.

Claims

The Claims I An optimum absorber loudspeaker foot used in sets of three

or more to provide considerable vibration suppression and improvement of loudspeaker performance by matching both or either of the two principle parts, the upper resilient damping element (16) and the lower structural foot element (17), to the speaker type/requirements and support surface and structure requirements.

2 Loudspeaker foot according to claim 1, having resilient damping element (16) of low damping, however with sufficient damping to suppress the adverse affects of standing wave resonances within the isolator element to reduce speaker cabinet excitation and enhance sound reproduction.

3 Loudspeaker foot according to claim 1 and 2, with stiffness sufficiently low not to cause resonance of the support structure and having a structural foot element (17) with a contact surface area to the support surface to form an optimum couple to that support structure whereby the mass of the structure contributes to the control of the vibration energy of the loudspeaker and offers isolation from the environment.

4 Loudspeaker foot according to claim I to 3, having a resilient damping element (16) with differential mobility far in excess of that of the loudspeaker cabinet and the support structure.

Loudspeaker foot according to claim 1 to 4, with compliance that improves the distribution of forces between the set of feet and in turn improves stability of the loudspeaker with less height adjustment of the feet to secure stability.

6 Loudspeaker foot according to claim I to 5, with a resilient damping element (16) made of cylindrical rubber element that separates the rigid parts of the structure.

7 Loudspeaker foot according to claim 1 to 6, with a structural foot element (17) of conical shape.

8 Loudspeaker foot according to claim I to 6, with a structural foot element (17) of hemispherical shape.

9 Loudspeaker foot according to claim I to 6 and 8, that is attached to the speaker using a semi-permanent double-sided adhesive tape (20) on the upper face of the resilient damping element (16). (figure 13 & 21) Loudspeaker foot according to claim 1 to 7, that is attached to the speaker using a semi-permanent double-sided adhesive tape (20) on the upper face of the resilient damping element (16) and a steel thrust plate (21) on the underside of (16) connected to threaded steel bar (18) and with locking nut (15) for adjusting the foot height. (figure 14 & 22) 11 Loudspeaker foot according to claim I to 7, that is attached to the speaker with a threaded steel bolt (14) and attached to a steel thrust plate (21) on the upper face of the resilient damping element (16) to distribute the speaker load without damage to the resilient material.

(flg9,17& 11,19) 12 Loudspeaker foot according to claim 11, with a steel thrust plate (21) on the underside of (16) connected to the threaded steel bar (18) and having locking nut (15) for adjusting the foot height. (fig 9,17) 13 Loudspeaker foot according to claim 11, with the resilient damping member (16) recessed in the steel threaded cap (24) that inserts to the female steel cap (25) with locking nut (15) to adjust the foot height and with a semi-permanent double-sided adhesive tape (20) to bond the female threaded steel cap (25) to the structural foot element (17). (fig 11,19) 14 Loudspeaker foot according to claim 1 to 6 and 8, that is attached to the speaker with a threaded steel bolt (14) and attached to a steel thrust plate (21) on the upper face of the resilient damping element (16) to distribute the speaker load without damage to the resilient material. (fig 10,18 & 12,20) Loudspeaker foot according to claim 14, with a steel thrust plate (21) on the underside of (16) connected to threaded steel tube (22) and having locking nut (15) for adjusting the foot height and a semi-permanent double-sided adhesive tape (20) to bond the threaded steel cap (23) to the structural foot element (17). Fig 10,18 16 Loudspeaker foot according to claim 10, with the following parts; element (16) is a soft hardness rubber of 40mm diameter and 20mm depth, and part (17) is a metal conical of 40mm diameter and 25mm depth, thrust plate (21) with 38mm diameter and 2mm thickness, M8 threaded rod (18) length 25mm, M8 locking nut (15), M8 T-nut fixing (26) and is suitable for small and medium sized speakers on carpeted floors.

17 Loudspeaker foot according to claim I to 7, that is attached to the speaker with a threaded steel screw (14) and attached to a steel thrust plate (21) on the upper face of the resilient damping element (16) to distribute the speaker load without damaging the resilient material and a locking nut (15) to adjust the height of the support. Fig 7,15 & 8,16 18 Loudspeaker foot according to claim 9, of fixed height with a semi-permanent double-sided adhesive tape (20) to bond the resilient damping element (16) to the structural foot element (17). (fig 13,21) 19 Loudspeaker foot according to claim 14, of fixed height with a semi-permanent double-sided adhesive tape (20) to bond the resilient damping element (16) to the structural foot element (17). (fig 12,20) Loudspeaker foot according to claim 17, with a semi-pennanent doublesided adhesive tape (20) to bond the resilient damping element (16) to the structural foot element (17). Fig 7,15 & 8,16 21 Loudspeaker foot according to claim 20, (Figure 7) with the following parts; M8 threaded rod (14) of 25mm length, thrust plate (21) of 38mm diameter and 2mm thickness, resilient damping layer (16) with diameter 40mm and thickness 20mm and hardness index soft, the structural support feet (17) of 15mm depth and 40mm diameter and made of medium hardness rubber suitable for a small speaker on a speaker support and a small floor standing speaker on a wooden floor without damage to their surfaces.

22 Loudspeaker foot according to claim 20, (figure 8) with the following parts; M8 threaded rod (14) of 25mm length, thrust plate (21) of 38mm diameter and 2mm thickness, resilient damping layer (16) with 50mm diameter and 10mm thickness and made of a medium hardness rubber, structural support feet (17) with 15mm depth and 50mm diameter and made of hard rubber suitable for a large floor standing speaker on timber or laminate flooring without damage to the surface.

23 Loudspeaker foot according to claim 12, (figure 9) with the following parts; M8 threaded rod (14) length 15mm, two number thrust plates (21) with 38mm diameter and 2mm thickness, resilient damping layer (16) made of hard rubber with 40mm diameter and 20mm thickness, the M8 threaded rod (18) length 25mm, M8 locking nut (15), M8 T-nut fixing (26), the structural foot (17) made of metal in a conical of 40mm diameter and 25mm depth and suitable for use of a medium speaker or sub-woofer on a carpeted floor.

24 Loudspeaker foot according to claim 15, (figure 10) with the following parts; M8 threaded rod (14) length 15mm, thrust plate (21) with 38mm diameter and 2mm thickness, resilient damping layer (16) made of medium hardness rubber with 40mm diameter and 20mm thickness, two number thrust plates (21) with 38mm diameter and 2mm thickness, a threaded steel tube (22) with diameter 22mm and length 15mm, a female threaded steel cap (23) with 28mm diameter and length 15mm, the structural foot element (17) is a wooden hemisphere 28mm diameter and 15mm depth to form a foot of significantly stronger structure to side forces and sheer forces and is suitable for large speakers and equipment stands requiring height adjustment.

Loudspeaker foot according to claim 13, (figure 11) with the following parts; M8 threaded rod (14) length 15mm, thrust plate (21) with 38mm diameter and 2mm thickness, resilient damping layer (16) made of medium hardness rubber with 40mm diameter and 20mm thickness, steel threaded cap (24) with 46mm diameter and 25mm depth, the female steel cap (25) of 52mm diameter and 25mm height, the structural foot element (17) has a wood conical fonn 40mm diameter and 20mm thickness to form a foot of significantly stronger structure to side forces and sheer forces and is suitable for use with large speaker and equipment stands requiring height adjustment.

26 Loudspeaker foot according to claim 19, (figure 12) with the following parts; M8 threaded rod (14) with 15mm length, the part (16) is of soft rubber with 50mm diameter and 20mm depth, the part (17) is a hard rubber hemisphere of 40mm diameter and 20mm depth, forms a foot with increase structural strength and smaller overall foot height, and is suitable for a small speaker on a stand or a small floor stand speaker on timber and hard floors.

27 Loudspeaker foot according to claim 18, (figure 13) with the following parts; element (16) is of medium hardness rubber and diameter 50mm and depth 10mm, the part (17) is a hard rubber hemisphere of 50mm diameter and 25mm depth, fonning a foot of greater structural strength with a smaller overall foot height, and is suitable for a medium speaker on a stand and a medium/large floor stand speaker on timber and hard floors.

28 An optimum absorber feet for electrical equipment and electrical equipment stands/furniture according to claim I to 15 and 17 to 20 where loudspeaker foot or feet reads electrical equipment foot or feet.

29 Electrical equipment foot according to claim 10 and 28, with the following parts: element (16) is a medium hardness rubber of 25mm diameter and 10mm depth, and part (17) is a soft hardness rubber conical of 25mm diameter and 15mm depth, thrust plate (21) with 20mm diameter and 2mm thickness, M4 threaded rod (18) length 15mm, M4 locking nut (15), M3 T-nut fixing (26).

Electrical equipment foot according to claim 18 and 28, element (16) is of medium hardness rubber and diameter 30mm and depth 10mm, the part (17) is a soft rubber hemisphere of 30mm diameter and 8mm depth.

31. Electrical equipment feet according to claim 13 and 28, with the following parts; M4 threaded rod (14) length 8mm, thrust plate (21) with 26mm diameter and 2mm thickness resilient damping layer (16) made of medium hardness rubber with 30mm diameter and 10mm thickness, steel threaded cap (24) with 36mm diameter and 13mm depth, the female steel cap (25) of 42mm diameter and 15mm height, the structural foot element (17) has a medium hardness conical with diameter 42mm and 10mm thickness.