been fixing Quads for a lonnngggg time
SDS Labs Refurbishing Price List:
Quad ESL-57
Power Supply Rebuild
(new rectifiers, lamps, power connectors, etc)
$200.00 pr
Input Transformer Rebuild
(new crossover components and input connectors)
$200.00 pr
Treble Panel Rebuild $325.00 ea
$600.00 pr
Bass Panel Rebuild $325.00 ea
$600.00 pr
$1000.00 set
Complete Rebuild
(all panels, power supplies, & input transformers)
$1800.00 pr
Quad ESL-63, 988, 989, 2805, and 2905
Element (panel) Rebuild $250.00 ea
$450.00 pr
$800.00 set of 4
$1200.00 set of 8
$1600.00 set of 12
Complete Rebuild
(all panels, new dust covers)
$1500.00 pr
$2000.00 pr (989, 2905)
New Grill Cloth
(Black, Brown, Grey, White)
$75.00 pr
General Labor
Hourly Labor Rate $60.00 /hr
Prices as of January 2017

Refurbishing is done by appointment. I typically have more work than I can handle. Please e-mail me if you are interested in my services. If you would like to try the process yourself, all the instructions and files related to using and rebuilding the Quad ESL's are in the Quad References section.

Complete rebuilds include all labor assuming no significant speaker issues exist such as very bad physical condition or significant previous mods. For work less than complete rebuilds, a labor rate of $60 / hr is used.

All panels and speaker rebuilds are measured against original panels and reference rebuilt panels. The plot below shows the response of a rebuilt pair of Quad ESL-63's They were measured in my rebuild shop, which is not an ideal place for good quasi-enechoic response measurements, but is very useful for gauging the precision of my rebuilds. Note that there is significantly less than 1dB difference between panels.

The plot shown below shows four rebuilt original Quad bass panels and a trace of a 30 year old panel which cosmetically appears to be in very good shape

The plot shown below shows two rebuilt original Quad treble panels. Note the very close matching between rebuilt units.

The plot shown below shows a complete rebuilt pair of Original Quad ESL, note the very good matching.

To see measurements of original Quad ESL's and my rebuilds as well as other companies rebuilds, click the link below:


I purchased my Quads in the early spring of 1995. The panels were in very good shape, but the cosmetics of the speaker were not so good. The first thing I did was to clean them thoroughly. I repainted the frames, and the front and back grilles. I made a new set of oak side panels. I also put grille cloth on the fronts of the speakers. I have also built oak stands (see plans in the references section).

quad picture

At this point the speakers looked much better, and I was loving the music pouring out of them. But one speaker seemed to be losing sensitivity. I heard that the high voltage modules get weak over the years, and should be replaced. I called QS&D and found out the rectifier blocks cost $80 each. I have a schematic of the rectifiers, and I saw that there was about $3 worth of parts inside each block. The blocks are just a simple Cockroft-Walton voltage multiplier. I also noticed that the modules consist of a wooden box, with the end of the circuit board sticking out of the top of it. The box is filled with bee's wax. I decided to repair the modules I own, and did the following: I unsoldered the modules from the speakers and placed both of them in a Pyrex brownie pan. I placed the modules in the oven (350 F) for about 15 minutes. I removed them when all the wax was melted. I carefully pulled the circuit boards out of the melted wax. I then unsoldered the diodes from the circuit boards, and replaced them with standard 1N4007 diodes (16 each board). I then put the circuit boards back into the boxes and poured the melted wax back into each box to cover the circuit boards. They have been working flawlessly for years now, and I expect many years of trouble-free service from them. However, for those of you who have the "older" Quad EHT blocks, which are solid epoxy, you must start from scratch. Fortunately, I have designed a circuit board which will bolt in place of the old epoxy blocks. The schematic and layout included in Adobe Acrobat format and are in the Quad References segment of this site.

I then replaced the dust covers on the panels. The high voltage used in the speaker attract dust. The panels have dust covers on the front and back to keep dust from getting into the panels shorting them out. The dustcovers are shrink film taped to frames on the front and back of each panel. Panels should be removed from the speakers. The panel is sandwiched between each dust cover frame. The whole assembly is held together with tape around the perimeter. I untaped the dust covers from the frames and pulled the old film off them . I cleaned off the old tape and adhesive. I bought several 3M window weatherizing kits (the official Quad dust cover replacement). These kits are available at hardware stores and home centers. They cost about $3 each. The actual process is quite involved and requires a bit of coordination, but it is not overly complex. It is time consuming; all four bass panels took about 10 hours to complete. I also rewired them, and replaced the high-voltage lines. Complete panel rebuilding instructions are available in my Positive Feedback artical and my Quad rebuilding book.

quad diagram

The diagram above shows the basic components of a Quad ESL. A speaker consists of two bass panels and a single treble panel situated between the bass panels. The treble panel is divided into three vertical strips. The input signal is fed through a transformer to step up the voltage and a high voltage crossover circuit divides the signal into three regions. The bass frequencies are routed to the bass panels after a voltage step-up of about 270 times. The midrange frequences are stepped up about 90 times and are fed to all three treble panel strips. The center treble panel strip handles the highest frequencies. The diaphragms in all three panels must be charged up to react to the electric fields produced in each panel. The power supply shown in the diagram above charges the treble diaphragm to 1500 volts and the two bass panels to 6000 volts.