# Crossover slopes



## atledreier (Mar 2, 2007)

Hi!

My processor cut my mains at 12dB/oct now, and I have no choice in the matter. I do however have a choice on subwoofer slope. Currently it's 24dB/oct. Do i want to use 12dB/oct, same as the mains?


----------



## bobgpsr (Apr 20, 2006)

Normally yes. I would have the sub match the processor mains for the crossover slope. This is intended to result in a proper combined audio output level that does not have a hole or peak at the crossover frequency. 

You are using only one place to do the crossover I hope. You do not want to also use the crossover built into the subwoofer, resulting in two crossover filters cascaded. So if you can not disable it, then set it to as high a frequency as possible (150 Hz) and let your processor do the crossover (80 Hz?). This assumes your processor has a subwoofer line level output.

The best way to go beyond the theory of the intended result is to measure with something like REW or other RTA software to see what works best.


----------



## ISLAND1000 (May 2, 2007)

You're not going to ruin anything if you experiment with these adjustments. Your room and/or listening environment may affect the way the crossovers match each other.


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

I’d stick with the 24-dB slope. The 12 dB will let too much upper bass “bleed” into the sub that doesn’t belong there, especially if your crossover frequency is up around 80-10 Hz. For instance, with a poorly equalized program that has too much low end into male voices (and I’ve heard plenty of them), you’ll hear them “mumbling” in the sub then the character is talking. Using the steeper slope can help alleviate problems like this.

Regards,
Wayne


----------



## brucek (Apr 11, 2006)

> My processor cut my mains at 12dB/oct now, and I have no choice in the matter. I do however have a choice on subwoofer slope. Currently it's 24dB/oct. Do i want to use 12dB/oct, same as the mains?


Your slopes are matched when the mains are at 12db/oct and the sub is at 24dB/oct.

The natural falloff slope (2nd order 12dB/oct) of a lot of mains themselves adds to the electronic 12dB/oct to result in a 24dB/oct drop overall. If your mains have very good extension then this may not apply, so you should consider the natural response of the mains I believe.

brucek


----------



## atledreier (Mar 2, 2007)

brucek said:


> Your slopes are matched when the mains are at 12db/oct and the sub is at 24dB/oct.
> 
> The natural falloff slope (2nd order 12dB/oct) of the mains themselves adds to the electronic 12dB/oct to result in a 24dB/oct drop overall.
> 
> brucek


Actually, it was REW that made me realize the slopes were different. I never was able to match the slopes of the mains with the target 24dB/oct. Changed it to 12dB/oct, and the mains matched the target perfectly. The subwoofer slope is set to THX in my processor, and that match the 24dB/oct slope of the REW target. I have an option to use 2nd order slope for the subwoofer. I don't have an option to change slopes of my mains. My mains are linear to about 30Hz, and capable of almost reference level down there, I cross them at 80Hz to get rid of some nastyness below that, and also they sound much cleaner when crossed at 80Hz. I'll experiment and see what I think.


----------



## brucek (Apr 11, 2006)

I think if you changed the sub to 12dB/oct, you'd then have a peak around the crossover.

My mains are quite capable too, so I use a cross of 60Hz. This means I have less eq control over the area from 60-80, but it all seems to work better than 80Hz for me...

brucek


----------

