I've been a member of this forum for many years, and spend most of my time lurking. Sometimes, I feel like many of you don't realize how valuable your knowledge, opinions, and suggestions are. This forum in particular is where I first learned about the possibilities that exist in the realm of subwoofers. Until coming here, I had never even considered a DIY solution.
I had a problem in my living room, with nulls around 40Hz and 80Hz, right at my primary listening position. I have a THT, which shakes the foundations at most points in the room, but it couldn't touch me where I spent most of my time. I added a Table Tuba to the back of the room, hoping that would smooth out the response and help me, and it did, but only up to a point.
I knew what my components were capable of, and I was really disappointed in my results. I looked at treating the room, building DIY bass traps, and all manner of everything else. I spent a day perusing threads on here, looking for tips, construction techniques, and materials suggestions, before I would start building something.
I stumbled across a thread, I don't remember who it was, I don't remember how long ago it was from. It described the characteristics of sound in a rectangular space (which is pretty close to what I'm working with), and it nailed my experience almost to the letter. The poster suggested adding a 2nd subwoofer at the midway point in the room.
I couldn't believe it could be so simple. I moved my TT (given the size, there aren't many places I can put my THT), placed it almost exactly at the midpoint in the room, and suddenly, the sound I had lost was magically returned to me.
It's not perfect, but it's within 2db of where it should be, and that's a FAR better result than I was ever getting before.
I still plan to build some room treatments, but I no longer have the sense of urgency, since acting upon this simple, yet effective tip.
I have no friends that are into this hobby to the extent that I am. I have no local experts or anyone that I can really trust. So thank you, to all of you that share your collected wisdom. At this time of year, it's normal to be thankful for all we have, and rest assured I am certainly thankful for all the people here who have provided me so much information (and entertainment) over the years.