Development of “Wood Cone Speaker”
Text: Shun Hing JVC Ltd.Utilization of wooden diaphragm for the first time in the world*1 using unique molding technologyDevelopment of “Wood Cone Speaker”(Total of 9 patents pending)
~ Realization of natural sounds that truly reproduce the original sounds of instruments and vocalists ~
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From left, “wood cone speaker” unit and diaphragm.
Victor Company of Japan, Limited (JVC) has developed for the first time in the world*1 the “wood cone” speaker that utilizes a diaphragm press molded from “wood” in the speaker for superior acoustic characteristics compared to diaphragm materials found in conventional speakers.
This technology, developed based on JVC’s quest for reproducing original sound and acoustic technologies cultivated over long periods of time, realizes natural sounds that truly reproduce the original sounds of instruments and vocalists.
<Main characteristics>
1. Development of wooden diaphragm for the first time in the world*1 that truly reproduces original sounds
Using JVC’s unique molding technology, wooden sheets of approximately 0.28mm thickness were molded into cone-type and dome-type diaphragms, while at the same time suppressing deformation from rapid changes in temperature and humidity. By molding the diaphragms without the loss of lignin, etc., which are the essential elements in reproducing natural acoustics in wood, natural sounds that truly reproduce the original sounds of instruments and vocalists were made possible. The tonal qualities can also be kept consistent by using wood on all speaker cabinets, diaphragm and center cap.
*1 As of March 25, 2003 as mass production technology
2. High propagation rates and ideal internal loss for realizing superior resolution*2 (See Table 1)
Materials with high propagation rates and internal loss are ideal for use as diaphragms. Wood is material that is closest to such ideal characteristics. Among the various types of wood, solid birch holding the most superior characteristics was used. The wood is light weight, rigid and reproduces crisp and clear sounds and outstanding resolution.
*2 Since shocks are damped internally, little loss causes resonance in speaker diaphragms.
3. Anisotropic characteristics that prevent generation of standing waves*3 (See Fig. 1)
With the anisotropic characteristic of wood where the propagation rates are different for flow with and against the grain, resonance due to generation of standing waves commonly found in even materials was prevented to realize natural and smooth acoustical characteristics.
*3 Phenomenon where reverberation of sound waves causes acoustical characteristics to become uneven.
4. Beautiful and luxurious appearance of wood grain
Since solid wood is used, the wood grain shows beautifully on the surface for a luxurious exterior.
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<Fig. 1 Propagation rate image>
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<Development background>
With the appearance of high-quality digital contents including DVD audio and SACD, there is increasing demand for speakers with capability of reproducing in detail the quality of the original contents.
Namely, materials used commonly as diaphragms for speakers are: paper and pulp, plastic and metals such as aluminum, etc. However, such materials have reciprocal physical characteristics in which those with high propagation rates have small internal loss and those with large internal loss have low propagation rates. Hence, there were advantages and drawbacks when used as diaphragms that ideally demanded high propagation rates and large internal loss. Furthermore, standing waves commonly occur in such even materials due to equal propagation rates in all directions and the sound quality is suffered as a result (with the exception of oblicone and elliptic speakers).
JVC focused on the fact that wood held anisotropic characteristics of high propagation rates and ideal internal loss and is furthermore light and high in rigidity. As a result, the “wood cone speaker” utilizing press-molded “wood” as the diaphragm was developed for the first time in the world.
<Technical description (diaphragm fabrication)>
- Wooden diaphragms are fabricated based on the flowchart shown below. Wooden sheets of 0.28mm thickness are cut from birch trunks using the rotary method then cut into appropriate sizes by adhering thin Japanese paper onto the back. A V-shape cutaway is then made into the sheets and then saturated with lubricant to prevent cracking during the molding phase.
(Lubricant softens the wooden sheets by adding moisture and keeps the moisture within the sheets.)
- During the 1st phase press, the basic cone shape is formed. After drying, the sheets are saturated with thermosetting resin and the shape is set while proceeding through the 2nd phase press, molding lubricant saturation and 3rd phase press. Finally, the cone-type diaphragms are completed by coating a moisture-proof agent and removing the center and contours.
- By using lubricant and setting optimal values for pressing pressure, tool temperature and pressing time in each pressing phase, fabrication with yielding percentage near 100% is possible. By furthermore combining thermosetting resin and moisture-proof agent, the material can also withstand rapid changes in temperature and humidity.
Diaphragm fabrication flowchart
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* Contents of this page as of the time of press release. Contents are subject to change in the future. Please note also that the product may already be out of production/sales at the time viewed.
For further information please contact:
Toshiya Ogata, Manager
Public Relations Office
Corporate Communications Department
Victor Company of Japan, Limited (JVC)
Tel: +81-(0)3-3289-1458
Fax: +81-(0)3-3289-0376
E-mail: ogata-toshiya@jvc-victor.jp
URL: http://www.jvc-victor.co.jp
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