Capacitor question

[Cal Weldon]

Brain cramp.

I have an 8 ohm tweeter that I crossed over at 12K, 6 dB with a 1.5 mfd cap. It was a little strong so I added a 4ohm resistor to it. The output is fine but now there is an overlap with the mid. What do I have to add to it to get back to the 12K XO point? I'm thinking it's around 9K right now.

Thanks for the help ahead of time,
Cal

Edit: I don't have any 1.1 mfd here right now or this would be easy. I have lots of other assorted so I would like to add to it rather than replace.

[RAW]

Cal
Shoot me the complete filter.I can crunch something before you come.
MLSSA is waiting.
Will have praxis to show you as well.


Al

[Cal Weldon]

Thanks Al,

I actually played around a bit and got it a little better. I'm thinking it's about as ready as it going to be for the test. I'm really enjoying having your LCR units here tonight. It was a real eye opener to hear yours vs mine. Are those gonig to be for sale one day?

Cal

[RAW]

NO no not LCR
LCR uses the 2 Extremis the CSS125 as a mid and a usher tweeter.

You have the RA241 for now.
Al

[Cal Weldon]

Oops,
Sorry old boy, didn't know they had a number. I'll stamp that one on my heart Anyway I sure do appreciate the use of them. Now I can see what happens when you spend the time to do it right.

How 'bout we have a duel tomorrow, 7pm, your place, ten paces, turn and fire your remote at the amp and we'll see who comes out on top. Mind you, mines bigger.

Cal

[quasi]

Originally posted by Cal Weldon
Brain cramp.

I have an 8 ohm tweeter that I crossed over at 12K, 6 dB with a 1.5 mfd cap. It was a little strong so I added a 4 ohm resistor to it. The output is fine but now there is an overlap with the mid. What do I have to add to it to get back to the 12K XO point? I'm thinking it's around 9K right now.

Thanks for the help ahead of time,
Cal

Edit: I don't have any 1.1 mfd here right now or this would be easy. I have lots of other assorted so I would like to add to it rather than replace.

By inserting the 4 ohm resistor on its own you changed the tweeters effective impedance to 12 ohms and this has changed the timing cct of the capacitor hence shifting the crossover point.

To fix this you need to add a 2.2 resistor in series after the 1.5 uF capacitor and an 18 ohm in parallel with the tweeter. This will bring the tweeter level down by about 3dB and maintain 8 ohms for the crossover capacitor.

Cheers

[Cal Weldon]

Hi quasi,

Thanks a lot for your response.
I did what I could with what I had on hand for now. I added an 8.2 across after the 4.2 in line, dropping the dB's heavy and basically bringing my XO back to the separation I had before and it actually sounds OK. The tweeter is quite efficient so no big deal.

Man, I am such a hack. I'll have another go atter tomorrow before I head over to RAW

I'm going to bed.

Cal

[planet10]

Cal,

the easy answer is to change the cap to 1 uF to get back the same nominal XO frequency (13,300 Hz). Nothing else required. If needed i'll teleport one over

dave

[quasi]

Originally posted by planet10
Cal,

the easy answer is to change the cap to 1 uF to get back the same nominal XO frequency (13,300 Hz). Nothing else required. If needed i'll teleport one over

dave

Hi Cal,

If he does that he will shift the crossover frequency back, but the level will be the same. I read that he wanted to bring the level down because it was too strong. Adding two resistors is still pretty easy.

Cheers

[planet10]

Originally posted by quasi
If he does that he will shift the crossover frequency back, but the level will be the same. I read that he wanted to bring the level down because it was too strong. Adding two resistors is still pretty easy

No it won't, the level will come down, with ~ 2/3 the voltage across the driver there was before.

an L-pad is more appropriate with a more complex XO or when you want to be able to dynamically change the level, but this is better when it is a simple cap XO.

dave