Are notch filter calculators accurate? - diyAudio
Go Back   Home > Forums > Loudspeakers > Full Range

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th March 2007, 11:33 PM   #1
diyAudio Member
 
Join Date: Apr 2005
Location: Bremerton, WA.
Default Are notch filter calculators accurate?

How accurate are the online software calculators for figuring out the components for a parallel notch filter? I have found more than a couple on the net. I'll be working on the 2 to 8Khz range.

I'm trying to tone down the highs on my Frugel-horn Fostex Fe108EZ's. I want to attenuate the range from 2Khz to 8Khz at least 3dB. I would need to buy high-quality capacitors, so buying and trying experimentation would get very expensive very fast.

Any advice or pointers would be greatly appreciated. Thanks.

Doug
  Reply With Quote
Old 9th March 2007, 08:10 AM   #2
diyAudio Member
 
Join Date: Apr 2006
Location: Reykjavík
The calculations are pretty straightforward, so the attenuation you'll get from the filter should be reasonably well represented in the calculator AFAIK. (I'm no expert.)

Here's a calculator you might not have found:
http://lautsprechershop.de/tools/t_p...ngkreis_en.htm
  Reply With Quote
Old 9th March 2007, 05:03 PM   #3
Speakerholic
diyAudio Moderator
 
Cal Weldon's Avatar
 
Join Date: Jan 2004
Location: Near Vancouver
Are you planning a series or parallel notch?
__________________
Next stop: Margaritaville
Some of Cal's stuff | Cal Weldon Consulting
  Reply With Quote
Old 9th March 2007, 05:40 PM   #4
diyAudio Member
 
Join Date: Apr 2005
Location: Bremerton, WA.
Kristleifur,

Yes, I did miss that one. Thank you. Using this calculator, I think I can shape the filter slope exactly how I want it. Just to be sure I understand this correctly, you use the C and L values to shape the slope and the R value for amount of attenuation? Is this correct, or am I off?

My one question now is how do I figure the amount of attenuation using this calculator? Sorry if this is a dumb question, but I honestly do not know.


Quote:
Originally posted by Cal Weldon
Are you planning a series or parallel notch?
Cal,

I'm doing a parallel. According to Fostex's specs on this driver, the impedance slope does not rise at all at higher frequencies. It appears to be 9-10 ohms all the way out. So I don't seem to need to fix that. As I asked above, my one question now is what value of resistance lowers the dB by how much. I read somewhere recently that resistance of 1 ohm reduces efficiency by about 1 dB, but I don't know how accurate that is as this was in relation to a discussion of speaker wires, and we all know how muddy those can get.

Doug
  Reply With Quote
Old 9th March 2007, 06:06 PM   #5
holdent is offline holdent  Canada
diyAudio Member
 
Join Date: Nov 2005
Location: Ontario
I think kristleifur got you only part of the way there. The tool you're looking for is a notch filter (the site linked called it a "Frequency Response Leveller") and can be found directly at http://lautsprechershop.de/tools/ind...ngkreis_en.htm. I like this calculater a lot becuase it shows the attentuation at various frequencies and let's you check what specific inductor, resistor, and capacitor values will do. It helped demonstrate to me the potential problems of having components (particularly inductors) that are not of relatively close tolerances. For example inductors 10% out of spec will create an audible change over 3 db at and around the target frequencies.
  Reply With Quote
Old 9th March 2007, 07:02 PM   #6
diyAudio Member
 
Join Date: Apr 2005
Location: Bremerton, WA.
Holdent,

Thank you. I probably would have found this one eventually, as it's on the same site, but thanks for pointing it out. It looks exactly what I need. Also, thank you for the head's up on inductors being so out of spec. I should be able to measure them, and I plan to use pretty high quality resistors and caps, so hopefully it will work out without too much fussing.

Doug
  Reply With Quote
Old 9th March 2007, 09:03 PM   #7
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Sounds like the one you are looking fore is "Frequency response leveller" at Strassacker - it shows attenuatin in db

Nice tools, but I also tweak by ear - cap and resistor are easily changed
  Reply With Quote
Old 9th March 2007, 10:12 PM   #8
diyAudio Member
 
Join Date: Apr 2006
Location: Reykjavík
Note that you can simulate a notch filter in software before building it, if you've got the attenuation values of the hardware filter.

If you're proficient in Javascript, you can look at the script that runs the filter calculator on lautsprechershop.

Here's an Excel spreadsheet I cooked up from the formula in the Lautsprechershop filter:
http://nemendur.ru.is/kristleifur04/...calc-ROUGH.xls

I don't understand the math anymore I don't have time to re-figure it out, but you could be able to make use of it nonetheless. I used this to make a software notch for the Cyburgs Needle, and that sounds fine - the math seemed to work OK
  Reply With Quote
Old 10th March 2007, 06:39 AM   #9
diyAudio Member
 
Join Date: Apr 2005
Location: Bremerton, WA.
I started playing around with the calculator on Strassacker tonight. Really neat stuff. It's amazing how you can customize the slope at the lower and upper ends. Luckily, I have pages of readings on these speakers via my trusty SPL meter. I hope to order up a selection of components soon and get to tweaking again. I sure would like to finalize this project though .

I can't say enough how thankful I am for everyone's help here. Just in the last two weeks, I'm finally feeling that my thinking regarding electricity and sound is starting to gel. It's starting to make sense to me. Not fully yet, but much closer, and since I am so terrible at math I really do need something like the Strassacker calculators for help.

Doug
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
need help wana change 60-Hz twin-T notch filter to 279 Hz filter prorms Solid State 0 10th February 2008 12:38 AM
Can Zaphs notch filter be used without the BSC filter? GuyPanico Full Range 0 21st July 2007 02:27 AM
fe 103 notch filter Jhovis Full Range 6 16th April 2007 10:43 PM
Active filter/EQ examples and calculators FullThrottleRic Multi-Way 4 28th November 2006 11:45 PM
Help with notch filter nobody special Multi-Way 1 11th June 2003 03:06 PM


New To Site? Need Help?

All times are GMT. The time now is 07:29 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2