Corner Trap Nonsense

[Bjorn]

Sincerely interested, please provide a source or link to those studies, if they are published!

I don't know if they are published. It's NWAA labs who have come to this conclusion. Not everything is open on the internet FIY.

NWAA Labs -- Complete High-speed Speaker and Material Testing

 

[Bjorn]

Porous materials only work in the medium and high frequency range. So any claims of them reducing something like a 60Hz mode effectively, are simply wrong.
You can't beat physics, even if some claim to do so.

This is wrong. Porous can work to the lowest frequencies when done correctly. That's been done for decades.
Here's an example of before and after measurement with porous. This is a room I desgined.

Before:

After:

There are no pressure based traps or EQ being used here. Only porous material.

 

[HiMu]

I don't know if they are published. It's NWAA labs who have come to this conclusion. Not everything is open on the internet FIY.

NWAA Labs -- Complete High-speed Speaker and Material Testing

Thank you, I had a bit of a hunch that you're referring to the material testing by Sauro and Brandt. I've been following their research for a couple of years and it's truly fascinating eg. possibilities of diffraction devices and the new method of measuring diffusion.

 

[Tim Link]

I see you gave it another meaning to trapp more audiophiles into buying your cardboard rolls?

Cardboard rolls? We provide a lot of information about the materials TubeTraps are made of if you are interested. The primary functional material is fiberglass. Other materials are used to add structural strength, cap off the ends, seal in the fibers, add treble reflection, and provide cosmetic covering.

You needed 16 traps to measure anything.

Not just to measure anything, but to get a precise measurement in a very large reverberation chamber. It's easy to get a measurable effect, but when you are doing testing to determine absorption coefficients at various frequencies you have to have an appropriate sample size for the space. For low frequencies you have to have a huge reverb chamber to get meaningful results. This makes testing bass traps hard. NWAA labs is arguably the best place in the world for such testing.

Can you tell us what 16 of these cost? Just like the BBC had to use a huge multiple of what they had planed for when they started. At that point you change the volume and dimensions of the room from disposing all these useless money trapps inside it. You could as well have stacked a numper of moving boxes instead of your cardboard rolls to get the same result.

You don't need 16 of them in a typical listening room. Remember, that reverberation chamber is huge! It has to be to get meaningful low frequency measurements. Often two TubeTraps is enough in a smaller home listening space. 16 can be great in a larger home setting, but generally that's overkill.
16 TubeTraps would not inexpensive, at least for me, especially for the larger ones. Prices are listed. It won't cost as much as some DACs.
I'm sure some cardboard moving boxes would do something, but there's a reason cardboard isn't touted much as an an acoustical absorber, especially for lower frequencies. You could make some sort of resonator out of it I suppose.

For the poor fools that thinks about buying such nonsense trapps: Just get some plain cardbox rolls from Home Depot. Place them inside your listening room at the rate you are shown (dozends of them!). It will have the same result by diffusing the audible sound. The only difference is the price, saving you an amount not worth mentioning, maybe like 10000$. And remember: If 10 don't work, buy another 10 and try again. The seller will be happy to assist in taking $ loads from your wallet.

I'm sure in a country of 335 millions, every morning some idiot wakes up and decides to throw a handfull of money out of the window. Why not with ASC, you are right. I just didn't think about that.

If you want to DIY some TubeTraps, don't buy cardboard rolls. Buy fiberglass pipe insulation. Big stuff for big industrial pipes. You'll have some work to do.

 

[Tim Link]

This is wrong. Porous can work to the lowest frequencies when done correctly. That's been done for decades.
Here's an example of before and after measurement with porous. This is a room I desgined.

Before:
View attachment 404580

After:
View attachment 404581

There are no pressure based traps or EQ being used here. Only porous material.

How much porous material does a result like this require. What percentage of surface area needs to be covered for this kind of result?

 

[HiMu]

How much porous material does a result like this require. What percentage of surface area needs to be covered for this kind of result?

This will give some idea if you've not seen this before.
Area: 10' by 12', thickness 4 inches of OC FR705 (Graph title is wrong) This is a lab test from NWAAlabs, not calculation/simulation.

 

[Tim Link]

This will give some idea if you've not seen this before.
Area: 10' by 12', thickness 4 inches of OC FR705 (Graph title is wrong) This is a lab test from NWAAlabs, not calculation/simulation.
View attachment 404668

Thank you. Is that flush against the wall?

 

[HiMu]

Thank you. Is that flush against the wall?

If I remember correctly that was E-mount. It was A-mount. Source: https://jhbrandt.net/wp-content/uploads/2022/11/204.pdf

 

[tmtomh]

This is wrong. Porous can work to the lowest frequencies when done correctly. That's been done for decades.
Here's an example of before and after measurement with porous. This is a room I desgined.

Before:
View attachment 404580

After:
View attachment 404581

There are no pressure based traps or EQ being used here. Only porous material.

Can you give us a sense of how thick the porous material was and what proportion or surface area of the space the material covered?

 

[krabapple]

This is wrong. Porous can work to the lowest frequencies when done correctly. That's been done for decades.
Here's an example of before and after measurement with porous. This is a room I desgined.

Before:
View attachment 404580

After:
View attachment 404581

There are no pressure based traps or EQ being used here. Only porous material.

What dimensions, and how many, and placed where?

 

[Bjorn]

Sorry guys. Information of how to treat a room, whether it's porous or something else, is only shared with my customers.

 

[krabapple]

Surely there must be parameters that aren't specific to that installation.

What is the porous device, what dimensions does it have to be to have X effect on X frequencies, how is placement determined, etc.

No confidentiality will be breached by enlightening us on those.

 

[Tim Link]

Sorry guys. Information of how to treat a room, whether it's porous or something else, is only shared with my customers.

Understandable. The important idea that I see being confirmed on this thread is that it really is possible to get meaningful bass control in a room using porous absorbers. Treatments in the corners work, but better results can be had if more treatment than just in the corners is distributed throughout the room. No surprise there. I'll hazard a guess that there's a considerable amount of treatment involved in your example.

 

[Esprit]

Sorry guys. Information of how to treat a room, whether it's porous or something else, is only shared with my customers.

Can we be your customers from afar?

 

[Randyman...]

Ceilings are prime real-estate for thicker rigid panels that can absolutely impact lower bass, and some even claim ceilings make the biggest improvement regarding broadband absorption (I tend to agree - especially in small "honky" rooms). 4"-8" thick (plus air gap if desired) can generally be had in 8' high rooms w/o robbing any floor space. I have higher 11' 6" ceilings in the tracking/drum room, and built 12" thick 4' x 8' hard-toped framed clouds full of pink-fluffy in my studio/drum room (hard-topped suggestion came from John Sayers to add back ambiance off the concrete ceiling while adding "apparent size" due to extra reflections being delayed - he is a well known studio designer and acoustician). Those clouds are angled, and spaced around 18"-24" off the ceiling (and are easily adjustable - closer to the floor/closer to the drums and a coupe of 4" 703 gobos for the front/sides can make a small/dead intimae ambiance, or raise it up and ditch the gobos for more room sound and more RT60).

And you've likely seen plenty of drop-ceilings where the tiles are acoustically transparent (at least in the bass) or even open crates, and above is completely full of 1'-2' of fluffy insulation or equivalent. That absolutely works as an effective porous bass trap w/o using any floor space. Basically using the entire sq footage of the ceiling as a 1'-2' deep porous bass trap - add some slats to bring back some high end liveliness.

 

[Digital_Thor]

Wait.... didn't Earl Geddes cover this 10 years ago?

I also remember someone pointing out, that there is nothing called "room gain", but rather a build-up of reflections, which we perceive as more bass - especially if we stand in corners. Which is where I believe the trend of corner-traps come from.

I quote from 16:16 into Earl's presentation :

"Damping is always an advantage at LF's - unfortunately it is undesirable at HF's and typical damping is ineffective at LF's
- Only damping designed into the structure will actually have a significant effect in the modal region
- Damping on rigid walls or "traps" are ineffective and hence not a solution to any of these problems."

 

[Randyman...]

- Damping on rigid walls or "traps" are ineffective and hence not a solution to any of these problems."

Yet there is data above plotting very effective results with (rather deep) porous absorbers (and hundreds of studios with the same) - not to mention my own experiences in two very different rooms. I'd wager less than 1% here (more like less than 0.1%) are actually listening in dedicated "purpose built / acoustically architected" spaces where very specific dimensions and acoustic design were the basis for construction.

Porous absorbers can and do work for bass/modes if you have the space - but they are not the most efficient things in the world. Add slats to bring highs back in.

And yes - Multiple subs FTW! Add a DBA while you are at it! But that won't get away from the need to deal with bass treatment and decay in smaller rooms...

I'm very anxious to try ART at some point - and see what "next gen" room correction can do here...

 

[napfkuchen]

Ceilings are prime real-estate for thicker rigid panels that can absolutely impact lower bass, and some even claim ceilings make the biggest improvement regarding broadband absorption (I tend to agree - especially in small "honky" rooms).

Absolutely agree. In my small office the reverberation was unbearable and DSP did absolutely not help. When listening to bass-heavy material, the cabinet on the back wall vibrated...
I first added absorbers to the front wall, corners and initial reflection points. Of course, these are not so voluminous that one could expect a massive improvement. But in particular the 4 absorbers (1 x 0.4 x 0.4m / 3.3 ft x 16" x 16") hung on the back wall with some distance from the ceiling have brought about a significant improvement; the RT60 is now between 200 and 300 ms from 60 Hz upwards. Of course you could philosophize for a long time about the lack of diffusion, but I simply don't have the space for it because of furniture/window/door. Hanging more absorbers from the ceiling - especially at the front wall - would be to intrusive.
Aside from listening to music, the room is also much more comfortable for conversations.

Of course, this is all a compromise and in an ideal hi-fi listening room perhaps less intervention with acoustic modules would be necessary. In my living room I mostly listen to surround/3D formats. I like the sound better despite the longer reverberation. Thanks to the use of the height speakers, everything simply seems much larger and at the same time the sound is still more precise in terms of stereo positioning.

My impressions of Acoustic Fields in general are that it's all about telling you what (supposedly) doesn't work, how stupid people are and which mistakes they make. I haven't heard any tips that really help from this guy. I think the videos are simply intended to unsettle the viewer and generate new customers.

 

[Geert]

I quote from 16:16 into Earl's presentation

A presentation for audiophiles, where Earl probably referred to the common 5 inch thick absorber panels sold on various websites. So lets look at the effect of 16inch/40cm thick porous absorption stacked 27inch/70cm high against 3 of the 4 walls in another studio:

You can see how absorbtion killed multiple resonances around 35Hz and 50Hz and in other places filled in dips (where EQ is not a solution as you know). Around 50Hz the absorption removed a peak of 7dB in the frequency response (everywhere, not just on the listening position), solving the main problem the client was struggling with.

The RT30 graph might give a clearer visualization of the effect in the low end:

Maybe the discussion can become a bit more nuanced after the different examples given in this thread. There's a difference between porous absorbers don't work in the low end versus I don't have the space to install a sufficient amount of it. And of course there are other types of acoustic panels which might be better suited for certain problems, but they will also require a serious area of walls to be covered.

 

[Randyman...]

Absolutely agree. In my small office the reverberation was unbearable and DSP did absolutely not help. When listening to bass-heavy material, the cabinet on the back wall vibrated...
I first added absorbers to the front wall, corners and initial reflection points. Of course, these are not so voluminous that one could expect a massive improvement. But in particular the 4 absorbers (1 x 0.4 x 0.4m / 3.3 ft x 16" x 16") hung on the back wall with some distance from the ceiling have brought about a significant improvement; the RT60 is now between 200 and 300 ms from 60 Hz upwards. Of course you could philosophize for a long time about the lack of diffusion, but I simply don't have the space for it because of furniture/window/door. Hanging more absorbers from the ceiling - especially at the front wall - would be to intrusive.
Aside from listening to music, the room is also much more comfortable for conversations.

Of course, this is all a compromise and in an ideal hi-fi listening room perhaps less intervention with acoustic modules would be necessary. In my living room I mostly listen to surround/3D formats. I like the sound better despite the longer reverberation. Thanks to the use of the height speakers, everything simply seems much larger and at the same time the sound is still more precise in terms of stereo positioning.

My impressions of Acoustic Fields in general are that it's all about telling you what (supposedly) doesn't work, how stupid people are and which mistakes they make. I haven't heard any tips that really help from this guy. I think the videos are simply intended to unsettle the viewer and generate new customers.

View attachment 404865

View attachment 404867

I just know those soffit traps are doing a lot of good in that room Looks clean too.

Ceiling treatment (clouds) made more of a subjective improvement in imaging/sound-field/phantom center than treating 1st sidewall reflection points for my small-ish listening room - but to be fair - there was much more area covered on the ceiling and ceiling/wall soffits (and thus helped immensely in the bass as well).