Eminent LFT-10 User manual

The LFT-10 Linear Field Transducer Car Audio
Loudspeaker

WARNING: Any car audio system should be installed only by experienced professionals.
All components should be securely fastened to factory authorized locations with proper
hardware. All wiring should be completed in accordance with the manufacturers
recommendations. Injury could occur if components are not fastened properly.
Position and fasten components so that in the event of an accident, injuries will not occur.
Eminent Technology, Inc. is not responsible for loss or injury do to accidents or improper
use of its products.
Hearing damage can result due to exposure to loud sounds. We recommend purchasing a
sound pressure level meter (Radio Shack sells one for about $30) and using it to learn to
listen to your sound system at something less than 90 dB sound pressure levels. Hearing
loss occurs slowly, you will not know you have lost your hearing until the damage is
done.
Strong magnetic fields exist in and around the LFT-10. Be careful when handling
hardware and tools during installation.

The LFT-10
The LFT-10 represents a technological breakthrough for sound reproduction in the
automobile. It is the first planar magnetic loudspeaker specifically designed for use in car
audio.
It is intended for car audiophiles who are serious about high quality sound reproduction.
If this is the goal, the LFT-10 will fundamentally change the way sound is listened to in a
car.
Most of the technical advances in loudspeaker technology for the automobile have been
evolutionary. The LFT-10 represents a revolutionary change. Consider the following:
-- The LFT-10 has distortion 10 to 100 times less than cone speakers at moderate levels.
It has distortion as low as amplifiers. For the first time in a car you will you will be able
hear distortion levels of the electronics and program material.
-- The LFT-10 is useable over a seven octave frequency range. Most other car
loudspeakers are only useful only over a 3 to 5 octave range.
-- The LFT-10 has accurate phase response over its full operating range. Cone
loudspeakers cannot make this claim. Because of the LFT-10's wide bandwidth, accurate
phase response, and impulse response, a car sound system's clarity and imaging are
improved to new levels.
-- The thin profile of the LFT-10 (less than 1 inch total) allows positioning where no
other loudspeakers can go.
-- Because of its thin profile, placement is limited to the imagination of the installer.
-- The LFT-10 can be used as a dipole mounted on a small flat baffle in free space.
-- The LFT-10 has sensitivity and sound pressure level limitations which should be
carefully considered for each application.

THE LINEAR FIELD TRANSDUCER
Eminent Technology's Linear Field Transducer, introduced as the LFT, represents a new
approach to the design and construction of a high-quality car loudspeaker*. It builds on
the strengths of previous planar designs while eliminating many of their drawbacks to
allow use in a car.
DIAPHRAGM CONSTRUCTION
The construction of the LFT-10 begins by laminating a very thin sheet of aluminum foil
to a half-mil-thick sheet of Mylar. A voice grid pattern, created by means of CAD
(Computer-Aided Design) technology, is silk-screened onto the foil side; the remainder
of the aluminum--the part not covered by ink from silk-screening is chemically etched
away, in a manner similar to the etching of traces on a printed-circuit board. The ink is
then washed away, leaving a voice grid of near perfect uniformity. This technique results
in a diaphragm/voice coil grid that is still less than two mils in total thickness, and also
permits relatively narrow spaces between the individual traces, so the diaphragm can be
evenly driven over its entire surface.
THE MAGNET / FRAME STRUCTURE
The magnet/frame structure developed for the LFT-10 is also unique. Eminent
Technology builds its magnets into individual steel channels, the size and shape of which
have been carefully designed to help "focus" the magnetic flux lines and concentrate the
strength of the magnetic field on the appropriate area of the diaphragm/voice grid. These
channels are then welded to steel frames, which in turn are bolted to the frame that holds
the diaphragm in place.
Interestingly, one of the biggest challenges faced in creating a true push-pull dynamic
speaker was not a design consideration but rather a matter of construction difficulty: to
assemble a perfect rigid structure with very powerful permanent magnets at the front and
the rear, both sides opposing each other with tremendous force. The second design
challenge is making a planar speaker both small enough and efficient enough for use in
car stereo.
* The design and construction of the LFT-10 is patented
By applying such new techniques to planar loudspeaker construction, Eminent
Technology has been able to eliminate many of the flaws inherent in earlier designs
Cloth is used on the back side of the speaker to resistively load the diaphragm. This
lowers the Q of the diaphragms free air resonance.

Since it is now possible to have a powerful, precisely aligned magnet structure on both
sides of the diaphragm, true push-pull operation has been achieved: Regardless of the
degree of excursion the diaphragm undergoes, the voice element is always optimally
positioned within the magnetic field. The result is extremely linear performance
throughout the audible range, with a profound increase in dynamic range and and
absolute minimum of distortion.

CHOOSING A MOUNTING LOCATION
Although the LFT-10 could be placed in a box it, was designed to operate in free space.
Not having a sealed enclosure behind the LFT-10 is preferable to mounting it in an
enclosure.
The LFT-10 is a dipole, meaning sound radiated from the back of the speaker is exactly
the same as what comes from the front of the speaker. It is not necessary in the
automotive environment to use the back wave.
The LFT-10 should not be mounted in a sealed or vented enclosure where a woofer's rear
wave pressurizes the same cavity. Since the LFT-10's diaphragm is almost as light as the
surrounding air and is very compliant, it would look like a hole in the box. Also, the
diaphragm would bottom due to pressure changes in the box from the woofer.
Door, panel, headliner, or dash mounting is acceptable as long as there is a small amount
of space behind the speaker. The cavity (even if it is a very small space) behind the LFT-
10 should be porous (not sealed). This is critical to good lower midrange performance.
The size of the cavity is not important, but it should not be sealed.
The LFT-10 could not be mounted on a rear deck with an open back to a trunk that also
had a woofer using the trunk as its enclosure. In this case, the back of the LFT-10 would
have to be sealed from the trunk in its own enclosure.
To make use of the wide frequency response of the LFT-10, the speaker should be
positioned so that the listener is no more than 30 degrees off of the narrow axis or 10
degrees off of the wide axis.
LOW FREQUENCY SYSTEM
The LFT-10 must be supported by a low frequency system with good lower midrange (up
to 400 Hz) response to blend smoothly. High quality bass/midbass 4" to 8" drivers that
are rated to several Khz are preferable to bring up the low frequencies and lower
midrange to the LFT-10. Larger drivers should not be used (10" or greater) to attempt to
blend with the LFT-10 due to poor lower midrange performance. They can, of course, be
used as subwoofers crossed over to the midbass drivers.

DASH MOUNTING
The LFT-10 can be mounted in any number of positions within the dash. The absolute
best performance will be obtained when separate stereo environments are created for each
seating position. Locations A, B, C, D and E, F, H, I are examples of this. These positions
will give the best imaging because the ear depends on time and amplitude cues for
location. Both parameters will be kept when the right and left speakers are an equal
distance from the listener's ears.
Positions J,L and E, I are less desirable for imaging but still take advantage of the LFT-
10's clarity and low distortion. Positions J, L use glass to disperse high frequency energy.
If possible, the LFT-10 can be mounted below the dash or radiate through the existing
perforations.
Positions K and G are excellent choices for center channel operation.

HEADLINER / SUN VISOR MOUNTING
Because of its thin profile, the LFT-10 can be mounted in a headliner or in place of a sun
visor. If the LFT-10 is positioned where a sun visor is normally located, for best
performance, material behind the speaker should be sound absorbing. If the headliner is
made of cloth with padding behind it, this will be sufficient. If the area behind the LFT-
10 is reflective (vinyl or plastic), this should be cut away and a sound absorbing material
added directly behind the speaker. (Good sound absorbing materials are cloth, felt, open
cell foam rubber, pillow stuffing, bed foam, carpet, carpet foam, etc.).
If the LFT-10 is to be placed behind the headliner, the fabric in front of the speaker
should be changed to a less sound absorbent type. Synthetic fabrics are generally best in
front of speakers (polyester, dacron, nylon, rayon, etc.) and there are many other choices
at fabric stores. A simple test for good sound transmission is to hold the fabric up to a
light or window. If it appears to pass at least 20% of the light when viewed through the
fabric, it will probably work in front of a speaker without much high frequency alteration.
DIRECTIVITY
The general rule is the smaller the speaker, the better its dispersion will be at high
frequencies. As a result, along the narrow axis, the LFT-10 has better high frequency
dispersion and is useable farther off axis. Because the LFT-10 has a large flat diaphragm,
it is highly directional at high frequencies. The best performance will be obtained when
the LFT-10's are used on axis (meaning positioned so they are pointed directly toward the
listeners ears.
If the LFT-10 is only going to be used as a midrange unit and not a tweeter, then
placement is less restrictive.
If the LFT-10 is to be door mounted, it should be positioned horizontally as close as
possible to the listening position and angled up toward the listener.

BAFFLE MOUNTING
The LFT-10 does not have to be panel mounted. It can be mounted in free space on a
baffle.
A baffle is nothing more than a flat plate. The LFT-10 is a dipole, meaning the same
sound is radiated from the front and back of the speaker. Because the rear wave is out of
phase with the front wave, longer wavelengths (lower frequencies) will come around the
speaker and cancel out (This is why a woofer has no bass when operated in free space). A
baffle helps prevent back wave cancellation and a larger baffle lowers the cutoff
frequency (the frequency where cancellation occurs). Baffle mounting or just using the
panel by itself in free space opens up a lot of possibilities regarding installation. Use your
imagination.

The best low midrange performance is attained when a baffle is used. Its size is not
critical, but a larger baffle allows a lower crossover frequency.
The LFT-10 mounted in a baffle can be installed in the rear area of fastback/hatchback or
rear deck of cars without the loss of much space. With this type of installation, the LFT-
10 can be directed toward the listener. When used as a dipole, the back of the speaker
should be at least 1" from any surface behind it, but the side of the baffle can be against
the side of the interior space.
A baffle can be constructed of plywood or particle board (or strips) as shown. It could be
painted or fabric wrapped to match an interior.
CROSSOVER
An electronic or passive crossover can be used with the LFT-10. If an electronic
crossover is used, a high pass section with its lower frequency limit set between 200-400
Hz is acceptable. Some overlap in the crossover frequency signal being fed to the LFT-10
is acceptable and may help in blending with the midbass drivers through the crossover
region. The midbass driver should be rolled off at 400 Hz quickly to prevent midrange
coloration. The LFT-10 is acoustically limited to about 350 Hz and resistive loading
prevents substantial output below that frequency. This allows some overlap in the
crossover frequencies. Eminent Technology can supply passive crossover components on
request.
The following graphs will aid in determining values for any passive crossover: