EQ Circuit before or after crossover circuit ??

[abel2b]

Hi Can someone clear this for me, I want to build a 3 way Active crossover and I want to be able to adjust frequencies, my best idea es to use EQ circuits, but I don´t know if it´s better to use active EQ before or after Crossover stage.

I was thinking to use a 3 band EQ with gyrators after each crossover stage to fine tune the frequencies...

What do you think??

[s3tup]

Depends what do you want to fix with these EQs.
If you plan to fix driver-related issues, then you probably should place the EQs on each driver's signal trace.

If you want to fix baffle problems, room EQ etc - then you should keep EQ before crossovers.

I'd suggest to place LPF after EQ section - like this
[IN] - [HPF]
.......\[EQ] - [LPF]
Then, if you'll have a hiss in EQ, it will be filtered by LPF.

3 bands for each... That's 4 opamps for each driver! (1 buffer + 3 gyrators).

I'd build a couple of simple buffer+gyrator sections, which you could place whereever you wish.

[abel2b]

Well I wan´t to have a crossover like the comercial automotive crossovers where the frequencies are variable for fine tuning, today I experimented with NI Multisim and placed the EQ before and after Xovers but I do not see a difference,

[s3tup]

Try to sum the crossover outputs:
[HP]---[R=10k]_(test point)__[R=10k]___[GND]
[LP]---[R=10k]/
and see what you get if EQ is tuned near the crossover frequency.
Each EQ affects phase response a lot - you'll see the phase errors during summation if EQ is placed in particular driver's chain.
That phase wiggle in EQ could fix driver's phase error (as long as the hump/dip on driver's response is linear - so every frequency curve is related to phase curve, and when you fix linear response dip, you fix the phase too).

[abel2b]

Thank you for the suggestion I will experiment and check as suggested !!

[cats squirrel]

I don't see the point. You will have to have different low, mid and top frequencies for each drive unit, as bass won't have any top, and top no bottom. Better to have a nine band graphic equalizer and you can play to your heart's content.

[abel2b]

Originally Posted by cats squirrel

I don't see the point. You will have to have different low, mid and top frequencies for each drive unit, as bass won't have any top, and top no bottom. Better to have a nine band graphic equalizer and you can play to your heart's content.

Originally Posted by s3tup

Depends what do you want to fix with these EQs.
If you plan to fix driver-related issues, then you probably should place the EQs on each driver's signal trace.

If you want to fix baffle problems, room EQ etc - then you should keep EQ before crossovers.

I'd suggest to place LPF after EQ section - like this
[IN] - [HPF]
.......\[EQ] - [LPF]
Then, if you'll have a hiss in EQ, it will be filtered by LPF.

3 bands for each... That's 4 opamps for each driver! (1 buffer + 3 gyrators).

I'd build a couple of simple buffer+gyrator sections, which you could place whereever you wish.

Your absolutely right, I wasn´t thinking straight, it would require 6 EQ for stereo channels, and would be hell to sync each pair not to mention the cost of all those op amps, 1 EQ before the crossover look simpler...