series vs parallel filter

[Marcelinho]

I'am experimenting with serial vs parralel filter. According to humble homemade hifi there is not much difference if the component value's are the same. (and well designed).

The drivers used are well matched, and measure according the spec. sheets

The drivers used are: scan speak d2905/9700
and the vifa 4" plw09...something in a closed box of approx 1 liter

The tweeter has a l-pad of 2,7 and 8,2 ohm
The midwoofer has a RC of 10uF + 10R(i believe)
So tweeter and midwoofer are about 6 Ohm from 20-20kHz

The 6 db filter consist of a 0,39mH inductor and a 10uF Capacitor
somewhere around 3000Hz (filtering at 2000Hz give more problems see below)

By listening and using a tonegenerator I find that the serial filter is playing louder (overall) and has a bump in de frequency range from 1800Hz to 3000Hz. (parrallel has no bump)
What is the explenation of both differences and how do i get rid of the bump

[Landroval]

Do you have the tweeter out of phase with the serial filter?

[Illusus]

Rod Elliot says the same thing...there is nt much difference, audible difference.
(ah! here it is) series vs parallel


I'e toyed around with parallel-series...I keep switching back and forth. There is a difference but I can't decide which is better. With series I get a detailed, focused sound and with parallel I hear a bigger soundstage with more ambience...but these differences aren't huge, just noticable

[rabbitz]

If you are getting a bump with the series, then you have an overlap on the drivers. Change the crossover frequency on the woofer so it's lower and/or change the crossover frequency on the tweeter higher.... an asymmetrical filter.

Also try ditching the L-Pad and use a single series resistor for padding before the tweeter and see how it sounds, but the cap value would need to be recalculated to suit the impedance of the resistor + the tweeter impedance at the xo frequency.

Just some suggestions.

[soongsc]

I've always had good results using serial, bur recently someone wanted biamping capability, so the parallel would have to work.

[Landroval]

Originally posted by soongsc
I've always had good results using serial, bur recently someone wanted biamping capability, so the parallel would have to work.

So what are the biggest differences in your opinion?

[Marcelinho]

Do you have the tweeter out of phase with the serial filter?

No, I will check if it makes a difference.

Oeps, I see that i forgot the RC network at the midwoofer.
With it, its a lot better, but stiil a bump starting at ca. 2000 Hz.

I think i have to do some more listening.

[soongsc]

Originally posted by Landroval


So what are the biggest differences in your opinion?

From a music point of view, I think I will know in a few weeks.
From an engineering point of view, series XO design is indegrated such that one change might alter both sides of the XO, which is good when you know how to use it. With parallel XO, I think the changes are indepenendt of each other. However, I have never tried the parallel XO design extensively. This might be my first.