Bass traps? (to solve a suck out)

Bass traps can help change the way audio waves flow through the room, thus help treat both peaks and nulls, but in my case, after i treated my room with bass traps, the nulls were not measurably better. while this is just my experience, i would imaging that it would be a pretty standard result.

What would need filling in? Below 16hz?

Those nasty suckouts. If you place the sub closer to the listening position and further from a wall/corner then you can hope to provide some "fill" where the main speakers produce a terrible suckout at your listening position. It won't completely cure a suckout but along with bass trapping it may help just enough to make an improvement. In this situation with full range speakers one could easily end up with overall too much bass - this is where a PEQ with notch filters can help on the sub to avoid adding to both peaks and troughs...you just add to the troughs and the sub peaks are EQ'd down. Of course you could notch filter the whole lot (mains and Sub) with a PEQ also (depending on the specific issues) or you could EQ each speaker and sub seperately...indeed the possibilities are many with the only caveat being that it is all too easy to overdo things and try to get ruler flat by placing dozens of filters which I suspect is a bad idea. At some point diminishing returns and the KISS - Keep It Simple Stupid rule of thumb applies....less "tweaking" may actually be better sounding than more.

after i treated my room with bass traps, the nulls were not measurably better.

Good point - I hope nobody goes away with the impression that bass traps can cure suckouts. I agre that it takes a significant amount of broadband bass trapping to make even a small difference. Tube traps (resonators) can do nore at specific frequencies but you really need to know what your doing - in this case best get an expert IMHO (I wouldn't dare play with tube traps given my limited knowledge and amount of time/effort I expect it would entail. Sticking large thick broadband absorbers in the room corners is a simple easy fix but designing tuned tube traps is a whole other matter...)

It is a while since I visited Realtraps website. There is a wealth of information here. I think Ethan does great service to audiophiles everywhere whether you buy his Realtraps or another acoustic company's products. I got GIK Tri-traps becuase I decided that the biggest thickest "superchunk" equivalents was what I needed most (of course I should have done much more if I wanted anytthing more than a very modest improvement but aesthetics will ultimately limit us all). Nevertheless, my choice to go with GIK did not stop me learning an awful lot from the material that Ethan has shared... you have to respect that!

i agree, i have some of his products now and i have spoken to him on a couple of different occasions. he is a nice guy and filled with loads of helpful information.