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What noise track are you using? If it's not correlated or mono pink noise then it won't sum.

Have your set TA?
If he gets 5db on mid bass it’s correlated

I’d be aiming for 6db unless it’s mounted in doors, then 5db is good…

I’d want 3-4db through mid and tweeters ideally… all pass can help below 1khz at most, above that I don’t bother, and I’m very careful about them using above 300hz if I’m honest… where a moving mic makes no difference is a good guide to where all pass are handy… not always positive though… so enable and disable

but see what summation you get, post a graph if you get chance of left/right and summed also
 

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I'll post a complete set of graphs here in a bit. What do you suggest though. If you are getting 6db for midbass and various for other drivers, do I work to get the final curve to match my house curve? Because that wont match the individual left and right. If so how do you go about tweaking?
As long as the tonality of left and right matches you are good to leave it as it is, I am not fussed what the curve looks like summed as long as it plays well, I often find that cuts which match drivers massively are sometimes not needed and often I find the mic doesn’t show what we hear at a few select freq’s or bands, I’ve not found a perfect measurement technique as yet that does the job 100% every time
 

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Audiofrog's guide also says to use mono for RTA.
Why do you say stereo for tuning?
Is one or the other objectively correct, or does it depend on what you're tuning?
If I'm only measuring a single channel, or two channels on the same side, does it matter?

View attachment 338278
It’s not mono or stereo… it’s phase coherent (correlated) or not…

always use correlated for everything in a two channel setup… rear fill that’s differential can be worked around with correlated also
 

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Correlated versus uncorrelated applies to signals coming from multiple speakers at the same time while measuring. If correlated, then the same measurement signal is coming from the speakers in phase. This is not good for determining EQ settings, you will end up with phase cancellation at some frequencies, phase reinforcements at other frequencies, and will get a totally crazy frequency response curve. Move the measurement mic a few inches, and you get a totally different crazy frequency response curve.

By using uncorrelated pink noise, the measurement signal coming out of each speaker is random and completely unrelated to all the others, so there will be no phase cancellations or reinforcements, and you get a sane looking frequency response curve.
I don’t even see the logic in what you just described…

All left or right drivers together will play a coherent signal that’s in phase with each driver as the pink noise is recorded in stereo regardless and all drivers on respective sides will play with the same phase whether correlated or uncorrelated

And when playing the two sides together you want to know where cancellations occur after eqing a flat response from each individual side

I don’t know why you’d want it to look artificially good? It doesn’t help or change anything? It won’t even show any evidence of timing being good or coherent at all…

I genuinely don’t get one reason why uncorrelated is ‘good’ for tuning a stereo front stage with subs
 
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