Cutting low frequency

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Member
Joined 2007
Paid Member
How is this calculated?

by much maths! see attached. The formula at the end is probobly the only bit of interest but I felt like showing why this works. Disadvantage of first order filters are there very slow roll off (-6dB/octave).

higher order filters must be constructed out of inductors and capacitors to be practical or be at line level.
 

Attachments

  • filter.jpg
    filter.jpg
    98.8 KB · Views: 291
by much maths! see attached. The formula at the end is probobly the only bit of interest but I felt like showing why this works. Disadvantage of first order filters are there very slow roll off (-6dB/octave).

higher order filters must be constructed out of inductors and capacitors to be practical or be at line level.

So i just have to use the same calculator that can be found for a first order filter to find the capacitor value, right?

-6dB/octave is exactly what I want.

By the way I have tried it with 1000uF and this does a wonderfull job. I will try diffenrent values to find the best value. But I think Im pretty close of my goal.
 
cap at speaker will work in some instances - but not all - here's a little horn with lower resonance 6" speaker and 36uF highpass - with just the cap it was trying to play bass way below its cutoff (imageshack lost my impedance graphs) and distorting badly - adding a impedance compensation network made it behave correctly
An externally hosted image should be here but it was not working when we last tested it.

here's a sealed box woofer - look at the effect of a 500uF cap in series and
also look at the impedance curves - where the boost occurs in this case is from a lower impedance in that area with the cap
-the box is now a 3rd order sealed box with the 500uF cap
An externally hosted image should be here but it was not working when we last tested it.
 
Last edited:
Member
Joined 2007
Paid Member
yes that is a problem speakers arn't actualy resistive but you can easily make an |impedance|/frequancy plot using a multimeter, signal gen and resistor. Infact if you made a phase plot aswell you should be able to completly describe the speakers electrical transfer function.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.