[abstract] this article is to study using the sound basin of special coating material on the surface of loudspeader basin after coating, the objective parameters such as stiffness of the static mechanical properties; T/S parameters and frequency response characteristics, harmonic distortion, such as electric acoustic characteristics, as well as the impact of subjective listening etc. Its research process are: 1. The low-frequency loudspeaker sound basin (not assembled into units) coated on the surface of different types of coating material after measuring impact on some of its static characteristics. 2. The finished product of low-frequency loudspeaker unit sound basin after coating coated on the surface of different types of materials measurement on its electric acoustic characteristics and subjective listening analysis, sums up the characteristics of the impact on the subjective and objective characteristics. 3. The factorial objective parameter change and influence of subjective listening some connection points. Try after will increase in the speaker sound cone surface coating effect on listening understood as made an impact on the speaker "tone" or have played an important role in regulating. 4. Salt basin of the sound other properties of the coating material and some application cases. 5. Knot, reasonable application of different types sound characteristics of the coating material, is can be adjust or improve the speaker's technical parameters and listening.

　　[key words] the speaker; Sound basin; Coating; Features; Influence; Application; Tone;

　　1 the introduction

　　To create the user satisfaction of the speaker unit is a design, processing and so on various production department striving goal. But in actual design process, can be carried out on the speaker's subjective listening flexible control, to meet the needs of different users is not easy, but it is also very important. For speakers into its basin is directly and the main effects on listening; For sound basin besides of material composition and processing technology, the post-processing is also the key, but it is not easy to inquiry or technical expertise of the manufacturer. The author observed the different speaker manufacturers at home and abroad can use the same type of basin and similar but finished speaker magnetic circuit structure between the subjective listening difference is very big; Also observed at present abroad is part of the speaker unit is quite clearly in its basin surface with coating, the coating material and different manufacturers use is not the same, their listening also have their own characteristics. So whether through increases in speaker sound cone surface coating method is to adjust or improve its technical parameters, or to the speaker's subjective listening personalized requirement can be an effective means of flexible control? This article will study this.

　　Based on the goods named "sant TM timbre regulator" C14B0416. 6, C010815, D11B0420 basin of the three types of sound special coating material for the experiment, the model for the D12-11 c speaker unit, the unit nominal diameter of 12 inches) (1 inch = 25.4 mm, the same below) and its basin for coated paper notes, study on low-frequency loudspeaker sound after the basin increased surface coating on its objective characteristics and the influence on its subjective listening, and introduces some application examples.

　　2 tone POTS on its objective characteristics after coating

　　2-1, the different type of solid content of coating material

　　Select four basin, one is not coated coating, the other three coated 3 different coating material, coating weight is 5 g. Changes in the weight of the natural air drying after they are shown in table 1. Visible, the solid content of different types of coating material about 39-54%.

　　2-2 in sound basin with the different influence on the static mechanical characteristics after coating material

　　Cut open the paper cone in table 1 to measure some static mechanics parameters: the stiffness of the tensile, burst, and the results are shown in table 2. Is coated with different coating of basin of static mechanics performance parameters have obvious change. Especially, the stiffness of the coated C010815 type coating has improved significantly.

　　3 different coating on the speaker unit of basin, the influence of the acoustic characteristics of some electric after coating

　　3-1, the effects of parameters such as T/S

　　Table 3 is three units respectively coated 3 kinds of coating and two without coating and coating unit each T/S before and after the coating and its parameters such as relative difference analysis, the coating weight is 5 g (the same as the coating weight in table 1).

　　Table 4 is in table 3 3 respectively coated unit and two of the three kinds of coating without coating unit T/S parameters change to carry on the classified processing and analysis, this is because considering basin is influenced by natural changes, and coated the TS parameters between different units after the coating material is relatively close, also for the sake of simplicity, in the analysis in the experimental model a limited number of cases to find out the common a try. Visible, low-frequency loudspeaker unit after coating, mainly affecting the speaker Fs in low frequency performance [1] by 2.7%, a fall of 8.7% for Qts signs, Vas fell by 2.3%; In addition a 8.2% drop in its Qms, sensitivity (simulation) SPL fell by 0.076%. So you can consider in this experiment, the speaker unit increase after coating on the properties of the low frequency effect is limited.

　　3-2, and the total harmonic distortion characteristic of frequency response characteristic

　　Figure 1 and figure 2 is the no 2 units before and after the coating and coating 2 times, the measured data of figure 3 is coated type 5 grams C010815 coating materials, figure 4 is coated type 5 grams D11B0420 coating material, figure 5 is coated 5 grams C14B0416. 6 type of coating material compared with the measured results of coating before coating.

　　In figure 1 to figure 5 can be analyzed out, the loudspeaker unit increase to 50-1800 h after coating mainly use little effects on the frequency response characteristics of the frequency band; Although in figure 4 frequency response characteristics of 27 units before coating shows the sensitivity of slightly tall, but the unit in figure 4 after coating the frequency response characteristics with other unit is close to the frequency response characteristics of before and after coating; In figure 6 with other instruments to measure the frequency response characteristics of "four units before coating," see, the sensitivity of the unit before coating with other unit is near; To infer that the measurements in figure 4 (before coating) slightly higher sensitivity may be related to measurement error.

　　According to the analysis of total harmonic distortion characteristics of three different coating material coating after the unit near the 1.2 k Hz frequency rate significantly lower total harmonic distortion of the common phenomenon, about reducing the 25-50%; While the total harmonic distortion of other frequency for different types of coating material, the phenomenon of the higher or lower, as shown in table 5.

　　3-2 of 2, 3, the influence of harmonic distortion characteristics

　　In the literature a regulating speaker unit 2, 3 methods of harmonic distortion introduced in [2], in the same speaker unit basin after coating on the surface of the coating, the 2, 3 times the impact of harmonic distortion characteristics as follows:

　　After coating C010815 type coating, the band has increased twice harmonic distortion; In addition to three harmonic distortion in 55 hz, 400-800 hz frequency has increased, mostly in the rest of the band is reduced.

　　After coating C14B0416. The type of coating, the two frequency harmonic distortion increase, 3 times harmonic distortion in decline in more than 600 hz frequency is larger.

　　After coating D11B0420 type coating, the two frequency harmonic distortion is decreased, 3 times harmonic distortion in addition to rising near the 500-600 hz frequency range, the rest of the spectrum is basically fell.

　　3-3, other characteristic measurement

　　Although these 5 units at the same Time the harmonic distortion, and four or five times before - after the accumulation of attenuation spectrum characteristics (waterfall figure), the Time - Frequency Energy (called wavelet analysis) characteristic analysis; The individual unit 10 times harmonic distortion measurement and distortion of the laser method is used for a variety of 3 d measurement, but because of the limit of the article so in this not introduced.

　　4 effects on subjective listening

　　Considering the low-frequency loudspeaker unit ultimately is to appear in the form of used in the system, so in the form of integrated into a system to the unit is subjective audition is appropriate, and not just to low-frequency unit alone.

　　4-1, audition with state of the speaker system technology

　　Use 5 does not increase coating process unit and 4, 27, 28 increase coating process unit is installed in the condition of the same system respectively: 48 litres (L) volume enclosure, 44 h - type A high-frequency compression type drive, horns, frequency divider, and so on (all) by the Chinese production to assemble into four points frequency speaker system, the frequency response and total harmonic distortion characteristics as shown in figure 7. From the point of measurement results, although the measurement of sound pressure level is higher than GB7313-87 "hi-fi speaker system minimum performance requirements of the rules, but its performance is basically reached the requirement of" fidelity ", has a relatively high noise reduction ability; Also the amplitude-frequency response difference between each system within 2 db system between the amplitude-frequency response of the relative difference is smaller.

　　The speaker system debugging process in 60 cubic meters of other instruments used in the common room of the measurement result is shown in figure 8, the frequency of the system of high frequency speaker points about 1.5 k Hz, the low-frequency speaker points higher frequency crossover point of sound pressure level increasing quantity is 5 db (theoretical ideal lifting capacity is 6 db) near intersection, the frequency spectrum of the basic characteristics of frequency response in a superposition state, few have offset the phenomenon of frequency offset and the amount is not big, prompt high frequency unit may have good acoustic frequency near the intersection of frequency phase alignment. All these objective parameters above show that the technology conditions of the speaker system is in normal state, can be used for the analysis and evaluation of subjective listening. In addition, the frequency response characteristics of the speaker system is characterized by the opinions of the reference [3], and is suitable for recreational use of to adjust the direction of the (note: in figure 7, high frequency slightly higher sensitivity in figure 8. Under the conditions of figure 8 on its high frequency drive again after 20 euro resistor in parallel, in 240 cubic meters of volume measured in the anechoic chamber frequency response characteristics of as shown in figure 7).

　　4-2, subjective listening evaluation opinions

　　Using contrast method, in order to use not coated unit system as a sample and use of coated unit system for listening, the contrast, listening respectively give advice, induction, analysis by the author. Audition is the process of the four speaker system to the staff involved in the listening respectively their studio or in the listening room, use the scene equipment such as audio, power amplifier and so on, listening to the music played talker customize and control the volume, playing songs types generally for classical music, different types of songs, card OK, different style and rhythm of music, and so on. Because it is in the audition personnel in their familiar environment and equipment condition of audition, might do so more conducive to improve the subjective audition evaluation reference value.

　　On the evaluation standard and expressions, reference and draw lessons from the national standard GB/T16463-1996 in terms of sound quality evaluation in [4], but some explanatory adjustment according to actual condition, in order to participate in the understanding of audition personnel, are shown in table 6 "to judge the wording". The opinions of subjective listening evaluation results are shown in table 6.

　　5-1, summarize the objective parameters affect the characteristics of

　　1) basin weight increased.

　　2) affects obviously some static mechanical parameters, such as tensile, burst and stiffness are increased.

　　3) the acoustic performance of some electric parameters such as TS, the main frequency of the speaker unit 50-1800 hz frequency response characteristic of the limited impact.

　　4) to the total harmonic distortion and 2, 3 times harmonic distortion has a significant effect.

　　5-2, summarize the impact on the subjective listening

　　Different types of coating material after coating in low-frequency loudspeaker unit sound basin, is the subjective listening has a different effect, these effects have both broadband period of changes in the listening, there are changes in the local spectrum listening.

　　5-3, analysis after the speaker sound cone surface increase coating due to objective parameter change affect subjective listening some connection points

　　5-3-1, the static mechanical characteristics affect subjective listening connection points

　　Coating type C010815 coating after its stiffness has improved significantly. Reflects the paper cone bending stiffness of the strength, stiffness is higher, the paper cone division of the more difficult it is to produce vibration or split the smaller the smaller the amplitude will thus distortion [5]. Can also be seen from table 6, coating and coating C010815 type on the unit of the comprehensive improvement of subjective listening effect is obvious. In addition, in the author for the various types of speaker unit nominal diameter from 2 inches to 18 inches, sound materials such as carbon fiber, paper, after coating the C010815 sound basin coating material, listen in general can significantly affect their subjective sense of the real degree and balanced degree.

　　5-3-2, electroacoustics performance impact on subjective listening connection points

　　The influence of the 5-3-2-1, total harmonic distortion

　　C010815 type coating at low frequency and high frequency significantly lower total harmonic distortion, subjective easier to accept its overall performance. But in near 500 hz of frequency increases, the total harmonic distortion is likely to be affected in the band to listen to one of the reasons.

　　Type D11B0420 coating on the total harmonic distortion of low frequency is lower but not much, feeling low frequency dynamics feeling stronger. Total harmonic distortion of low and medium frequency band have increased and reduce the frequency, reduce the total harmonic distortion in frequency, in the overall active and subjective listening high frequency is clear, the spectrum biased "boring" feeling.

　　C14B0416. 6 sound regulator in 600-1200 hz frequency band have significantly lower total harmonic distortion, listening on the cell in the spectrum is a clean and soft, broadcast listening more moderate voices.

　　The 5-3-2-2, 2, 3 times harmonic distortion effect on the subjective listening

　　After coating and coating due to impact the distortion characteristic of the original 2, 3, harmonic and see the impact of subjective listening in a specific introduced in literature [2] 3-3, here refer to the following:

　　"C010815 tone type regulator allow it to increase twice harmonic distortion and the decrease of the harmonic distortion, 3 times mean that subjective listening easier to accept its overall sound performance?

　　Listening D11B0420 type of low-frequency dynamics sense is stronger, but owe music; Most of the audience think its suitable for use in a karaoke bars and other places of entertainment. On the technical parameters, which frequently section has increased the total harmonic distortion of also have reduced frequencies, two harmonic distortion is basically increased, harmonic distortion in 3 times more than 600 hz frequency decrease.

　　C14B0416. 6 sound regulator, listening on the unit's spectrum is clean and loose, good vocal accept, this is an objective parameter corresponding to the benefits of low distortion. On the objective indicators, it twice harmonic distortion increase; But three significantly lower harmonic distortion, especially near the 1 k Hz frequency harmonic distortion reduce the proportion of 3 times larger. As at 1200 hz 3 times harmonic distortion fell from 0.76% to 0.31%. Dropped by 59%, as shown in figure 9. Listening on the unit of frequency band is a clean, soft, replay voices when listening to feeling more comfortable. This is the corresponding objective parameters to reduce the effects of three harmonic distortion. And its low frequency distortion increase (mainly increase twice harmonic distortion), also affects the low frequency of listening. "

　　Speaker in the literature "the practical technical manual introduced in [6]," odd harmonic distortion for ordinary people, are more likely than even order harmonic distortion to detect ", "odd harmonic sound more hair dry......" .

　　In literature "install short circuit ring speaker review introduced in [7]," auditory sensitivity threshold smell (valve) and nonlinear contact is obvious, when there is a low harmonic, twice, three times, for audio signal, the smell of valve is 0.1%, for piano music for 1-2%, and for playing music, audibility threshold of 7%. Auditory sensitivity also has contact with harmonic order of time, three times of harmonic distortion awareness (З а м е т н о с т ь) more than two times the second harmonic, and five times and higher order harmonic distortion of awareness is high than second harmonic distortion awareness 6-10 times.

　　So after the speaker sound cone surface increase coating, because of the changed the characteristics of the secondary harmonic distortion speaker unit 2, 3 will have obvious influence on the subjective listening.

　　5-4, try to will increase in the speaker sound cone surface coating after impact on listening to understand as made an impact on the speaker "tone" or have played an important role in regulating

　　Can be seen from the above analysis, the speaker sound basin increased after coating, is the influence on subjective listening, and also performed on objective parameters on the change of the harmonic distortion and so on, whether this change can be summarized as "sound quality" of the speaker unit or "tone" effect?

　　In the dictionary of electroacoustic [8] is introduced: "tone, also known as the" timbre ". One on the subjective feeling so as to distinguish the same loudness and pitch of two characteristics of the voice. It is a complex feeling depends mainly on sound wave, but also related with loudness and pitch ". In this experiment, loudness and pitch can be considered to be not changed, the possibility of change is more waveform.

　　In the speaker system, introduced in [9] : "people can hear the voice, whether it's voices, the sound of the Musical Instruments sound, or other objects, to be able to immediately identified..... The voice of the people to distinguish very approximate, correspond to the distinction of auditory impression, known as tone......., the key factors of timbre is: 1, the harmonic structure; 2, the time structure". In this experiment, the sound basin increased after coating on the structure of "time" is not changed, but the "harmonic structure" is having an effect.

　　In this experiment, the author thinks that the main factors influencing the "tone" is a waveform and harmonic structure. To use the same source speaker for sound playback, the waveform and harmonic distortion may be the main factors that affect their listening. , therefore, the author try to this effect that is to change the "tone", or understood as sound basin increased after coating is the speaker has influenced the overall "tone" or have played an important role in regulating.

　　6 the other properties of the coating material and application cases

　　6-1, other characteristics of the coating material

　　6-1-1, can flexible use of coating material

　　In addition to the above the coating materials as a single uniform coating ingredients used in sound basin, according to different characteristics of the speaker unit and the demand of the subjective listening, can be through the flexible use of different types of coating material and weight to different parts of the basin and coated area, in order to achieve comprehensive adjustment subjective listening for the purpose of the speaker unit (see 6-2 application cases).

　　In the 6-1-2 s, the effect of the coating material

　　Although this is only for use on the speaker unit after the coating materials for the influence of the character of statics and electroacoustics, actually the coating materials and other functional characteristics, such as waterproof, moistureproof, toughening (associated with burst degree), hard (associated with stiffness), and other functions, is for the coating material, in addition to its can rise to adjust electric acoustic parameters and the effect of subjective listening, also can solve some of the use of functional requirements, such as waterproof, moistureproof, etc. If above C010815 type coating is used in the experiment has a good waterproof performance and some hard work. Once the coating in the use of paper plates produced by the British UKM's speaker, after drying the sound overall bubble water for a few days, take out the visual almost no change, after drying and can be used normally; A user after using this type of coating material coated paper basin, through the enterprise internal quality control standards of "a type of organic solvent n hour soaking test".

　　In 6-1-3, this product has the environmental protection, the use of no special excitant odour, no smell after drying; Viscosity has adapted general can be used directly; Water-based, don't need to use organic solvent, can use water to clean before drying.

　　In the 6-1-4 s, the coating material apart from the above three kinds of models, there are very rich product series and models (see 6-2).

　　6-2 application cases

　　From now on other experiments, the sound basin to adapt to a wide range of coating materials, various models of the coating material in addition to use on the paper cone, can also be used in composite materials of basin. Speaker unit scope of the coating contains a unit from the power of large diameter low frequency (18 inches) to a small power small unit (e.g., 2 inches full frequency unit).

　　As in the basin evenly coated on the surface, is used to adjust the speaker low frequency listening: listening near 40 hz frequency C0108 series, used to adjust the near 60-80 hz frequency listening A16B series, near 80 hz frequency conditioning for listening D11B series; For different types of imported paper plates: UKM (manufacturer) paper cone (soft) pressure C0104 series, UKM paper cone (press) C0102 series, U - SONICS (manufacturer) of paper cone C0102 and D11B04 series, LC (manufacturer) paper cone (D11 SongYa type) series and C0108 series, 7 df (manufacturer) of paper cone C0108 series; The coating material is also suitable for use in the domestic advanced loudspeaker paper cone, such as used in this paper the above experiment is domestic paper cone. For sound basin of non-paper-made material: such as D11B coating on glass fiber woven sound basin can improve the elasticity of round degree and low frequency, there are users will C010815 coating for carbon fiber woven sound basin. To import the finished product of the speaker unit also has a user application B# brand in Spain, the United States E# brands, Thailand P# unit and so on.

　　7 summary

　　Through the analysis of the objective parameters and subjective listening, and some application cases of introduction, you can see, comprehensive, flexible, reasonably using different types of basin characteristics of the coating material, is can be used as adjustment and improvement of the speaker's technical parameters and listening.

　　8 afterword.

　　The author years ago began to use "to increase the sound basin coating method to adjust the speaker unit of listening, then is to make some finished speaker unit imported from Europe's subjective listening is more suitable for the Chinese market sales need, and then through constant research and use up to now, is already accumulated certain experience.

　　This article objective parameter change and influence the basis of analysis of the correlation of subjective listening is inadequate, in addition to the need to raise the level of experiment and do more for the sample analysis, also need to be further research and analysis, such as: higher harmonic distortion measurement, 3 d intermodulation distortion measurement, a variety of distortion measurement, measurement and analysis, and so on.

　　9 credit

　　Thanks to guangzhou guoguang electric appliance co., LTD. YuJin yuan chief engineer to provide information and guidance, and many times for this article puts forward amendments; Thank you Mr Yi-zhen wang; Thanks to the southeast university professor zong-han wu provides information and advice; Thank the state key laboratory of pulp and paper engineering, south China university of technology's greatest loudspeaker paper cone research base Liang Naizhong Dr/general manager to assist and static mechanical properties measurement; Thanks for guangzhou di at audio technology co., LTD. To assist and anechoic chamber electroacoustics measurements; Thanks to the assistance of guangzhou hongzhi acoustics co., LTD and distortion of basin of a variety of 3 d measurement.

　　reference

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　　[9] (day) yamamoto Beowulf, yi-zhen wang Wu Guangwei Zhang Shaogao school. The speaker system. [M]. Beijing national defence industry press, 2010, 56.