How do you add a low freq. filter to a 2way crossover? Bypassing worth it?

[GuyPanico]

I'm getting ready to make a simple 2way LW second order crossover for my NSB array. Since these cheap little drivers dont play low, i'm wanting to bandpass them (90hz - 3300hz). How do I add a 6db highpass to my midrange? Do I simply place my 220uF cap inline with the midrange? If so, where?

Also, i'm using cheap electrolytic caps. Which only makes sence since i'm using $.49 midrange drivers. However, would it be advantageous to bypass my 4uF electrolytic cap on the tweeters with a .10uF film and foil poly cap?

 

[Jonathan Bright]

I'm having a bit of trouble fitting the idea of a midrange into the diagram you have posted but from what I can work out you just put the cap (220 uF) in series with the mid range. IE amp out put---cap---mid. Just make sure the cap is bipolar which means if the one you have is not then you need to put two caps of about 440uF back to back to get an equivalent value. By the way I think it is genearlly advised to swap one speaker polarity when used in a 12db/octave xover. The answer to the last question is probably yes and as it will cost little should not be controversial.

 

[GuyPanico]

Should I place the cap before, or after the inductor in the 2nd order crossover? Or does it not even matter?

 

[Jonathan Bright]

for the usual 2nd order network the inductor goes across the speaker terminals and the cap comes before the inductor. That is to say just like the top portion of your illustration but if you use inductors and capacitors it will be a 12 db/octave not 6db. But that is not a bad thing by anymeans.

 

[paulspencer]

Just remember with electro caps, they degrade over time and their value will change, hence they need to be replaced over time. This is why most aim to use poly caps. For long term use you really want polys.

 

[Irwin AR]

Do consider a polypropylene cap instead.
I use 150uF which should give a -6db attenuation at around
130hz... provided your mid is safely at 7 - 8 ohms actual measured.

Solen has this for only ~$40.00 if i'm not wrong.
Yes it is big in size but you could always put it outside your
speaker box as it is not considered part of the XO.
It's purpose are just to protect/allow adequate freq. range
for your mid-tweeter.


EDIT : Oops...you mentioned a $0.49 drivers? i guess my
comments is irrelevant here.