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How to filter out low frequencies


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sab0276 
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Posted: April 29, 2006 at 9:11 AM / IP Logged  

I have some 3.5" coaxial speakers that I would like to filter out the low frequencies.  Is there like a base cap or a resistor or something I can put inline?  I would like some thing cheap and easy if possible.  I don't really want to use a crossover or anything. 

Thanks.

-Scott

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haemphyst 
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Posted: April 29, 2006 at 10:09 AM / IP Logged  
A 400µF cap will filter anything around 100Hz and down. Two of these, wired in SERIES, will give you 500µF, at 70 volts, which will lower the crossover point to around 80Hz. If this is still too much bass, you'll want to move to the 400µF caps...
It all reminds me of something that Moličre once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
boomer_106 
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Posted: April 29, 2006 at 11:02 AM / IP Logged  

You can also buy simple bass blockers. Here is just one example of them.

http://www.crutchfield.com/S-amYh6TiVkYz/cgi-bin/ProdGroup.asp?g=761

Steven Kephart 
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Posted: April 29, 2006 at 1:18 PM / IP Logged  
If you choose to use a capacitor, be sure it is non-polar. 
stevdart 
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Posted: April 29, 2006 at 1:51 PM / IP Logged  
https://www.the12volt.com/caraudio/cross.asp
Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
sab0276 
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Posted: April 29, 2006 at 8:08 PM / IP Logged  

The [url=http://www.pioneerelectronics.com/pna/product/detail/0,,2076_4087_35549_tab=B,00.html?compName=PNA_ProductDetailComponent]3.5" speakers[/url] I have have a frequency range of 60Hz-28kHz. 

What will a [url=http://www.radioshack.com/product/index.jsp?productid=2102506]470µF capacitor[/url] filter?

What about the [url=http://www.radioshack.com/product/index.jsp?productid=2102507]1000µF capacitor[/url]?

Thanks.

-Scott

2002 GMC Yukon SLT non-Bose
Pioneer AVIC N3
coppellstereo 
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Posted: April 30, 2006 at 12:12 AM / IP Logged  
if you use a polar cap, which way do you hook it up?
geepherder 
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Posted: April 30, 2006 at 6:54 AM / IP Logged  
You don't- unless you want it to explode.  Polar caps are used for dc voltage applications, not ac.
My ex once told me I have a perfect face for radio.
haemphyst 
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Posted: April 30, 2006 at 10:57 AM / IP Logged  
boomer_106 wrote:

You can also buy simple bass blockers. Here is just one example of them.

http://www.crutchfield.com/S-amYh6TiVkYz/cgi-bin/ProdGroup.asp?g=761

Those frequencies are FAR too high... You still want SOME bass, right? You are just trying to filter the deepest bass to prevent "flapping", right? These are WAY more expensive, too... All those are? Expensive capacitors... The SAME as I linked for you in my original post.
sab0276 wrote:

The 3.5" speakers I have have a frequency range of 60Hz-28kHz.

What will a 470µF capacitor filter?

What about the 1000µF capacitor?

Thanks.

-Scott

The 470µF is close to the 500 that I suggested in my first post. 80Hz. Also, those RS caps you linked to are non-polar caps, you can't use them just like they are in this application... See the last portion of this post...
The 1000µF will be somewhere around 40Hz, and you could use them, but THAT'S too low. Might as well not even put them in, if you're gonna use those... But, again, polarized caps, and unusable in this application. Use the caps I linked to ORIGINALLY, in the method I suggested, and you'll be just fine.
geepherder wrote:
You don't- unless you want it to explode.  Polar caps are used for dc voltage applications, not ac.
You absolutely can use polarized caps, but you have to use two of them, wired in series, either + to + or - to -. That is the same (electrically) as a non-polar cap... Also, you must use TWICE the capacitance you actually want, as caps in series behave the same as resistors in parallel. Two 1000µF caps in series is a net 500µF capacitance. Benefit to this though is that you double your voltage handling...
It all reminds me of something that Moličre once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
stevdart 
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Posted: April 30, 2006 at 12:10 PM / IP Logged  

Good thing the thread came this far then.  Wired in series with one cap reversed is a bit different than wired in series.  Huh, haemphyst?  And that latest info you gave is new to me, too.  I didn't know that about overcoming the polarized issue.

"But, again, polarized caps, and unusable in this application."

Is that a typo?  Because if not it makes your entire statement contradictory. 

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
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