Tweeter protection Cap

static · 14th January 2004, 02:21 PM

Hi

I would like to protect my tweeter, as I plan to go from passive X-over to an active one.
So I'd like to slap a good quality film cap on both tweeters.
The question is what value should it be? These are two ways with X point @ 3kHz, so ideally i'd probably want the cap to filter out anything else below like 1kHz or so (suggestions?)

I remember reading that Peter Daniel has a single cap on his tweeter, what value is it?

Thanks
Alex

tiroth · 14th January 2004, 02:39 PM

Ideally you would want the corner to be at least 2 octaves below crossover, unless you are using it as a pole in the real crossover network of course. So, corner at 750Hz would be ideal, 1kHz should be fine if that is what you have the parts for.

static · 14th January 2004, 02:47 PM

wow - that was a quick one

well, the figure of 1kHz I just guesstimated

So what value of the cap should i get for 750Hz, as per your recommendation?
Also what brand: i was looking at Auricap and more $$$ Hovlands.
Do Hovlands make a noticable difference?

Thanks
Alex

Pan · 14th January 2004, 04:20 PM

Not that I´ve done it myself but it really makes sense to use the DC blocking cap as a pole together with the active.

You can use a smaller cap, which means higher quality for the same money.

/Peter

tiroth · 14th January 2004, 04:30 PM

The only downside to using the cap as a pole is that the pole will vary as the tweeter's impedance varies, throwing away some of the benefit of going active. It's cheaper though.

For a tweeter that doesn't dip below 7 ohms you would need a cap of (2*pi*750*7)^(-1) or ~30uF.

static · 14th January 2004, 05:23 PM

sorry guys, but you will have to be a little patient with me

First of all can anyone explain the "pole" cap concept? Never heard about it, unfortunately.

30uF!?! are you sure? Then how can 20Hz make it through a 2.2uF DC blocking cap almost unaffected (not rolled off). I will have to pay dearly for a very good quality 30uF cap.

Thanks
Alex

fdegrove · 14th January 2004, 06:17 PM

Hi,

Quote:

Then how can 20Hz make it through a 2.2uF DC blocking cap almost unaffected (not rolled off).

Because it's working with a much higher impedance.

Quote:

For a tweeter that doesn't dip below 7 ohms you would need a cap of (2*pi*750*7)^(-1) or ~30uF.

If you look at the figure 7 in the formula, that's the 7 Ohms of the tweeter.

BTW...If you don't have DC at the output of your tweeter amp then I don't see any point in using a blocking cap for the tweeter.

Cheers,

sreten · 14th January 2004, 07:32 PM

Quote:

Originally posted by fdegrove
BTW...If you don't have DC at the output of your tweeter amp then I don't see any point in using a blocking cap for the tweeter.

Cheers,

Protects the tweeter against a DC amplifer fault,

sreten.

Pan · 14th January 2004, 08:52 PM

"Protects the tweeter against a DC amplifer fault, sreten."

Girly girly...

/Peter

static · 14th January 2004, 09:06 PM

Thanks for the explanation on capacity and impedance. It all makes sense now.

Quote:

Girly girly...

thats unless you have $$$$ tweeters in your speakers.
Since I have $20 tweeters in mine, i guess i can avoid the cap.

Sorry for the bother.
Alex

14th January 2004, 02:21 PM	#1
static diyAudio Member Join Date: Apr 2003 Location: Toronto	Tweeter protection Cap Hi I would like to protect my tweeter, as I plan to go from passive X-over to an active one. So I'd like to slap a good quality film cap on both tweeters. The question is what value should it be? These are two ways with X point @ 3kHz, so ideally i'd probably want the cap to filter out anything else below like 1kHz or so (suggestions?) I remember reading that Peter Daniel has a single cap on his tweeter, what value is it? Thanks Alex

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14th January 2004, 02:39 PM	#2
tiroth diyAudio Member Join Date: Dec 2001 Location: Pittsburgh, PA, USA	Ideally you would want the corner to be at least 2 octaves below crossover, unless you are using it as a pole in the real crossover network of course. So, corner at 750Hz would be ideal, 1kHz should be fine if that is what you have the parts for.

14th January 2004, 02:47 PM	#3
static diyAudio Member Join Date: Apr 2003 Location: Toronto	wow - that was a quick one well, the figure of 1kHz I just guesstimated So what value of the cap should i get for 750Hz, as per your recommendation? Also what brand: i was looking at Auricap and more $$$ Hovlands. Do Hovlands make a noticable difference? Thanks Alex

14th January 2004, 04:20 PM	#4
Pan diyAudio Member Join Date: Sep 2002	Not that I´ve done it myself but it really makes sense to use the DC blocking cap as a pole together with the active. You can use a smaller cap, which means higher quality for the same money. /Peter

14th January 2004, 04:30 PM	#5
tiroth diyAudio Member Join Date: Dec 2001 Location: Pittsburgh, PA, USA	The only downside to using the cap as a pole is that the pole will vary as the tweeter's impedance varies, throwing away some of the benefit of going active. It's cheaper though. For a tweeter that doesn't dip below 7 ohms you would need a cap of (2pi750*7)^(-1) or ~30uF.

14th January 2004, 05:23 PM	#6
static diyAudio Member Join Date: Apr 2003 Location: Toronto	sorry guys, but you will have to be a little patient with me First of all can anyone explain the "pole" cap concept? Never heard about it, unfortunately. 30uF!?! are you sure? Then how can 20Hz make it through a 2.2uF DC blocking cap almost unaffected (not rolled off). I will have to pay dearly for a very good quality 30uF cap. Thanks Alex

14th January 2004, 08:52 PM	#9
Pan diyAudio Member Join Date: Sep 2002	"Protects the tweeter against a DC amplifer fault, sreten." Girly girly... /Peter

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