"Match Response to target" results seem spotty

[wus]

I have used REW a few times (not often, basically I'm still new to REW) to generate files to be used in EQ APO and thought that I understand it, but the results that "Match Response to target" gives me seem sometimes spotty.

I measured the frequency responses of 2 JBL 305P Mk II active monitors that are placed at ear height to the immediate left and right of my "computer monitor" (it's actually a 55" TV that I use), pointed at my listening position.



Then I used REW's EQ funtion to generate filter sets in the range of 40 to 300Hz for the 2 measurements. For the R channel, this looks okay-ish:



It could do better in the 80 to 110Hz range, but this one region should be relatively easy to equalize with a manually set up filter.

For the L channel, REW seems to completely forget the range below 100Hz:



Why is that?

 

[EarlK]

For questions like yours ( iow; How to EQ ? ) I suggest it's best to always attach your REW file .

 

[John Mulcahy]

REW won't try and EQ anything below the point the response first crosses that target or above the point it last crosses the target, to avoid trying to push drivers beyond their working range. Could just reduce the target level.

 

[wus]

Thanks for the explanation, John!

This target level, does it have any other purpose than to define the working range of the automatic match response function?

If I equalize 2 channels individually (for stereo), do I need to select equal target levels for both channels?

 

[John Mulcahy]

This target level, does it have any other purpose than to define the working range of the automatic match response function?

No, that's pretty much it.

If I equalize 2 channels individually (for stereo), do I need to select equal target levels for both channels?

You don't have to, but if there are level differences between the channels afterwards that will cause shifts in the balance in those regions so you might need to do some trimming of levels afterwards. Shelf filters can be useful for that.