SPOTLIGHT

Quality Cones From AsiaYen LungBy Jimmy Ying and Rob Baum

This month’s profile is part of Voice Coil’s series on Chi-nese cone manufacturers. With so much of the speaker as-sembly business moving to China, European and Americanspeaker designers need to know more about Chinese softpart vendors. It is likely that the frames and magnetic struc-tures were already sourced from China when the speaker wasassembled in the US or Europe, but the cones were sourcedfrom American factories.

Now, with Chinese assembly, it is expedient to source asmuch local content as possible. A number of the Chinesecone vendors are seeking US marketing and sales partnerswho already have a customer base, tooling, paper beatingtechnology, and the pulp formulations European and Amer-ican customers prefer.

One Chinese cone vendor that fits this description is YenLung (which means “develop continually, run perpetually”).

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FIGURE 2: Surround detail.

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Established in 1983, Yen Lung (Photo 1) was one of the lead-ing cone paper producers in Taiwan. In 1995, with manu-facturing costs rising in Taiwan and their customer basemoving to China, they shifted to southern China to followboth their customers and lower production costs.

The Taiwan factory continues the production of high-valueand upscale cones. A workforce of 800 produces 6.5 millioncones per month. Yen Lung supplies brand names includingSharp, Sony, JBL, Sansui, Infinity, Pioneer, Onkyo,Blaupunkt, and Kenwood. Most of Yen Lung’s exports are toEurope; only a small percentage of their output ends up in theUS, and now they would like to expand their exports there.

The factory in Dongguan in southern China contains11580m2 of usable factory space, with 1700m2 of warehousespace for materials and 600m2 of space for finished goods;the total land area is 17,333m2. Yen Lung is 100% Tai-wanese, and owns the land and buildings. They passedQS9000 inspection in September 2001.

There are a dozen cone factories in south China alone.From afar, it would be easy to lump all these factories to-gether. But once you begin working with them, you findthatlike in the USnot just dedicated, but also interest-ing, characters run them.

Perhaps Yen Lung’s Michael Lin (Photo 2) “takes thecake.” Michael started out with formal training in pre-med,initially making his living doing autopsies in a coroner’s of-fice. Then he became a high school math teacher (his wife isstill a teacher). This did not seem to agree with him, andeventually he founded Yen Lung in Taiwan.

Lin’s favorite activity is racing around the neighborhood onhis motorcycle. Since Yen Lung is a major factory in the town,

25MARCH 2004

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the mayor and local police chief are afraid of losing a key em-ployer in a motorcycle accident. So whenever Michael speedsoff on his bike, the police chase him down and give him a rideback home in a police car. Aside from motorcycle racing downcity streets, a morning exercise run is part of his routine.Michael Lin and his associates at Yen Lung (General Managerof Dongguan Yenlung, Edward Lin, and General Manager ofSuzhou Yenlung, Yu Tian Lin) are a committed, decent, andhonest group of men who work hard to make a good productand try their best to satisfy their customers.

ProductsYen Lung offers a wide variety of materials: paper (in-

cluding pressed, semi-pressed, and non-pressed); variousgrades of polypropylene (including premium grades fromNike); and premium cone materials such as carbon fiber andKevlar. Surrounds include foam (and water-resistantfoam), rubber, and fabric.

IMSS SurroundsYen Lung, working with Advanced Elastomer Systems (a

subsidiary of ExxonMobil Chemical) implemented andcommercialized the Injection Molded Santoprene Sur-round (IMSS) process. While many speaker cone manufac-turers thermoform Santoprene rubber sheets for surrounds,the IMSS process is unique, with significant benefits (Figures1 and 2).

Menlo Scientific first explored Santoprene rubber whenMonsanto developed it in the 1980s. While Santoprene rub-ber is stable and essentially immune to flex fatigue and envi-ronmental effects, it is difficult to glue, and edge resonanceis sometimes an issue. It seemed that Santoprene rubberneeded to be a bit lossier to reduce the edge resonance notchin the response, so in the case of autosound, subwoofers, andoutdoor speakers, the robustness outweighed the slight in-crease in the edge response notch.

When a few high-end manufacturers began using Santo-prene rubber for soft dust caps and achieved superb results, weshould have realized the problem was not in the (lack of) lossi-ness or damping of Santoprene rubber. Instead, in a thermo-formed Santoprene rubber edge, the typically hard adhesivejoint between the cone and surround (primer plus an epoxy orCA) results in a mechanical impedance mismatch, causing areflection of mechanical energy back down the cone. Also, theuniform thickness of the surround edge of a thermoformedsheet of Santoprene rubber is a less than optimal cross-sectional profile. Injection-molded surrounds permit designfreedom and precise control of the cross-sectional profile.

Yen Lung researched IMSS and devised an optimum cross-section surround profile. To everyone’s surprise the injectionmolded Santoprene rubber edge significantly outperformedthe response of modified butyl rubber and foam surrounds.Not only was the edge notch gone, but also the general re-sponse shape was smoother. The IMSS displayed a slightlybetter frequency response than rubber or foam, and a weightfar less than rubber and only slightly greater than foam. Thecost increase for this overmolded/shuttle molded surroundfeature is less than ten cents per cone.

At the beginning of 2003, Yen Lung joined the Engi-neered Fibers Technology (EFT) program. EFT is a US-

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based paper science consulting firm based in Connecticut.They analyze pulp and paper processes, instruct regardingadditives, and provide paper characteristic testing services.See www.eftfibers.com/ for details.

New HorizonsThe Shanghai FactoryJust as US cone companies watch with dismay as their

business drains to the East, Yen Lung has seen its businessshift first to the south China coast, and now to the mid-northern coast, to the region just west of Shanghai. Demandhas surged from Japanese, local customers, and all the Tai-wan transplants from Dongguan moving into the Shanghaiarea. So, to supply them all, in November of 2002 Yen Lungbuilt a new factory in eastern China, in Suzhou, 80kmnorthwest of Shanghai.

The “5S” Approach to ManufacturingYen Lung is also gradually promoting the “5S” approach,

which is arguably more important than their recent ISO 9002certificationnice as that is. The term “5S” came about be-cause the original Japanese names of each of the five principlesbegan with the letter S. Lest we forgetin our mad rush tosend all our business to China in search of a better priceit isthe Japanese who are truly the masters of heavy industrialmanufacturing, Toyota Motor Corp being the gold standard.Rob Baum visited Toyota factories in the Nagoya/Toyota Cityarea of Japan (while obtaining his MBA), as the guest of aJapanese industrial firm. He was truly impressed, not just withwhat he saw, but what he didn’t see: waste.

“5S” is essentially a highly organized, common sense ap-proach to manufacturing; an area-based system of controland improvement, as opposed to a project or product basedsystem. The concept of “5S” refers to the five basic elementsof organizational effectiveness. They are simple principles de-signed to ensure that processes and equipment perform pre-dictably, minimizing waste.

The ideas behind the “5S” principles are generally lost intranslation, but here they are anyway:

• Seiri = tidiness (clearing up/separating/sorting),• Seiton = orderliness (organizing/simplifying/coordinating),• Seiso = cleanliness (cleaning/sanitizing/sweeping),• Seiketsu = neatness (standardizing/systems/standards/

continuing),• Shitsuke = discipline (training and discipline/standardiz-

ing/self monitoring/cooperating).

This is important for Yen Lung and all manufacturingcompanies that wish to improve themselves, since waste hasmany formsand most waste is invisible. Material, timespent not adding value, idle equipment, and excess invento-ry are examples. Most companies waste substantial amountsof their available resources. Attention to “5S” also goes alongwith a key tenet of the legendary Toyota Production System:all work processes must be controlled and scientific experi-ments constantly modified and improved by the people whoactually do the work. That Yen Lung is paying attention tosuch ideas is indeed a good sign for their future as a qualitycone supplier.

Production FacilityPaper making machine: 34 setsForming machine: 22 setsCutting machine: 30 setsAttachment machine: 15 setsCoating machine: 6 setsNeck enforcement machine: 26 setsPad printing machine: 1 setPower generator 330kva: 2 setsAir-compressor: 4 setsLathe: 5 setsCNC: 1 setMilling machine: 1 setDrilling machine: 4 setsTesting EquipmentTemp and humidity chamber: 2 setsHeater: 2 setsF0 testing machine: 2 setsHeight gauge: 5 setsVernier caliper: 55 pcsThickness gauge: 16 pcsElectronic scale: 17 setsTensile strength test gauge: 7 setspH value tester: 3 pcs Dissolve tester: 1 setFoam hardness tester: 2 pcsRubber hardness tester: 2 pcsDensity gauge: 10 pcsTest of glue consistency gauge: 1 setReposition gauge: 2 sets

AdministrationDirector: Mr. Michael Lin (Contact for US and Europeancustomers)General Manager of Suzhou Yenlung: Mr. Yu Tian LinGeneral Manager of Dongguan Yenlung: Mr. Edward Lin

Contact InformationSongmushan Area, Dalong Town, Dongguan City, Guangdong Province, China e-mail: szyenlum@pub.dgnet.gd.cn(Attention: Michael Lin) +86 769 3101715FAX +86 769 3319303e-mail: yenlum@dgnet.netwebsite: http://www.yenlung.com7, Alley 68, Lane 206, Nan Feng ST.Taoyuan, Taiwan, R.O.C

Santoprene rubber is a trademark of Advanced Elastomer Sys-tems. See www.santoprene.com for details.

Michael Klasco is the President of Menlo Scientific, Ltd. inRichmond, Calif., a consulting firm to the loudspeaker industry.Jimmy Ying is an associate of Menlo Scientific.

All rights reserved. This article cannot be reprinted or translatedin whole or in part without permission of the publisher.

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