@ comfynumb -- I already suggested that, note that on Onkyo the "Flat" curve is called "Music".
See here: a)7. What are the Audyssey 'Movie' ('Reference') and 'Music' ('Flat') curves?
Not a tone control but you can set 3 levels of 'effect' for PLIIz with Onkyos. From memory, it's Speaker Setup > Audio Adjust > Dolby > PLIIz > Low. Medium, High. If that menu sequence doesn't take you there, poke around and you'll find it.
BTW, all this discussion of DSPs is interesting but it's way off topic.
Older and lower end Onkyo's do not have the option. Only way to get flat/music is to use THX Music mode or THX Movie with Re-Eq off.
Remember that only affects the level of the Height channels though and has no bearing on their frequency response as such. I find I leave the PLIIz setting on High all the time, and it is still fairly subtle.
^No, don't mess with the crossover, simply trim down the sub ch in the AVR. More options: if you have DEQ on then turn it off as it boosts bass, or you could be sure to use DVol with it on eve or midnight to limit the overall loudness. It also helps to isolate the sub from the floor using a SubDude or homemade equivalent. A few new AVRs have Audyssey LFC which is supposed to work great for this.
^Yes. Then you can always easily put it right back when they go on vacation.
this is from the FAQ- but in your case you'll trim down rather than up
It is absolutely not recommended to hold the mic in your hand, period. The resulting calibration cannot be guaranteed to be even approaching good. Yo can buy a boom mic stand for less than 20 dollars, which makes it much easier to do the calibration and gives a reliable result.
More information here:
Of course, you are free to do the calibration any way you choose - but if you encounter any problems you won't get any support here because the first thing people will tell you to do is use a mic stand or a tripod. Entirely up to you how you do it, but it's anyone's guess if you are even getting close to a good calibration when you hand-hold the mic.