How to filter out low frequencies
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=77007
Printed Date: April 28, 2024 at 7:54 AM
Topic: How to filter out low frequencies
Posted By: sab0276
Subject: How to filter out low frequencies
Date Posted: April 29, 2006 at 9:11 AM
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 ------------- 2002 GMC Yukon SLT non-Bose
Pioneer AVIC N3
Replies:
Posted By: haemphyst
Date Posted: April 29, 2006 at 10:09 AM
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."
Posted By: boomer_106
Date Posted: April 29, 2006 at 11:02 AM
You can also buy simple bass blockers. Here is just one example of them. https://www.crutchfield.com/S-amYh6TiVkYz/cgi-bin/ProdGroup.asp?g=761
Posted By: Steven Kephart
Date Posted: April 29, 2006 at 1:18 PM
If you choose to use a capacitor, be sure it is non-polar.
Posted By: stevdart
Date Posted: April 29, 2006 at 1:51 PM
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.
Posted By: sab0276
Date Posted: April 29, 2006 at 8:08 PM
The [url=https://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=https://www.radioshack.com/product/index.jsp?productid=2102506]470µF capacitor[/url] filter? What about the [url=https://www.radioshack.com/product/index.jsp?productid=2102507]1000µF capacitor[/url]? Thanks. -Scott ------------- 2002 GMC Yukon SLT non-Bose
Pioneer AVIC N3
Posted By: coppellstereo
Date Posted: April 30, 2006 at 12:12 AM
if you use a polar cap, which way do you hook it up?
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Posted By: geepherder
Date Posted: April 30, 2006 at 6:54 AM
You don't- unless you want it to explode. Polar caps are used for dc voltage applications, not ac.
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My ex once told me I have a perfect face for radio.
Posted By: haemphyst
Date Posted: April 30, 2006 at 10:57 AM
boomer_106 wrote:
You can also buy simple bass blockers. Here is just one example of them.
https://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."
Posted By: stevdart
Date Posted: April 30, 2006 at 12:10 PM
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.
Posted By: DYohn
Date Posted: April 30, 2006 at 12:23 PM
I don't want to put words into haemphyst's mouth but what I believe he is saying is polarized caps cannot be used in crossovers BY THEMSELVES in the same way non-polar caps are used. He then goes on to say it is possible to configure polarized caps for this purpose, but that they must be used differently than non-polar ones. I will add my 2 cents that one should NOT use polarized or electrolytic caps for audio crossovers even if electrically it is possible to do so because they simply sound bad. Non-polar non-electrolytic caps (and for bass blockers you need them to have at least a 100 volt rating) are the best solutions, and yes some of them are very expensive indeed. It is not unusual for a passive crossover to cost more to build than the driver it is controlling. ------------- Support the12volt.com
Posted By: haemphyst
Date Posted: April 30, 2006 at 12:38 PM
stevdart wrote:
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.
All right, all right, all right... ya caught me. What I MEANT to say was this: right out of the package, without properly connecting a second one, they will be unusable in this application... 
sab0276 wrote:
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
And while Dyohn is absolutely correct in his statement above, I was looking for the least expensive (i.e. "cheap" - $1.69 * 4 = $6.76, as opposed to $9.99 plus freight for the lowest frequency "bass blockers"), as well as the fastest method (i.e. "easy" - trek to the local RS and walk out with 'em, as opposed to waiting a week for Parts Express) for him to reach his desired destination. While not COMPLETELY wrong, my suggested method will work, with 100% safe and satisfactory results, sometimes offering additional safety, due to the increased voltage capabilities of two caps in series, rather than a single high voltage cap. I have done it before, on MANY occasions. ------------- 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."
Posted By: stevdart
Date Posted: April 30, 2006 at 1:25 PM
...and we get a good learning thread out of the deal, too. Can't complain about that!  ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: geepherder
Date Posted: April 30, 2006 at 5:32 PM
Yes, that's interesting to know about polarized caps.
-------------
My ex once told me I have a perfect face for radio.
Posted By: boomer_106
Date Posted: April 30, 2006 at 8:38 PM
[/QUOTE]
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:
I was only showing him an example of a bass blocker. It's up to him to choose what he wants thats all.
Posted By: sweatyogre
Date Posted: April 30, 2006 at 9:29 PM
I'm currently using 200 Hz bass blockers on my 6x8s. Is that too high? The lowest frequency they're supposed to be able to handle is 37 Hz.
Posted By: sab0276
Date Posted: May 01, 2006 at 10:49 AM
Excellent information here. Thank you.
Just to throw another monkey wrench into the equation. The 3.5" are replacements for the 2.5" in the very back of my Yukon. After I installed them I realized that they are wired in series. They only work if both are connected. How will this effect adding a cap?
Thanks again.
-Scott
-------------
2002 GMC Yukon SLT non-Bose
Pioneer AVIC N3
Posted By: DYohn
Date Posted: May 01, 2006 at 11:23 AM
sab0276 wrote:
Excellent information here. Thank you.
Just to throw another monkey wrench into the equation. The 3.5" are replacements for the 2.5" in the very back of my Yukon. After I installed them I realized that they are wired in series. They only work if both are connected. How will this effect adding a cap?
Thanks again.
-Scott
If both speakers are 4-ohms, then the total load in series is now 8-ohms. This will change the crossover frequency by a factor of 2. For example, if you use a 4uf capacitor, it will serve as a 6db/oct high-pass filter at 100Hz for a 4-ohm load, but at 50Hz for an 8-ohm load. If you want 100Hz HP with an 8-ohm load, you want a 2uf cap. And, since both speakers are in series, you only want to use one cap on the positive leg of the speaker closest to the amp. ------------- Support the12volt.com
Posted By: sab0276
Date Posted: May 01, 2006 at 11:52 AM
I'm not sure which one is wired closest to the amp. Does it matter?
Also since the speakers have a range of 60Hz-28kHz and I'd like to lose as little bass as possible would the 4uf cap that high pass filters at 50Hz be ok?
Thanks.
-Scott
-------------
2002 GMC Yukon SLT non-Bose
Pioneer AVIC N3
Posted By: DYohn
Date Posted: May 01, 2006 at 12:04 PM
Ah crap, I composed too quickly and committed the old "shifted decimal place" error. Instead of "4" and "2" uf as I wrote above, it should read " 400" and " 200." Thanks to stevdart for being my proof-reader.  ------------- Support the12volt.com
Posted By: DYohn
Date Posted: May 01, 2006 at 12:05 PM
sab0276 wrote:
I'm not sure which one is wired closest to the amp. Does it matter?
Yes, the signal must pass through the cap before it reaches the speakers. Use your multimeter and yo can identify which speaker lead goes straight back to the amp. And like I wrote above, it should read 400, not 4. ------------- Support the12volt.com
Posted By: sab0276
Date Posted: May 02, 2006 at 9:10 AM
So can I use just one of the RS caps, or do I need 2 in series? Which cap(s) should I use to get the closest to 60Hz for my application (ie. speakers run in series)?
Thanks.
-Scott
-------------
2002 GMC Yukon SLT non-Bose
Pioneer AVIC N3
Posted By: stevdart
Date Posted: May 02, 2006 at 9:29 AM
sab0276 wrote:
The 3.5" are replacements for the 2.5" in the very back of my Yukon.
You sure you need these bass blockers? Those OEM speakers wouldn't have had a full-range signal going to them. ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: sab0276
Date Posted: May 02, 2006 at 10:15 AM
True. The seem fine now, while running off of the stock stereo system. But I plan on adding the AVIC N3 and running the rears off of the head unit. I'll probably re-use the stock speaker wires if possible. At that point I think I probably would need the caps. -Scott ------------- 2002 GMC Yukon SLT non-Bose
Pioneer AVIC N3
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