# Foam Corners vs GIK 244



## bpape (Sep 14, 2006)

We are asked frequently how our products compare to corner foam bass traps that you see all over the internet. To help give a fair comparison to our customers we purchased 16 2' foam bass traps and did testing in our lab at GIK Acoustics. To make it a fair comparison we used 8 GIK 244 Bass traps that are 2'x4' so the surface area is the same. No attempt was made to achieve a perfect frequency response. The main goal was to show the effect of low end control with corner mounted foam vs our 244 panel . The products were placed in corners around the room and both products were in the same places for the test.


*Frequency Response * 

Test 1 is the frequency response of the lab/room empty 











Test 2 is the frequency response with the 16 foam corner bass traps vs. the empty room.











Test 3 is the frequency response with 8 GIK 244s vs. the empty room.











As you can see from the test results the 244 did a great job from the deep bass and up, while the foam wedges seem to do very little to nothing until you reach 250hz. Proper bass trapping in the corner can improve frequency response, but trapping in the corners will have a large, if not larger, impacted on decay times as we will show next. 



*Waterfall Graphs* 


Before we move on to your next set of tests, here is a little background on decay times and waterfall graphs and why they are so important to view (if not more important then frequency response). As a sound plays through your speakers it doesn't just get to you and stop but continues to bounce around the room and slowly fades away over time. This is sometimes referred to by others as ringing or reverb. A waterfall graph allows you to visualize how quickly or slowly a given frequency decays over time.

Low frequencies tend to be stronger and stay more intense longer than higher frequencies. Higher frequencies are also easier to control. Things like people, furniture, carpet, curtains, and even air tend to have a much more significant impact on the higher frequencies than lower ones. In addition, high frequencies are much more directional where low frequencies tend to spread like a sphere in 3 dimensions. In a bare room, there really isn't much that has any significant impact on low frequencies which is why it is critical to have proper bass trapping . As the low end keeps bouncing around the room there are other things that you are trying to hear but the frequencies that are ringing are masking imaging cues, harmonic textures, and even cancelling and/or reinforcing themselves. 


When someone refers to a room that sounds "tight" or "clear" they are most likely in a room that the low end decay times are under control with bass traps.


Test 4 is the waterfall graph of the empty room











Test 5 is 16 corner foam wedge bass traps











Test 6 is 8 GIK 244 Bass Traps











You can see that 16 of the foam wedge bass traps had virtually no effect on the decay time below 200 hz while the GIK 244 decreased the 65 hz decay time and up by a significant amount. With even some effect at even 45hz. The goal of bass trapping, which the 244 shows, is to have a controlled decay time throughout the low end. This helps bring a tightness and better clarity to the room.


----------



## KalaniP (Dec 17, 2008)

Impressive! I'd love to add some of those to my LR.

I think my interior designer wife would not be pleased with my additions to the home decor, however. 

I'm going to try to convince her on the art panels, however... just have to pick the right time to broach the matter.


----------



## bpape (Sep 14, 2006)

Those items tested are actually our least expensive, 244 panel. We have many other options for 'living' areas that will perform better than those tests above. Look specifically at the Pillar Trap for broadband bass control. They, along with the Art Panels, can be a very effective combination that looks good enough for a living room.

Bryan

P.S. Broaching after a couple glasses of wine and a dozen roses works better :laugh:


----------



## kadijk (Jan 23, 2011)

Nice results Bryan. So my plan to build 5" thick panels with poly facing using rht 40 is acceptable? I'm tempted to move up to a 6" panel based on other discussions I've read. Or...place normal batt insulation behind the panels to loosely fill the void? What do you think ? 

By the way...were the foam traps open celled foam? What were the dimensions?


----------



## localhost127 (Jan 2, 2011)

kadijk said:


> Nice results Bryan. So my plan to build 5" thick panels with poly facing using rht 40 is acceptable? I'm tempted to move up to a 6" panel based on other discussions I've read. Or...place normal batt insulation behind the panels to loosely fill the void? What do you think ?
> 
> By the way...were the foam traps open celled foam? What were the dimensions?


why would you place pink fluffy (lower GFR) *behind* the rigid fiberglass panel (high GFR)?

if anything - you want the lower GFR (closest to impedance of the medium (air)) and then more dense (higher GFR) as you approach the rigid boundary.

why do so many insist to have the dense (high GFR) material as the exterior layer (of which such a dramatic change in acoustical impedance will result in a reflection!) - and then lower GFR behind? this does not compute at all. could someone better explain this to me as to why such is suggested to be implemented?

or - if one were forced to use porous insulation as their LF absorber - why not simply construct thick traps made from low GFR such as pink fluffy attic insulation (loosely filled / uncompressed!) - of which will simply outperform higher GFR absorbers? - and be cheaper to construct as well?


----------



## kadijk (Jan 23, 2011)

Local host...I'm confused. If a GIK 244(2'x4 x4") absorber, spanning a corner, is an effective bass trap, and poly facing under cloth limits HF over absorption, then wouldn't only gains be made if the void behind was filled with optimal LF absorbing material? Certainly it seems to me that nothing is lost...maybe it's a waste of effort at the very worst? My intent is to "help" my 5" panel...others would argue a minimum of 6", which I don't have the material for( but can acquire if need be). 

Ps. Please define GFR. Thanks


----------



## localhost127 (Jan 2, 2011)

i responded to your comment of which was quoted: "Or...place normal batt insulation behind the panels to loosely fill the void?"

gas flow resistivity of pink fluffy (normal batt insulation) *behind* the straddled panel as you suggested in such a scenario would mean you have a material/boundary layer of porous insulation with relatively high gas flow resistivity as exterior (with respect to that of air), and then lower GFR as interior (closest to rigid boundary).

that is inverse of what would be expected if one were adhering to basicphysics. - , no ?


----------



## kadijk (Jan 23, 2011)

Maybe. I'm really not sure. I'm only informed by the knowledge and opinion of a few acoustics pros. Bryan from GIK here on HTS, user/member SAC, the GIK web site, and Rives audio web site. So I only harvest info and rely heavily on what they say. Maybe one of them will "wade in". I appreciate your conversation though...anything to get the brain working more is great.


----------



## bpape (Sep 14, 2006)

The point is that you will still gain additional absorption by filling behind. If you already have 4-6" of the moderate density material in the front (for reasons of stability and ease of wrapping/staying in place over the long run) the difference between using higher and lower density material behind is going to be minimal - as long as there is some thing there with moderately good gas flow. It then becomes primarily a matter of cost. 

Purely very light density absorbers, if thick enough, can certainly perform very well - though they do require more thought in how they are framed to keep things in place over time. More rigid materials don't 'slump' over time.


----------



## diffserv (Dec 3, 2011)

bpape said:


> The point is that you will still gain additional absorption by filling behind.


do you by chance have any data regarding this statement? even modeling (eg, AFMG SoundFlow)? thanks,


----------



## bpape (Sep 14, 2006)

I do not - sorry. I speak based on previous experience only.

Bryan


----------

