Brick, Drywall, Wood and SMAART

[mtmrwilson]

Hello everyone! I am looking to get some direction for my church sanctuary. It is a bit long, but all of you seem to ask very intelligent and detailed questions, so here it is.

Recently I had someone with the SMAART software and an Earthworks measuring mic come in to look at different areas of our sanctuary. We blasted the room with pink noise and measured six different locations. And the results of the software indicated/confirmed what we were experiencing, and that some frequencies are not heard as well as others in different locations.

The physical construction of our church walls are 70% Masonary Brick (not concrete block) with 1/2" deep grout lines, 20% Drywall, 5% partition folding door made of a "plastic" wood grain colored rigid material, 5% doors and windows. Walls are approximately 15' tall.

The ceiling is 1/2" tongue and grove pine that is angled to a peak on all sides. Peak of the ceiling is approximately 25'. 8" thick architectual/structural wood beams run floor to peak in all six corners

The floor is carpeted concrete.

The room is a hexagon.

My initial thoughts is that the porous surface of the brick walls with the deep grout lines are working to my advantage by diffusing/absorbing the frequencies that hit it. I reserve the right to be wrong. I am thinking that that the drywall needs some type of treatment to it as well as the baptistery which I have not yet described. Basically it has an 8' wide opening to a 20'Wx8'Dx20'H chamber with drywall on the walls. I know I have sound bouncing around in there and coming out.

People have described our sanctuary as "live" but it is not very reverberant. Our chief complaint is not feedback, but not hearing a good mix from the worship team. Part of it is the inadequacies of our PA-Bose system installed in 1997 and our super stack o'stuff in the rack. It was great for the pastor, song leader and individual vocalist and still is. But not so much for the larger worship formats we are employing.

I guess I would like some direction on how to spend my time. Treat everything/drywall only/baptistery only/leave well enough alone until I get a new PA? Our first priority is saving for a new mixer (Yamaha LS9), that will simplify the processing end of things.

[cmchamp]

What did the person with the SMAART rig use as a source of sound? An independent source, or the existing PA speakers?
If the existing PA speakers, the results of the test for acoustics sake are useless as the inadequacies of the PA speakers to adequately cover the room.
Proper acoustical testing would require an independent sound source. I use 24" latex balloons with multiple mics throughout the space and record the pops.
Others use clip-board snaps, which are adequate for speech intelligibility, but not for full range situations.
Yet others will utilize a dodecahedron speaker to provide an omni-directional impulse response or the ability to sine sweep.
My first reactions to the room is that it is to address the drywall areas appropriately with diffusion/absorption products and provide some LF absorption.
Proper corrective measures would need to be addressed after testing and physically being in the room.
C.

[mtmrwilson]

He piped in thru the PA. We knew our PA system was inadequate, we just did not know exactly how much inadequate it was. The pics from SMAART were very helpful. We were able to correct a 2 issues from that.

We are saving for the board first because that will not change no matter what we do to the room because we have +4 worship teams that rotate thru two services on Sundays, plus all of the additional children's programs.

Just did not know what was the horse and cart-acoustical treatment or PA systems.

[cmchamp]

Again, the speakers are probably the wrong tool for the job and you're probably having to push them for your services. In order to truly know the acoustical environment of the room, it needs to be properly tested specifically for that.

[Brad Weber]

It all depends on what you are trying to do. Measurements of the room and system combined can tell you a great deal about what you have overall but may not tell you much about either component individually. Some measurement systems let you somewhat take the room out of the picture but as Cory noted, there's not much you can do to eliminate the sound system from the results if you use the system for the measurements.

Their using pink noise suggests they may have simply been using SMAART as an RTA, not doing Transfer Function or IR measurements. Do you know if they looked at just the frequency response or also looked at the Impulse Response, decay times, Intelligibility or any other measurements?

[mtmrwilson]

I am not intimately familiar with the software, but we did look at spectrum and frequency response by the pics I have.I am pretty sure we did decay times but I do not have any of those pics. I have included overlays of a series of three snapshots we did. Basically, each color is a different part of the room. In this series of shots, we did Mains and Monitors, Monitors Only, Mains only. I am not sure if you guys can distinguish anything by it. We had a huge Main VS Monitor issue in our sanctuary that we finally fixed as well as a troublesome offending frequency from our pulpit mic. We also hooked up smaart to the out put of our rack-o-stack o'stuff to see what components are doing what to the signal. that was truely enlightening. Now I know why they say "Bose: Where the highs are high and the lows are low". The Bose controller does some interesting things.

[mtmrwilson]

But to get back on point...generally speaking, does masonry brick (not painted concrete block) tend to diffuse or absorb any range of frequencies? By reading other posts, I can form an opinion about drywall and wood. I can find stuff on concrete blocks but I have not found anything on brick.

[cmchamp]

Yes, but . . .

Here's the absorption info on unglazed brick at the following octaves
63, 125, 250, 500, 1k, 2k, 4k
.02,.03, .03, .03, .04,.05, .07

Here's Gypsum board
.3, .28, .1, .05, .04, .07, .09

C.

[Brad Weber]

In addition to typically having limited absorption, while the variations in the brick surface and the grout lines may provide diffusion the relatively small dimensions involved in a standard brick wall result in any diffusion provided being primarily at rather high frequencies.

Often overlooked is that if you look at Cory's number, gypsum board walls provide fairly significant low frequency absorption compared to most standard building materials.

The SMAART results shown do appear to be a simple frequency response, information that while very useful for some things, such as finding the offending frequency for the pulpit mic, provides very limited information as far as room acoustics or intelligibility.

[cmchamp]

I have Goolged™ to what seems no end and have yet to find a diffusion chart for unfaced clay brick. I've called in a ringer and am waiting my mentor's response. I am not home to go through my acoustics books. I remember sample diagrams in the F. Alton. Everest book, but I don't remember what building products and surface finishes were in those diagrams.
I'll try to remember to look for what I have this evening.

[mtmrwilson]

Thanks for the information.
As for the horse and cart thing. Does the room get treated before a new PA is purchased or the other way around?

[Brad Weber]

Originally Posted by mtmrwilson

As for the horse and cart thing. Does the room get treated before a new PA is purchased or the other way around?

You would usually want to address the room first. Not only might knowing what you plan to do for acoustics affect the system design but it will also likely affect the system tuning. If you install and tune the systems first then you may have to retune and tweak it after you make any major changes to the room. In addition, the acoustical treatments will hopefully help the room in ways other than just how it relates to the audio system.