AVS Forum Special Member
Join Date: Nov 2006
Location: Bushnell's Basin, NY
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Steve, your rooms belie a degree of effort based on partial understanding. Most of what I can suggest is common sense, and I apologize if it seems too basic.
I see "wasted effort" in looking for solutions before a problem has been defined. Don't ask if panel size is related to room size, ask what panel characteristics you need to accomplish your goal.
Define your goals first, then ask how to achieve them.
How do you define your specific goals? There are some things that nearly everyone agrees are "good." Uniform low bass response with frequency and with seating location is one. Imaging is one that garners lots of disagreement, between the "pinpoint imaging" folks and the "speakers disappear" folks. You have to understand your preferences, your desires, what sounds good to you to maximize bang for your buck. Then stick to your guns when someone tells you you're "wrong."
The most important variable in small room acoustic optimization is room construction: what are the walls/ceiling/floor made of, how much sound is reflected at these boundaries, how much is absorbed, how much leaks out. Any room below grade is a candidate for worst-case bass modes, due to the very low absorption and transmission losses from cinderblocks backed by earth. Conversely, above-grade, stick construction is rife with acoustic leakage paths and absorption devices in the room, resulting in an absence of bass modes, and potentially a need to reduce bass loss in extreme cases to achieve flat response.
Thankfully, bass issues aren't hard to find, either with ears and test tones, or with simple acoustic measurement gear. If you have excess bass reflectivity in your room, your corner treatments aren't going to address it. Panel approaches are disadvantaged by their very nature as resistive absorbers - they work at pressure nodes, where air displacement is maximized. That means away from walls - no resistive absorber has low bass effect hung on the wall. Infrasonic control requires a different approach, designed for low bass absorption.
Just define the problem first, so you can test effectivity as you go.
In the photos, I see lots of absorber-type stuff hung on walls at tweeter/ear level. The panels at first reflection points tells me you've designed both your rooms for pinpoint imaging, and MTMs are a good choice for such a room goal. I am firmly rooted in the opposite camp, but... If you want to treat first reflections, an Energy Time Curve (ETC) measurement provides the pertinent data. I would suggest an itterative process using mirrors to identify first reflections, and test panels to verify which peaks in the ETC correspond to a given mirror location. I suspect this is all very familiar to you...
This is one place where Localhost is exactly correct; if you want to kill first reflection points, do so with a broad-band absorber. Your thin panels start to lose effectiveness in the lower midrange, and the effect is a change in timbre, just what you alledgedly seek to preserve by this treatment. Otherwise, take whatever localhost says with a grain of salt. He can't explain most of his advice...
The one treatment type I don't see is diffusers. Diffuser design varies from simple polycylindrical devices to fractal quadratic residue devices, and they have a degree of absorption resulting from the diffusion. I personally find their effect to be subtle, but there are cases where diffusion is the only absorption used, and it's not subtle aurally or visually.
So... what have you got behind those walls? What are the problems you'd like to addresss?