Rake Angle

[ogs]

Aha, I see.
Usually I just use a bubble level on top of the speakers, but with a rounded cabinet this may not be possible. I must say I find Sumiko's advice a little strange. If all speakers where equal (as in identical cross over and slope) this advice could apply, but this is not the case. By tilting the speakers backwards a little you change the timing behaviour and may achieve some of what Sumiko suggests. Take a look at the step response measurement from Stereophile: https://www.stereophile.com/content/bowe...asurements JA's comment on moving the mic down a few degrees sums it up.
As you can see your speakers are not time coincident. That may not be a problem, but 3-D imaging will often suffer some. Take a look at how Kii deals with this: https://www.stereophile.com/content/kii-...asurements The Kii's are active DSP speakers so your 804D is not directly comparable. To achieve a similar step response and get better imaging without any tilting of the speakers you could use the convolver in Roon and for example Audiolense (XO) to create filters. If that seems daunting, Accurate Sound might be worth a try: https://accuratesound.ca/