[JohnM]

REW is quite fussy about what it considers to be a peak because it is looking for modal resonances, which have particular characteristics. You can add filters yourself and still use the Optimise PK Gain & Q and Adjust PK Gains buttons to get REW to adjust them, though.

If you are finding that a peak does not respond to a filter in the way REW predicts there are a few possible explanations:
- If you have speakers running other than the channel which has the filter applied (e.g. a main speaker when only filtering the sub) the peak may be coming from one of the opther speakers
- If you have any smoothing applied to the measurement you may not be seeing the true response
- The peak may be the result of two or more closely spaced resonances and your filter has only affected one of them, or your filter's centre frequency is not at the frequency of any of those resonances but somewhere between them - try plotting a waterfall of the response, resonances stand out better in the waterfall so you can more accurately work out what frequency they are at
- If none of the above apply the peak may be a result of a combination of resonances and/or reflections that are not amenable to correction by a parametric filter (to be technical, the peak may not be a minimum phase feature of the response)