crossover lower with ported?

[regal]

I have been working with the ported.xls program from diysubwoofer.com.

When I insert a 80hz 12db crossover the frequency plot shows the rolloff starting about 30hz lower (50hz.) It does do this on a sealed plot.

Is this correct does a ported box effectively lower your crossover point? This would be a real advantage if you have a reciever with too high a crossover.

 

[Kravchenko_Audio]

Try posting some pics of what you did and what you got/

Then we could make some sort of answer. Out of the blue my best guess is that you are unfamiliar with the program or you entered some incorect data.

Mark

 

[regal]

I double checked everything. When you put a crossover of a given frequency on a sealed box the crossover point occurs at a higher frequency than with a ported box.

 

[richie00boy]

I think you are looking at max SPL plots instead of reference 1W or 0dB plots.

 

[simon5]

Maybe the ported box SPL response is peaking around 50 Hz without a crossover, so yes if you use a crossover at 80Hz it will begin to rolloff at a lower frequency because you need to kill the peak first.