Well, I have some results. I think I am moving forward, apart from some unexpected issues with my system and room.
Every time I make a working directory with Acourate, I write myself a note so that I can understand my motivation for doing this project and the steps that I took. This is a copy of my text file. Skip reading this if you wish, it's only for Acourate users:
Once the filters were created, I went on to do the verification measurements.
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This is a nearfield MMM of left and right speakers. Ignore the horrible bass for now, will comment on it later. It is nice to see that it corrects pleasingly flat, so the "room transfer function" correction seems to work as intended.
There right speaker (green curve) has a step at 5kHz. I am working on sorting out the issue, which is a bit too involved to discuss in this thread (and will drag it off topic). For now it has something to do with how Acourate reports the result of an SPS vs. MMM. I am chatting with Uli about it.
However, the MLP measurements are quite different:
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The top curve (red/green) are MMM's at MLP. Bottom curve (brown/blue) are SPS at MLP. As you can see, the responses are very similar, and quite unusual.
Unexpected result #1: I would have thought that the SPS would look different, because they are windowed to remove reflections, whereas the MMM should capture speaker sound power.
Unexpected result #2: See the rising treble response in both measurements? Somehow,
flat nearfield results in rising treble response at the MLP. This is completely opposite of what I would expect and totally confusing. I have never seen this kind of behaviour in the past, because my previous practice involves correcting the response at the MLP to a falling target curve.
Unexpected result #3: The bass has not been corrected with this procedure.
Listening Impressions: As I expected, it sounds horrible. Waaaay too thin sounding. Voices are all top end and sibilant with no body. That "one note" bass is really evident, cellos sound almost comical (all top end with some notes having a huge bass boost).
Conclusions / things to do: This result is unlistenable but it was an interesting experiment, even though I consider it a partial failure. I had some expected results, and some unexpected results. I will need another method to correct below Schroder. I don't think this method works. I need to figure out why my room produces a rising treble response (hopefully others will post their results so I can see the difference between NF and MLP measurements).