# Capacitor value for tweeters running active



## HCWLSU101 (Apr 30, 2009)

Does anyone have the formula? My tweeters are Morel MT300’s which are 6ohm and have an fs of 1000.


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## DaveG (Jul 24, 2019)

For 6 ohm you'll have to do a little math. At 1000hz you'll need about a 33 microfarad.


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## Holmz (Jul 12, 2017)

Is that your only highpass scheme?

33uF maybe good for a case of general protection against DC... But if you want to be high passing at say 2.5*Fs, then around 15uF may be better?

Have you tried googling the formula?


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## DaveG (Jul 24, 2019)

Holmz said:


> Is that your only highpass scheme?
> 
> 33uF maybe good for a case of general protection against DC... But if you want to be high passing at say 2.5*Fs, then around 15uF may be better?
> 
> Have you tried googling the formula?


He's running active. The caps are just for protection.


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## dumdum (Feb 27, 2007)

33-35uf would be good


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## mrexcitement (Jan 23, 2019)

As long as you have a good amp you don't need them , I don't use them with my Alpine PDX-F6 active setup , no pops , clicks or turn on noise at all , very quiet.


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## DaveG (Jul 24, 2019)

mrexcitement said:


> As long as you have a good amp you don't need them , I don't use them with my Alpine PDX-F6 active setup , no pops , clicks or turn on noise at all , very quiet.


That’s not why we use them. If ever you make a dsp setting error ( and you will), caps will help to keep you from letting the magic smoke out! Cheap insurance.


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## HCWLSU101 (Apr 30, 2009)

I am assuming the 33uf 100v non-polarized from Parts Express will work?








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## ckirocz28 (Nov 29, 2017)

I'm gonna tag along here.
Can anyone recommend capacitors for CSS Audio LD25X tweeters, 8 ohm? I'm thinking 20 microFarads for a 1000 hz frequency. Please recommend a type/brand that will last, I looked around at Parts Express and there are just too many choices. Mylar? Electrolytic? Nothing over $100 a pair though.








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## SNCTMPL (Nov 23, 2014)

ckirocz28 said:


> I'm gonna tag along here.
> Can anyone recommend capacitors for CSS Audio LD25X tweeters, 8 ohm? I'm thinking 20 microFarads for a 1000 hz frequency. Please recommend a type/brand that will last, I looked around at Parts Express and there are just too many choices. Mylar? Electrolytic? Nothing over $100 a pair though.
> 
> 
> ...


I just ordered some yesterday for a pair of Scan 3004’s. I have been reading as much as I could on sizing capacitors just for protecting active tweeters. Some things I found were complicated and some not. Finally I went back to the first video I watched, the guy from Car Audio Fabrication, I found his formula the most thorough and easy to follow.

0.159
(FS x 2)re 865x2= 1730x6.4= 11072 

0.159
11072 = .00001436 = 14.36uf for 1730hz

If you want to go a little lower hz, parts express doesn’t list a 20uf, so maybe split the difference.









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## ckirocz28 (Nov 29, 2017)

SNCTMPL said:


> I just ordered some yesterday for a pair of Scan 3004’s. I have been reading as much as I could on sizing capacitors just for protecting active tweeters. Some things I found were complicated and some not. Finally I went back to the first video I watched, the guy from Car Audio Fabrication, I found his formula the most thorough and easy to follow.
> 
> 0.159
> (FS x 2)re 865x2= 1730x6.4= 11072
> ...


Got any suggestions for something more likely to survive an Alabama summer in a non-AC black car? Are mylar capacitors suitable for this?


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## SNCTMPL (Nov 23, 2014)

ckirocz28 said:


> Got any suggestions for something more likely to survive an Alabama summer in a non-AC black car? Are mylar capacitors suitable for this?


I am not sure which capacitors would be suitable for those conditions, but I do have a suggestion, get AC😂😂😂. Sorry but you teed that one up for me.


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## ckirocz28 (Nov 29, 2017)

SNCTMPL said:


> I am not sure which capacitors would be suitable for those conditions, but I do have a suggestion, get AC. Sorry but you teed that one up for me.


Yeah, I figured that comment was coming.  88 Camaro, no AC is planned, ever.


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## ckirocz28 (Nov 29, 2017)

SNCTMPL said:


> I am not sure which capacitors would be suitable for those conditions, but I do have a suggestion, get AC. Sorry but you teed that one up for me.


So, got an opinion on this?








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## DaveG (Jul 24, 2019)

ckirocz28 said:


> So, got an opinion on this?
> 
> 
> 
> ...


Those will work just fine. 20uf is about 1500hz @ 8 ohms. These will get you to a 1000hz:









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Or if you're feeling over indulgent:









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## ckirocz28 (Nov 29, 2017)

DaveG said:


> Those will work just fine. 20uf is about 1500hz @ 8 ohms. These will get you to a 1000hz:
> 
> 
> 
> ...


Over indulgent it is! Thanks man!


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## SNCTMPL (Nov 23, 2014)

Looks like Dave has got you all set up.


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## Ge0 (Jul 23, 2007)

DaveG said:


> View attachment 295092
> 
> For 6 ohm you'll have to do a little math. At 1000hz you'll need about a 33 microfarad.


Where did you find this chart? It's way off...


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## DaveG (Jul 24, 2019)

Ge0 said:


> Where did you find this chart? It's way off...


Man I have no idea. I saved it to my laptop forever ago because it was laid out so straight forward. Never thought to double check.. @ckirocz28 you catching this? Double check the values I gave you. Good catch Ge0. Thanks & I'll delete the chart if you say it's wrong.


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## Ge0 (Jul 23, 2007)

DaveG said:


> Man I have no idea. I saved it to my laptop forever ago because it was laid out so straight forward. Never thought to double check.. @ckirocz28 you catching this? Double check the values I gave you. Good catch Ge0. Thanks & I'll delete the chart if you say it's wrong.


Never mind, brain fart. I was thinking 2nd order filters...


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## ckirocz28 (Nov 29, 2017)

DaveG said:


> Man I have no idea. I saved it to my laptop forever ago because it was laid out so straight forward. Never thought to double check.. @ckirocz28 you catching this? Double check the values I gave you. Good catch Ge0. Thanks & I'll delete the chart if you say it's wrong.


It's ok, even if the values produce a 750 hz Xover point it'll still provide the pop protection I need.


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## ckirocz28 (Nov 29, 2017)

Now I see why no one recommends mylar capacitors for this use, these things are huge!


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