Eminent LFT-6 User manual

1
A complete technical description of the LFT-6 is included in this
manual and begins on page 8. It is recommended that you become
familiar with this information as a thorough understanding of the
LFT principals will assist you in the proper set up of these
loudspeakers.
Position the box on its side and open the end of the shipping carton.
Remove the padding from the bottom and slide the speaker from the box as
shown below.
Open
After removing the speaker from its carton it can be leaned against a wall
standing up or placed with the front face of the speaker flat on the carpet.
Then the bubble wrap should be removed. The wrap also holds the baffles
(black triangular boards) and the grill cloth (covered by a large cardboard
sheet) to the speaker. After the wrap is removed these will separate from
the speaker.
Do not attempt to remove or loosen hardware on the drivers
themselves. The magnents are held together under great force and
personal injury could result.
Installation of
the LFT - 6
Unpacking the
Speakers

2
Assemble the feet and baffles with the speaker lying front face down on the
carpet. Use the drawing below to identify the correct hardware locations.
Grill cloths snap into place with velcro fasteners at each corner on the front
and back of the speaker.
10-32 x 3/4 Socket Head
Screw (6)
10-32 x 3/4 Socket Head
Screw (4)
10-32 x 3/4 Socket
Head Screw (2)
It may help to have two people remove the speakers from the boxes
because of their weight .
Speaker Assembly

3
Speaker placement is critical for correct imaging, frequency balance,
low frequency performance, and efficiency.
Low frequency performance in particular can be determined by the shape of
the room and the speaker's distance from the wall immediately behind
them. Typically, the optimal distance between the LFTs and the rear wall
is 2 to 5 feet in an average room. Because the diaphragm of the LFT-6 is
very low in mass relative to the air around it, the air can act to mass-load
the diaphragm, preventing large physical excursions required for deep bass
reproduction; this effect occurs when the speaker is too close to the rear
wall.
The LFT-6 comes with one felt pad applied to the back of each panel.
These pads are used to reduce the amplitude (Q) of the bump int the low
frequency responce of each panel. Each panel has a diffrent resonance
frequency in an attempt to smoth the low frequency response of the
speaker. In general all three felt pads may not be necessary. This will
depend on the room and listening position. A general rule would be if more
bass output is desired from the speaker, remove felt pads, and if less bass
output is desired, add felt pads. If you need more than is supplied with each
speaker contact the factory.
The above is not, however, the only consideration in determining the best
distance between the LFTs and the wall behind them. At certain exact
distances from the wall behind them, dipole speakers can exhibit multiple
low-frequency cancellation effects, causing bumpy, “comb-filter”-like bass
response. At the same time, low-frequency information can be reinforced
by experimenting with the distance between the listening area and the wall
behind it. Generally, if the listener is seated close to the wall behind him,
there will be more apparent low frequency information; as the listener
moves away from the wall behind him, toward the center of the room, low
frequency reinforcement will decrease. Trial and error remains the best
way to sort things out and achieve the best bass response; there are no hard
and fast rules.
Positioning the
Speakers in the
listening room
Felt Dampers

4
The overall frequency balance of the LFT-6 is somewhat affected by the
degree to which the speakers are toed in toward the central listening
position. The on-axis frequency response of the LFTs is essentially flat,
and it is often best to position the speakers so that the main listening
position is about on axis with each speaker.
SEE TEXT FOR DISTANCE
2 TO 5 FEET
2 TO 5 FEET
The Listening Room
Slight midrange frequency balance changes can be obtained by pointing the
speakers slightly away from the listening position. This balance can also be
altered by adjusting the speakers’ degree of vertical tilt with the pointed
feet.
Overall Balance
and Toe-In

5
The high frequency performance of the LFTs can be tailored with the
tweeter lever control. A jumper is mounted under the crossover cover.
There are three tweeter level positions. If the jumper is disconnected, the
treble energy is rolled off slightly and this is the lowest setting. When the
jumper is connected to the third terminal up from the bottom of the right
hand row of six terminal points, the tweeter output at its middle position.
The highest tweeter level setting is achieved when the jumper is moved up
one terminal to the fourth one. It is best to start with the tweeter level
jumper disconnected, position the speakers for the best overall frequency
balance, and the decide if more high frequency energy is needed.
Overall imaging depends primarily on the distance separating the two
speakers relative to their distance from the preferred listening position; it is
also affected by the degree of toe-in. We cannot accurately predict what
will work best in your listening room, and can suggest only that you begin
with the drawing on the previous page as a starting point or general
guideline. Keep in mind that the parameters that affect frequency balance
also tend to affect imaging properties, and vice versa, so it is best to adjust
speaker placement in small increments and to note carefully all of the
changes effected by each shift in position before proceeding further.
The LFT-6 is wired for 6-Ohm operation, and is appropriate for use with
most higher-powered tube and solid-state amplifiers. The efficiency is
83dB with a 2.83 volt drive (1 “8” Ohm watt). This efficiency rating is
lower than average. However, the LFT radiates a planar wavefront, and as
such its apparent efficiency at the listening position is higher than the
numerical rating implies. The LFT-6 has a minimum requirement of 100
watts per side, whether tube or solid-state. It can handle “music power”
levels (short-term bursts) of 500 watts or more without difficulty. In
general, the limit of the speaker is only reached when the diaphragm
actually “bottoms out” against the magnets.
The above minimum requirements are really only estimates and depend on
listening taste and the listening environment. More power will be required
if the listening room is large, or if average sound pressure levels higher than
90 dB are desired.
The Tweeter Level
Control
Imaging
Amplifier
Requirements

6
The LFT-6is configured to allow bi-wiring or bi-amping with a minimum of
trouble. The two pairs of inputs on the crossover are connected together
internally, hot to hot and ground to ground. During normal use, speaker
cables can be connected to either the top or bottom pair of inputs.
For bi-wiring or bi-amping, the internal jumpers connecting the upper and
lower input terminals must be severed. Remove the four phillips-head
screws that hold the crossover cover in place and carefully remove the
cover; there is just enough slack in the wiring between the speaker and the
cover to allow this. Sever the two jumper wires with cutting pliers and
bend them slightly so they cannot contact one another or touch the metal
cover. Severing the jumpers divides the inputs so that now the lower
terminals power the low /midfrequency drivers, and the upper terminals
power the high frequency drivers. Both pairs of inputs continue to power
their drivers through the internal crossover, which cannot be bypassed.
JUMPERS INSIDE
TWEETER INPUT
MID/WOOFER
INPUT
Bi-wiring simply means connecting a single stereo amplifier (or two mono
amps) to a pair of speakers by using two pairs of speaker cables. Connect
the hot and ground conductors of a pair of cables to the same output
terminals on one channel of the amplifier; the other ends are connected to
the now-separate woofer/mid and tweeter inputs of the LFT. (All speaker
cables should be the same length.) The effects of bi-wiring tend to be
subtle, the slight improvement may be worth the relatively modest cost of
an extra pair or speaker cables. Bi-wiring also permits experimenting with
different types of cables for the two inputs; you may find that one type is
best-suited for bass\mid performance, while another works best on the
treble side.
Bi-Wiring and Bi-
Amping
Cutting the
Terminal Jumpers

7
Bi-amping requires and additional stereo amplifier or pair of mono amps.
You will also need some means of insuring that only the desired portion of
the frequency range reaches each amplifier. The simplest way to
accomplish this is with an external electronic crossover; however, this can
also be done by hard-wiring low-pass and high-pass filters into the inputs
of the bass/mid and treble amplifiers, respectively. For the low/mid-
frequency amp, a 10kHz low-pass filter (6 dB/octave) is required; for the
treble amp, a 10kHz. high-pass filter (also 6 dB/octave) is required. If you
wish to pursue this method, your dealer or the manufacturer of your
amplifiers should be able to help you determine the specific parts necessary.
Note that you will also need a level control on either one of the stereo
amps or on the crossover, regardless of which approach you take to bi-
amping.
Bi-Amping

8
The Eminent Technology Linear Field Transducer is a
full-range, push-pull, dynamic planar loudspeaker. In
a sense, it is the magnetic equivalent of a push-pull
electrostatic loudspeaker, differing in that it requires
no step-up transformer or bias voltage, and that the
audio signal is applied directly to its diaphragm.
the LFT-VI
To fully understand the strengths of the LFT design, one must first
consider the design and operation of this speaker's three most notable
Technical
Description

9
antecedents: the push-pull electrostatic loudspeaker (ESL); the traditional,
single-ended planar magnetic loudspeaker, and the ribbon loudspeaker.

10
The electrostatic starts with a very thin (half mil or less) diaphragm made
of mylar or a similar material, to which a light coating of mildly conductive
substance such as graphite has been applied. This diaphragm is suspended
on a rigid frame and sandwiched between two stationary conductive grids
(usually perforated metal plates) called stators.
FRAME
REAR STATOR
RESISTOR
TRANSFORMER +
--
TO
AMPLIFIER
TO BIAS
VOLTAGE
SUPPLY
[PERFORATED
METAL PLATE]
FRONT
STATOR
CONDUCTIVE
DIAPHRAM
A DC charge of high voltage (in the thousands of volts) but very low
current, known as the bias voltage, is applied to the conductive diaphragm
and kept constant. A step-up transformer is introduced to increase the
usable voltage of the amplifier's output (while simultaneously decreasing
the current), and the two ends of the transformer's output coil are
connected to the two stators.
As the amplifier produces a continuously varying AC voltage, (the
amplified music signal), the charge on the two stators will also
continuously change in synchronization with the music; and since the two
stators are connected to two different ends of the transformer's output, one
stator will take on a predominantly negative charge at the same time and to
the same extent that the other stator takes on a predominantly positive
charge. The constant-charge diaphragm will thus undergo a continuously
changing state of attraction to and repulsion from the two stators as their
polarization changes, and it is this motion that excites the air to the front
and rear of the speaker and produces sound.
Electrostatic
Loudspeakers