Question about crossover slopes

[e-side]

Hello,

I'm wondering if there are any (dis)advantages of using different slopes for the low- and high-pass section for a two-way passive crossover. For example, 12 dB/oct for low-pass and 18 db/oct for high-pass. Could someone please tell me about it?

regards

Erwin

 

[Khron]

That's a great question, I'm real curious too about it. I've seen some bookshelf projects on the web, using "odd" xover slopes (like 15dB/octave) etc. I'll be keeping an eye on this thread...

 

[myhrrhleine]

There's no problem with different slopes if you design with that in mind.
Each 6dB/oct adds to the phase.

At some frequencies the phase adds up to 180°
Then no sound at those frequencies (at 180° the sound cancel).

 

[e-side]

Each 6dB/oct adds to the phase.

At some frequencies the phase adds up to 180°
Then no sound at those frequencies (at 180° the sound cancel).

How many would each 6dB/oct add to the phase exactly?

With a second order x-over there's the same problem (W/T out of phase), isn't there? Is the phase of the tweeter 90 or 180 degrees different from the phase of the woofer?

regards

 

[richie00boy]

Each 'order' or 6dB causes 90 degrees phase shift max. Using odd electrical slopes is often done to end up with a matched acoustical slopes. In the case mentioned the bass-mid driver might be rolling off naturally at the crossover frequency, so only needs a 12dB/oct filter to net an overall 18dB/oct acoustic response, which matches up with the tweeter.