# BFD as a low-pass?



## Guest (Aug 2, 2007)

I guess this message can go here...

I'm wanting to build a sub and I was wondering if a BFD could take care of both the room EQ'ing and as an active low-pass filter. That way I only need to buy it and an amp.


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## brucek (Apr 11, 2006)

Yeah, I use my 2nd BFD in my back room as a low pass for the sub and also as an eq. The receiver I use there has no crossover and neither does my sub. I run the speakers full range and the sub is crossed at 50Hz using the BFD.

What I did was (and I can help if you need it), set a target line in REW (at the crossover that you want, i.e. 60Hz), and then create filters by hand in REW displaying the filters and target using the least number of filters possible (a real fun puzzle). This all done off line with your PC and REW only. Remember that the only two boxes you want checked in REW is Filters and Target (not Filters+target). You should be able to do it with 4 filters....... Use the knowledge that you sub has a natural upper limit that doesn't need filtering. You could even use REW to find that limit.

Then enter these created filters into the BFD (as perhaps #9, 10, 11, 12). Now you have a crossover that you don't touch.

Now clear the filters from REW and use it as usual to EQ your sub. (Of course you only have 8 filters you can use). But that's enough or you're doing something wrong.....

brucek


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## Guest (Aug 2, 2007)

I think my brain is starting to fail... I completely forgot that the receiver has a built-in crossover for the sub. I can just use that to feed the amp directly.


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