How can I tell REW how to define a PEAK?

[lovingdvd]

Last night when recalibrating with REW I encountered something I haven't seen before when using it. It was not predicting my results correctly based on its recommended filters.

For instance, it identified a peak and suggested a filter, but when I applied the filter it only moved the real measurement down some but not enough. In the past I've found REW to be excellent and predicting this so I wasn't sure what could be causing this. Anyone know?

OK so then after it didn't flatten out the peak enough, I told it to FIND PEAKS again hope to apply more filters to correct it. However REW would come back and say "NO PEAKS FOUND". Yet at the same time clearly the measured result was about 3 db above my reference line (via the house curve).

Is there a setting in REW where I can tell it to consider anything greater than X dB to be a peak? Thanks.

[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)

[adogand6kids]

Is there a setting in REW where I can tell it to consider anything greater than X dB to be a peak? Thanks.

You can take complete control of the REW filters by clicking on the icon labeled "EQ Filters" along the top of the main REW screen. This will bring up all the filters REW has identified through the process of "find peaks > assign filters > optimise > adjust...". Now what you have in the EQ Filters box is REW's suggestions for filters. The far left side of the box will be a column of numbers - 1 through 12. These are the 12 filters you can input into your BFD. If REW has assigned a filter, the third column over (labeled "type") will say "PA". If the filter has not been used, it will say "None". If you see a peak in your room response that you want to filter, but that REW does not identify with the "find peaks" command, you can assign a filter there manually. Just change the "Type" box from "None" to "PA". Then in the "Frequency" column, type in the center frequency of the peak you want to tame. This can be found by placing your cursor over the highest point in the peak and clicking. This should bring up a blue line through the tip of the peak. At the bottom of the blue line is the center frequency of the peak. Now move over the the "Gain" column and start making the number in the column more negative. Watch your room response graph and you should see the "filters" line and the "corrected" room response prediction changing as you move the "gain" up or down. When it looks right to you, then adjust the bandwidth or "BW/60" column the same way. Continue to adjust these parameters and watch the predicted response. When it looks like what you want, your done with that filter and its time to move it over to your BFD. If your graph isn't showing a "filters" line, or a "corrected" response line, look at the bottom of the graph screen and make sure you have checked the box in front of those titles.

Hope this helps. Beware that once you start fiddling with the EQ filters yourself it can become addicting!