Eminent LFT-11 User manual

The LFT-11 Planar Magnetic Multimedia Reference Loudspeaker
Congratulations on purchasing the Eminent Technology LFT-11. The LFT-11 is the
most advanced loudspeaker technology available for computer multimedia. With proper
care and use, the LFT-11 should last many years. To get the most out of the LFT-11,
please read the manual carefully. Do not forget to fill out the warranty form in the back of
the manual so we can register your purchase.
UNPACKING
The shipping box should contain a Manual (This document), Woofer Cabinet,
Amplifier, Two Planar Desktop Speakers, Monitor Stand, and Connecting Cables.
Remove all of the components. Be careful with the speakers in the woofer cabinet making
sure that you do not push inward on the speaker cones through the cloth covering as
damage could result.
SETTING UP THE LFT-11
The woofer cabinet is designed to be positioned underneath or beside a desk.
Ideally it should be positioned on the floor underneath the monitor firing in the direction
of the listener however this is not critical to achieve the best performance.
A stand is supplied to provide a location for the amplifier directly underneath the
monitor. In some installations, this may not be practical, however we found that it is a
user-friendly location allowing quick access to the volume and tone controls. In any case,
be sure and position the amplifier where nothing is directly on top of it preventing heat
from escaping.

The Planar Desktop Speakers are designed to be positioned on either side of the
monitor. They could be placed anywhere around the monitor. Generally they should be
at least three inches from the wall behind them for best sound quality. This is the only
limitation. We recommend placing them on the desktop so that they can aim directly at
the listener’s ears. For the best high frequency performance the right speaker should aim
up and toward your right ear and the left speaker should aim up and toward your left ear.
Make the electrical connections to the speakers as shown on the next page. Plug in
the right desktop speaker cable (1/4 inch phone plug) into the socket on the back of the
woofer cabinet designated "right" and the left desktop speakers cable into the left socket.
The cable coming from the amplifier speaker output terminals is attached to the center
connector.

Eminent
Technology
Incorporated
225 East Palmer Street
Tallahassee,FL 32301
R
LFT
LINEAR FIELD TRANSDUCER
MODEL NO. LFT-11
SERIAL NO.
Made in the United States U.S. Patent #4,837,838
Amplifier Input
Left Desktop Right Desktop
Speaker Speaker
Electrical connections from the amplifier to the woofer cable are as follows:
Red = right channel positive
Green = right channel ground
White = Left channel positive
Black = Left channel negative

GETTING THE BEST PERFORMANCE FROM THE LFT-11
The LFT-11 is designed to be an accurate transducer. As a result it will reveal many
limitations in the playback medium and recordings. Differences in sound quality between
different sources such as AM or FM radio, the compact disc, or different digital recording
schemes and sampling methods will be readily apparent.
The LFT-11 is designed to have flat on axis frequency response. This may present
a problem depending on your listening taste with some program material when listening
to the speakers at low volume levels. The human ear is only sensitive to midrange and to
a lesser degree high frequencies at low sound pressure levels. Because of this, the
speakers will sound bright or thin when listened to at very low sound levels. We
recommend using the tone controls to compensate for this to obtain the frequency balance
you like. To get a more natural tonal balance at very low sound levels the treble control
could be turned down and possibly the bass control turned up slightly.
Each desktop speaker panel is purposely designed to be very directional. This
characteristic improves the ability of the speaker to project three-dimensional acoustic
images by preventing the sound from one channel from interfering with sound from the
other channel. The speakers should point directly toward the listener’s ears at a distance
of about 30 inches from the center of the speaker to each ear; if the frequency balance is
too bright when the speakers are aimed directly toward your ears then aim them slightly
outward. Well-recorded music can contain information, which will place musical
instruments and voices between and around the speakers. Position the speakers to get the
best tonal balance and maximize this effect. If positioned correctly they can project
apparent sound sources well beyond the boundaries of the speakers provided that the
program material contains the correct information.

Most Computer systems are installed in areas where the wall behind the speakers is
acoustically reflective. To get the best tonal balance from the LFT-11 we would suggest
experimenting with placing some sound absorbing material on the wall behind the
desktop speakers and monitor. Open cell foam and carpet are good choices as sound
absorbers.
WOOFER POSITIONING
The frequency balance of the LFT-11 was designed to have essentially flat
response in the average computer desktop installation. Because the LFT-11 woofer
section has extended low frequency output it easily excites room resonance modes, which
may result in too much or too little bass output depending on its position. We found a
large variation when moving the system from computer system to computer system in
different rooms. An alternate position for the woofer is shown below:
The above woofer position may have slightly less bass output.
There are many possible positions for the woofer cabinet to achieve the best
performance. We recommend using recorded music on a compact disk as the reference to
determine the best position of the speakers for sound quality.

AMPLIFIER
Any audio amplifier can be used with the LFT-11. The minimum recommended
amplifier power rating is 10 watts RMS per channel. We do not believe any built in
amplifier that is included on an internal sound card has sufficient amplifier power to drive
the LFT-11 to useable levels directly without the use of an external amplifier. The Radio
Shack Optimus STA-300 amplifier included with the LFT -11 is rated at 15 watts RMS
per channel and will drive the LFT-11 to suitable levels for most situations. Any other
power amplifier or receiver can be used with the LFT-11 with a RMS power rating of
between 10 and 50 watts per channel.
USING THE LFT-11 AS A HOME STEREO SYSTEM
Although the LFT-11 can fill a room with sound, this is not what the speaker is
designed for. The same characteristic that gives the LFT-11 superior performance as a
close up on axis speaker causes limitations in sound quality off -axis. Because the planar
panels are purposely designed to be very directional, their off -axis high frequency
response rolls off quickly and the overall frequency balance of the speaker will change.
When you are not directly in front of the speaker, the low frequency output of the speaker
will be emphasized and high frequencies will be lost. You can use the tone controls to
compensate for this somewhat to get a satisfactory off axis performance.
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 multimedia loudspeaker*.
It builds on the strengths of previous planar designs while eliminating many of their
drawbacks to allow use with computers.

DIAPHRAGM CONSTRUCTION
The construction of the LFT-11 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.
With this construction the entire diaphragm area of the LFT-11 is driven full range.
For midrange and high frequencies the wavelength of sound is smaller than the
diaphragm making the speaker very directional. This characteristic substantially improves
performance for separation and three-dimensional effects over speakers that use
conventional cone drivers. It also lowers off axis sound levels.
THE MAGNET / FRAME STRUCTURE
The magnet/frame structure developed for the LFT-11 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. These channels reduce stray magnetic fields preventing monitor
convergence problems or damage to magnetic media in close proximity to the speaker.
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 computer multimedia.
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 backside of the speaker to resistively load the diaphragm.
This lowers the Q of the diaphragms free air resonance.
* The design and construction of the LFT-11 is patented
Ceramic Magnets S N N S
Magnetic Field
Focusing Channels Voice Grid
Speaker Frame
Mylar Diaphragm
Diaphragm Frame
LFT-11 LINEAR FIELD TRANSDUCER
Top View Cross Section
S N N S
S N N S
S N N S
Spacers

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.
TECHNICAL SPECIFICATIONS
Frequency Response 35Hz -20Khz + or -4dB
Maximum power input 50 watts RMS per channel
Maximum sound pressure level 103 dB at 1 meter
Crossover Frequency 200Hz
Woofers 2 X 6.5 inch Eminence
Impedance 8 ohms nominal

+
+
_
C1 L1
R1
C2
_
+
C1
C3
R1
L1
L2
L3
C1= 220 uF
C2= 3.3 uF
C3= 330 uF
L1= .55mH
L2= 5.5mH
L3= 1.5mH
R1= 8 ohms
Woofer resistance = 8
LFT panel resistance = 5.6
Note: If additional low frequency output is desired for your application an additional
10 watt-8 ohm resistor can be placed in parallel with R1. This resistor is located on the
back of the woofer. Contact the factory for the resistor or if you have any questions
regarding this.

The LFT-11 Measured Frequency Response
The LFT-11 Impedance Curve
Copyright © 1995-2003

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Eminent Technology
Warranty Form LFT-11
Please complete this form and return to :
Eminent Technology Inc.
P.O. Box 6894
Tallahassee, FL 32314
USA