Super chunk bass traps in front corners

Ok, I'm going to take a swing with the expectation I'll be corrected. Here we go.

Regarding "no bass in front, boomy in the rear" I'm guessing it's a combination of two things: 1. Your superchunks are absorbing the bass that's going through the drywall and your room just is relatively more bassy in the rear and 2. You might have modal peaks in the rear and nulls in the front.

Also, there is no "early reflection bass". There's something called the Schroeder frequency which says your room is basically one huge resonator at related frequencies below this cutoff. So, it's much less of "f<S bounces off my side walls and screws up my imaging" as it is "my room is at the mercy of f<S everywhere and is only mitigated by absorption." Hence, early reflections refer to f>S (i.e. "mid and highs") and "bass trapping" serves to control f<S where f is a frequency band and S is the Schroeder cutoff.

You can enter in your dimensions here: amroc.andymel.eu/ but suffice it to say, as is convention in measuring, that everything below 300Hz is "bass" and is what you're seeking to control in your corners etc.

If you take of the drywall, your chunks are just going to be more effective across all frequencies. 

-m

Schroeder frequency is a law akin to gravity - it's up to you to obey or disobey, there's no good or bad about it. I'm guessing the only rooms absolved of it's power are those that can accommodate a 20Hz wave in it's entirety in all dimensions (greater than 60ft high, wide and deep). However, those spaces (like a stadium) have their own acoustic challenges such as true reverb at sub-bass frequencies.

Before I analyze your chart you should be aware that "hovering over" a graph with your mouse reveals relevant info.

Ok, let's look at those charts.
1. You've entered in your dimensions.
2. The piano is a musical and visual way to see where your room resonates. I'd say you have a relatively even distribution of modal support which is good - i.e. the lines are equally and progressively spaced.
3. The Bonello (modes per third) Graph is good. It should be continuously ascending. While you have four all at one, it could be worse (as is in the case of my room where one of the pillars are less than the value of a previous one. As alluded to in (2) your modal instances should be more and more frequent (and even) as the frequency ascends. What SHOULDN'T happen is any inverse of said principle.
4. The Room 3D shows pressure zones of modes. So, if the colors (red and blue are equal) are at boundaries, that means you have a full or half wavelength standing at your dimensions. If you have three colors parallel it means you have double the mode and so on. See the text list below your screenshot for more detail - AX is axial (two surfaces) TAN is tangential (three surfaces) and OBL is four surfaces. Axial modes are your primary concern.
5. Bolt Area: See that X? It's not in the white area. This isn't surprising considering your room's volume is 1995ft3. The minimum recommended is 2500ft. Ideally your room will fall within that area. Oh well - tough cookies.
6. Volume: as I mentioned - your room is small.
7. Surface: good to know if you're going to treat some proportion of your total surface.
8. RT60 - Irrelevant in small rooms.
9. Schroederfrequency: they make it oneword which was initially confusing for me. I like when this is lower (right or wrong?) but yours happens to be 206Hz. Therefore when doing acoustic analysis with REW or equivalent make sure your response and waterfall bandwidths are unsmoothed to 206Hz. Essentially your room is a big coke bottle up to that frequency and everything beyond that is "bouncing around".
10. Critical distance: I have NO clue.
11. Equivalent absorption area: Look - you need as much absorption as possible to don't bother with these ivory tower numbers.

Ok? You owe me a beer.

Thanks

m

Lastly, see how none of your room's dimensions are equal or multiples? That's good. The main two monsters you have are a low ceiling (<11ft) and lack of space (<2500ft3).

We all know that Mr. Winer is the guru.  However, I've condensed his, and some other, relevant info into my own series of how to set up a room.  Please watch it - I have vids going up every thursday and they may be relevant to your interests as they cover just about everything I know.  Here's the playlist: www.youtube.com/playlist?list=PLf112S63WiBsq_oWZ8Pa5RLACk_O18qhY

Ok I'm done.

Let me know if you have more questions - it helps me too.

Thanks,

-m

Hi Kevin,

On the less technical side, and at the risk of stating the obvious, you know you need to remove the drywall from your super chunks, right? There is no way to audibly assess the sound of your room with the DW in place. So when you do remove it, paper faced insulation should face the room. I know Ethan has tested rigid FG with FRK but since I'm not positive fluffy with paper facing gives the same increase in LF absorption, I can only guess that it does and ask if anyone else knows for sure. If not, I'd still suggest going with it. (your rear corner traps should have membrane facing the room too.)

As far as how to cover the super chunk: One very simple way is the frame the perimeter with furring strips. Bevel the vertical edges to the wall angle. Then staple and trim cut your material. Finally, attach moulding trim over the staples and around the super chunk.

BTW, you'll notice Hexspa's design is to make the super chunk portable but my description is for a permanent installation.

Cheers,
Rock