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One of my original Quads is playing at much lower volume than it should.
I purchased a new EHT board and installed it, but the problem is exactly the same. Each panel seems to be working, all at the same lower volume.
Anybody have any ideas? Thanks.
Follow Ups:
In addition to the EHT transformer ~600vac output, the HV section of the EHT needs checking: ~4500vdc on the bass panels, ~1500vdc on the treble. I would try without any panels, then connect them one at a time, and see chat happens to the high voltage.
Of course this takes much more disassembly skills and safety precautions than simply swapping the EHT. As always, get help if you aren't comfortable checking all this or if you don't have the correct meters and HV probe.
Good suggestion... but I doubt that anyone who has an electrostatic voltage meter or a gigOhm divider would be looking for help with debug here!
...if you already have a decent Fluke meter with a 1M-ohm input impedance, all you need is a $40 HV probe that works well enough. That's all I had to buy and well worth it if you own 'Stats.
I assume you switched amp channels to be sure it wasn't the amp(or preamp if thats seperate).
Yes... definitely the speaker's problem, not anywhere else in the chain.
If you plan a DIY repair you need to isolate the problem. Used EHT units, crossovers, and bass panels are available from QUAD "disassemblers" in the UK via ebay. Of course new or rebuilt components are available from Germany or the US at higher cost.
If you have one good speaker to use as a donor you are in good shape to find the problem component and then replace it.
Are you sure that all three panels have reduced output? You might consider using a Radio Shack SPL meter or Harbor Freight DVM/SPL meter along with downloaded signal generator software to measure and compare the near-field output of all six panels.
never heard of doing a test like that before. Would it apply to ESL 63's as well? I can just see my OCD kicking in and I, and everyone else for that matter, may start checking the panels in their stats! Why? Well, because we can.Cheers!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Edits: 01/18/16
Some people are more sensitive to L-R channel imbalance than others... Some speaker companies match their speakers veneers, others match their frequency response, others--apparently--do no matching at all.
FYI: I have owned four pairs of QUADs over the years, the best pair were balanced to within 0.5dB between 100Hz and 4000Hz, the worst were off by 2dB. To my ears 2dB channel imbalance is noticeable. I have owned 9 pairs of Magneplanars and they have typically measured within 1 dB over the same narrow range.
The SPL meters I mentioned above are not laboratory grade nor are they wideband. They are cheap and available and can help you debug a broken speaker component or better understand your setup.
Thread the meter onto a camera tripod to make more repeatable measurements. Compare near field and far field results to gauge the impact that your room and placement have on frequency response.
I do have a Radio Shack SPL, camera tripod, and noise generator.
Cheers!
Ed
"I know just enough to get into trouble. But not enough to get out of it."
I would check the EHT transformer to confirm it is working properly. Given the age of the speakers I am starting to see EHT transformers fail. They will still produce voltage but less than they should.
Normally the EHT transformer will produce voltage in the 600-650VAC range. When they fail the voltage will drop quite a bit , 300VAC is not uncommon.
If the transformer voltage is OK and the EHT board is working properly I would suspect excess leakage of one or more panels. This will pull down the voltage and the panels will not properly charge. They still play but with reduced output.
Best to check both the transformer and EHT board with the panels disconnected.
Should have mentioned that the problem happened suddenly, not gradually.
Another test you can do is swapping the EHT blocks between your speakers to see if the reduced output follows the EHT unit.
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