DIYAudio is a better place for technical questions like this, but I'll try.
First, what speaker is this?
So the schematic says 26.7uF (not exactly an off the shelf value).
When you say the actual values are 25.7 and 28.1 are you going by measured values or marked values? What are the tolerances?
The values you quote (25.7uF and 28.1uF) are 3% and 5% off of 26.7uF. Lots of less expensive caps have a tolerance in that range. It is possible they either:
a - Don't care that much
b - Actually measured the caps individually to get to the desired value.
c - Matched the caps to the actual drivers
I'm going to bet on (b) or (c) because it is VERY irregular for a factory to start changing parts willy nilly. Either they would always be over or under, or they took exceptional care to either measure the actual cap values and/or are matching caps to the drivers.
I would measure your situation carefully. Also, be exceptionally careful in replacing shunt caps. That is caps that are in parallel to the drivers and go to ground. The ESR is much more critical to the circuit design.
Best,
E
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So the allowable tolerance is 2%. I was just going on what was printed on the caps |
Maybe the caps the factory used ware not accurately labelled. Question is, how accurate are the labels on the jantzen standard z caps
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It's strange because on the first crossover there is a 10uF, another 10uF, a 4.7uF and a 1uF, making 25.7
The second crossover it had a 10uF another 10uF, a 6.8uF and a 1uF making 27.8
These are only what is printed on the caps.
Again the schematic calls for 26.7
I'm thinking they likely measured each cap to make the 26.7 |
I think I'll just mirror the other crossover, any thoughts on this |
Also on the 25.7 crossover the 1uF cap it said 1.0m100v, I assumed this meant 1uF.
On the other crossover the 1uF cap had the stripes, I punched in the stripe code online and it said it was 1.3uF-1.6uF at 100v
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Why not get a meter and measure the actual value of caps from both crossover and go from there?
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Measure what you have. Don't just mirror.
Best,
Erik
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Ditto on measuring. I would take the group of 4 caps you removed from each board and measure their capacitance in parallel and that is the value I would use for the new ones.
The design value may 26.7 but chances are the manufacturer tested every driver and tweaked the caps to allow for variations in driver paramenters to meet overall design specs. (If one of the four caps is much smaller in physical dimension than the others, then that is almost certain what they did).
Without measuring the original caps, your best bet is to install 26.7uF total. |
I looked at my buddy's pair and his are 26.3, two 10uf, a 4.7 and a 1.5.
Here's the question... can they be measured on the board. I have taken this crossover apart a million times and I'm not going to desolder the finished crossover to measure each cap.
So the question is do I put it back at what was original with the 28uf, or do I get it close to the other side 25.7.
Or just get it as close to the 26.7, which if I leave the 6.8 in there and leave the 1uf out. I'd have 26.8
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Here's something kinda interesting, the 4.7 on my buddy's pair look identical in shape and color to the 6.8 that's in place of the 4.7 on mine. It sounds stupid but I'm wondering if the gut putting it together thought it was a 4.7 but it was actually a 6.8 |
Also I can't measure all the original caps because the last one broke, it was damaged when I removed it. It was the one with the stripes which came out as 1.5uF I think |
I think i will buy the meter and test the old caps, excerpt for the broken one and see if there all as labelled, then I can get an idea where it was set at. Maybe the factory had this one a pinch above the spec |
You don't need to measure each cap separately. Measure the bundle. That's the whole point.
Best,
E
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Stupid question, but can you do that on the board are no. I realize that it's the bundle that has be measured I just thought I would just add the values
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So going back-to what GS5556 said is it probable that Mirage Deviated from what the schematic said of 26.7 depending on what the drivers read. This would mean that each speakers crossover May have a different value depending on The drivers that it had.So for instance The mid range circuit in one speaker might have a total capacity its of 27.5 and the mid range circuit in a different speaker would have maybe 25 asper how they matched it to the individual drivers in the cabinet 26 being the baseline but the factory would deviate as-needed. is this likely
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I've heard these older pairs were hand built, so I guess it makes sense the midrange circuit of each speaker could be slightly different from each other. |
Update
So measured the old caps.
In speaker A, the midrange circuit measures 24.7
In speaker B, the midrange circuit measures 26.3
It's a 1.3 uF difference.
Speaker A midrange circuit has been replaced with 25.7
Now I'm trying to determine whether I should put speaker B the same as speaker A (25.7) or back to where it was at (26.3) or 26.7 which is what the schematic calls for.
Your thoughts
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Not sure it makes a difference but speaker A is actually 25uF, not 24.7 |
On speaker B I could use 2, 10uF and a 6.8, or
2, 10uF a 4.7 and a 1.5.
Is there a benefit to using the 4.7 and the 1.5 over using the 6.8 |
There is a small amount of series inductance that is proportional to the capacitance. The smaller the cap, the smaller the unintended inductance.
Modern caps have gotten a lot better at reducing inherent inductance, so this is less of an issue than it was before. Chances are good this no longer matters.
But, given a choice of all things being equal, choose the combination with the smallest cap.
However, that's from the design perspective. What you really should do is match both sides identically to ensure they have the same characteristics of capacitance as well as inductance and equivalent series resistance.
Best,
E
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