High pass filter does not work

Home / the12volt's Install Bay / Car Audio / High pass filter does not work (

Topic Closed)

Welcome Guest :)

Members

< Prev Topic Next Topic >

nunog

Member - Posts: 24

Joined: September 27, 2004

Location: Portugal

Posted: September 27, 2004 at 12:20 PM / IP Logged

Hi.

I have read your information about passive crossovers and this is the situation:

What i want is to create a filter so that my car's front speakers don't receive lower frequencies then 100hz. If they receive too much bass, the door starts to vibrate and the speakers will distort.

What i did was i bought a capacitor with 100v and 470uf (following the instructions i saw on this site) and connected it in series.

What happened was that there was no difference at all. Everything stayed as it was before.

The speakers are JBL with 135 watts peak, 50 watts nominal power and 4 ohm impedance.

Please let me know what i am doing wrong and how i can solve this annoyance.

Thanks in advance.

Nuno Gomes

DYohn

Moderator - Posts: 10,741

This member has made a donation to the12volt.com. Click here for more info.

This member has been recognized as an authority in Electrical Theory. Click here for more info.

This member has been recognized as an authority in Mobile Audio and Video. Click here for more info.

Joined: April 22, 2003

Location: Arizona, United States

Posted: September 27, 2004 at 1:12 PM / IP Logged

A 470 uf cap will (assuming a 4-ohm speaker) provide a 6db / octave high pass at approximately 80Hz. Assuming it is a non-polar cap, you should be able to connect it in series with the positive leg of the woofer and it will cross at that frequency. If it is a polarized cap, you will indeed get no effect since it will only function on half the sine wave. Perhaps the X-over frequency is too low to have a noticable effect in your application. I suggest changing it with one rated at 398uf (+/- 10%) if you want to cross at 100Hz (into 4 ohms.)

Support the12volt.com

forbidden

Platinum - Posts: 5,352

Joined: November 01, 2003

Location: Alberta, Canada

Posted: September 27, 2004 at 1:13 PM / IP Logged

470uf cap with a 4 ohm load will give a 6db slope of about 90hz. So this is still pretty low and will help some but not tons. Consider raising the point to about 400hz with a 100uf cap instead and see how it sounds.

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

nunog

Member - Posts: 24

Joined: September 27, 2004

Location: Portugal

Posted: September 27, 2004 at 1:25 PM / IP Logged

Basically what i want is to keep almost all the bass from reaching the front speakers.

I asked for a non-polarized capacitor at the store, but (sorry for the ignorance) it has the (-) sign on it. Does it mean it's polarized? the guy at the store told me about other types of capacitors with 3 pins (i don't know if it's the right name for it). This one has 2 pins, it says "REC" (brand) and has the minus sign on it.

Can you please tell me the values for a capacitor that allows no bass at all to reach the speakers? (they would work almost as tweeters).

Thank u very much

Nuno Gomes

DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: September 27, 2004 at 1:29 PM / IP Logged

If the cap has + or - on it, it is most likely not non-polar. This page has a good general reference chart for you. If you want to "block all bass," you will need to cross over at about 400 to 600Hz like Rob suggested. HERE is a good on-line source for audio crossover capacitors.

Support the12volt.com

nunog

Member - Posts: 24

Joined: September 27, 2004

Location: Portugal

Posted: September 27, 2004 at 1:33 PM / IP Logged

I will try your solution and of course give you a feedback.

Let me just say that i've been using the internet and a few forums for about 8 years and i could never get help like the one u gave me.

Thank you.

Nuno Gomes

nunog

Member - Posts: 24

Joined: September 27, 2004

Location: Portugal

Posted: September 30, 2004 at 6:59 AM / IP Logged

Hello once again

I´ve searched this little city where i live that is Coimbra-Portugal, and i couldn't find a capacitor of 100uf. I was asked if i was sure of that value that is not commonly asked for. I found a 22 uf capacitor maximum. I guess i'll eventually connect 5 of them.

Thank you once again for your precious informations.

Nuno Gomes

nunog

Member - Posts: 24

Joined: September 27, 2004

Location: Portugal

Posted: October 08, 2004 at 6:33 PM / IP Logged

I got 4x 22uf, 100v capacitors and connected them in parallel on my car's front speakers and it works just as i wanted. I know that the final value is not the one i was aiming for (the crossover point must be around 1000hz), but it sounds as i wanted it to.

Thanks

Nuno Gomes

Sorry, you can NOT post a reply.
This topic is closed.

Printable version

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Search the12volt.com

Follow the12volt.com

Disclaimer: *All information on this site ( the12volt.com ) is provided "as is" without any warranty of any kind, either expressed or implied, including but not limited to fitness for a particular use. Any user assumes the entire risk as to the accuracy and use of this information. Please verify all wire colors and diagrams before applying any information.

High pass filter does not work

Sorry, you can NOT post a reply.This topic is closed.

Sorry, you can NOT post a reply.
This topic is closed.