# Auto EQ filtering in REW v5



## gperkins_1973 (Aug 25, 2008)

After playing around with the Auto filtering in REW v5 I have noticed that it automatically tries to boost dips in the un EQ'd response which in turn just introduces more ringing and delay at that frequency. I would have thought it would not boost at that particular frequency if this was to end result.

Is it better to simply manually enter the filters or rely on REW to do the job for you to get the best result.

cheers

Graham


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## JohnM (Apr 11, 2006)

gperkins_1973 said:


> After playing around with the Auto filtering in REW v5 I have noticed that it automatically tries to boost dips in the un EQ'd response which in turn just introduces more ringing and delay at that frequency. I would have thought it would not boost at that particular frequency if this was to end result.


Boost filters in REW are subject to several limits:

- A limit on the gain of any individual filter, if this is set to zero REW will not allow any boost
- A limit on the overall gain of the combined effect of the filters, if this is set to zero REW may assign boost filters to compensate for the cutting effect of other filters but the overall result will not add any gain
- A limit on the 60dB decay time of the filter, which depends on its gain and Q settings. REW limits this to 300ms.

So you can choose whether to allow boost filters or not, and if you allow them REW makes sure the 60dB decay time will not exceed 300ms. You can also see the effect the filters have on the time domain performance by looking at the waterfall of the equalised response. For more see the EQ Window help.


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

gperkins_1973 said:


> After playing around with the Auto filtering in REW v5 I have noticed that it automatically tries to boost dips in the un EQ'd response which in turn just introduces more ringing and delay at that frequency.


Not necessarily. If you’ve seen any waterfall graphs, where there is a dip or trough in response you have much less ringing than what is observable at other frequencies. Boosting the dip or trough via EQ is most likely only going to bring its decay times in line with the rest of the frequency spectrum, and nothing more. You could only legitimately claim that ”more ringing was introduced” if the EQing increased the trough’s decay times to something _worse_ than the rest of the frequency spectrum.

Regards,
Wayne


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