# 10 Filters for BFD using REW??



## sam1000 (Jan 16, 2009)

I got BFD last week and got my first measurements yesterday with M-Audio USB Pre. While I was reading up on REW/BFD combination, I read comments that you should not need more than 4-5 filters to have relatively flat response curve. However, REW recommended 10 filters to me. Most of the filters were in the range of 20 to 32 Htz (Sorry, I do not have the details at this time, will post the filter details later). I thought only couple of filters should have done the job to negate 10-15db gain I was seeing between 20-32 Htz.

Is having too many filters a bad thing because then BFD will need more time to process thereby adding some lag?


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## brucek (Apr 11, 2006)

> Is having too many filters a bad thing because then BFD will need more time to process thereby adding some lag?


No. Often REW requires extra filters to properly match the room mode it is attempting to counteract. There's more to a peak than its high level - there's the decay time to worry about. REW tries to get the best center frequency and bandwidth match to do so.

brucek


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## sam1000 (Jan 16, 2009)

thanks brucek for the quick response!!


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

sam1000 said:


> However, REW recommended 10 filters to me. Most of the filters were in the range of 20 to 32 Htz (Sorry, I do not have the details at this time, will post the filter details later). I thought only couple of filters should have done the job to negate 10-15db gain I was seeing between 20-32 Htz.


Hard to say without seeing any graphs, but if REW was recommending that many filters in such a narrow area, I'll hazard a guess that it was way above the Target curve ("10-15 dB gain" = way above the Target curve). Did you run the Set Target routine before running the EQ routine?

Regards,
Wayne


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## sam1000 (Jan 16, 2009)

Hi Wayne,
Yes, the room gain was close to 10-14 DB between 20 to 35Htz. 
I'm having trouble posting an image.

I did not run the set target routine before running the EQ routine. I'll try that. Thanks for your input.


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