This disclosure relates to a surround for supporting a diaphragm that is used to create acoustic waves. The surround and diaphragm can be part of a passive radiator or acoustic driver.
Passive radiators and acoustic drivers have been traditionally designed with half roll surrounds having a circular or elliptical cross section. Such half roll surrounds are typically made of high durometer materials. This arrangement provides approximate linear force-deflection response until the surround reaches a high strain that results in a non-linear response. In many surround designs, issues of buckling and hoop stresses can result in an unstable dynamic response (like sub harmonic rocking) which is detrimental to the acoustic performance. A challenge in designing a passive radiator is the unstable behavior or non-axial motion of the diaphragm which can occur under dynamic loading. This is largely related to the nonlinear force deflection relationship of the passive radiator which is due to the geometry linearity and material linearity. Instabilities due to nonlinear force-deflection have been avoided by limiting the magnitude of passive radiator excursion, resulting in less acoustic output for a given size passive radiator.
U.S. Pat. No. 7,699,139 discloses a surround for supporting a diaphragm used to create acoustic waves. The surround includes a rib section extending away from the diaphragm and a membrane section that is supported by the rib section. The membrane section has a thickness in a direction substantially normal to opposing top and bottom surfaces of the membrane section which is substantially thinner than a thickness of the rib section in a direction substantially normal to opposing top and bottom surfaces of the rib section. A restoring force returning the diaphragm to a home position is contributed to more due to deformation of the rib section than to deformation of the membrane section.
In one aspect, a surround for supporting a diaphragm used to create acoustic waves includes a first rib section extending away from the diaphragm and a second rib section having two end portions and a middle portion. An end of the first rib section is secured to the middle portion of the second rib section. The first rib section is closer to the diaphragm than the second rib section. A first membrane section is supported by the first rib section and has a thickness in a direction substantially normal to opposing top and bottom surfaces of the membrane section which is substantially thinner than a thickness of the first rib section in a direction substantially normal to opposing top and bottom surfaces of the first rib section. A point on the middle portion of the second rib section that is closest to the diaphragm is located farther from the diaphragm than a point on at least one of the end portions of the second rib section that is closest to the diaphragm.
Embodiments may include one or more of the following features. The point on the middle portion of the second rib section can be located farther from the diaphragm than respective points on both of the end portions of the second rib section that are closest to the diaphragm. The thickness of the membrane section can be substantially thinner than a thickness of the second rib section in a direction substantially normal to opposing top and bottom surfaces of the second rib section. At least a portion of the membrane can have a curved shape. The surround can further include a third rib section extending away from the diaphragm and a fourth rib section having two end portions and a middle portion. An end of the third rib section can be secured to the middle portion of the fourth rib section. A second membrane section can be supported by the third rib section. The membrane section can have a thickness in a direction substantially normal to opposing top and bottom surfaces of the membrane section which is substantially thinner than a thickness of the third rib section in a direction substantially normal to opposing top and bottom surfaces of the third rib section. A point on the middle portion of the fourth rib section that is closest to the diaphragm can be located closer to the diaphragm than a point on at least one of the end portions of the fourth rib section that is closest to the diaphragm. The point on the middle portion of the fourth rib section can be located closer to the diaphragm than respective points on both of the end portions of the fourth rib section that are closest to the diaphragm. The thickness of the membrane section can be substantially thinner than a thickness of the fourth rib section in a direction substantially normal to opposing top and bottom surfaces of the fourth rib section.
In another aspect, a surround for supporting a diaphragm used to create acoustic waves includes a first rib section extending away from a frame which supports the surround and a second rib section having two end portions and a middle portion. An end of the first rib section is secured to the middle portion of the second rib section. The first rib section is closer to the frame than the second rib section. A first membrane section is supported by the first rib section and has a thickness in a direction substantially normal to opposing top and bottom surfaces of the membrane section which is substantially thinner than a thickness of the first rib section in a direction substantially normal to opposing top and bottom surfaces of the first rib section. A point on the middle portion of the second rib section that is closest to the diaphragm is located closer to the diaphragm than a point on at least one of the end portions of the second rib section that is closest to the diaphragm.
Embodiments may include one or more of the following features. The point on the middle portion of the second rib section is located closer to the diaphragm than respective points on both of the end portions of the second rib section that are closest to the diaphragm. The thickness of the membrane section is substantially thinner than a thickness of the second rib section in a direction substantially normal to opposing top and bottom surfaces of the second rib section. At least a portion of the membrane has a curved shape. The surround can further include a third rib section extending away from the diaphragm and a fourth rib section having two end portions and a middle portion. An end of the third rib section can be secured to the middle portion of the fourth rib section. A second membrane section that is supported by the third rib section can have a thickness in a direction substantially normal to opposing top and bottom surfaces of the membrane section which is substantially thinner than a thickness of the third rib section in a direction substantially normal to opposing top and bottom surfaces of the third rib section. A point on the middle portion of the fourth rib section that is closest to the diaphragm can be located farther from the diaphragm than a point on at least one of the end portions of the fourth rib section that is closest to the diaphragm. The point on the middle portion of the fourth rib section is located farther from the diaphragm than respective points on both of the end portions of the fourth rib section that are closest to the diaphragm. The thickness of the membrane section is substantially thinner than a thickness of the fourth rib section in a direction substantially normal to opposing top and bottom surfaces of the fourth rib section.
In yet another aspect, a surround for supporting a diaphragm used to create acoustic waves includes a first rib section extending away from the diaphragm and a second rib section having a zigzag pattern and being secured to an end of the first rib section. As the diaphragm starts moving away from a home position in an intended direction of travel which is substantially perpendicular to a plane in which the diaphragm lies when the diaphragm is in the home position, the zigzag pattern of the second rib section starts to straighten out.
Embodiments may include one or more of the following features. A point on a middle portion of the second rib section is located farther from the diaphragm than respective points on both end portions of the second rib section that are closest to the diaphragm. A thickness of a membrane section is substantially thinner than a thickness of the second rib section in a direction substantially normal to opposing top and bottom surfaces of the second rib section. At least a portion of the membrane has a curved shape. A point on a middle portion of the second rib section is located closer to the diaphragm than respective points on both end portions of the second rib section that are closest to the diaphragm.
In a still further aspect, a surround for supporting a diaphragm used to create acoustic waves includes a first rib section extending away from the diaphragm and a second rib section secured to an end of first rib section. The second rib section extends about at least a portion of a perimeter of the diaphragm. As the diaphragm starts moving away from a home position in an intended direction of travel which is substantially perpendicular to a plane in which the diaphragm lies when the diaphragm is in the home position, a geometric shape of the second rib section starts changing from a shape which is less similar to the at least portion of the perimeter of the diaphragm to a shape which is more like the at least portion of the perimeter of the diaphragm.
Active and passive acoustic sources (e.g., drivers and passive radiators) typically include a diaphragm that reciprocates back and forth to produce acoustic waves. This diaphragm (which may be e.g., a plate, cone, cup or dome) is usually attached to a non-moving structure, such as a frame, using a resilient surround member.
For example, as shown
The diaphragm 22 is exposed to acoustic waves created by another source such as an acoustic driver in a common acoustic enclosure. The acoustic waves cause the diaphragm to vibrate back and forth in an intended direction of travel that is substantially perpendicular to a plane in which the diaphragm lies when the diaphragm is in a home position (at rest). This vibration causes additional acoustic waves to be created and propagated. A group of four holes 24 in the diaphragm 22 is used to secure a mass (not shown) to the diaphragm. The mass may be added to the diaphragm 22 to tune an acoustic system to a desired resonant frequency of vibration.
The surround 26 is secured to and supports diaphragm 22. The surround may be made of a solid or foam elastomer, and in this example is a thermoset soft silicone elastomer such as ELASTOSIL® LR 3070 which is made by Wacker Chemie AG, WACKER-SILICONES, Hanns-Seidel-Platz 4, D-81737 Munich, Germany, www.wacker.com, silicones@wacker.com. Alternatively, the surround 26 may be made of a thermoplastic elastomer such as Uniprene 2012 which is made by Teknor Apex, 505 Central Avenue, Pawtucket, R.I. 02861, 866.438.8737, www.teknorapex.com The thermoset elastomer used to make the surround 26 preferably has (i) a Shore A durometer of between about 5 to about 70, and more preferably has a durometer of about 27; (ii) a 100% elongation static modulus of between about 0.05 MPa to about 10 MPa, and more preferably has a 100% static modulus of between about 0.6 MPa to about 2 MPa; (iii) an elongation at break above about 100%, and more preferably an elongation at break of about 400%; and (iv) a static stiffness of between about 0.05 newtons/mm to about 50 newtons/mm when the diaphragm is at its neutral travel position, and more preferably a static stiffness of about 3 newtons/mm. However, these properties may change depending on various factors (e.g., passive radiator system tuning frequency, air volume in the acoustic enclosure).
Generally speaking, as the size of the surround gets smaller, a lower durometer material can be used. The use of a soft durometer material gives better design control for low free air resonant frequencies of the diaphragm to keep this resonant frequency away from the tuning frequencies of the moving mass of the diaphragm/surround assembly and an acoustic enclosure in which the surround is used.
The frame 28 is secured to and supports surround 26, and in this example is made of the same material used for diaphragm 22. Alternatively, the frame 28 and the diaphragm 22 can be made of different materials. The frame 28 includes a series of holes 30 that are used with fasteners (not shown) to secure the passive radiator 20 to another structure such as a housing defining an acoustic volume. The arrangement of the frame 28, surround 26, and diaphragm 22 provides a substantially linear force-deflection response of the diaphragm, which can advantageously result in low harmonic distortions and better dynamic performance as the diaphragm moves away from its home position in an intended direction of travel.
The passive radiator 20 is typically made by forming the diaphragm 22 and the frame 28 in separate injection molding operations. The diaphragm 22 and frame 28 are then placed in an insert mold, and a thermoplastic or thermoset elastomer is injected into the mold. The elastomer is allowed to cure, thus forming the surround 26. The thermoset elastomer covers the surfaces of the diaphragm 22 and the frame 28 which face the surround 26. This assists in securing (joining) the surround 26 to the diaphragm 22 and the frame 28. The elastomer preferably also covers at least part of surfaces 32 and 36 (and their opposing surfaces, not shown), thereby helping to secure the surround 26 to the diaphragm 22 and the frame 28.
Turning now to
Each membrane section 40 is supported by a support section 42. In this example the support section includes a pair of radial ribs 44, 46 (rib sections) as well as a generally zigzag shaped rib 48 (rib section) which all support the membrane section 40. The rib 48 extends about the perimeter of the diaphragm (the rib 48 extends about at least a portion of the perimeter of the diaphragm in some embodiments). The ribs 44 and 46 extend away from the diaphragm. All three of these ribs (44, 46, 48) have a thickness T2 of between about 6 mm to about 25 mm. The ribs 44, 46 and 48 each have a surface 47 (a top surface) that is substantially flat and substantially perpendicular to an intended direction of travel of the diaphragm 22 (
In another portion of the rib section 48, a point 70 on a middle portion 72 of the rib section 48 that is closest to the diaphragm is located closer to the diaphragm than respective points 74 and 76 on end portions 78 and 80 of the rib section 48 that are closest to the diaphragm. In a preferred example, the point 70 is located closer to the diaphragm than at least one of the points 74 and 76 of the rib section 48. It should be noted that a middle portion of one rib section can also be an end portion of an adjacent rib section. For example, end portion 80 can also be a middle portion of a rib section immediately to the right in
The length of the rib 48 needs to get longer as the diaphragm 22 is deflected away from its home position. If the rib 48 had a straight shape in the home position instead of a zigzag shape, it would go into tension as soon as the diaphragm 22 was deflected away from its home position. The consequence of such a straight center rib going into tension would be that the surround stiffness would increases at high diaphragm excursions, resulting in an undesired non-linearity in the force versus deflection curve of the surround. In general, a tensioned rib is more nonlinear than a bending rib. By configuring the rib 48 in a generally zigzag shape, it can get longer with much less tension than in the case where the rib 48 was straight in the home position. This reduction in tension with the zigzag rib 48 results in less of an increase in stiffness, thus improving the linearity of the force versus deflection curve of the surround 26.
Another way to describe the surround geometry shown in
With reference to
In
With renewed reference to
In general, the ribs of the support section provide a linear force-deflection response and the thin membrane provides a non-linear force deflection response. The total stiffness is a summation of the ribbed and the membrane responses, so it is desirable to minimize the contribution of the membrane. One example provides a substantially linear performance of the system over a 22 mm peak-to-peak travel of the diaphragm. In one example using a soft silicone rubber, the rubber of the surround goes through an elongation or strain of about 30%.
The zigzag rib described above improves geometry linearity, and therefore improves the overall force-deflection relationship of the passive radiator with a given set of material properties. With improved linearity of the force deflection relationship, the passive radiator will also have better dynamic stability. An additional advantage of the zigzag rib described above is that it increases the in-plane (of the diaphragm at rest) to axial (the intended direction of travel of the diaphragm) stiffness ratio, which helps to raise the in-plane stiffness without increasing the axial stiffness.
While the invention has been particularly shown and described with reference to specific examples shown and described above, it is evident that those skilled in the art may now make numerous modifications of, departures from and uses of the specific apparatus and techniques herein disclosed. For instance, while the examples described herein are generally rectangular in shape, surrounds can be created in a number of other forms such as square, circular or race-track shaped. Additionally, there are many different ways of arranging the ribs and membranes of the surround in addition to the several that have been described herein. For example, although a zigzag pattern has been shown for the rib 48, other types of patterns may be used for this rib which allows the rib to straighten out when the diaphragm is moved in an intended direction of travel. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features presented in or possessed by the apparatus and techniques herein disclosed and limited only by the spirit and scope of the appended claims.
Number | Name | Date | Kind |
---|---|---|---|
1514511 | Fischer | Nov 1924 | A |
1621670 | Jokel | Mar 1927 | A |
1732351 | Borkman | Oct 1929 | A |
1744032 | Baldwin | Jan 1930 | A |
1759725 | Young et al. | May 1930 | A |
1821933 | Darnell | Sep 1931 | A |
1829355 | Houghton | Oct 1931 | A |
1832608 | Abrahams | Nov 1931 | A |
2020705 | Stenger | Nov 1935 | A |
2302178 | Brennan | Nov 1942 | A |
2439665 | Marquis | Apr 1948 | A |
2439666 | Marquis | Apr 1948 | A |
2442791 | Wente | Jun 1948 | A |
2624417 | Brennan | Jan 1953 | A |
2863520 | Manley | Dec 1958 | A |
3154173 | Petrie | Oct 1964 | A |
3436494 | Bozak | Apr 1969 | A |
3563337 | Kawamura | Feb 1971 | A |
3925626 | Stallings, Jr. | Dec 1975 | A |
3961378 | White | Jun 1976 | A |
3983337 | Babb | Sep 1976 | A |
3997023 | White | Dec 1976 | A |
4056697 | Heil | Nov 1977 | A |
4198550 | Matsuda et al. | Apr 1980 | A |
4235302 | Tsukamoto | Nov 1980 | A |
4257325 | Bertagni | Mar 1981 | A |
4321434 | Irie | Mar 1982 | A |
4324312 | Durbin | Apr 1982 | A |
4353432 | Hasegawa et al. | Oct 1982 | A |
4433214 | Jasinski | Feb 1984 | A |
4440259 | Strohbeen | Apr 1984 | A |
4552243 | Melillo et al. | Nov 1985 | A |
5094404 | DesRosiers et al. | Mar 1992 | A |
5148492 | Uzawa et al. | Sep 1992 | A |
5150417 | Stahl | Sep 1992 | A |
5204501 | Tsao | Apr 1993 | A |
5319718 | Yocum | Jun 1994 | A |
5371805 | Saiki et al. | Dec 1994 | A |
5418337 | Schreiber | May 1995 | A |
5455396 | Willard et al. | Oct 1995 | A |
5650105 | Yocum | Jul 1997 | A |
5740264 | Kojima | Apr 1998 | A |
5748759 | Croft et al. | May 1998 | A |
5749433 | Jackson | May 1998 | A |
5881989 | O'Brien et al. | Mar 1999 | A |
6044925 | Sahyoun | Apr 2000 | A |
6075866 | Frasl et al. | Jun 2000 | A |
6169811 | Croft, III | Jan 2001 | B1 |
6176345 | Perkins et al. | Jan 2001 | B1 |
6219432 | Fryer et al. | Apr 2001 | B1 |
6224801 | Mango, III | May 2001 | B1 |
6305491 | Iwasa et al. | Oct 2001 | B2 |
6347683 | Schriever | Feb 2002 | B2 |
6390232 | Kirschbaum | May 2002 | B1 |
6396936 | Nevill | May 2002 | B1 |
6449375 | Hutt | Sep 2002 | B1 |
6611604 | Irby et al. | Aug 2003 | B1 |
6697496 | Frasl | Feb 2004 | B2 |
6725967 | Hlibowicki | Apr 2004 | B2 |
6851513 | Stead et al. | Feb 2005 | B2 |
6889796 | Pocock et al. | May 2005 | B2 |
6920957 | Usuki et al. | Jul 2005 | B2 |
6957714 | Takahashi et al. | Oct 2005 | B2 |
7054459 | Kuze et al. | May 2006 | B2 |
7306073 | Frasl | Dec 2007 | B2 |
7397927 | Pircaro et al. | Jul 2008 | B2 |
7428946 | Honda et al. | Sep 2008 | B2 |
7480390 | Tabata et al. | Jan 2009 | B2 |
7510047 | Muto et al. | Mar 2009 | B2 |
7699139 | Subramaniam et al. | Apr 2010 | B2 |
7839052 | Wu et al. | Nov 2010 | B2 |
7931115 | Silver | Apr 2011 | B2 |
20020150261 | Moeller et al. | Oct 2002 | A1 |
20030015369 | Sahyoun | Jan 2003 | A1 |
20040106454 | Walker et al. | Jun 2004 | A1 |
20060162993 | Honda et al. | Jul 2006 | A1 |
20070201712 | Saiki | Aug 2007 | A1 |
20070261912 | Langberg | Nov 2007 | A1 |
20080212808 | Omoda | Sep 2008 | A1 |
20090139794 | Silver | Jun 2009 | A1 |
Number | Date | Country |
---|---|---|
1278397 | Jan 2003 | EP |
1381251 | Jan 2004 | EP |
329278 | May 1930 | GB |
52055736 | May 1977 | JP |
10257590 | Sep 1998 | JP |
Entry |
---|
International Search Preliminary Report on Patentability, dated Jul. 28, 2009 issued for PCT/US2008/063562 filed May 14, 2008. |
International Search Report and Written Opinion in Application No. PCT/US2008/063562, dated Sep. 4, 2008. |
Japanese Examined Utility Model Application, Second Publication No. S55-006237. No English version available, Feb. 13, 1980. |
Japanese Examined Application, Second Publication No. 531-004159. No English version available, Mar. 29, 2009. |
Japanese Utility Model Application No. S59-038266. First Publication No. S60-150890. No English version available, Oct. 7, 1985. |
Published Japanese Translation No. H07-503108 of PCT International Publication No. WO193/14608, Mar. 30, 1995. |
Japanese Examined Patent Application, Second Publicatioon No. S45-025827, Aug. 26, 1970. |
JP Office Action dated Jun. 30, 2011 for CN 2010510405. |
CN Office Action dated Jan. 12, 2012 for CN 200880016976.0. |
Second Chinese Office Action dated Nov. 15, 2012 for CN 200880016976.0. |