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Speaker crossover mod. Your advice?

I'm considering modding the crossovers of my Focal 1027s. Specifically, I am thinking about replacing the capacitor associated with the tweeter. I have received some helpful advice from another A'gon member who has done a similar mod to his crossovers (on a different model speaker from the same manufacturer).

I would greatly appreciate any suggestions from folks who have experience with this sort of thing. In particular, what sort of improvements can be achieved with this kind of mod? Any thoughts on which caps to use? Any common mistakes I should avoid? Is the whole thing a bad idea?

Thanks for your input.

Bryon
bryoncunningham
tiggerfc
153 posts
 
Any opinions on the Cardas caps?
bryoncunningham OP
903 posts
 
Thanks, John, for your advice. I will take a look at the Mundorf thread. I don't know the first thing about caps, so hopefully that will help.

I think the plan at this point is to replace the 2 caps for the tweeter, and possibly the resistor for the tweeter. I am going to leave the inductors alone.

As far as the midrange, I may do that down the line, if I am happy with the tweeter results. But for a first step, I am going to restrict myself to the tweeter. With that in mind, I have a basic, possibly stupid, question as I look around for replacement caps:

The caps for the tweeter are labelled "3.6J" and 6.8J." Does the "J" after the number mean joule? In my preliminary search, all the caps I am seeing are rated in µF. I don't see any caps labelled with "J". Why is that?

Bryon
jeffreybehr's avatar
jeffreybehr
805 posts
 
J indicates value tolerance; I don't know what exactly 'J' means, but I"m sure someone does.
.
bryoncunningham OP
903 posts
 
Thanks, Jeff. Just discovered this: "J" indicates a 5% tolerance, according to capacitor codes. In light of this...

Is it a safe assumption that the 3.6 and 6.8 caps are 3.6µF and 6.8µF? Are those typical values for caps associated with tweeters?

Also, finding a 3.6µF cap has been a little difficult. The caps I've found so far from various manufacturers are either 3.3µF or 3.9µF. I assume that using a different value will change the frequency of the high pass filter. Is that a bad idea? Or is the difference - .3µF - small enough to be ignored? Should I just keep searching for a 3.6µF cap?

Anyone?
almarg's avatar
almarg
9,670 posts
 
Hi Bryon,

Yes, those are undoubtedly 3.6uF and 6.8uF. FWIW, though, I would not feel comfortable introducing an 8.3% error into the nominal value of the 3.6uF cap, especially in a crossover network that is designed, as this one appears to be, to have sharp slopes.

It might prove helpful to keep in mind that using two caps in parallel, where their individual capacitances sum to 3.6, would be a way of achieving the correct value. I believe 1.8uF is a standard value.

Best regards,
-- Al
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