Merc asked, -"If you do not use an SPL meter or even any type of volume based analysis, how do you know which frequencies are impacted by room nodes-"

You have that a little wrong... I have a custom made test tone disc w/ full range pink noise @ 1Hz per track, plus tracks w/ frequency sweeps in the sub range and full range. The volume based analysis is my listening to these tones and sweeps and hearing any fluctuations (nulls and peaks).

I'm sure you could hear just as easily as I can where exactly where the nulls and peaks are and record what tracks what things happen at (track 54=54Hz for exa.).

The details of the exact db's of the nulls and peaks aren't that important to dealing with them to a great extent, in addition to the SPL meter not being exact enough to tell you those exact details if they were that critical anyway.

My main bass peak was ~69Hz-75Hz. I set my mains to 80Hz (best setting for the mains anyway -a brush of good luck) and then flipped the phase on my sub amp's output.

This cancellation countered that peak really well -flatteing it out. As would a bass e.q (I don't hate bass e.q.'s).
A bass e.q. could be even more exacting, but I find the cost of adding one and filtering the bass signal through it just to get an 'nth' degree of further improvement to be tweakin' overboard.

I also have a lesser peak @ ~150Hz but not much to do about that.
I'm just Not gonna ever add an e.q. into my main's chain. And the problem's fairly small anyway so no big deal.

"-and therefore, how to correct those room problems by using tube traps and other sound absorbing materials? If I remember correctly, you are a huge advocate of correcting the room and not using EQs to correct these room induced problems."

Yes, I very much believe an e.q. can't correct a room problem. I'm esp. against these new 'room e.q.'s that claim to fix your full range of audio by using e.q.+phase shifting ot counter room effects. The probs are that -
1)You can only correct (at the very most) one specific point of the room, making the phase and the e.q. change worse in the rest of the room.
2) So far many have said that these systems kill the detail ('life') of the audio by so heavily processing it before output.
Why risk it when room treatments treat the room directly and cheaply too.

Bass traps absorb standing waves evenly down to their limits (determined by the inner dia. of the trap). You don't really need to know the exact db's or the exact freq. of your bass peaks
to use them.

They counter whatever standing waves are present. They don't adjust speaker freq. response, or mess with your speakers at all -just the reflections.

Sorta like cleaning a dusty TV screen. You don't need to know the volume of dust present or what elements of the picture the dust most degrades. You simply clean the screen and gain full benefit from doing so.

Placing the bass traps in the corners of the room cuts the standing waves whatever they may be (unless they're below the trap's tuning). From there, if you need to use and e.q. on non-directional bass or to improve your speaker's freq. response, then you'll be in a much better position than trying to use that e.q. to fight strong room modes -a losing battle of apples vs. oranges.

Again, I claim no golden ear, but rather I think most here could do the steps I take to calibrate my system and effectivly calibrate it to end up w/ no lesser 'correctness' than picking amongst the assorted variables that must be chosen when using an SPL meter method.

An SPL meter's only $30-$40 bucks. It'not like I'm saying "$10,000 speakers are a massive rip off" (because secretly I can't possibly afford them). You must see that I only question the methodology and not the tiny amount of money I think it wastes.

I'd ask for everyone to stay civil about this and I'll continue to answer those questioning my ideas and methods.

I think the main reason I first posted was that it seemed like so many found they had their surrounds WAY too high, and sub somewhat too high.
I have no doubt that if my surrounds aren't dead on correct, that they're not more than a db or two off.
I popped in Cast Away where the ocean is washing front to back all around you and find it to be extremely even. I popped in Metallica S&M concert DVD where there are sections with even crowd noise in the mains and rears -again sounding totally even. No way this is very or even slightly incorrect.

As for sub level.
Look at a site like SVS where they rec. using an SPL meter, but only to get a general point and then rec. you tweak by ear to what level you'd like it to be (+/- several db above your mains/surrounds). And Cd's / DVD's vary so much there is no one perfect setting to match to.

Play a CD with no weak bass on the kick drum, then bottom out your sub on the THX intro on Phantom Menace. The sub level set w/ an SPL meter and not changed either time. I 've never done this, but I know people who have from online.