Eminent LFT-16 Owners Manual

EMINENT
TECHNOLOGY
INCORPORATED

LFT XVI

HYBRID LINEAR FIELD TRANSDUCER LOUDSPEAKER

REFERENCE MANUAL

Revised:

12/28/05

Eminent Technology, Inc. 225 East Palmer Street Tallahassee, Florida 32301

Phone:

[phone]

FAX:

[phone]

Email:

[e-mail]

Website:

www.eminent-tech.com

Strong magnetic fields are present
at and around this loudspeaker.
Devices that are adversely affected
by high levels of magnetic flux,
such as television sets and
pacemakers, should be kept at
least three feet away from each
speaker. Also, keep in mind when
any ferrous objects are brought
close to the speakers. Hold steel
tools securely when setting up and
adjusting the LFT-XVI, to prevent
a hex key or screwdriver from
slipping from your hand and
damaging the Mylar diaphragm.

ATTENTION:
STRONG
MAGNETIC
FIELDS
_____________

2

TABLE OF CONTENTS

Installation of the LFT-16 ........................................................... 5

Unpacking the Speakers ............................................................. 5

Speaker Assembly ...................................................................... 5

Positioning the Speakers in the Listening Room ....................... 5

Imaging ...................................................................................... 6

The Tweeter Level Control ........................................................ 6

Amplifier Requirements ............................................................. 6

Bi-Wiring and Bi-Amping ......................................................... 7

Bi-Amping .................................................................................. 7

Technical Description .................................................................. 8

Electrostatic Loudspeakers ......................................................... 8

Planar Magnetic Loudspeakers .................................................. 9

Ribbon Loudspeakers ............................................................... 10

Evaluating Earlier Approaches ................................................ 11

Electrostatics ............................................................................ 11

Planar Magnetics ...................................................................... 12

Ribbons .................................................................................... 12

The Linear Field Transducer .................................................... 12

Diaphragm Construction .......................................................... 13

The Magnet/Frame Structure ................................................... 13

Panel Frequencies ..................................................................... 15

General Specifications ............................................................... 15

LFT-16 Impedance Curves ........................................................ 16

LFT-16 Impedance Data ............................................................ 17

Crossover Information ............................................................... 17

Frequency Response ................................................................... 18

LFT-16 Mid-Range Panel Specifications ................................ 19

Mid-Range Panel Design ........................................................... 20

LFT-16 Woofer Specifications .................................................. 20

Additional Woofer Specifications ............................................. 22

Woofer Design ............................................................................ 22

Woofer Enclosure ....................................................................... 23

3

Warranty ..................................................................................... 24

4

A complete technical description of the LFT-16 is included in this
manual and begins on page 7. It is recommended that you become

familiar with this information because an understanding of the LFT

principals will assist you in the proper set up of these loudspeakers.

Installation of the LFT-16

The LFT-16 is shipped in one box. The box contains the two hybrid linear field
transducer loudspeakers. Remove the padding from the top and remove the grill
cloth frames, which are wrapped in cardboard. Then remove one speaker
separately from the box. Be careful not to put too much pressure on the woofer
cone when lifting the speaker out of the box. After removing the speaker from its
box place on the carpet or a soft surface.

Do not attempt to remove or loosen hardware on the drivers themselves.
The magnets are held together under great force and personal injury could
result.

There are two-assembly requirement for both speakers. To attach the grill cloth
frames, place the additional Velcro fasteners to the corners of each speaker.
Then snap the grill cloth into place. Second, adjust the setscrews at the bottom
of the speaker. Use a 3/32 allen hex wrench to adjust the desired height.

Do not attempt to remove setscrews for the bottom of each speaker.

Unpacking the Speakers

Speaker Assembly

Speaker placement is critical for correct imaging, frequency balance, low
frequency performance, and efficiency.

The LFT-16 speakers are a mirror imaged pair and should be set up with the
tweeter panels to the inside. Ideally the base of the speaker should be above the
floor 2 feet or more. The use of a speaker stand is recommended. Wall mounting
is suitable for home theater use.

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 LFT’s and the rear wall is 1 to 5 feet
in an average room.

The overall frequency balance of the LFT-16 is somewhat affected by the degree
to which the speakers are toed in toward the central listening position. The on­axis frequency response of the LFT-16 is essentially flat, and it is often best to

5

Positioning the Speakers in the Listening Room

position the speakers so that the main listening position is about
on axis with each speaker. Slight mid-range frequency balance
changes can be obtained by pointing the speakers slightly away
from the listening position. Adjusting the speakers’ degree of
vertical tilt with the pointed feet can also alter this balance.

Imaging

The Tweeter Level Control

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 high frequency performance of the LFT-16 is adjusted with
the tweeter level control. There are three tweeter level positions:
High, Mid and Low. These levels adjust the tweeter output in
approximately 3 dB increments. It is best to start with the tweeter
level setting in the middle position. Adjust the speakers for the
best overall frequency balance and then decide if more or less
high frequency energy is needed.

Amplifier Requirements

The LFT-16 is wired for 8-ohm operation and is appropriate for
use with most moderately powered tube and solid-state amplifiers.
The efficiency is 85dB with a 2.83-volt drive (1 “8” ohm watt).
The efficiency rating is lower than average. However, the LFT­16 radiates a planar wave front, and as such, on axis its apparent
efficiency at the listening position is higher than the numerical
rating implies. The LFT-16 has a minimum rating of 25 watts per
side, tube or solid state. It can handle “music power” levels (short
term burst) of 200 watts or more with out difficulty. The largest
recommended amplifier size for the LFT-16 is 200 watts.

The LFT-16 does not require a high current amplifier. A receiver
may be used if it has sufficient power. Tube amplifiers should be
used with the 8-ohm tap.

6

The LFT-XVI is configured to allow bi-wiring or bi-amping with a
minimum of trouble.

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 separate woofer and mid/tweeter inputs of the LFT-16
(All speaker cables should be the same length). The effects of bi­wiring 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 performance, while
another works best on the mid/treble side.

Bi-Wiring and Bi­Amping

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/ frequency amp, a 180Hz low-pass filter (6 dB/octave) is
required; for the mid/treble amp, a 180Hz. 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. Contact Eminent
Technology or refer to the schematic in the back of this manual to
modify the crossover for proper speaker operation.

7

Bi-Amping

The LFT-XVI

Technical Description

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.

Electrostatic Loudspeakers

To fully understand the strengths of the LFT design, one must
first consider the design and operation of this speaker's three most
notable antecedents: the push-pull electrostatic loudspeaker
(ESL); the traditional, single-ended planar magnetic loudspeaker,
and the ribbon loudspeaker.

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

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