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V O L U M E

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I S S U E

F E B R U A R Y

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I N

TH I S

I S S U E

F o cu s

New High-Performance Cone and

Diaphragm Technology

FOCUS

By Mike Klasco

New High-Performance Cone and

Diaphragm Technology

By Mike Klasco (Menlo Scientiﬁc, Ltd.)

ew diaphragm materials for speakers, from woofers to

tweeters to compression drivers to headphones, will

always be a hot topic for

Voice Coil.

It is no mystery that

lighter diaphragms with higher Young’s modulus with good

internal loss (tan delta) are the “Holy Grail.” Woven carbon

fiber has found acceptance in many revered speakers, but

the potential in achieving lighter weight has been elusive.

The issue is that the typical carbon fiber yarn used for woven

cones is too thick and to fix the shape and seal the cone

too much epoxy binder is needed. The resulting existing

construction is a superior cone, but it is limited to woofers

and midranges. While there has always been the promise

of carbon fiber compression drivers, super tweeters, and

headphone diaphragms, the carbon fiber would have to be

finer than linen.

Loudspeaker Cone Industry Suppliers 2019

DIRECTORY

By Nora Wong

ACOUSTIC PATENTS

TEST BENCH

By James Croft

Legendary 6.5” Woofer from MISCO

By Vance Dickason

INDUSTRY WATCH

By Vance Dickason

Welcome to 2019. Oxeon of Sweden has introduced thin ply

carbon diaphragms—a new category of speaker diaphragms

based on its TeXtreme thin ply carbon reinforcements (see

Photo 1).

Founded 15 years ago, Oxeon is an advanced

composites fabrication specialist and holds patents both for its

technologies and unique materials. A thin ply carbon material

is created by arranging layers of carbon fiber in an optimized

manner.

Materials can be anisotropic with the same properties in

all directions (e.g., molded paper cones), while commonly

extruded materials, such as thermoformed poly (PP) cones,

O x eo n ’ s T h i n P l y C ar b o n D i aph r ag m s

Photo 1: TeXtreme thin ply carbon fiber cone

RUSH

Studio quality sound on the go

SOUND

Today’s audiophiles aren’t just discerning; they’re

also mobile. Their #1 take-along? Headphones

that deliver the kind of crystal-clear, distortion-free

sound you can achieve only with genuine beryllium.

That’s right: Truextent

acoustic beryllium domes

now come in sizes ideal for headphone design. You’ll

capture accurate, studio-quality sound that rocks

their world — no matter how fast it’s moving.

VOICE COIL

EAM

PRESIDENT:

CONTROLLER:

EDITOR:

KC Prescott

Chuck Fellows

Vance Dickason

INTERNATIONAL EDITOR:

EDITORIAL COORDINATOR:

GRAPHICS:

ADVERTISING COORDINATOR:

João Martins

Shannon Becker

Grace Chen

Nathaniel Black

UPPORTING

OMPANIES

ALMA International 2019

AXPONA 2019

BESTON Technology Corp.

BMS Speakers GmbH

Celestion

FaitalPRO

Fountek Electronics Co., Ltd.

KLIPPEL GmbH

LaVoce Co., Ltd.

Loudspeaker Components, LLC

Materion Electrofusion

Menlo Scientific, Ltd.

MISCO

PanaSound, Ltd.

Solen Electronique, Inc.

Vance Dickason Consulting

Wavecor, Ltd.

YuonYunn Membrane Co., Ltd.

NOT A SUPPORTING COMPANY YET?

Contact Peter Wostrel (voicecoil@smmarketing.us, Phone: 978-281-7708, Fax: 978-281-7706)

to reserve space in the next issue of

Voice Coil.

February 2019

ISSN 1521-091X

Voice Coil, (ISSN 1521-091X), The Periodical for the Loudspeaker Industry, is published

monthly by KCK Media Corp., PO Box 417, Chase City, VA 23924 US,

(434) 533-0246, FAX (888) 980-1303.

Head Office:

KCK Media Corp. Phone: (434) 533-0246

PO Box 417 Chase City, VA 23924

Subscriptions:

Subscriptions to Voice Coil are available in print and digital versions. To subscribe, please visit

our website at www.voicecoilmagazine.com and complete a qualification form.

Qualified subscriptions run for one year. Renew on-line at www.voicecoilmagazine.com

Address Changes/Problems: customerservice@circuitcellar.com

Postmaster: Send address changes to Voice Coil Circulation Dept., PO Box 417,

Chase City, VA 23924.

When you qualify, you will receive an e-mail confirming your subscription. The current

issue of each digital Voice Coil will be posted to www.gotomyvcoil.com at the end of the

month. To access, use the link in the e-mail notification, or you can simply log into the

website to view your issue along with the archived issues.

For those overseas, the cost of a printed subscription is $150.00 per year. Please contact

customer service or order your subscription online at www.voicecoilmagazine.com.

US Advertising:

Strategic Media Marketing, Inc.

2 Main St., Gloucester, MA 01930 US

Phone: (978) 281-7708, Fax: (978) 281-7706, e-mail: voicecoil@smmarketing.us

Advertising rates and terms available on request.

E-mail Nathaniel Black with artwork inquiries at: advertising@audioXpress.com.

Editorial Inquiries:

Send all press releases and information to: Voice Coil, KCK Media Corp.

Editorial Dept., PO Box 417, Chase City, VA 23924.

FAX material to: (888) 980-1303 or e-mail: editorial@audioXpress.com

Legal Notice:

Quotation from Voice Coil is forbidden without written permission of the publisher.

Printed in the United States

VOICE COIL

and film diaphragms (e.g., those for tweeters, headphones,

and microspeakers) can have a machine direction (MD) or

even be biaxially oriented such as those in some polymer

films used in tweeters and headphones. The properties of thin

ply carbon materials can be application-specific and tailored

in different directions from cross-ply 0/90, but also tri-axial

offset plies and more. By optimizing the way the layers are

organized, mechanical performance can be maximized, weight

minimized, and the part can be engineered to behave in

certain desired ways in different areas and different directions.

The speaker cone breakup modes can be reduced by

breaking the symmetry in the diaphragm, as Bowers &

Wilkins pioneered with its well-known yellow aramid (Kevlar)

cones or as Scan-Speak does with its elliptic voice coils.

With thin ply carbon diaphragm technology, this can be

taken several steps further and applied to high-frequency

diaphragms. Not only is the symmetry broken, but the fiber

architecture can be engineered to optimize and control the

breakup behavior. For example, if stiffness in one direction

is preferred, then more fibers in that direction are used—

and might be beneficial in an oval headphone driver or

“race-track” smartphone speaker diaphragm, providing

controlled and precisely defined characteristics. Defining the

characteristics throughout the membrane to suppress modal

buckling will enable the design engineer to avoid the usual

notches in response of shallow diaphragm transducers.

Thin ply carbon diaphragms are application-specific

anisotropic and, therefore, have varying stiffness over the

diaphragm area and in different directions. By optimizing

the fiber architecture, the symmetric breakup modes are

replaced with more but smaller and local breakup modes.

This creates a distributed breakup with smaller peaks in

the frequency response and ultimately smoother and more

natural sound without harshness.

Oxeon engineers advanced composite constructions to

fully exploit the potential not only being as light and stiff as

possible, but also to behave in certain ways when subjected

to a load, excitation, temperature or other variables. Initial

applications required the absolute highest performance in

combination with ultralight weight from cryogenic tanks

for space applications, the next generation of commercial

airplanes and Formula One cars, and ballistics. Consider

the form of seats for commercial airplanes—while having

the ultimate goal of being as light as possible, they must

behave in certain ways when subjected to extreme forces.

Or consider a golf driver head that should maximize the

speed of the ball in a controlled manner while producing the

right sound when impacted.

Application Specifics

the conditions and challenges faced when developing

loudspeakers. “The more people we spoke to the more we

felt they were looking for the things we are specialized in—

ultralight weight and high mechanical, tailored performance,”

says Martin Turesson, Head of Thin Ply Carbon Diaphragms

at Oxeon. “Initial basic simulations of thin ply carbon

diaphragms showed that the breakup frequency could be

pushed up considerably, but we didn’t know how they would

behave when finally breaking up, even less how they would

sound.” There were concerns that, given that they were

stiffer and with a considerably lower density than aluminum,

that they would breakup badly and sound harsh.

Oxeon decided to manufacture thin ply carbon diaphragms,

have them built into drivers, measure and listen to them.

Oxeon teamed up with a major audio company and made

ten 80 mm midrange cones to compare with their premium

aramid (Kevlar) midrange cones. Measurements showed a

considerably pushed up breakup frequency and a smooth

frequency response curve. Turesson said, “Then we knew

the thin ply carbon cones measured well, but how would

they sound?” In listening tests, the acoustic team of one

of the audio companies in the trials concluded that the

sound quality was considerably improved compared to

their premium aramid cones. In the words of the acoustic

engineers: The sound was cleaner, more detailed and had a

better room representation. Details in the music that were

not audible in the aramid cones (e.g., the light tap on the

cymbal, were now clearly heard using the thin ply carbon

cones. The placement of the musicians was much clearer

with no “holes” in the stereo imaging. “This is when we

knew we had something,” Turesson said. Most surprising

was the sound, despite being clear and detailed, was not

at all harsh but smooth and natural. How come they could

sound so smooth despite the high stiffness and low weight?

Next, the Oxeon team wanted to explore whether these

same attributes could be used in speaker diaphragms to

help improve the sound quality by enabling a combination

of high breakup frequency with controlled breakup behavior

for low distortion and freedom from ringing and self-noise.

Oxeon talked to the audio industry to understand

Speaker Diaphragm Tests

Speaker diaphragms should be light and stiff to allow

for pistonic movement. For a number of variables, such as

diaphragm geometry and topology (size and shape), the

speed of sound of the material itself and the size of the

diaphragm vs. the wavelength dimensions, the diaphragm

will breakup at some transition frequency. The higher the

Young’s modulus (speed of sound through the material) the

higher the frequency point where the response gets jagged

and we have seen this transition point in the response curve

in all the speakers with which we work. If the diaphragm

material is well damped the response anomalies will not be

severe but in a poorly damped material (e.g., titanium),

the breakup will result in trashy self-noise (stress noise)

rattling/ringing and the corresponding irregular response.

Traditionally, the effects of the breakup can be reduced by

increasing mass (damping) but the stiffness is reduced by

loading on constrained layers, damping goop, etc.

Consider the analogy of a silk scarf compared to

aluminum foil—and in the case of speaker diaphragms, the

noisy rattling generated by the aluminum foil (titanium

would be worse) would be an “after taste” imposed on the

audio, masking the more subtle elements of the signal.

FEBRUARY 2019

Controlling Breakup

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