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Summary of Contents for Eminent LFT VIII
- Page 1 EMINENT TECHNOLOGY INCORPORATED LFT VIII HYBRID LINEAR FIELD TRANSDUCER LOUDSPEAKER REFERENCE MANUAL Revised: 7/22/03 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...
- Page 2 Extremely strong magnetic fields are ATTENTION: present at and around this STRONG loudspeaker. Devices that are MAGNETIC adversely affected by high levels of FIELDS magnetic flux, such as television sets _____________ and pacemakers, should be kept at least three feet away from each speaker.
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Page 3: Table Of Contents
TABLE OF CONTENTS Installation of the LFT-VIII............5 Unpacking the Speakers.............5 Speaker Assembly..............6 Positioning the Speakers in the Listening Room .......7 Imaging ..................7 The Tweeter Level Control............8 Amplifier Requirements.............8 Bi-Wiring and Bi-Amping ............9 Bi-Amping .................9 Technical Description ..............10 Electrostatic Loudspeakers ............11 Planar Magnetic Loudspeakers ..........12 Ribbon Loudspeakers...............13 Evaluating Earlier Approaches ..........14... - Page 4 Woofer Design................29 Woofer Enclosure ..............30 Warranty ..................31 Appendix A – Hex Cam Spacer Installation ......33 Appendix B – Tweeter Diaphragm Replacement....36...
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Page 5: Installation Of The Lft-Viii
Installation of the LFT-VIII A complete technical description of the LFT-VIII 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-VIII is shipped in 3 boxes. -
Page 6: Speaker Assembly
Speaker Assemble the panel to each woofer cabinet as shown below. Assembly 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. -
Page 7: Positioning The Speakers In The Listening Room
Speaker placement is critical for correct imaging, frequency Positioning balance, low frequency performance, and efficiency. the Speakers in the Listening The LFT-VIII speakers are a mirror image pair and should be set Room up with the tweeter panels to the inside. 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. -
Page 8: The Tweeter Level Control
The Tweeter The high frequency performance of the LFT’s can be tailored with the Level Control tweeter level control. The high frequency performance of the LFT-VIII 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. -
Page 9: Bi-Wiring And Bi-Amping
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... -
Page 10: Technical Description
Technical The Eminent Technology Linear Field Description 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. -
Page 11: Electrostatic Loudspeakers
Electrostatic The electrostatic starts with a very thin (half mil or less) diaphragm made of Mylar or a similar material, to which a light Loudspeakers 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. -
Page 12: Planar Magnetic Loudspeakers
Planar Magnetic The traditional planar magnetic also starts with a thin Mylar Loudspeakers 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. -
Page 13: Ribbon Loudspeakers
Ribbon The third and final antecedent to consider is the ribbon: a distinctly different sort of transducer, but one that is similar (in Loudspeakers principle, at least) to the single-ended planar magnetic. The ribbon’s primary distinction is that its “diaphragm” and “voice element”... -
Page 14: Evaluating Earlier Approaches
Evaluating Not surprisingly, each of the approaches described above has its own Earlier unique set of pros and cons. The electrostatic, because its diaphragm is so thin and light, offers exceptionally good transient response and Approaches reproduction of subtle, low-level musical detail. And, because it is a true Electrostatics push-pull device (i.e., its diaphragm is, by design, driven from both the front and the rear), the ESL operates in a linear fashion. - 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 to move the permanent magnet structure from the edges of the element to one entire side of the element, and/or to bond the element to a “host”...
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Page 16: The Linear Field Transducer
It was not until Eminent Technology developed a special method for this assembly procedure that the Linear Field Transducer became a reality. - 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 used for reasons of economy and ease of manufacture.) thus...
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Page 18: Panel Frequencies
Panel Each LFT-VIII has two individual driver panels and a cone type Frequencies woofer. The placement of the individual drivers is shown in the following diagram. 10 KHz and above 180 to 10 KHz To 180 Hz... -
Page 19: General Specifications
Technical information General Specifications: Power Requirements 75 Watts minimum 84 dB (pink noise, 20 - 20kH) at 1 Sensitivity watt/1 meter (2.83 V) 25 Hz-20 kHz ±4 dB (typical Frequency Response room) Phase Accuracy ± 20 100 Hz -31 kHz Flat, - 6dB, -12dB at 20kHz High Frequency Level smooth roll off... -
Page 20: Lft-Viii Impedance Curve
Technical information LFT-VIII Impedance Curves The LFT-VIII 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 (75 watts per channel or more). -
Page 21: Lft-Viii Impedance Data
Technical information LFT-VIII Impedance Data The impedance curves are shown for the woofer and mid-range/tweeter inputs separated and connected. The separate woofer curve shows an impedance peak at 35 Hz (60 ohms) and a steady rise above 100 Hz due to series inductance. The mid-range and tweeter section impedance curve shows a slight rise below 150 Hz and around 10 kHz with a drop at 20 kHz. -
Page 22: Crossover Information
Technical Information Crossover Information LFT-VIII Crossover Schematic LFT-VIII Crossover Physical Layout... -
Page 23: Square Wave Performance
Technical Information Square Wave Performance The square wave performance of the LFT-VIII 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 frequency response, phase response, impulse response and transient response. -
Page 24: Frequency Response Curve
Technical Information Frequency Response... -
Page 25: Lft-Viii Panel Specifications
Technical Information LFT-VIII 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 Peak-to-Peak Diaphragm .180 Displacement Tweeter Diaphragm area 10 sq in Tweeter Peak to Peak .050 Displacement... -
Page 26: Mid Range Panel Design
Technical information 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. -
Page 27: Lft-Viii Woofer Specifications
Technical Information LFT-VIII Woofer Specifications Box Volume 23 Liters 1403 in 3 .812 ft 3 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% 0.6570 E 99.8Grams 37.62 Liters 6.02... -
Page 28: Additional Woofer Specifications
Technical Information Additional Woofer Specifications 31.73 Hz 6.79 Ohms 23.3 46.2 3.610 0.623 0.531... -
Page 29: Woofer Design
Technical Information 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 operate over a much wider bandwidth than is desirable for the LFT-VIII. -
Page 30: Woofer Enclosure
In order for the woofer to successfully blend with a planar mid-range driver, it must be very neutral. Eminent Technology engineers have a great deal of experience performing mode shape analysis using instrumentation on many different structures. The experience gained from this research was put into the design of the woofer enclosure. -
Page 31: Warranty
Under the terms of this warranty, Eminent Technology expressly does not insure for loss of use of the LFT due to failure or periods of repair. Warranty repairs will be carried out by the factory. The LFT... - Page 32 EMINENT TECHNOLOGY, INC. LFT-VIII WARRANTY FORM Name_______________________________________________________ Address_____________________________________________________ City________________________________________________________ State_______________________ Zip_________________________ Dealer Purchased From_________________________________________ Dealer Address_______________________________________________ City________________________________________________________ State_______________________ Zip_________________________ Date Purchased _______________ Serial Number R________________ L________________ Please complete this form and return to: Eminent Technology 225 East Palmer Street Tallahassee, FL 32301...
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Page 33: Appendix A - Hex Cam Spacer Installation
Appendix A HEX CAM SPACER INSTALLATION AND ADJUSTMENT FOR THE LFT-VIII Tools needed: 5/32 Allen Wrench 7/16 Open End Wrench (aluminum recommended INSTALLATION Remove machine screws (4) and spacers (8) at the 4 centrally located crossbars along outside edge of diaphragm frame (opposite tweeter) taking care not to damage diaphragm. -
Page 36: Appendix B - Tweeter Diaphragm Replacement
Appendix B TWEETER DIAPHRAGM REPLACEMENT FOR THE LFT-VIII Revised 5/24/2002 Removing The Tweeter Driver From The Frame and Separating Its Front and Back Channels Back Channels Separate the tweeter driver completely from the speaker frame. Cut the spade lug from the black tweeter wire and detach the white tweeter wire from the mid- range terminal board using a soldering iron.
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