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- LFT-8b
- Reference Manual
Eminent LFT-8b Reference Manual
Summary of LFT-8b
Page 1
Eminent technology incorporated lft-8b hybrid linear field transducer loudspeaker ® reference manual revised: 10/30/07 eminent technology, inc. 225 east palmer street tallahassee, florida 32301 phone: (850) 575-5655 fax: (850) 224-5999 email: info@eminent-tech.Com website: www.Eminent-tech.Com.
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Extremely 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...
Page 3: Table Of Contents
Table of contents installation of the lft-8b ........................................................... 5 unpacking the speakers ............................................................. 5 speaker assembly ...................................................................... 6 positioning the ...
Page 4
Woofer enclosure ....................................................................... 30 warranty ..................................................................................... 31 appendix a – hex cam spacer installation ............................ 33 appendix b – tweeter diaphragm replac...
Page 5
A complete technical description of the lft-8b is included in this manual and begins on page 10. 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. The lft-8b is shipped in 3 boxe...
Page 6
Assemble the panel to each woofer cabinet as shown below. Fasten the feet to the bottom of the woofer cabinet. 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. Bolt the woofer box...
Page 7
Speaker placement is critical for correct imaging, frequency balance, low frequency performance, and efficiency. The lft-8b speakers are a mirror image pair and should be set up with the tweeter panels to the inside. Low frequency performance in particular can be determined by the shape of the room ...
Page 8
The high frequency performance of the lft’s can be tailored with the tweeter level control. The high frequency performance of the lft-8b 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 d...
Page 9
The lft-8b 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 ...
Page 10
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 direct...
Page 11
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 (...
Page 12
The traditional planar magnetic also starts with a thin mylar diaphragm, one side of which is coated with adhesive and fitted with an aluminum wire voice grid, (analogous to the voice coil of a conventional cone driver). The diaphragm is held taut in a metal frame. On the front of this frame is a la...
Page 13
The third and final antecedent to consider is the ribbon: a distinctly different sort of transducer, but one that is similar (in principle, at least) to the single-ended planar magnetic. The ribbon’s primary distinction is that its “diaphragm” and “voice element” are one and the same. A ribbon drive...
Page 14
Not surprisingly, each of the approaches described above has its own unique set of pros and cons. The electrostatic, because its diaphragm is so thin and light, offers exceptionally good transient response and reproduction of subtle, low-level musical detail. And, because it is a true push-pull devi...
Page 15
Also, when a ribbon is operated at frequencies approaching the element’s own resonant frequency (which is naturally quite low, due to its high compliance), the ribbon element stretches and “bows” to a point where it is no longer within the magnetic gap. To get around either of these problems means t...
Page 16
Eminent technology’s linear field transducer, introduced as the lft, represents a new approach to the design and construction of a high-quality loudspeaker*. It builds on the strengths of the above designs while eliminating many of their drawbacks. The construction of the lft –8b begins by laminatin...
Page 17
By applying such new techniques to planar loudspeaker construction, eminent technology has been able to eliminate many of the flaws inherent in earlier designs. The use of a welded channel-and-crossbar frame dispenses with the need for perforated sheet metal (an “off-the-shelf” material presumably u...
Page 18
Each lft-8b has two individual driver panels and a cone type woofer. The placement of the individual drivers is shown in the following diagram. 10 khz and above 180 to 10 khz to 180 hz panel frequencies 18.
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General specifications: power requirements 75 watts minimum sensitivity 84 db (pink noise, 20 - 20kh) at 1 watt/1 meter (2.83 v) frequency response 25 hz-50 khz ±4 db (typical room) phase accuracy ± 20 100 hz-31 khz ˚ high frequency level flat, - 6db, -12db at 20khz smooth roll off impedance 8 ohm r...
Page 20
Lft-8b impedance curves the lft-8b impedance is shown below. The impedance generally averages much higher than 8 ohms. This means that the speaker does not require a high current amplifier. Because of the lower than average efficiency you will still need an amplifier with a fairly high power rating ...
Page 21
Lft-8b impedance data the impedance curves shown below are for the woofer and mid-range/tweeter inputs measured individually. The woofer curve shows an impedance minimum at 75hz (10 ohms) and a steady rise above 100 hz due to series inductance. The mid-range and tweeter section impedance curves tren...
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Crossover information lft-8b crossover schematic lft-8b crossover physical layout technical information 22.
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Square wave performance the square wave performance of the lft-8b is shown below at different frequencies. Measurements were made in a normal listening room, and the microphone position was optimized for each frequency. In order for a loudspeaker to reproduce a square wave, it must have good frequen...
Page 24
Frequency response 1/3 octave, one watt, one meter technical information 24.
Page 25
Lft-8b panel specifications magnet type ceramic 8 mid-range diaphragm area 126 sq in foil thickness .00033 mylar thickness .0005 laminate adhesive thickness .00015 gap between conductors .03 peak-to-peak diaphragm displacement .180 tweeter diaphragm area 10 sq in tweeter peak to peak displacement .0...
Page 26
Mid-range panel design do not attempt to disassemble these panels. The steel frame is preventing the panel from collapsing on itself. Removal of the cap screws that hold the panel together will surely cause damage to the diaphragm and may pinch hands and fingers. The mid-range panel design (shape an...
Page 27
Lft-8b woofer specifications box volume 23 liters 1403 in3 .812 ft3 speaker diameter 8 inch magnet weight 33 oz. Impedance 8 ohms dc resistance 6.79 ohms inductance 3.89 mh free air resonance 19.65 hz ±15% c ms 0.6570 e -03 m/n m ms 99.8grams v as 37.62 liters q ms 6.02 q es .361 q ts .34 b 1 15.32 ...
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Additional woofer specifications f c 31.73 hz r e 6.79 ohms f 1 23.3 f 2 46.2 q m 1 2 f f r f − o c 3.610 q e 1 − o m r q 0.623 q t e q q q q + m e m 0.531 technical information 28.
Page 29
Woofer design the design goal for the woofer is good transient response, low q, low cutoff frequency and minimal coloration near the crossover region. For the cabinet size dictated by design, no available off the shelf woofers met our design requirements. Most off the shelf woofers are designed to o...
Page 30
Woofer enclosure the design goal for the woofer enclosure is: (1) to be as resonance free as possible (rigid) to prevent low frequency and mid-range colorations. (2) to provide sufficient internal volume to give the desired frequency response. (3) to visually appear smaller than it is when attached ...
Page 31
Eminent technology inc. Warrants the lft loudspeaker to be free from defects in materials and workmanship for a period of 30 days from the date of purchase. Within that period, any failure of the lft will be corrected without charge for parts, labor, or transportation from the factory. After this pe...
Page 32
Eminent technology, inc. Lft-8b warranty form name_______________________________________________________ address_____________________________________________________ city________________________________________________________ state_______________________ zip_________________________ dealer purchas...
Page 33
Hex cam spacer installation and adjustment for the lft-8b tools needed: 5/32 allen wrench 7/16 open end wrench (aluminum recommended) installation 1.) remove machine screws (4) and spacers (8) at the 4 centrally located crossbars along outside edge of diaphragm frame (opposite tweeter) taking care n...
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Page 36
Tweeter diaphragm replacement for the lft-8b revised 10/26/2007 remove the tweeter driver completely from the speaker frame. Disconnect the black tweeter wire spade lug from the barrier terminal block and detach the white tweeter wire from the mid-range terminal board using a soldering iron. Remove ...
Page 37
Assembling and installing the tweeter driver re-assembly of the tweeter driver should be done in the exact reverse order as it was disassembled. Re-install the tweeter driver into the speaker frame placing the spacers in their original locations. Run the black and white tweeter wires next to the two...