GB2435086A

GB2435086A - A hi-fi speaker stand with rigid fixing

Info

Publication number: GB2435086A
Application number: GB0602818A
Authority: GB
Inventors: Peter Robert Roots
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-02-13
Filing date: 2006-02-13
Publication date: 2007-08-15
Also published as: GB0602818D0

Abstract

An audio speaker stand has a method of fixing structural parts that uses compression force P to induce reaction force RF with elements in all dimensions whilst maintaining minimal contact area. A ball 6 is trapped between two circular 7, 8 of lesser diameter. The surfaces 6, 7, 8 meet to form narrow circular contact areas 9, 10, where reaction forces RF are induced perpendicular to the surface of the ball 6. Vibratory movement is impeded in all directions by these reaction forces that hold the fixing perfectly rigid, reducing the detrimental effects on the sound quality from the speaker stands vibrating under force of an active speaker unit. The 'ball trap' can be used in a variety of fixing designs (see Figs 6 , 7 and 8); but designs with consideration for equal distribution of pressure between traps are preferred.

Description

1 2435086 Hi-Fi Speaker Stand With Rigid Fixing This invention relates

to a stand designed to reduce the detrimental effects of resonance in-order to improve the sound quality of hi-fl speakers by reducing freedom for lateral movement be-tween structural parts.

Conventional speaker stands are designed to improve the sound quality of hi-fl speakers by offer-ing a sturdy support that will allow unwanted sound energy to transmit to the floor without the poor resonance characteristics offered by placing bookshelf' speakers on wobbly tables and shelving. However speaker stands have their own resonance problems.

When two parallel surfaces are fixed by bolt or screw they are held in fonn rigid enough for most applications. Vibrations that pass through the fixing are not a concern. Where vibration is a con-cern it is usually for the loosening and hence failure of the fixing. However the joint can easily be induced into resonance and creates noise that distorts the audio speaker signal. Welding the parts is a solution but this reduces the product flexibility effecting costs and marketability.

This invention intends to control the detrimental effects of fixing joint resonance' in audio speaker stands by fixing structural parts by ball bearing trap'; where upper and lower parts trap a number of ball bearings inside upper and lower holes of lesser diameter, inducing reaction forces that will inhibit vibratory movement within the joint whilst maintaining minimal contact area between parts to eliminate chattering' between part surfaces.

A contact surface is positioned between parts, at an angle to the fixing pressure in-order to induce a reaction force which will reduce vibratory movement, in both lateral and vertical directions.

The vibratory forces must first overcome the reaction force within the joint to induce movement and create detrimental resonance.

Resonance is reduced further by creating a minimal contact surface area; this is achieved by trapping a ball between upper and lower holes of smaller diameter fixed by vertical pressure.

This ball trap' feature maintains the favorable reaction forces that will resist vibratory move-ment in all directions. Three or more of these ball traps' can be used to create a fixing that is perfectly rigid, which significantly impedes the detrimental effects of resonance on the sound quality from speaker stands vibrating under force of an active speaker unit. The optimum per-formance of this fixing can be ensured, by creating even distribution upon each ball bearing trap'.

An alternative fixing arrangement with a single ball trap' and a simple method of holding the correct angles, can also be used to ensure perfect rigidity between parts; allowing the fixing to be created along a narrow path.

A preferred embodiment of the invention will now be described with reference to the accompa-nying drawings in which: FIGURE 1 shows the nature of forces within a normal fixing with resonance caused by lateral freedom for vibratory movement FIGURE 2 shows a fixing with resonance controlled by contact surfaces presented at an angle to fixing pressure FIGURE 3 shows the different effects of high frequency and low frequency resonant distortion on the audio signal observed by the listener FIGURE 4 shows the nature of forces created within a ball bearing trap' FIGURE 5 shows the preferred use for the ball bearing trap with 3 ball traps offering separation between upper and vertical structural parts FIGURE 6 describes the ideal positioning of pressure points in a 3 ball trap for I,2,3 and 6 posi-tions allowing design freedom FIGURE 7 shows a side view of an alternative fixing arrangement using one ball trap designed to allow rigid fixing along a narrow path FIGURE 8 shows a front view of the alternative fixing mentioned in figure 7 The problem When vibratory forces take effect on a fixing they must first overcome the reaction forces be-tween surfaces in-order to induce any movement. (Much like lifting a heavy mass under gravita- tional force, the weight of the mass must be overcome to remove it from the floor; any lifting ef-fort below this force will fail to induce movement).

In a standard' fixing between two parts shown by figure 1 the parallel surfaces of upper part I and lower part 2 are forced together by a bolt creating compression force P. A reaction force RF perpendicular to the surfaces is induced to oppose the compression force P. This reaction force will inhibit low frequency waves (with low dynamic forces) to a greater degree than high fre-quency waves, that carry higher dynamic forces. The opposing reaction forces RF, will therefore cause the high frequency natural resonance Res:h in the vertical directions (figure 1).

However vibratory movement in the lateral direction is not inhibited by these reaction forces.

The upper part 1 and lower part 2 will be able to resonate freely at lower frequencies Res:L in the lateral direction (figure 1). The lower resonant frequencies Res:L cause greater distortion to the original audio signal (refer to figure 3), and hence have a detrimental effect on the perform-ance of the audio speaker.

The solution In figure 2 the upper part 3 with a countersunk hole is designed to receive lower part 4 with a tapered extrusion. They are pushed together by force P and contact at the angular surfaces 5. The reaction forces RF are induced to oppose force P. The reaction forces RF are induced at an angle to both force P and the parallel upper and lower parts 3 and 4, hence creating vertical and lateral forces to resist movement. Since vibratory movement is resisted in all directions the joint may only resonate at high frequencies inducing the resonance Res:h. The high frequency resonance causes little distortion to the original signal (figure 3), hence giving improved performance over the standard joint shown in figure 1.

The resonance induced can be reduced, by decreasing the total contact area, which will increase the pressure on contact surfaces. Figure 4 describes a design which maintains the principles of angular reaction forces shown in figure 2, whilst reducing contact surface to an absolute mini-mum.

In figure 4 a ball bearing 6 is trapped and compressed by a the outer edge of two holes 7 and 8 with a diameter less than the diameter of the ball bearing 6. This forms two narrow circular con-tact areas 9 and 10. The compression force P induces reaction forces RF which are perpendicular to the tangent of the contact areas. These reaction forces resist vibratory movement in all direc-tions parallel and perpendicular to the upper and lower parts. The total contact area of surfaces at 9 and 10 in figure 4 is significantly lower than the contact surface 5 in figure 2; resonance will be of a higher frequency and greatly reduced, thus further decreasing the distortion to the origi-nal audio signal.

Figure 5 shows a simple design where the ball bearing trap' shown in figure 4 can be used to create an effective fixing method. Three ball bearing traps 11 separate the upper part 12 from the lower structural part 13 with compression offered by two bolts 14. In a simple design like this three or more bearing traps must be used in-order to hold structural parts 12 and 13 in position; although three is the preferred number since it ensures all bearing traps' can receive equal pres-sure regardless of manufacturing tolerances. If pressure on one ball bearing trap is reduced it may resonate freely at low frequencies and create audio distortion.

Figure 6 indicates the preferred placement of pressure points (whether they be created by bolting or any other means) for either one, two, three or six points in a three bearing trap' design.

Placement in one point in a central position is ideal since it ensures pressure on all bearing traps is equal. With two pressure points positioned in figure 6 the front ball bearing trap will receive pressure from both pressure points; and therefore the pressure point is moved closer to the rear bearing traps but kept on or close to the line between front and rear traps to evenly distribute the pressure. With three or six pressure points the pressure points can be moved closer to the centre provided movement of each is equal. In all cases it is preferred that pressure points will be kept inside the triangle to prevent over-tightening of one pressure point from reducing pressure on the opposite ball bearing trap.

Figures 7 and 8 show an alternative design where a ball bearing trap 16 is used to provide rigid- ity between an upper flat part 15 and lower narrow structural part 16. A tapered joint 17 is in- ci uded at the rear of the arrangement to hold the correct angle between parts 15 and 16 and pre-vent rotational freedom around the axis of ball bearing trap 14. The design offers the advantage of greater design freedom where fixing along a narrow path is an advantage.

Claims

CLAIMS

1. An audio speaker stand with a method of fixing structural parts that uses tapered contact sur-faces, positioned at an angle to the supplied fixing pressure from a component such as a bolt or screw, in-order to restrict movement between parts caused by vibratory energy of the audio speaker, and hence reduce the effects of resonance on the listeners perception of audio quality.

2. An audio speaker stand as in claim 1 wherein tapered or angled contact surfaces between structural parts are created by positioning and trapping a ball between upper and lower holes with a smaller diameter than the trapped ball, thus maintaining rigidity from movement under vibratory energy, with a very small contact surface area, and therefore reducing the influence of resonance between parts by limiting resonant frequencies to the higher ranges that have less ef- :. * fect on the audio signal. I...

* ... 3. An audio speaker stand as in claims I and 2 wherein a method of fixing structural parts is achieved with three or more ball traps' between part surfaces and pressure on each ball is dis- * * tributed evenly by placing pressure in suitable locations by means of suitable components such a * one or more bolts or screws. ***

S

4. An audio speaker stand as in claims 1, 2 and 3 wherein a method of fixing structural parts is : achieved with only 3 ball traps, located between parallel part surfaces, and separated to form a : triangle with bolt or screws placed in 1, 2, 3 or 6 locations positioned carefully inside the trian- * gle, to distribute pressure evenly between the 3 ball traps and negate any negative effects of manufacturing tolerances.

5. An audio speaker stand as in claims I and 2 wherein a method of fixing perpendicular struc-tural parts is achieved by using only one ball trap' and a tapered contact joint, separated by a short distance along a line at which the perpendicular parts meet. The ball trap' acting to limit movement from detrimental resonance, and the tapered joint acting to prevent movement in the fixing structure.

6. An audio speaker stand substantially as described herein with reference to figures 1-8 of the accompanying drawing.