Diffusion - possible to have too much?

[Josh0311]

Was it solid styrofoam or just a fascia? I've seen something in the past called Dry-Vit (sp) which was something like 2" styrofoam over a frame which was then covered with a stucco type product. I've only seen it used on exteriors though...
Wondering if this is a whole new product you saw, Drew...???

[[Director] drew ryan]

It was solid they just stacked the foam up to make the risers, framed out the containment for the concrete and poured. Kinda crazy. I will see if I can get the low down on the stuff.

Dryvit is very cool. I just got back from doing some consulting in Poland and there was a distro center just south of Warsaw. I believe the church used their product to redo the front of the building.

[Josh0311]

Cory, here's a one-line of the auditorium with a few pictures.

Construction materials are as follows:

Floor - concrete
Ceiling - construction grade suspended tile
Walls - 5/8" gyp on 2x4 metal studs 16" O.C.

[cmchamp]

Oh boy, this is going to be fun!
What are the dimensions of the proscenium? (stage opening)
You've got ample surface area for combination products, those being diffusion and absorption.
Working on the model now.
C.

[Brad Weber]

With a large ACT ceiling and all the angled walls that doesn't really look that bad, or at least not to where the basic shell room is an obvious problem. How would you subjectively describe the acoustical environment and any specific problems?

I'm going to be interested to see what any recordings and subsequent analysis show but my initial guess based solely on the pictures and dimensions is some echo off the rear wall and a high RT60 time due to the room volume (especially with an empty room), but with a big dip in the room response around the 100-125Hz area where the gypsum board walls flex. The speakers aimed what appears to be straight out probably exacerbates any rear wall issues. The walls probably provide very few beneficial reflections and I would also guess that due to the ceiling height and material, congregational interaction is difficult. At over 100' across, I would be a little surprised if flutter echo between the side walls is a real problem. Does any of that mesh with your subjective experiences?

[cmchamp]

Josh
There are a couple of measurements that don't add up on your one-line, basically because it's not to scale.
What is the gross width of the room and the stage area drawn?
I'm having trouble making your 21.25' angled wall meet up with the 54'x31' rear section.

[Josh0311]

Cory, the actual counter-sunk stage area is 24'W x 8'D

As you're looking at the one-line, 150' from the far left wall to the far right.


Room attributes:

• Very reverberant

• Significant slap-back with at least (4) countable repeats

• LF anomalies (boomy and muddy, but can't generate LF energy)

• Lacks intimacy, poor crowd interaction (Brad, you nailed that one)

• Overall sound seems harsh (like certain HF are being amplified)

[cmchamp]

Those were my instincts.
Thanks for the stage recess information - I think I can make a better looking room model now.
. . . .
Ok, IF the angled wall measurements are accurate, the widest the room could possibly be would be 100'
I've attached a .pdf of the mockup I have created with the angled walls being 40' and 21.25' - circles have radii of those lengths.

[Josh0311]

Yep, you're correct. The room is 100' at it's widest - my mistake.

[cmchamp]

At least we're not attempting to change the laws of physics or develop some sort of worm hole to stretch that width

[tedanderson]

It was solid they just stacked the foam up to make the risers, framed out the containment for the concrete and poured. Kinda crazy. I will see if I can get the low down on the stuff.

I guess that would be no different than putting wood or steel forms in place other than the fact that you don't have to remove the styrofoam after it has cured. Styrofoam can hold more than 100 times its own weight but I imagine that the concrete itself is strong enough to stand on its own and support the weight of the people once it has hardened.

[cmchamp]

I've attached three RT60 estimates. However, RT measurements at any length of time, 60, 40, 30, etc., assume a diffuse soundfield. I am hoping that anyone from off the street can see that this is no diffuse room.
Both the Sabine and Eyring estimates provide the 250Hz low mid 'hump' while the Fitzroy estimate explains the perceived mid-high to high tail and apparent brightness in the room.

These are preliminary, preliminary. After I took these window shots, I found that I apparently have an inverted face or two in my model and I have to figure out how to un-invert them.