Abstract:
A process for the manufacture of a speaker cover comprises loading the speaker cover into a plasma chamber, introducing a fluoro monomer into the plasma chamber, pulsing plasma for processing, removing any excess monomer gas from the plasma chamber, and removing the speaker cover from the plasma chamber.

Description:
BACKGROUND OF THE INVENTION 
     Typical speaker material used to cover a speaker may consist of a polyester knit material. These materials work well because they are light and thin and more acoustically transparent than many heavier fabrics or other materials. However, these materials are susceptible to being torn or stretched. A more durable speaker fabric may be desired to cover a speaker, particularly for speakers that are portable and handled frequently by a user. However, more durable fabrics typically consist of thicker and/or denser material and thus, are not acoustically transparent or cause degraded acoustic transparency when placed in front of speaker drivers. For example, material such as thick fabrics, metal, wood or plastic may offer more protection to the speaker but since these materials are not acoustically transparent, sound quality is lost. A polymer such as a polyurethane spray could be applied to the speaker fabric to make the fabric water resistant. However, putting a coat of polyurethane paint or varnish over speaker fabric may also reduce acoustic transparency. What is needed is a durable speaker fabric that is also acoustically transparent. 
     Embodiments of the invention solve these and other problems individually and collectively. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments of the invention are directed to a method and apparatus for a speaker cover and speaker product treated by a plasma process. 
     One embodiment of the invention is directed to a process for the manufacture of a speaker cover comprising loading the speaker cover into a plasma chamber, introducing a fluoro monomer into the plasma chamber, pulsing plasma for processing, removing any excess monomer gas from the plasma chamber, and removing the speaker cover from the plasma chamber. 
     Another embodiment of the invention is directed to a speaker cover comprising a material treated by a plasma process comprising receiving the material into the plasma chamber, achieving a predetermined minimum vacuum, introducing gas into the plasma chamber for a pre-cleaning treatment phase, pulsing plasma for pre-cleaning, introducing a fluoro monomer into the plasma chamber, pulsing plasma for processing, removing any excess monomer gas from the plasma chamber, and releasing the vacuum. 
     Another embodiment of the invention is directed to a speaker cover comprising a porous material having an initial first acoustic transparency, a plasma coating on the porous material causing a second acoustic transparency, and an attachment member for attaching the porous material to a speaker housing. 
     Another embodiment of the invention is directed to a speaker product comprising a housing, at least once driver positioned substantially within the housing, and a speaker cover coupled with the housing, the speaker cover comprising a material and a coating of fluoro monomer on the material. 
     These and other embodiments of the invention are described in further detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a flowchart illustrating steps in a method according to an embodiment of the invention. 
         FIG. 2  shows an exemplary speaker product according to an embodiment of the invention. 
         FIGS. 3-4  show acoustic performance of a speaker cover treated using a plasma process according to an embodiment of the invention. 
         FIG. 5  shows exemplary components of a speaker according to embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention provide for a durable speaker cover without degrading the acoustic performance of a speaker product by using a plasma process to coat a speaker cover or entire speaker product. When the inventors were looking for a more durable fabric to use for a speaker cover, they tried numerous different types of fabrics. They then decided to try a plasma treatment. The inventors expected the acoustic transparency to decrease with the plasma treatment because it is generally known that anything that is added to fabric typically decreases the acoustic transparency. The fact that testing showed that speaker cover fabric with the plasma treatment did not decrease the acoustic performance of the speaker, is an unexpected result of the present invention and stands in sharp contrast to the results predicted by the inventors. It is counterintuitive that adding something to the material of a speaker cover would not decrease the acoustic transparency of the speaker cover. 
     Applying a plasma treatment to a speaker cover or speaker product provides for many additional advantages. For example, treating the speaker cover or entire speaker product with plasma allows for a water and dirt resistant product. This may be particularly advantageous for portable speaker products that may be handled frequently by a user and taken outside, traveled with, or generally moved around frequently. The plasma treatment allows the speaker cover/fabric to stay cleaner so that the acoustic performance does not decrease because of clogged pores due to something spilled on the speaker product. 
       FIG. 1  shows a flow chart including a general method according to an embodiment of the invention. 
     First, one or more speaker products may be placed into a plasma chamber. The plasma chamber may be manufactured by a company such a Europlasma. The plasma process may be similar to the process described in U.S. Pub. No. 2012/0308762 directed to using a plasma process for a printed circuit board to protect the printed circuit board from physical contamination. A speaker product has very different characteristics than a printer circuit board and thus, different considerations were made to apply such a process to a speaker product. Appropriate parameters for a speaker product were determined by hard work and experimentation by the inventors. 
     The speakers described throughout this application may comprise a housing  525  and speaker components positioned substantially within the housing as shown in  FIG. 5 . Exemplary speaker components may include at least one driver  510 , control circuitry  505 , connectivity circuitry  515 , and a power source  520 . The power source  520  may include a battery, and/or circuitry to connect to an external power source (e.g., an electric outlet). The driver  510  can refer to a device that converts electrical signals from an electrical source into sound for a listener. 
     As shown in  FIG. 2 , the housing  205  may comprise a speaker cover  210  that may cover one or more of the speaker components. The speaker cover may comprise a material such as metal, plastic, fabric, etc. An exemplary speaker cover fabric may include woven or knit fabrics consisting of nylons, polyesters, elastomers, combinations of these or other man made polymers (e.g., woven blends of 2%-13% thermoplastic polyurethane, 11%-21% polyester and 72%-82% polyamide, pure polyamide woven materials, pure polyester woven materials and pure thermoplastic elastomer woven material). The speaker cover may comprise a porous material. The speaker cover may have an initial first acoustic transparency before treatment by a plasma process and a second acoustic transparency after treatment by a plasma process. The entire housing may comprise the speaker cover, or the speaker cover may comprise a portion of the housing. The speaker cover may comprise at least one attachment member for attaching the speaker cover to the housing. An attachment member may include a clip, glue, or other attachment means. 
     The housing  205  may include input ports (e.g.,  225 ) to connect to various audio input sources (e.g., mobile phones, tablet devices, MP3 players, etc.) through a physical connection (e.g., using a cable to plug into the audio input source) or via wireless means, or to connect power, etc. The housing may include an LCD screen or various buttons to control features of the speaker such as a power button  220 , volume controls  230 , etc. 
     The entire speaker product may be placed or loaded into the plasma chamber or just the speaker cover may be placed in the chamber. Placing just the speaker cover in the chamber may allow for a larger quantity of speaker covers to be coated at once, reducing the cost of coating the speaker cover. This may be advantageous if the end speaker product is a large product where not many would fit in the plasma chamber at one time. This may also be advantageous if the speaker product contains components that should not be exposed to the plasma process. Placing the entire product in the plasma chamber may allow for the entire product to be treated including, for example, connectors, drivers, any buttons exposed, etc. 
     To place the one or more speaker cover or entire speaker product into the plasma chamber, the one or more speaker cover or entire speaker product may be placed onto one or more racks and then the racks may be placed or loaded into the open plasma chamber. The plasma chamber door is then closed. 
     After placing or loading the one or more speaker cover or entire speaker product into the plasma chamber (step  101 ), ambient air from the plasma chamber may be removed by achieving a vacuum (step  102 ) of between 10 millitor (mT) and 1000 mT. Through hard work and experimentation, the inventors found that when placing an entire speaker product in the plasma chamber, a lower maximum vacuum may need to be used because a higher pressure may result in damaging the driver (e.g., sucking the diaphragm out of the driver) and thus, the speaker product may be damaged. For example, in testing the speaker product in  FIG. 2 , the inventors found that a minimum of 20 mT worked best to be sure most of the oxygen and water, etc. was removed from the plasma chamber and a maximum of 100 mT worked well to be sure the product was not damaged. If just one or more speaker covers are in the plasma chamber, the inventors found that a higher pressure may be obtained without damaging the covers because speaker covers typically do not have more fragile components (e.g., such as a diaphragm). 
     Once a predetermined minimum vacuum is achieved (e.g., 10 mT, 20 mT, 50 mT, etc.), then gas may be introduced into the plasma chamber to pre-clean the one or more speaker covers or speaker products (step  103 ). Before introducing the gas, there may be a predetermined stabilization period (e.g., 60 seconds) for which the minimum vacuum must be sustained before introducing the gas to be sure that all the ambient air has been sucked out of the plasma chamber. There may be a maximum a time (e.g., 2400 seconds) for which to achieve the minimum vacuum, after which the vacuum may turn off or an alert may be provided (e.g., red light on the plasma chamber) to indicate that the minimum vacuum was not achieved. 
     Examples of gas used to pre-clean the one or more speakers covers or speaker products may include oxygen, nitrogen or helium. In a preferred embodiment nitrogen or helium may be used over oxygen because the inventors found that oxygen may be too aggressive to use on a speaker cover or speaker product and may cause discoloration of the speaker fabric or other material used for the speaker cover. Nitrogen may be preferred over helium because it may be less expensive than helium. 
     The gas may be introduced for a predetermined amount of time (e.g., 60 seconds). Next plasma is pulsed (e.g., at 250 watts, 350 watts, etc.) for a predetermined time for pre-cleaning (step  104 ). 
     Next, a predetermined amount of fluoro monomer (e.g., 120 sccm) may be introduced into the plasma chamber (step  105 ) for a predetermined amount of processing time (e.g., pulsed at 250 watts for 900 seconds) (step  106 ). The fluoro monomer may be introduced via a hot plate and the hot plate may have a predetermined temperature for heating the fluoro monomer (e.g., between 60-100° C.). An exemplary fluoro monomer may include: 1H,1H,2H,2H-TRIDECAFLUOROOCTYL METHACRYLATE. 
     After processing is complete any excess monomer gas may be removed from the chamber (step  107 ) and the vacuum may be released (step  108 ). The finished speaker products or speaker covers may then be removed from the plasma chamber (step  109 ). 
       FIGS. 3 and 4  show acoustic performance of a speaker cover treated using a plasma process according to embodiments of the invention. As explained earlier, the inventors expected the acoustic transparency to decrease with the plasma treatment because it is generally known that anything that is added to fabric typically decreases the acoustic transparency. The fact that testing showed that speaker cover fabric with the plasma treatment did not decrease the acoustic performance of the speaker, is an unexpected result of the present invention and stands in sharp contrast to the results predicted by the inventors. It is counterintuitive that adding something to the material of a speaker cover would not decrease the acoustic transparency of the speaker cover. 
       FIG. 3  shows the transmission loss or acoustic transparency test results of a fabric that is a blend of thermoplastic elastomer, polyamide and polyester weave treated using a plasma process according to embodiments of the invention. The graph in  FIG. 3  shows the average high frequency transmission loss difference between plasma-treated and non-plasma-treated fabric, as shown by the middle line  301 . The frequency range tested is between 500 Hz and 20 kHz. 
     The top line  302  and the bottom line  303  show +/− two standard deviations of results of testing non-plasma-treated fabric. The top line  302  is plus two standard deviations and the bottom line  303  is minus two standard deviations. The middle line  301  indicates the average high frequency transmission loss difference between the plasma-treated fabric and the non-plasma-treated fabric. The fact that the middle line falls in between the top line  302  and the bottom line  303  indicates that there is no statistically significant measurable difference between the plasma-treated fabric and the non-plasma-treated fabric. Moreover, the fact that the middle line  301 , is between the two lines  302  and  303 , shows that the results are within a 95% confidence interval. Any differences in the measurement of transmission loss cannot be distinguished from sample to sample variation and test set up variability. Accordingly, as can be seen by line  301  of the graph, there is no statistically significant measurable difference in acoustic transparency between the plasma treated speaker cover fabric, and the non-plasma-treated speaker cover fabric. 
       FIG. 4  shows the transmission loss or acoustic transparency test results of a fabric that is polyester knit material treated using a plasma process according to embodiments of the invention. The graph in  FIG. 4  shows the average high frequency transmission loss difference between plasma-treated and non-plasma-treated fabric, as shown by the middle line  401 . The frequency range tested is between 500 Hz and 20 kHz. 
     The top line  402  and the bottom line  403  show +/− two standard deviations of results of testing non-plasma-treated fabric. The top line  402  is plus two standard deviations and the bottom line  403  is minus two standard deviations. The middle line  401  indicates the average high frequency transmission loss difference between the plasma-treated fabric and the non-plasma-treated fabric. The fact that the middle line falls in between the top line  402  and the bottom line  403  indicates that there is no statistically significant measurable difference between the plasma-treated fabric and the non-plasma treated fabric. Moreover, the fact that the middle line  401 , is between the two lines  402  and  403 , shows that the results are within a 95% confidence interval. Any differences in the measurement of transmission loss is not distinguishable from sample to sample variation and test set up variability. Accordingly, as can be seen by line  401  of the graph, there is no statistically significant measurable difference in acoustic transparency between the plasma-treated speaker cover fabric, and the non-plasma-treated speaker cover fabric. 
     Through hard work and experimentation, the inventors found that using the following parameters worked well for the speaker product in  FIG. 2  using a particular plasma chamber: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Step 
                 1 
               
               
                   
                 Basepressure (mT) 
                 20 
               
               
                   
                 Max pumpdown (s) 
                 2400 
               
               
                   
                 LR extra (s) 
                 0 
               
               
                   
                 LR test time (s) 
                 0 
               
               
                   
                 Max allowed LR (mT) 
                 0 
               
               
                   
                 Stabilize time (s) 
                 60 
               
               
                   
                 Work pressure (mT) 
                 50 
               
               
                   
                 Gas switching time (s) 
                 60 
               
               
                   
                 RF power (W) 
                 350 
               
               
                   
                 RF pulse 
                 on 
               
               
                   
                 Flow MFC 1 (sccm) 
                 0 
               
               
                   
                 Flow MFC 2 (sccm) 
                 0 
               
               
                   
                 Flow LMC (sccm) 
                 120 
               
               
                   
                 Process time (s) 
                 900 
               
               
                   
                 Max temp (° C.) 
                 100 
               
               
                   
                 Temperature 
               
               
                   
                 heater 1 Cannister (° C.°) 
                 160 
               
               
                   
                 heater 2 Cann-LMS (° C.°) 
                 160 
               
               
                   
                 heater 3 LMS-Chamber 
                 150 
               
               
                   
                 (° C.°) 
               
               
                   
                 heater 4 pumptubing (° C.°) 
                 70 
               
               
                   
                 heater 5 chamber 1 (° C.°) 
                 40 
               
               
                   
                 heater 6 chamber 2 (° C.°) 
                 40 
               
               
                   
                 heater 7 chamber 3 (° C.°) 
                 40 
               
               
                   
                 heater 8 chamber 4 (° C.°) 
                 40 
               
               
                   
                 heater 9 chamber 5 (° C.°) 
                 40 
               
               
                   
                 heater 10 door (° C.°) 
                 40 
               
               
                   
                 Max time to temp (m) 
                 60 
               
               
                   
                   
               
             
          
         
       
     
     The parameters may vary depending upon the characteristics of the particular speaker cover or product, the size and type of the plasma chamber, etc. 
     The detailed embodiments described herein are illustrative and should not be taken as limiting the invention. The invention includes all such embodiments as may come within the scope and spirit of the following claims and equivalents thereto.