using V Cap Odam To Improve SQ In mid band of speaker XO

OP: 

Ahh, well the conventional wisdom is that the caps in series with the drivers matter more than the  caps in parallel, but a couple of users have reported that even with some positive effects from stepping from electroclytic caps to at least a film. 

I strongly encourage you to experiment for yourself with affordable parts. :)

Best,

Erik

OP: Not sure what you are asking, but let me clarify.

Generally speaking, the basic filter components are either in series with a driver, or parallel to it. It’s the later I refer to as shunting to ground because a cap becomes a short at high frequencies. Likewise a coil becomes a short at low frequencies.

A difference of 0.2-0.5 Ohms in series with an 8 Ohm driver is not a big deal, but if the part is parallel with the driver, a difference of this much can be major.

The special case of a Zobel, with a cap going to ground with a larger resistor (>4 Ohms often) is again a situation where the ESR/DCR is less critical.

OP:

Something else you should be aware of is that when parallel caps became fashionable (1980s) caps weren't nearly as good as they are today.  Electrolytics in particular had high ESR's and high inductances and were not easily available any better.

I strongly encourage you to experiment on your own here, and in order to experiment you need to have affordable parts.  Try out some affordable Mundorf MKP caps and splurge a little on small Audyn TruCopper as well. Axon makes affordable film caps which can be greatly enhanced with either of the other two.

I like Mundorf MKPs a lot for the price, and physical size, but they sound a little dark.

Best,

Erik

OP:

DIYaudio is a great place to ask about speaker design and crossover mods. In general, the % of difference is what you want to be aware of more than absolute values. If your original cap is +- 10% vs. marked, it’s still good but the original designer probably intened to use the marked, not measured cap. Especially true with older caps.

Next, if the cap is shunting to ground (parallel with the driver) , maintaining or compensating for the original ESR may matter. If there’s a large R (> 2 Ohms) in series it is less important than if there is no R or a very small R value (<2 Ohms) on it’s way to ground. In these cases the combined ESR + R are critical values which may be needed to prevent the impedance from collapsing.

Keep this in mind as using parallel caps may have unintended consequences, and the ESR of the entire assembly should be measured and taken into account.

Lastly, if this cap goes to ground the big improvements are going from electrolytic to film, and less so after that.  If you have already made that change getting fancier is a tiny difference if any.

OP:

If you mean ADDING it so the total uF = 2.7 + 3 = 5.7uF, then absolutely not.

If you meant replace, then 2.7 is right on the edge of what I'd recommend trying without compensation.  I'd add a .27uF to get close to the original 3. 

An easier and cheaper alternative all around though is adding an Audyn TrueCopper cap in the range of 0.1uF to the existing.