capacitors as high pass crossover

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erinh

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Joined: January 07, 2004

Posted: February 06, 2004 at 11:38 AM / IP Logged

when using capacitors in the positive speaker wire, which way does the arrow on the capacitor need to be facing? towards the headunit or towards the speaker?

DYohn

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Joined: April 22, 2003

Location: Arizona, United States

Posted: February 06, 2004 at 12:01 PM / IP Logged

If you're using the correct type of cap (non-polar Mylar or polypropylene) it doesn't matter. Be sure your capacitor's voltage rating is high enough for the expected amplifier power.

erinh

Copper - Posts: 91

Joined: January 07, 2004

Posted: February 06, 2004 at 1:19 PM / IP Logged

i couldn't find either that you mentioned. the ones i bought at radio shack were 100µF 35V 20% Radial-lead Electrolytic Capacitor. will these work? they also had ones that were axial-lead. i'm not running an amp on these speakers.

DYohn

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Joined: April 22, 2003

Location: Arizona, United States

Posted: February 06, 2004 at 2:16 PM / IP Logged

No, this is not a good choice. First of all, a 100µF capacitor at 4 ohms will be about a 400Hz high pass filter at 6 db/octave, which is an odd choice unless you are installing mids. A 35V rating will be good to only about 40 watts RMS amplifier power. 20% accuracy is pretty poor quality (which means the X-over point will be unstable) and I bet you bought a standard polar cap designed for electronic circuit design, not one designed fro audio application.

HERE is a guide for choosing component values. Design your system than go to Parts Express and buy the proper audio-grade caps.

If you are simply trying to keep low bass out of some 5-1/4 coaxs or something, buy some pre-made bass blockers.

erinh

Copper - Posts: 91

Joined: January 07, 2004

Posted: February 06, 2004 at 3:56 PM / IP Logged

okay i'll return them and order from parts express. i just didn't want to buy bass blockers from the stores if they were just capacitors inside them. best buy had them for $10 a pair. seemed a little high since all they add are a peice of wire and a peice of plastic.

DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: February 06, 2004 at 3:59 PM / IP Logged

Well... some bass blockers are just capacitors. The good ones are full-blown 12db/octave high-pass crossovers. $10 a pair is pretty cheap, and you'll be far better off than trying to do it yourself if you are unsure what you are doing. Good quality caps cost $10 apiece and more, by the way.

forbidden

Platinum - Posts: 5,352

Joined: November 01, 2003

Location: Alberta, Canada

Posted: February 06, 2004 at 9:10 PM / IP Logged

I agree, thanks for helping out DYohn, I was not in the shop at all this afternoon.

Top Secret, I can tell you but then my wife will kill me.

eargasm

Member - Posts: 48

Joined: November 16, 2003

Location: Australia

Posted: February 07, 2004 at 3:14 AM / IP Logged

on this topic.

if you were to use polarised capacitors (as i have before) you need to use 2. one pointing in each direction.

wire them in parallel and their values should be half each of the total you were looking for.

b.t.w. capacitor values add when in parallel. and you need one facing each direction to take care of the AC signal.

2001 Ford Fairmont

Alpine DVD, screen,

5.1surround processor,

5ch Class-T amp, TV tuner

and centre channel.

Focal 3way Utopia splits.

VDO navigation. Stinger cap.

Soundstream Exact subs.

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capacitors as high pass crossover

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