Originally Posted by KurtCocain
So what is the consensus on limiting equalization with the app - 200Hz, 300Hz, 500Hz? What is considered the transition frequency below which we want to manipulate with EQ?
There's no consensus, and honestly I would challenge anyone to hear a difference between 300Hz and 500Hz.
The other factor to consider is the target curve -- if you're using the MultEQ app to shape a little more downward slope in the speakers response (i.e. trying to shift the Audyssey curve more towards the Harman curve) then the EQ cutoff point is also the cutoff point for your ability to shape the target. So in that respect, EQ'ing a bit higher is better. Personally, I think 300Hz is a bit conservative, up to 500Hz is still going to be in the "transition region" with fairly dense modal variation and I doubt Audyssey is doing much harm tightening things up there.
Some measurements... the first photo is my LCR speakers with no EQ (Direct mode), and the second photo are the speakers with Audyssey up to 1,000 Hz. Subs turned off with a 110Hz crossover. This is with variable smoothing (so it's very high resolution down low gradually increasing up to 1/3 smoothing in the highs, so you can still see the low frequency jiggles but the top end isn't crazy jaggy). All three speakers are identical model Triad Silver LCR (the center is flush against the wall which is why there's that crazy bass boost below 200Hz on the purple line in the first graph).
As expected, things are buck wild with no EQ below 250-300Hz, and Audyssey makes huge improvements down there. But I think it's clear Audyssey is still cleaning up some mess at least up to 500Hz, at minimum shaping it better into the smooth downward slope I'm going for.