AUDIO SPEAKER

Ferrofluids have been extensively used in audio speakers for over 25 years. They offer significant performance advantages in tweeters, mid-ranges, woofers, compression drivers and automotive speakers. Some of the advantages in using ferrofluid include increased power handling capabilities, smoothing of frequency response curve and reduced distortion. Ferrotec, the world leader in magnetic fluid technology, offers a wide range of fluids for audio applications. Ferrofluid resides in the air gap of the magnet and completely fills the space between the coil OD/pole and coil OD/top plate. No physical containment is needed as the fluid is held in place by the strong permanent magnetic field. The choice of ferrofluid depends on specific loudspeaker requirements in terms of the damping required and the field in the gap.Two key properties of the fluid determine the correct fluid for any application: the viscosity and the magnetization value. The higher the viscosity of a ferrofluid, the greater the viscous damping of the moving mass. A fluid with the correct magnetization value must be chosen to ensure retention of the fluid in the air gap. All ferrofluids, independent of viscosity, essentially provide the same heat transfer from the voice coil to the magnet structure.

Every speaker design is unique. Some speakers, for example supertweeters, require only light damping but need very high colloidal stability of the fluid, whereas tweeters often require high viscosity fluids. To accommodate this there is a complete range of ferrofluids with varying viscosity values and magnetization properties. This means that whatever your requirements in terms of mechanical damping and fluid retention, there is probably a suitable fluid from one of our standard ranges. If not, our team of experienced audio engineers can custom engineer a new fluid to meet the performance objectives of your loudspeaker.

DOMAIN DETECTION

Ferrofluids are extensively used for the study of magnetic domain structures in magnetic tapes, rigid and floppy disks, magneto-optical disks, crystalline and amorphous alloys, garnets, steels and geological rocks. Commercial applications include the quality control of magnetic recording media and the identification of micro-defects in steel.

Ferrofluid is applied to the magnetic tape, disk or other specimen so that a thin layer of ferrofluid covers the surface. When the carrier liquid evaporates, the particles congregate at the domain boundaries. These appear as dark lines in visible light and can be viewed with a microscope. A small external magnetic field can be applied to the specimen to enhance the contrast of the pattern.

The EMG series of ferrofluids, which includes both water and mineral oil based fluid, has been developed specifically for this purpose. Domain detection kits which include samples of different ferrofluid, wetting agent and solvent are also available. Users of ferrofluid for domain detection include many audio and video tape manufacturers, TV and recording studios, forensic science laboratories and research institutions. A range of water-based and mineral oil-based domain detection fluids are available. 

OPTICAL PICK-UP

Ferrofluids are becoming increasingly popular for use for actuator damping in a variety of devices including CD players, Laser Disc players, CD-ROM drives and, DVD-ROM drives.

Introduction

The actuator in such a device is an electro-mechanical device comprised of two magnetic circuits and two discreet coils, oriented perpendicular to each other. The coils and objective lens are mounted on an integral bobbin/carrier assembly which, in turn, is suspended in the magnetic air gaps by four strands of Beryllium Copper wire. The suspension is damped by the presence of silicone rubber at its termination. In spite of the presence of the silicone rubber "damper bond", the actuator still exhibits a strong mechanical resonance which affects its settling time and vibrational characteristics. This resonance can cause errors in reading information from the disk, particularly in high speed CD-ROM and DVD-ROM drives.

Ferrofluid Solution

Ferrofluid is used to dampen vibration in various commercial dampers as well as in consumer audio loudspeakers and CD/DVD-ROM devices. Ferrofluid damping is very reliable as the viscosity and retention capability of the fluid can be easily controlled to meet device requirements. In addition to the damping benefits in audio loudspeakers, ferrofluid also provides an efficient heat transfer medium to conduct heat away from the coil. In the actuator design, ferrofluid is applied to the surface of the magnets until the quantity is sufficient to maintain intimate contact with the bobbin/carrier assembly. The fluid is retained in the magnetic field and its viscosity provides the desired mechanical resistance (damping) to the moving assembly. This improves the actuator's settling time and vibrational characteristics. Access time is also improved, particularly on warped or eccentric discs. Developed specifically for optical pickup actuators, the CF Series of ferrofluids posses the necessary wide temperature range, colloid stability and low volatility required for long term performance in these applications. Please call for full specifications for the CF Series of fluids.

OTHER DEVELOPMENT APPLICATIONS

There are a whole host of other applications for ferrofluid. Many of these are still at the R&D stage but some have already achieved a degree of commercial success. Ferrotec carries out research into new applications for ferrofluids both on its own and through strategic partnerships with other companies. Other applications areas in which ferrofluids have been used include material recycling, power and distribution transformers, quiet solenoids, sensors and switches.

Material Recycling

Ferrofluid has an unique property in that its apparent density can be increased by applying a magnetic field to the ferrofluid. This physical characteristic creates the ability to separate objects of different density through floatation or sinking. Ferrofluids have been used for years in material separation processes in the mining industries, although with limited economic advantage. Ferrotec has been working with material recycling and mining industry leaders to commercialise this application. To enhance the economic viability of these processes, Ferrotec has developed a patent-pending process for the reclamation and reconstitution of ferrofluids. This innovation will create economic advantage for the separation industries to enhance the existing separation performance characteristics of the materials.

Electrical Transformers

Ferrotec Corporation has been working in partnership with a major manufacturer of electrical power equipment, to develop ferrofluid for liquid-filled transformer applications. Ferrofluids have been shown to provide both thermal and dielectric benefits to transformers. Ferrofluid can be utilized to improve cooling by enhancing fluid circulation within transformer windings. Ferrofluid can also be applied to increase transformer capacity to withstand lightning impulses, while also minimizing the effect of moisture on typical insulating fluids. The benefits of ferrofluid may be utilized to design smaller, more efficient new transformers, or to extend the life or loading capability of existing units.

Quiet Solenoids

The introduction of a ferrofluid into a solenoid dramatically reduces the noise level of certain equipment, such as home care kidney dialysis machines. This in turn reduces the need for noise suppression insulation, allowing a more cost effective and simpler design that is more portable. In addition to the obvious benefits of quieter operation and portability, the ferrofluid-based solenoids make the equipment more reliable.

Sensors & Switches