Audio High Pass Filter - is there a difference between C and RC filter designs?

Thread Starter

pmap93

Joined Aug 15, 2016
15
Hello!

First off, I do hope i'm in the right section of the forums to post this.

I've been researching and reading about DIY audio lately, and I'm making a DIY boombox!

My amplifier is a two channel amplifier with 30W+30W (total of 60W) of power, each channel has a full range speaker and now, I want a tweeter.

By my understanding, I need a high pass filter in-line with the tweeter. I used this site to calculate the values as well.
I wanted a first order high pass filter and it shows me a Capacitor only design. (http://www.the12volt.com/caraudio/cross.asp#hp)



However, some other websites how an Capacitor with Resistor (RC) HPF design.



I'm wondering now, if there is a difference? And which one should I pick for the tweeter?
 

Thread Starter

pmap93

Joined Aug 15, 2016
15
Can I ask another question? What Type of a capacitor would be good for this application?

I'm thinking of going for a Solen Polypropylene Axial Non-Polarized Capacitor.
http://www.ebay.com/itm/2x-Solen-5-...213659?hash=item33808f669b:g:iA8AAMXQTT9RyyTK
(I wonder if it's original though)

Is the 400V rating, a maximum? So it wouldn't be a problem right?
Is there a 'wattage' rating to a Capacitor?
I'm guessing, an AC (Alternating Current) Capacitor is a Non polarized capacitor?

Any decent, not so expensive capacitor brands that I can buy from eBay? I only know Solen (France) and Dayton.
 

Thread Starter

pmap93

Joined Aug 15, 2016
15
To be honest, for this DIY project, I think Solen is a little bit expensive. Because of it's 400V rating which seems unnecessary?
 

MrChips

Joined Oct 2, 2009
23,232
Do some simple calculations.
What would be the signal voltage feeding 30W into 8Ω?
About 15Vrms. Hence even a 25V non-polar capacitor will be fine.
 

Thread Starter

pmap93

Joined Aug 15, 2016
15
For my stereo, both channels is in this configuration.

ONE CHANNEL Connection.

Speaker A = Full Range
Speaker B = Tweeter. (w/ Capacitor 5.6uF)

Total Imp = 2.66667 Ohms



IF My amplifier supports 4-8OHMS only, can i 'ADD' impedance?
 

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crutschow

Joined Mar 14, 2008
26,996
For my stereo, both channels is in this configuration.

ONE CHANNEL Connection.

Speaker A = Full Range
Speaker B = Tweeter. (w/ Capacitor 5.6uF)

Total Imp = 2.66667 Ohms



IF My amplifier supports 4-8OHMS only, can i 'ADD' impedance?
No you don't want to add a resistance in series with the amp.
That reduces its power output and fouls up the damping factor.

How did you calculate an impedance of only 2.67 ohms?
What are the speaker impedances?

For a proper crossover you should also have an inductor in series with the large speaker to roll off the high frequencies that go to the tweeter (and also increase its high frequency impedance).
 
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