Do you mean using your won house curve with a tilt and not use DEQ? If so, don't you have to use different house curve for different master volume and/or sources?
Most people tend to find a general house curve that works across their usual listening ranges and most content, which takes the sliding scale out of the equation (and maintains consistent level matching). I like what DEQ aims to do IN THEORY... but it is dependent upon sources being mastered to a known reference. Movie mixes were more consistently done so back in the 5.1/7.1 days, but lately, they're all over the map (especially when comparing physical discs to streaming).
Consider bjmsam's preferred curve using DEQ with the 10dB offset. Assuming he measured that response at his normal preferred listening level, then any movie mastered to reference such that he doesn't have to change master volume would play back with that response curve applied. But what if it's say... a Disney title that is -8dB down from other titles? He then has to boost master volume by 8dB to reach his typical listening level, which flattens out the curve he observed at his normal level. In fact, with the 10dB offset, if he turns master volume to -10dB relative, that curve he likes is completely gone for any MV at and above that (which is what the offset defines).
The other issue is that in addition to the frequency shaping DEQ does, it does coarse boosts to the levels of the surrounds by shifting the entire inverse filter (because it doesn't have direct control over your channel trims). Now, back when Audyssey created DEQ, this made sense because it was in a 5.1/7.1 context. You might want the surrounds to be slightly boosted as you get lower than reference. However, if you have an Atmos/DTS:X setup, what DEQ ends up doing by altering the surround levels this way is shifting imaging from where the respective renderers are attempting to place objects. From measurements I've seen, DEQ applies that boost to side/rear surrounds AND rear heights... but not front heights. The problem here is say, for instance, you have an object placed between the heights in a x.x.4 layout. If the levels are matched and the Atmos renderer does its thing by steering the sound 50/50 between the two height rows, it should image directly above you. But if DEQ is engaged and you're below 0db MV (or -10db MV if still using the 10dB offset setting), your rear heights might be getting a 1-2dB coarse level boost, essentially dragging the image further back than the renderer meant it to be placed. Many Atmos titles (unfortunately) use 2 static objects at the top mid location with some pre-panning applied rather than dynamic objects that move throughout the layout, so in this case, DEQ would be shifting those static objects behind the listener due to the level change. Likewise, if you had an object placed at ear level in the front wide position in a 7.1.x layout, the boost DEQ does to the side surrounds would shift the intended image back toward the side surround instead of imaging it at the correct location in your room.
I've argued for a while now that if Audyssey would separate the surround presence boost from the loudness element of DEQ, it would make it more useful with the immersive audio formats. But as it is, I think you're better off turning DEQ off altogether and just implementing your own compromise house curve/tilt that gives you good results across the range of your usual listening levels. DEQ makes everything like hitting a moving target on top of a train with the shooter in a helicopter. I've even seen people argue for trying to change the surround and rear height levels to mitigate those changes somewhat, but that just introduces more unpredictability if you have to change master volume to suit the level of content.
