Not sure what you're trying to achieve here? A quick fix or simple solution like replace a panel and be done?
My first impression, the drop around 300-500 Hz of almost 20 dB is too deep in the left speaker. It should be around half that value max IMHO.
And that weird move between 2-3K in that same speaker. ??
So my impression is that the balance between the panels is off, or at least the unbalance is bigger in the left speaker.
Maybe one is off in one direction and the other one is off in the other.
I'm assuming that OTA have replaced all the resistors etc on the transformers?
Never assume. Always ask, always check. Short cuts are made.
My first impression, the drop around 300-500 Hz of almost 20 dB is too deep in the left speaker. It should be around half that value max IMHO.
And that weird move between 2-3K in that same speaker. ??
So my impression is that the balance between the panels is off, or at least the unbalance is bigger in the left speaker.
Maybe one is off in one direction and the other one is off in the other.
I'm assuming that OTA have replaced all the resistors etc on the transformers?
Never assume. Always ask, always check. Short cuts are made.
No, just off in frequency characteristics.
Could be coating, could be electronics, could be Mylar stretching, could be ..... anything.
Could be coating, could be electronics, could be Mylar stretching, could be ..... anything.
Maybe I will order and replace all the resistors etc as suggested it seems by rayma. At least I will know that they are all up to spec. I saw someone on YouTube soldering new components onto the transformer! Many thanks. Rodney.
Better first check before ordering anything.
If they were replaced (as claimed) the problem may lie somewhere else and money is wasted.
If they were replaced (as claimed) the problem may lie somewhere else and money is wasted.
If I took a photo of each audio transformer would you be able to tell if they look as if they have been replaced?
I could do that tomorrow.
I could do that tomorrow.
No problem.
You have to take the back off, unscrew the transformer and take a picture of the bottom inside without damaging the dust cover of the bass panel behind it.
Not an easy job.
You have to take the back off, unscrew the transformer and take a picture of the bottom inside without damaging the dust cover of the bass panel behind it.
Not an easy job.
Last edited:
May I respectfully suggest that you slow down and do more testing and investigation?
There is a long list of things that could be wrong with a set of Quads, but some of them are pretty involved repairs and you're dealing with a fragile speaker. If you don't want to do a full rebuild, I would be careful about randomly doing things.
Figuring out how to do some of the acoustic tests previously suggested is a worthwhile use of time. Sheldon has a lot of experience and data. If you measure things like he tells you to, he can likely guide your investigation more effectively.
If you are experiencing phasey-ness in listening, that is not likely to be related to resistor drift, a bad panel, etc. Sheldon gave a good explanation of what can cause this problem.
Phase data is in the step and impulse response.
If you're trying to isolate one panel from another, near-field measurement should be very near, like within a quarter inch of touching something (grille, panel, whatever). 12 inches is far enough away that you can still get significant contamination from other panels at many frequencies.
There is a long list of things that could be wrong with a set of Quads, but some of them are pretty involved repairs and you're dealing with a fragile speaker. If you don't want to do a full rebuild, I would be careful about randomly doing things.
Figuring out how to do some of the acoustic tests previously suggested is a worthwhile use of time. Sheldon has a lot of experience and data. If you measure things like he tells you to, he can likely guide your investigation more effectively.
If you are experiencing phasey-ness in listening, that is not likely to be related to resistor drift, a bad panel, etc. Sheldon gave a good explanation of what can cause this problem.
Phase data is in the step and impulse response.
If you're trying to isolate one panel from another, near-field measurement should be very near, like within a quarter inch of touching something (grille, panel, whatever). 12 inches is far enough away that you can still get significant contamination from other panels at many frequencies.
I won't be doing anything too drastic quite yet!
No doubt you may have seen today's comments I've had with Wout31. He has kindly agreed to look at a couple of photos of the audio transformers which I will take tomorrow. This might show whether the components have been replaced recently by OTA.
With the speakers connected electrically out of phase I really can't say that I can hear any phasey-ness that bothers me.
Yes, I agree with you about doing a very close-up measurement and did think at the time whether 30cm was too far away for a meaningful measurement.
Thank you for following me!
The fact that you have to invert phase in one speaker is pointing me to a mis-wired treble panel. We won't know until you check the wiring one speaker to the other. It's very unlikely that a bad panel or drifted resistors could do that.
Sine you bought these units as "completely rebuilt", you probably don't want to go changing stuff at this point. Hopefully it's a simple fix, but if it isn't then you messing with parts would make it a lot less likely that you can get the refurbisher to fix it for you. I'd fix it for free, but I'd give you a ration of crap for messing with it before returning it.
This sounds like something the rebuilder should have easily caught...
Sheldon
Sine you bought these units as "completely rebuilt", you probably don't want to go changing stuff at this point. Hopefully it's a simple fix, but if it isn't then you messing with parts would make it a lot less likely that you can get the refurbisher to fix it for you. I'd fix it for free, but I'd give you a ration of crap for messing with it before returning it.
This sounds like something the rebuilder should have easily caught...
Sheldon
BTW, this is what an un-rebuilt input transformer looks like underneath. This is the more modern design, earlier units only had one capacitor instead of three. Later units had blue caps, but the caps aren't the issue because they very very rarely go bad (and are responsible for some of the sound of the speaker, so I often leave them). Concentrate on the resistors, these here are the original white ceramic shelled carbon comp resistors.
If you are going to replace them, you'll need high voltage ones, I recomend vishay vr68 series
Here's a stock un-rebuilt transformer:
Here's a rebuilt pair (not the same as above):
Sheldon
If you are going to replace them, you'll need high voltage ones, I recomend vishay vr68 series
Here's a stock un-rebuilt transformer:
Here's a rebuilt pair (not the same as above):
Sheldon
Hi Sheldon, I purchased these speakers on ebay in July last year from Steve of OTA. He told me that they were his own speakers he had been listening to at home. I don't remember the details of the sale, except that they were restored. They have already been back within days of buying them as the left speaker was so down in level. They came back better a bit better. I asked what had they found wrong but never got a reply. I'm reluctant to return them both or at least the left speaker as I doubt they would do any critical measurements. As I said at the very beginning, they would just say I am being too fuzzy.
I'm certain if the treble panels were out of phase I would be well aware of that.
I'm certain if the treble panels were out of phase I would be well aware of that.
The problem is that all the panels overlap so much that is can be tricky to pick out exactly what is the problem and which one it is. Something is out of phase because you have to reverse input phase on one speaker.
Sheldon
Thank you for showing me the photos. . Tomorrow I will be taking picture of my transformers. Will be very interesting to compare.
Can he try the old trick of facing the speakers close together and playing a mono signal in both?
At least the bass panels should be in phase if the sound doesn't cancel out.
At least the bass panels should be in phase if the sound doesn't cancel out.
That should make an interesting test. Will try it tomorrow with pink noise. It certainly should show up if any of the drivers are out of phase. What a brilliant idea.
It's an old trick, but if only some of the panels are out of phase, you could get ambiguous results.
Maybe no bass, but still there are highs, etc.
If all the sound cancels when they are IN phase facing each other, maybe the connections
to the main output terminals on just one of the speakers are reversed.
Maybe no bass, but still there are highs, etc.
If all the sound cancels when they are IN phase facing each other, maybe the connections
to the main output terminals on just one of the speakers are reversed.
First of all, thank you for suggesting this method. I couldn't wait to try this out before going to bed as I want to power them off over night before I remove the backs tomorrow morning
It turns out that one of the Tweeter panels are out of phase with each other. So when the Quads are connected electrically in-phase the bass panels are out of phase and the tweeter panel in phase. With the Quads connected electrically out of phase as I normally use them, the bass panels are in phase and the tweeter out of phase. So obviously I need to change both bass panels in one of the speakers. That will correct the terminal connections.
At this point I will do some more measurements and if the left speaker is still down in the bass region or the speakers are not matching well then I will need to look at the crossover.
That's me finished tonight. R