[Prof.]

That is an impressive looking house structure!..:T
You mentioned the walls will be dark brown, but in the photos they look bluish!..Has there been a change of plans?

 

[Prof.]

Very nice drivers Scott..It should sound great..:T
Pics of the build would be nice..

 

[Prof.]

Nice chairs Scott and the screen looks great!.:T
What is that sub you're trying to position now?..

 

[Prof.]

One thing you could try...and I seem to remember someone else having a similar problem...is to place the sub in a front corner location, angled into the room, to obtain maximum bass emphasis, and then raise it up off the floor by about a foot or so..
Might be worth a shot..

 

[Prof.]

Sorry to hear nothings working for you!
Probably best to wait until the new subs arrive at this stage..

Spikes on a sub will generally help to give a cleaner/tighter bass, but I don't think it's going to help your extreme null at the listening position..

My guess would be that the particle board flooring is maybe causing a problem..That's not a normal flooring board..
That being the case, you may need to put something solid under the subs, like a concrete slab or similar..
I finished up putting a sand filled box under my sub., with a layer of that sheet packing plastic/ foam on top (can't remember the correct name for it) before I could get a smooth extension to the lower frequencies..with minimum peaks and dips..

I hope the new subs. work out better for you..

 

[Prof.]

Prof.

Many thanks mate. Thats interesting about the particle board. I am wondering if it's vibration may actually be interacting with the low frequency sound waves in the room, contributing to the null(s) at the seating position? I mean if a large flat moving mass (the floor) is vibrating at the same frequency as the sound waves, could it not be acting as a large speaker, cancelling out the original sound from the subwoofers? Seems extreme, but it would kinda explain my room issues.

It's quite possible..The natural resonance of particleboard would be different than normal floor boards..
Anything that resonates in harmony with low frequencies, will have a cancelling affect..

I have some cement pavers coming next week, I'll try sticking the new subs on spikes on top of those. I may even try some of the foam, though I am not totally sure which kind you mean? The white styrofoam?

No..It's the flexible plasticy foam sheet material that a lot of AV gear comes wrapped in..It's not very thick but it's quite spongey..
I think it's called Exo Foam!.or something like that..

 

[Prof.]

Nice neat job Scott..:T
How many thicknesses did you finish up using in the traps.?

 

[Prof.]

Shouldn't be a problem Scott..
My rear traps are only 4'6" high..because of a similar window problem, and they do the job..