Au dio L ab s The Quad ESL Refurbishing Picture Book Sheldon D. Stokes Ph.D. stokes@spinn.net http://www.quadesl.
Dedicated to my loving and tolerant wife. And my parents who instilled a sense of wonder and a confidence to try things that seemed difficult or impossible. It is also dedicated to my dog Madison, who’s enthusiasm and zest for life keeps me young.
Chapter 1 Introduction The Quad ESL 1 , introduced in 1957, has become a true icon in the realm of high performance audio. It was revolutionary when it was introduced, the first production full range electrostatic speaker. For many, it was a revelation, the first uncolored speaker capable of showing what was really buried in those LP’s and tapes. For others it was a quirky little speaker that couldn’t play loudly, and was bass shy.
CHAPTER 1. INTRODUCTION is unrivaled, even by modern speakers that have the benefit of forty plus years of technology advancement and larger final costs. Chances are that if you are interested in the Quad ESL and this book, you are one of the people who understand the magic of the Quad ESL, and I am “Preaching to the choir” so to speak. Many words have been written about the amazing performance of the original Quad ESL’s.
Chapter 2 General ESL Operation Electrostatic Speakers are conceptually very simple devices, an electrical diagram is shown in figure 2.1. The heart if the speaker is a stretched thin film diaphragm that is suspended between perforated conductive stator panels. The distance between the stators and the diaphragm is typically small, on the order of 1/16th to 1/8th of an inch for the treble and bass panels respectively. The diaphragm is coated with a slightly electrically conductive coating.
CHAPTER 2. GENERAL ESL OPERATION 6 Diaphragm Stator Power Supply Audio Signal in Input Transformer Figure 2.1: Basic Electrostatic Loudspeaker Components and the treble to be more dispersive (this speaker was designed back when 15 watts was a lot of power). The schematic for the later model Quad ESL is shown in figure 2.2. The left side of the schematic (shown within the dotted box) is power supply which is bolted to the right side of the speaker when viewed from the back.
Treble Panel Audio Transformer 180 kΩ 180 kΩ Black 15 240v 220v 0.01 µF 0.01 µF 0.01 µF 4 14 Brown 330 kΩ 5 10 150 kΩ Blue Rectifier Block 180 kΩ EHT Unit Bass Panel Bass Panel 7 8 2 x 560 pF 3 0.01 µF 9 110v 0.01 µF 0.01 µF 0.01 µF Front Back 16 Brown 0.01 µF Input 13 7 180 kΩ 2.2 mΩ 120v 1500 PIV 270 kΩ 560 pF Blue 150 kΩ 12 White 2 6 11 1 Black 180 kΩ 180 kΩ Mains In Loading Choke Cabinet Grilles EHT Unit Treble Panel Bass Panel Bass Panel Figure 2.
CHAPTER 2. GENERAL ESL OPERATION Quad ESL Panel (Exploded View) Diaphragm Stators Dust Cover Frames Figure 2.
Chapter 3 Major Parts & Disassembly The Quad ESL is relatively easy to disassemble, but care should be taken not to damage the thin front grille and not to damage the panel dust covers if they are not going to be replaced. The first step is to remove the three wooden feet, this is done by gently laying the speaker on it’s front grille on any padded surface. The feet are held to the frame by four wood screws each.
CHAPTER 3. MAJOR PARTS & DISASSEMBLY chapter. The input transformer and crossover is located in the metal box bolted to the frame base on the left side, and is also shown in figure 3.5. Also shown here in figure 3.6 is a broken input banana connector. Quad used plastic input connectors that can be, and often are, broken or loose. The treble panel is in the center and is covered by felt damping material. On either side of the treble panel is a bass panel.
Figure 3.1: Removal of Wooden Trim Strips After the input transformer screws have been removed. the transformer box can be tipped on it’s side and the ground and panel connections unsoldered, as shown in figure 3.15. After the wires are unsoldered, and pulled through the grommet in the input transformer box, the transformer assembly can be set aside. After the input transformer is removed, the left side of the speaker will look as shown in figure 3.16.
CHAPTER 3. MAJOR PARTS & DISASSEMBLY Figure 3.2: Cut Grille Grounding Wires Figure 3.
Figure 3.4: ESL Power Supply Assembly Figure 3.
CHAPTER 3. MAJOR PARTS & DISASSEMBLY Figure 3.6: Broken Input Banana Connector Figure 3.
Figure 3.8: Removal of Front Grille Retaining Screws Figure 3.
CHAPTER 3. MAJOR PARTS & DISASSEMBLY Figure 3.10: Removal of Front Grille Foam Padding Figure 3.
Figure 3.
CHAPTER 3. MAJOR PARTS & DISASSEMBLY Figure 3.13: Removal of Power Supply Retaining Screws Figure 3.
Figure 3.15: Unsolder Input Transformer Connections Figure 3.
CHAPTER 3. MAJOR PARTS & DISASSEMBLY Figure 3.
Figure 3.18: Unsolder Bass Panel Connections Figure 3.
CHAPTER 3.
Chapter 4 Bass Panels 4.1 Disassembly Both the bass and treble panels are rebuilt in essentially the same way. The electrical connections differ between the panels and this changes the rebuilding subtleties somewhat. However, the basic technique is the same. The major failure mode for bass panels is either the diaphragm getting brittle and splitting, or the dust cover splitting and not being repaired.
CHAPTER 4. BASS PANELS bias supply wire must be removed, it is attached to a wiring harness and bolted through two rivets on the panel. A small screwdriver or a wrench is used to remove this wiring harness. Figure 4.5 shows this wiring harness and the wrench used to remove the small nut and bolt. After the nut and bolts are removed the rear dust cover should be free from the stator assembly, and the rear dust cover can be set aside to be recovered later.
4.2. STATOR INSPECTION AND REPAIR 25 Figure 4.1: Quad ESL Bass Panels different stators to be interchanged. 4.2 Stator Inspection and Repair Bass panel stators rarely arc badly enough to melt the plastic. The real problem with the bass panel stators are that the insulating grey paint starts to flake off and make a mess. This isn’t really a big issue and all that needs to be done is to take a stiff brush and remove any of the loose paint and vacuum out the stators.
CHAPTER 4. BASS PANELS Figure 4.2: Removing The Dust Covers Figure 4.
4.2. STATOR INSPECTION AND REPAIR Figure 4.4: Un-soldering Front Bass Stator Wire Figure 4.
CHAPTER 4. BASS PANELS Figure 4.6: Removing The Bass Stator Insulating Tape Figure 4.
4.2. STATOR INSPECTION AND REPAIR Figure 4.8: Bass Panel Diaphragm Figure 4.
CHAPTER 4. BASS PANELS 4.3 Diaphragm Replacement After the stators have been cleaned and inspected, the next step is to install a replacement diaphragm. The original Quad bass diaphragms were a saran type material that has a lower modulus of elasticity than the mylar used for the tweeter panels. This allows that bass panel to have a lower resonant frequency. It is a material very similar to the bass panel dust covers.
4.3. DIAPHRAGM REPLACEMENT 31 takes a lot of pressure and is real drudgery. The coated area of the diaphragm will turn a darker color and won’t easily wipe off if the graphite is being applied with sufficient force. All the area of the diaphragm has to be coated. When the whole area that was masked off has been coated with graphite, vacuum off the whole top surface and surrounding area to remove any stray graphite powder. Any graphite flakes that find their way into a panel is a sure short.
CHAPTER 4. BASS PANELS 32 Mylar streching Jig for Quad ESL Panels 1/4 x 6" Carrage bolt Washer, and Wingnut 18.0" 33.5" 42.5" 2" flat corner braces (both sides) All lumber 2" x 1" poplar (actual dimention 1.5" x 0.75") 6.0" 8.5" 17.5" (Increase these dimentions to 24", 15" and 9" for rebuilding bass panels) Figure 4.10: Diaphragm Stretching Jig Plans After all the bolts have been tightened, the panel can be cut away from the rest of the film on the jig. A razor blade works well for this.
4.3. DIAPHRAGM REPLACEMENT Figure 4.11: Diaphragm Stretching Jig Figure 4.
CHAPTER 4. BASS PANELS Figure 4.13: Bass Panel Diaphragm Curing Figure 4.
4.3. DIAPHRAGM REPLACEMENT Figure 4.15: Bass Diaphragm Rivet Hole Melting Figure 4.
CHAPTER 4. BASS PANELS Figure 4.17: Bass Panel Insulating Tape Application Figure 4.
4.4. DUST COVER REPLACEMENT 37 4.4 Dust Cover Replacement This section is useful as a final step when completely rebuilding panels or if the bass panel is working fine, but the dust cover is split or has holes. The dust covers and the wooden frames should be removed by cutting the parameter tape as described in the panel disassembly section. The wires are then unsoldered as described in the disassembly section.
CHAPTER 4. BASS PANELS Figure 4.19: Bass Panel Dust Cover Removal 4.25. The front stator wire is carefully fed through the hole in the stators and quickly soldered to the tab on the front stator. After the wiring is complete, the dust covers and stators can be re-vacuumed and taped together. Figure 4.22 shows a stator panel being vacuumed. Figure 4.23 shows the dust covers and stator being taped around the parameter.
4.4. DUST COVER REPLACEMENT Figure 4.20: Bass Panel Dust Cover Supplies Figure 4.
CHAPTER 4. BASS PANELS Figure 4.22: Bass Panel Dust Removal Figure 4.
4.4. DUST COVER REPLACEMENT Figure 4.24: Bass Dust Cover Heat Shrinking Figure 4.
CHAPTER 4.
Chapter 5 Treble Panels 5.1 Introduction The Quad ESL treble panels do not suffer from the degradation over time that affects the bass panel diaphragms and dust covers. So, if the treble panel is not over-driven and arced, it’s performance should not change over time. However, the treble panels are easily arced when using high powered amplifiers with the Quads. A picture of an arced treble panel is shown in figure 5.1. The Quads were designed during a time when 15 watts of power was a lot.
CHAPTER 5. TREBLE PANELS Figure 5.1: An Obvious Treble Panel Burn The felt pad is stapled to the rear of the treble unit through the wooden strips. These can be removed by carefully prying the wooden strip away from the dust cover frame on the back of the treble panel. Figure 5.2 shows the bottom of the felt pad being pulled away from the rear of the treble panel. The dust cover is prevented from vibrating and rattling by four tensioning points.
5.2. DISASSEMBLY 45 corner rivets, that the stators are not cracked by exerting too much force when drilling out the rivets. At this point, the two stators can be carefully pulled apart to expose the old diaphragm. If the panel has been arced, it should be fairly obvious. A treble panel arc is shown in figure 5.8. Not only does an arc destroy the diaphragm, it frequently has enough energy to damage the stators in the area of the arc.
CHAPTER 5. TREBLE PANELS Figure 5.2: Removing The Rear Felt Pad When learning the rebuilding technique, it’s not uncommon to have to rebuild a panel several times. Heat shrinking the diaphragm requires a careful technique and too much heat will melt a hole in the diaphragm. The tweeter panels may need to be rebuilt decades from now as well. So being able to remove the epoxy prior to another rebuild is an important part of a panel rebuild.
5.2. DISASSEMBLY Figure 5.3: Removing The Dust Cover Retaining Screw Assemblies Figure 5.
CHAPTER 5. TREBLE PANELS Figure 5.5: Removing The Insulating Tape Figure 5.
5.2. DISASSEMBLY 49 Figure 5.7: Drilling Treble Panel Rivets Figure 5.
CHAPTER 5. TREBLE PANELS Figure 5.9: Removing The Old Treble Panel Diaphragm Figure 5.
5.3. DIAPHRAGM REPLACEMENT 51 Figure 5.11: Grinding Epoxy On Previously Rebuilt Panel 5.3 Diaphragm Replacement The diaphragm can now be replaced, this is done in a very similar manner as the bass panel diaphragms. Figure 5.13 shows the stretching jig, stators and a pice of mylar. The mylar is taped to the inner portions of the stretching jig such that it is free of wrinkles. This is most easily done by positioning the mylar then taping opposite sides while pulling it taught with the tape. Figure 5.
CHAPTER 5. TREBLE PANELS Figure 5.12: Treble Panel With Previous Epoxy Ground Off lock lubricant, to a cotton ball and firmly rub the graphite into the film. This takes a lot of pressure and is real drudgery. The coated area of the diaphragm will turn a darker color and won’t easily wipe off if the graphite is being applied with sufficient force. All the area of the diaphragm has to be coated.
5.3. DIAPHRAGM REPLACEMENT 53 of the film so that it is lined up on the stator like it was when it was masked off. Then lower the jig so the film touches the stator. Rub the parameter of the stator with a paper towel to squeeze out the epoxy, as shown in figure 5.17. Then place the front stator directly over the rear stator like they were assembled. Then pile books or other heavy objects on top of the front stator. Stacks of books at least 6 inches high work well, as seen in figure 5.18.
CHAPTER 5. TREBLE PANELS 54 Figure 5.13: Panel Repaired And Ready To Rebuild covers, this is shown in figure 5.22. Great care should be taken when testing a panel as shown. The audio transformer can produce lethal shocks and should not be touched while in operation. A function generator is useful for producing the audio input signals. The insulating tape that was removed around the parameter of the stator assembly can now be replaced.
5.4. DUST COVER REPLACEMENT Figure 5.14: Mylar Diaphragm Taped To Stretching Jig Figure 5.
CHAPTER 5. TREBLE PANELS Figure 5.16: Application of Treble Panel Epoxy Figure 5.
5.4. DUST COVER REPLACEMENT Figure 5.18: Weighting Panel While Epoxy Cures Figure 5.
CHAPTER 5. TREBLE PANELS Figure 5.20: Applying ITO Coating To Treble Panel Figure 5.
5.4. DUST COVER REPLACEMENT 59 Figure 5.22: Testing Treble Panel plies needed are shown in figure 5.23. These include enough mylar film to cover the two dust covers, a bottle of ordinary rubber cement or a common contact cement, some masking tape, scissors, and a table large enough to hold the dust covers. The dust cover film is placed flat on the table and pulled tight using several strips of masking tape around the parameter of the film.
CHAPTER 5. TREBLE PANELS Figure 5.23: Treble Panel Dust Cover Ready To Be Rebuilt have two layers of tape; one from each adjacent side. After all four sides have been taped, the dust covers can be tensioned using the heat gun. The heat shrinking process is the same as the diaphragm tensioning, and thus requires careful application of heat to prevent a hole from being melted in the dust cover. The dust cover should pull tight with no wrinkles. The completed panel can be seen in figure 5.25.
5.4. DUST COVER REPLACEMENT Figure 5.24: Treble Panel Dust Covers Glued To Frames Figure 5.
CHAPTER 5.
Chapter 6 Power Supply 6.1 Introduction The Quad ESL power supply is typically problem when a Quad ESL that has never been abused looses efficiency. This is manifested as one speaker becoming less loud over time when compared to the other. This is caused by the rectifier diodes in the rectifier block becoming leaky and not producing enough bias voltage. The power indicator lights on the back of the power supplies are often burned out or blinking.
CHAPTER 6. POWER SUPPLY available from digikey. The two 750megohm resistors are placed in series making one 1500 megohm resistor, and this resistor is used with a multimeter’s internal 10 megohm resistance to form a voltage divider. The negative terminal of the multimeter is attached to the frame of the power supply. The positive test lead is clipped to one end of the two series resistors and the other end of the resistors is touched to the 1500 volt tap and the 6 kV tap.
6.3. LAMP REBUILD 65 back into the boxes and the potting wax poured back into the boxes. After the boxes have cooled, they can be reinstalled in the power supplies, and the two transformer wires reattached. Extra bee’s wax can be purchased from craft stores or candle making shops. However, the wax doesn’t need to completely cover the caps, as long as the diodes and cap leads are covered. 6.3 Lamp Rebuild The Quad power supplies have neon lamps to indicate that the speakers are powered up.
CHAPTER 6. POWER SUPPLY 66 EHT Block Circuit and Replacement Board Bass Panels (6000v) 2.2 mΩ Power Transformer Treble Panel (1500v) 330 kΩ All Diodes: 1N4007 All Capacitors: 0.01 µF 2 kV Notes: When bolting circuit board to power supply frame, use 1/4" stand-offs to insure that the traces are far enough away from the metal frame to prevent arcing. Bass Treble Gnd Quad ESL EHT Block SDS Labs Coating the circuit board with corona dope or conformal coating is recommended to prevent corona.
6.4. BULGIN REPLACE Figure 6.2: Quad ESL Power Supply Figure 6.
CHAPTER 6. POWER SUPPLY Figure 6.4: Unscrew EHT Block Figure 6.
6.4. BULGIN REPLACE Figure 6.6: Wax Ready To Be Melted Figure 6.
CHAPTER 6. POWER SUPPLY Figure 6.8: Cooled Boards Ready To Rebuild Figure 6.
6.4. BULGIN REPLACE Figure 6.10: Unsolder Neon Bulb Leads Figure 6.
CHAPTER 6. POWER SUPPLY Figure 6.12: Neon Lamp Parts are often sold without the plugs. The need to replace the connectors stems more from the inability to find replacements rather than any shortcoming on the part of the connector. The connectors can be replaced with IEC connectors, but the IEC connector is square and the old bulgin connector is round. This is shown in figure 6.14. This is the classic dilemma, of trying to fit a square peg in a round hole.
6.4. BULGIN REPLACE Figure 6.13: Unscrew Broken Bulgin Connector Figure 6.
CHAPTER 6. POWER SUPPLY Figure 6.15: Grinding Round Hole For A Square Plug Figure 6.
Chapter 7 Input Transformer The Quad input transformer is an essentially trouble free portion of the speakers. The audio input jacks are a weak point in this component. They are very cheap quality banana connectors with plastic bodies and threads. Most of the ESL’s have loose banana connectors, and if they have been handled badly, the connectors can be broken. The plastic input jacks can be easily replaced with higher quality modern equivalents. The input wiring must be unsoldered, as seen in figure 7.1.
CHAPTER 7. INPUT TRANSFORMER Figure 7.1: Unsolder Audio Input Jacks ufacturing tolerances. So a discharge tube that arcs at a low voltage will protect the tweeters. One model of gas discharge tube that works well is made by ”CP Clare” and is model number CG3-1.5L. It looks like a fat ceramic resistor that is soldered in place under the input transformer. It is connected electrically to the tweeter secondary winding on the input transformer.
Figure 7.2: Unbolt Audio Input Jacks Figure 7.
CHAPTER 7. INPUT TRANSFORMER Figure 7.
Chapter 8 Wiring & Reassembly Reassembly of the Quad ESL requires reversing the steps taken to disassemble the speaker. However, extreme care should be taken to not puncture the fragile dust covers. The vertical treble panel support members in the frames have 4 metal pins that pierce the rear treble panel dust cover frame, and are an extreme hazard to the treble panel dust covers. The pins help to hold the treble panel in place.
CHAPTER 8. WIRING & REASSEMBLY Figure 8.1: Treble Panel Installed In Frame outer lip a bit of a struggle. Care must be taken not to puncture the dust cover when performing this final installation step. Figure 8.4 shows both bass panels pushed into place. After the two bass panels are firmly seated in place, the treble panel can be centered between the two bass panels.
Figure 8.2: First Bass Panel Installed In Frame Figure 8.
CHAPTER 8. WIRING & REASSEMBLY Figure 8.4: Bass Panels Pushed Into Position Figure 8.
Figure 8.6: Installing the Bottom Retaining Bracket Figure 8.
CHAPTER 8. WIRING & REASSEMBLY Wiring Both bass panels in the Quad ESL are wired in parallel. This step is performed first when reassembling a speaker. In most cases the original wiring can be reused. Wiping the wiring down with alcohol to remove the decades of dirt and grime is a good idea. In cases where the wire cannot be used due to insulation damage or insufficient length, other high voltage wire can be used.
for the treble and bass panels. The newer input transformer style is shown at the bottom of figure 8.11. The required connections for the bass and treble panels are labeled. There is a third input transformer possibility that is discussed in Appendix A, which is an old style transformer which has been modified to the new circuit style. The connections for this modified transformer are shown in Appendix A. The ground wire also need to be soldered into place.
CHAPTER 8. WIRING & REASSEMBLY Figure 8.8: Soldering Bass Panel Wires Figure 8.
Figure 8.10: Soldering Input Transformer Connections Final Mechanical Assembly The front and back grilles can now be reinstalled. First the foam pads need to be re-glued to the front of the bass panel dust cover frames. The foam strips are attached with a suitable adhesive; rubber cement works quite well. Figure 8.17 shows the rubber cement being applied to the bass panel dust cover frames. Figure 8.18 shows the front pads being attached.
CHAPTER 8. WIRING & REASSEMBLY 88 Back 1 Front 2 3 brown brown 6 7 5 4 8 9 10 11 12 bass blue blue bass 13 gnd Old Style 1 2 brown back 6 3 4 5 9 10 brown front 7 8 11 12 13 bass back blue back 14 blue front 15 bass front 16 gnd New Style Figure 8.
Figure 8.12: Soldering Bias Resistors In Place Figure 8.
CHAPTER 8. WIRING & REASSEMBLY Figure 8.14: Wiring Neatly Dressed and Ready For Final Assembly Figure 8.
Figure 8.16: Power Supply Finished and Bolted In Place panel can be easily seen. A simple solution if you have found damage to the bass panels before rebuilding them is to trim off the ends of screws as seen in figure 8.22. Shorter screws can also be used and are probably a better idea, although trimming the ends of the screws works quite well.
CHAPTER 8. WIRING & REASSEMBLY Figure 8.17: Applying Glue For Front Grille Pads Figure 8.
Figure 8.19: Stapling Rear Felt To Treble Panel Figure 8.
CHAPTER 8. WIRING & REASSEMBLY Figure 8.21: Problems Caused By too Long Side Panel Screws Figure 8.
Chapter 9 Improvements & Add-Ons Probably the biggest two improvements to the Quad ESL’s are elevating them using stands and replacing the fairly opaque original grilles. The original grilles can be replaced by a variety of perforated metal or mesh screen materials. However some sort of grille should always be used, due to the high voltages present on the outside of the bass panels when in operation, and the delicate nature of the dust covers.
CHAPTER 9. IMPROVEMENTS & ADD-ONS Figure 9.1: Cutting Wire Mesh To Size For Replacement Front Grilles Figure 9.
Figure 9.3: Attaching The Grille Cloth To The Mesh Figure 9.
CHAPTER 9. IMPROVEMENTS & ADD-ONS Figure 9.5: Suggested Hardware For Stand Mounting for mounting stands. Figure 9.5 shows one type of possible hardware useful for mounting stands. The heart of the system is threaded ”T” nuts that are installed inside the bottom of the frames. The holes are drilled in the frame bottoms as shown in figure 9.6. The installed T-nuts are shown in figure 9.7. The hardware shown above to install stands works well with the stand design shown in figure 9 and figure 9.8.
Figure 9.6: Drilling Holes For Stand Hardware Figure 9.
CHAPTER 9. IMPROVEMENTS & ADD-ONS 100 18.000 5.000 R4.000 2.500 11.250 3.000 8.000 11.250 0.750 Feb 6, 1996 http://www.quadesl.com By Sheldon D. Stokes 0.750 Quad ESL Stands R1.
Speaker Bottom http://www.quadesl.com Feb 6, 1996 By Sheldon D. Stokes Quad ESL Stands 101 5.000 12.2° 17.500 18.500 3.000 Figure 9.8: Quad ESL Stand Design 5.
CHAPTER 9. IMPROVEMENTS & ADD-ONS no impact on the ESL circuit performance. When the voltage across the tube is exceeded, 1500 volts in this case, the tube strikes over and is essentially a dead short, capable of sinking hundreds of amps. The device can strike over thousands of times without any damage to the device. The point of the circuit is that the tube will arc over before the treble panel does.
Quad Treble Panel Protection Circui:t 7 QUAD Parts: Diodes: GP02-30 Zener Diodes: BZT03C220 9 Part Specs: Diodes: 3 KV ??? Zener Diodes: 220 Volts 5 Watts SDS Labs Suggested Replacement: CP Clare CG3-1.5L (1500 volts) Gas Discharge Surge Protector 7 9 Figure 9.
CHAPTER 9.
Chapter 10 System & Room Considerations The Quad ESL is an amazingly transparent and detailed speaker. It will easily show deficiencies in source components. However, it is a polite speaker, never harsh or boomy. It allows even badly recorded albums to be listened to without the sort of harsh reminders that many other high resolution speakers can possess. The user would be well served to make sure the rest of the audio system is up to the Quad ESL performance standards.
CHAPTER 10. SYSTEM & ROOM CONSIDERATIONS by the pressure field generated by a close proximity to a wall or other large object. If room considerations permit, the speakers should be placed a couple feet away from a rear wall if not more. Due to the directionality of the high frequencies, the speakers should be aimed at the listening chair.
Chapter 11 Shipping & Storage The Quad ESL’s are large speakers, there’s no doubt about it. As such, shipping can be a problem. The speakers aren’t as fragile as they seem, the grilles and wooden frames provide protection for the delicate parts inside. However, don’t underestimate the abuse that a shipping company can inflict on a large package. The cheapest way to ship a set of Quad ESL’s is via UPS.
CHAPTER 11.
Chapter 12 Needed Supplies & Tools There really aren’t any exotic tools needed to repair a set of ESl’s. Patience and care are the keys to success. A large flat table is essential for panel rebuilding. Some people prefer to buy a piece of thick glass slightly larger than a bass panel to use as a flat surface for rebuilding. this isn’t necessary if a flat sturdy work surface is available. The tools and supplies listed below are what I use, but many other types will work well.
CHAPTER 12. NEEDED SUPPLIES & TOOLS 110 Tools: Item Brand Stretching Jig See Figure 4.
of the speaker, so the thicker mylar does not impact the speaker performance in a negative way. The ESL Information eXchange provides the expensive and difficult to obtain items required to make an ESL speaker system. These include the following: Mylar to make diaphragms Audio matching transformers Power supply transformers for the bias supply. (For both domestic and overseas markets.) Parts kits for the a conventional power supply as well as a switching power supply. Other products are planned...
CHAPTER 12.
Appendix A Quad ESL Service Manual The notes in this section are for the guidance of the engineer who has some experience of carrying out repairs to these speakers together with the necessary proper materials for the repair. The QUAD electrostatic speaker consists of five components: two bass units, one treble unit, an audio transformer unit and an EHT supply unit.
APPENDIX A. QUAD ESL SERVICE MANUAL Figure A.
No output at all Suspect EHT unit or audio transformer unit after checking more obvious things like external connections, not forgetting the leads under the transformer unit connecting the input sockets. Background Noise One cause of background noise in the electrostatic loudspeaker is internal discharge of the EHT supply at times of high humidity, or high voltage, or both. This may be reduced by lowering the EHT voltage and a tap is provided on the EHT mains transformer for this purpose.
APPENDIX A. QUAD ESL SERVICE MANUAL 116 The component loudspeaker units of the QUAD electrostatic loudspeaker must be handled with the utmost care partly because when not supported by the rigid frame of the cabinet they are more liable to physical distortion which would reduce the small internal clearances, and partly because the dust covers are necessarily made of very thin and therefore fragile plastic film.
Figure A.2: Rectifier Block Types and Connections viewed from the rear). This is held in position solely by four screws whose heads are accessible below the baseboard of the speaker. If the speaker is tilted to provide access to slacken these screws it must be restored to its upright position before they are removed or the transformer will have no support other than its connecting wires.
APPENDIX A. QUAD ESL SERVICE MANUAL To replace the rectifier block of the EHT unit, undo the two 4BA nuts securing it to the framework of the EHT unit and remove it. If the replacement block is found to be of a different type it will still be electrically and physically interchangeable with the earlier type, and the equivalent connections are shown in figure A.2.
their positions, and remove the board. Clean all loose dust cover material from the wooden frames since any pieces left to flap will buzz. Spread enough of the new dust cover material on to any clean, solid, flat surface to leave about 6” surplus all around the frame, and hold in position with pieces of adhesive tape at each corner and at intervals along the sides as required. The materials should not be over stretched but just tightly enough to remove the wrinkles.
APPENDIX A. QUAD ESL SERVICE MANUAL Figure A.3: Input Transformer Modification Figure A.
Undo the screws all around the periphery of the rear grille and remove the grille. Tilt the loudspeaker to permit access to the underside of the baseboard. taking care not to dent the front grille. Remove the four screws holding the audio transformer (large can on the left hand side) in place, remembering to support the transformer before it is freed or it may slip and damage the left hand bass unit dustcover.
APPENDIX A. QUAD ESL SERVICE MANUAL Figure A.
Appendix B ESL 63 Information Serving the newer Quad electrostatic speaker, the Quad ESL63, is really beyond the scope of this book, however rebuilding the panels can be done using essentially the same techniques. The schematic of the ESL63 is shown in figure B.1. The panels are very easy to rebuild. They are held together with clips around the parameter and two bolts through the center. The speaker dust covers come off as a unit and cover all four assembled panels. The same 0.
APPENDIX B. ESL 63 INFORMATION Figure B.
Bibliography [1] Sanders, Roger The Sanders Electrostatic Loudspeaker, The Audio Amateur, April 1975, pp 18-28 [2] Sanders, Roger The Sanders Electrostatic Amplifier, The Audio Amateur, January 1976, pp 12-16 [3] Sanders, Roger Electrostatic Speaker System Part 1, Speaker Builder, Febuary 1980, pp 20-36 [4] Sanders, Roger Electrostatic Speaker System Part 2, Speaker Builder, March 1980, pp 20-27 [5] Sanders, Roger Electrostatic Speaker System Part 3, Speaker Builder, April 1980, pp 26-30 [6] Sanders, Roger
