Where exactly should I add the capacitor?

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Hi all - apologies in advance for my ignorance but I'm still new to this game...

I've nearly finished all the cutting of 18mm oak veneered Baltic birch ply for my Dallas II enclosures and am now turning my attention to the fostex drivers (208ez / sigma, and T90a), the R80b attenuator, the wiring.... and the capacitor....

Question is.... can I solder the cap directly to the relevant terminal of the attenuator or would it be better elsewhere?

The attached image is effectively what I will have.

Also.... any advice on whether to go for a 1.0uf or 1.5uf cap initially is hugely appreciated!

Cheers all.

Wayne.
 

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Hi Wayne, since there is only the one component I don't see any issue soldering it direct to the attenuator. The bigger the cap the lower the tweeter will play, 1.0 - 1.5uF means it will be rolling off at a high frequency, I assume to fill in the top end where the fostex is drooping. I suspect it is largely a personal preference thing. Perhaps someone who has built will chime in.

I'm not sure if this would be best in the multiway, or the full-range forum...

Tony.
 
You can solder it to the attenuator, or you can solder it to the connector on the rear panel of the enclosure. Or you could screw a terminal strip to the inner wall and solder it there with wires running to the two other places. What really matters is the part is secure and supported, not just hanging from a solder terminal. Yes, ther are plenty of speakers that solder a cap to the tweeter terminal and let it hang, but to me that is not good practice in speaker building.

In my view the part itself should be secured by either soldering both ends to something or by using a cable clamp or some such to strap the cap to a wall inside.
 
If you are still figuring out the right crossover point why don't you just get a couple WIMA polypropylene capacitors in different values? They're roughly a pound each and you can get them at the store, if you have an electronics parts shop in your area.
Figure out a value that suits your drivers and go from there.
 
And when it’s sorted out, then you can mount the final part in a way that won’t allow the leads to break, or have the parts flopping around.
I like to use zip-ties to strap the capacitor to something that will attach with a screw or two, like metal plumbers tape/strapping.
 
Hi guys. Following your kind advice I've ordered some cheap caps so that I can test before investing in some really decent ones, but I've been looking at the crossover frequency for those 2 different caps Fostex recommend and I can't work out why they've recommended them as it makes the crossover point very high indeed.... which doesn't make sense given a) the lower end frequency range of the T90a super-tweeter and b) the range of human hearing (especially my 40 year old ears). Can anyone help me understand? Images attached to support my confusion...
 

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With my limited speaker knowledge a super tweeter is intended to fill in the frequency range above that of a normal tweeter so that is probably why those 2 cap values are recommended . You could do with feedback from someone who has used this combination , I suggest you get this thread bumped over to multi-way now .
 
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I can't work out why they've recommended them as it makes the crossover point very high indeed.... which doesn't make sense given a) the lower end frequency range of the T90a super-tweeter and b) the range of human hearing (especially my 40 year old ears). Can anyone help me understand?

The crossover point may be high but it is a first order filter which means you can still hear the frequencies below it. To test it, just listen to the tweeter with the 1uF. If your old ears cannot hear it then there is probably no use using 1uF there. But don't under estimate your ears, it may be able to hear things you think you can't.

This kind of super tweeter project is only for the rich (like you?). For the poor I will suggest to stay away.
 
The crossover point may be high but it is a first order filter which means you can still hear the frequencies below it. To test it, just listen to the tweeter with the 1uF. If your old ears cannot hear it then there is probably no use using 1uF there. But don't under estimate your ears, it may be able to hear things you think you can't.

This kind of super tweeter project is only for the rich (like you?). For the poor I will suggest to stay away.

I'm certainly not rich. Thanks for your response anyhow
 
Sorry to go on a tangent Wayne. I promise to keep it short :eek:

What are the formulas to calculate the size of the cap? If I want to protect a tweeter from eventual pops in an active setup, which is xo at 2kHz, which size cap should I use? I guess a size such it would significantly attenuate anything below 1kHz?
 
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