Building super-chunk trap, is 703 good enough?

Sorry to reply back to my own thread, but I went and re-read through Ethan's site again.

I guess my plan to put a sheet of rockboard in front of the superchunck traps in the corner, wouldn't perform nearly as well as taking 4 sheets and placing them at the ceiling to wall boundries, will it? I've got REW so I'll take a few before / after waterfall plots to show you guys the different, let me know which one is better.

I've already filled my entire drop ceiling with 8" R32 fluffy stuff, this is just sort of icing on the cake, if you would.

Here are some pics I just uploaded of the theater:


This first picture shows where the 7.5 ' traps will go, in each corner. The SVS sub on the left (behind the wine-colored curtain) is along the wall, so it will sit pushed up against the trap. That is a full-length brick fireplace behind the curtain, so it does nasty things to the acoustics in the room.



The second picture is a rear view I snapped off, showing the challenges I face in the rear. The room is approx 25' by 13' at the front, and 15' at the rear. ON the right is Office #1, and I have very little room (only 2') to put a mini-superchunk trap. On the left is the bar, and behind it is a fridge, so I'll have only 63" of vertical space for the 4th trap. I might move the fridge though, just no other location for it.

You know, looking at those graphs it doesn't look so bad. However, I think *this* graph will explain what I'm trying to tame. *ick*. It's room mode madness. :doh:

Just moving my listening position a few inches results in wildly different response. I'm sure part of my issues is my screen, which is 3/4" melanin, paired with the bipolar nature of the towers (2 midranges firing both forward and back gives me 10 mids and 5 tweeters in the front sound stage) so things are a bit blurry.

I've considered treating the front wall, but what's the point? After putting the bass traps up, there will be 1 foot of hard surfance on three sides of the screen (top & sides) and 3 feet on the bottom. The screen isn't acoustically transparent, so I can't trap behind it, and even if I did, that defeats the whole purpose of a bi-polar. Granted, stereo music sounds *great* on them, and the sound stage sounds, at least to my ill-trained ears, expansive. But I still struggle to hear dialog at my lower listening levels (i usually watch movies at ~65dB)

Just a quick update, here are two photos I snapped of the two "almost done" traps installed in the rear of the theater. I had to make due with the limited space back there. Each trap is wrapped in a single sheet of polyfill. Keeps the highs from bouncing off the wood framing.

I ended up using 1x3" firring strips, with a 3/4" triangle of plywood at the bottom, and a 5/8" triangle at the top. These two are strictly filled with straight 2.5 lb density roxul mineral wool. I ended up beveling the front edges of each of the firring strips to keep a straight face on them.

I have some black burlap to cover them both, just wanted to get all the traps done before I start gluing.

I'll post some more pics tomorrow of the other two "full-height" traps tomorrow that will show the framing. In those, the top and bottom 16" are Roxul 60 Rockboard (6.0lb density), with the middle being 2.5.

Had I really thought about it, I would have gone 6.0 the whole way. The 2.5 stuff is too floppy and compresses down, so I ended up having to use more than I calculated. Whoops... :dunno:

It's done! Here are some the final graphs...

I can say that the bass certainly *seems* tighter. The graphs don't really show what I hear though. Maybe it's because I "want" to hear a difference. Once thing I did notice is that I still have a null in the middle of the room, just not as bad.

In the two frequency graphs, the blue line is the original untrapped response, and the green is the trapped response. Same goes for the LF waterfall. It would appear that blue has a slightly greater resonance, but that could be also accounted for the slightly less decibal output. I had to turn the volume up a bit (maybe -3dB) to get the graphcs that close.

I should mention that the SVS sub sits pressed up against the left front trap. Not sure if that's ideal or not, but the response is still quite good, so I think that's ok. The bass is certainly tight.