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Why are my crossovers different

So the schematic on my m1 crossovers says that c2 circuit (midrange circuit) should total 26.7uF
The crossover that I just recapped had the c2 circuit at 25.7uF.
The crossover I’m working on right now has the c2 circcuit at 28.1.
It does not appear these have not been tampered with since the factory.
So the question is should I make the second c2 circuit match the 25.7 of the first or should I put it back the way it was at 28.1

I could make the second one a 26. 8uF. I accidentally damaged a 1.3uF that was in the 28.1. So I’m debating on whether I should replace it or leave it out.

Your input would be appreciated
idahifi

Showing 5 responses by erik_squires

erik_squires
16,653 posts
 
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
erik_squires
16,653 posts
 
You don't need to measure each cap separately. Measure the bundle. That's the whole point.

Best,

E
erik_squires
16,653 posts
 
You can use Room EQ Wizard, or DATS to measure your caps with high accuracy and the correct ESR.

https://www.roomeqwizard.com/help/help_en-GB/html/impedancemeasurement.html

https://www.parts-express.com/dayton-audio-dats-v2-computer-based-audio-component-test-system--390-8...

Also some handheld meters I know nothing about.

Best,

E
erik_squires
16,653 posts
 
Measure what you have. Don't just mirror.

Best,

Erik
erik_squires
16,653 posts
 
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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