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QUAD 2805 low volume one side
QUAD 2805 low volume one side
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Old 24th August 2021, 01:43 PM   #1
awkwardbydesign is offline awkwardbydesign  England
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Default QUAD 2805 low volume one side

As I haven't got on with these in my room, I put them up for sale. Someone came to listen, and pointed out that one speaker had a lower volume. I knew there was a slight imbalance, but thought it was room acoustics, however swapping the speakers over it became obvious that it was the speaker. This problem wasn't apparent until recently.
I don't yet know if it is one panel or all of them, but his HF hearing is better than mine, and he thought it was the whole speaker.
Before I start investigating, what are the most likely culprits? Polarising voltage? Crossover/delay components? Or something else? Sending or taking them to One Thing Audio or QUAD would be expensive and complicated due to the distances involved. I do have REW and a Umik mic, sig gen and Tandy SPL meter plus I bought a Dayton Audio DATS V3 (for testing the Tannoys I have just built).
Any pointers welcome.
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Old 24th August 2021, 10:24 PM   #2
stokessd is offline stokessd  United States
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If you are lucky, it's your high voltage power supply. But more likely is that you have a panel that has gone bad. Is there any sounds coming from the panels with the amp off but the speaker on? put your ear right up to the grille and move around to listen everywhere. Anything buy dead silence is an indicator of a bad panel.

I'm guessing panel from the age and my experience with the 2805's. But I'd love to be wrong.

Sheldon
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Old 25th August 2021, 04:37 PM   #3
awkwardbydesign is offline awkwardbydesign  England
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Hi Sheldon. Just tried that, and it is dead silent. Without running a test signal, it appears to be a general lowering of sound level, rather than one particular range of frequencies. I will use a sig gen and listen next to each panel as soon as I can. Remind me, which panels run full range? Is it the two bass panels, with the centre pair only radiating the higher frequencies? Or the other way round?
I have -6dB attenuators on each channel of the preamp, and reducing the opposite channel by the full 6dB almost centres the image again.
And how do I go about checking the HT supply? And they were serviced by One Thing Audio in October 2019.
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Last edited by awkwardbydesign; 25th August 2021 at 04:51 PM.
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Old 25th August 2021, 11:24 PM   #4
stokessd is offline stokessd  United States
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I check the high voltage supply with a high voltage probe. I'd consider just replacing all 8 of the diodes in the high voltage supply, just to be sure.

Sheldon
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Old 25th August 2021, 11:28 PM   #5
esl 63 is offline esl 63  Sweden
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All panels gives bass..
Sweep with a signal generator in the bass from 30-50 hz you will hear the buzz and rattle.
Lock also on the flasing lamp how often it blinks. Should be at least 10 seconds.
On a dry winter day 1 minute.
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Old 26th August 2021, 12:56 AM   #6
rayma is offline rayma  United States
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When using test tones, the acoustic volume level must be very low, or damage can be done
to the drivers. Do not rely on the setting of the volume control, use your ears.
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Old 26th August 2021, 01:18 AM   #7
mattstat is offline mattstat  United States
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From the ESL-63 service manual:
"When applying Steady State input signals to the loudspeaker these should not exceed 10 V rms."

From the resonance checks section that uses 8 V rms:
"Gradually sweep up and down the frequency range. The loudspeaker response should be pure and free from rattles at all frequencies except at approximately 50 Hz where diaphragm resonance occurs."
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Old 26th August 2021, 04:22 PM   #8
awkwardbydesign is offline awkwardbydesign  England
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I would keep the volume very low if I used the sig gen. But a sweep with REW should tell me if the FR is even, especially compared to the other speaker.
I have been looking at the 63 schematic (can't find the 2805 for now) and the 8 HF diodes appear to be GP02-30. And the bridge is a DF02M. If they are the same in the 2805 then RS have them cheaply;. I just need to work out where they fit, as I don't have a picture of the pcb. If I am lucky, that will be the solution.
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Old 26th August 2021, 08:40 PM   #9
esl 63 is offline esl 63  Sweden
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When the membrane gets loose and it starts to leak current from membrane to stator then the volume drops. So by sweeping you can listen closely after the rattling sound from the loose membrane.
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Old 27th August 2021, 01:21 AM   #10
stokessd is offline stokessd  United States
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If they sound normal, but low, I'd put my money on the power supply. Yes, they are GP02-30's I'll be glad to walk you through it.

If you look at this picture: http://quadesl.com/photos/esl2805electronics.jpg

The HV diodes are nestled in amongst the blue disk caps. At the bottom right of the PCB.

As was mentioned earlier, you should look at the neon bulb (by the curly power wire in my pic). If it looks like it's on solid, or blinking rapidly, that indicates that you have a panel problem that is pulling the power supply down. This is typically accompanied by some sort of sound from the panels (squealing, hissing, etc). If you have a problem with the power supply the neon bulb will not blink or blink at a much slower rate than the other speaker.

The power supply in that speaker is essantially the same as the newest 63's and everything after it.

Here's a good schematic to use. Keep in mind that there is a 1.5uF cap missing that normally lives across the input transformer primaries. but that's not the part of the schematic that you care about at the moment.

Sheldon
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