Corner Trap Nonsense

[Justdafactsmaam]

Right, I get that. But most people are putting standard rockwool in the corner, not a trap that will actually work correctly for the application.

That definitely won’t work.

 

[FrantzM]

Hi

Thanks @Keith_W for starting this thread.. I was about to acquire some doodads similar to those in the video ...
Saved me a bunch...
We, also, fall for these snake oil products ...

Thanks again

Peace.

 

[Keith_W]

As usual ASR provides some useful and not-so-useful responses

Not useful responses: attacking the guy or his company. Just because he is wrong about some things does not mean he is wrong about others. What I am interested in is whether this particular claim is incorrect.

Useful responses: pointing out that velocity absorbers in corners do not work, you need pressure absorbers. However, pressure absorbers like panel traps and Helmholtz resonators are narrowband absorbers and must be tuned to specific problem frequencies.

However, what has not yet been discussed is whether a panel trap works better on the wall or in the corner. Is there a comparison between the effectiveness of the two, in terms of attenuation and size? i.e. can you get away with a smaller panel trap if it is placed in the corner?

I guess that's the gist of it?

 

[ernestcarl]

However, what has not yet been discussed is whether a panel trap works better on the wall or in the corner. Is there a comparison between the effectiveness of the two, in terms of attenuation and size? i.e. can you get away with a smaller panel trap if it is placed in the corner?

You put it against all wall boundaries -- if at all possible -- does not matter a whole lot whether it works "better" if placed at the corners *only or along walls *only. *At least that's what I remember Ron Sauro's remark was when asked about it from John Brandt's youtube channel.

https://www.youtube.com/@JHBrandt/videos

 

[Justdafactsmaam]

However, what has not yet been discussed is whether a panel trap works better on the wall or in the corner.

Yes. It will be one or the other. Probably not the answer you want.

Is there a comparison between the effectiveness of the two, in terms of attenuation and size? i.e. can you get away with a smaller panel trap if it is placed in the corner?

It’s too complicated to predict. Unfortunately trial and error is the final arbiter.

What I can say with confidence is don’t skimp on the quality of the trap based on the idea that positioning will give you better results. Size is only part of the formula for pressure traps.

Get traps that target the trouble frequencies, offer the best objective absorption and experiment with placement until you get the best results

 

[Chromatischism]

Useful responses: pointing out that velocity absorbers in corners do not work, you need pressure absorbers.

This is not strictly true; it depends on the thickness. The better products are 10-20" deep so they do provide absorption in the room. I have measurements showing midbass absorption with corner traps.

 

[Keith_W]

Yes. It will be one or the other. Probably not the answer you want.

It’s too complicated to predict. Unfortunately trial and error is the final arbiter.

If "trial and error" is the answer I do not want, then I definitely do not want that answer! But if you are saying that a wall bass trap vs. a corner bass trap is too complicated to predict, I can deal with that. For me (and I suspect many people), room intrusiveness and effectiveness are the main consideration. I want the minimum impact into living space and aesthetics but with maximum acoustic impact. This is why I have left off any bass room treatment and only relied on DSP, but DSP can only get you so far.

What do you think the inputs that would be required to predict whether a wall trap is more effective than a corner bass trap, assuming both are pressure absorbers?

What I can say with confidence is don’t skimp on the quality of the trap based on the idea that positioning will give you better results. Size is only part of the formula for pressure traps.

Get traps that target the trouble frequencies, offer the best objective absorption and experiment with placement until you get the best results

What I have been thinking of for some time is to DIY my own bass traps, either a membrane absorber or a Helmholtz resonator. It would need to be tuneable. I am leaning towards a Helmholtz because it is easier to construct and easier to make it tuneable. All I need to do is to construct a box and place 5-10 BBQ air vents like this (if a bigger hole is required, I can simply remove some air vents). But I am not sure whether it a Helmholtz resonator would be more compact than a panel absorber, or whether corner placement would make it more effective.

This is not strictly true; it depends on the thickness. The better products are 10-20" deep so they do provide absorption in the room. I have measurements showing midbass absorption with corner traps.

Velocity absorbers depend on thickness and the air gap from the wall, it needs to be 1/4 wavelength of the lowest frequency desired to be effective, and it rapidly loses efficiency under that. At least, that is my understanding.

 

[Justdafactsmaam]

If "trial and error" is the answer I do not want, then I definitely do not want that answer!

I get it. It’s a sucky answer. I don’t like it either. But as simple as the math is when it comes to waves in a three dimensional space (I joke, not simple) mathematical modeling generally assumes smooth simple boundaries and infinite rigidity. Real world spaces are ridiculously complicated and really screw you on predicting room behavior.

But if you are saying that a wall bass trap vs. a corner bass trap is too complicated to predict, I can deal with that.

Just to be clear, I’m talking about positioning any pressure bass trap. Not about different trap designs.

For me (and I suspect many people), room intrusiveness and effectiveness are the main consideration. I want the minimum impact into living space and aesthetics but with maximum acoustic impact. This is why I have left off any bass room treatment and only relied on DSP, but DSP can only get you so far.

I totally get that. IMO effective bass trapping is pretty much the domain of dedicated listening rooms

What do you think the inputs that would be required to predict whether a wall trap is more effective than a corner bass trap, assuming both are pressure absorbers?

I think this is a case where the general rule of thumb will be your best predictor. Corners are your best bet.

What I have been thinking of for some time is to DIY my own bass traps, either a membrane absorber or a Helmholtz resonator. It would need to be tuneable. I am leaning towards a Helmholtz because it is easier to construct and easier to make it tuneable. All I need to do is to construct a box and place 5-10 BBQ air vents like this (if a bigger hole is required, I can simply remove some air vents). But I am not sure whether it a Helmholtz resonator would be more compact than a panel absorber, or whether corner placement would make it more effective.

Anyone who has the time, tools and skills should DIY! I’d avoid the Helmholtz. By everything I have read and heard they are so specific that they miss the mark more often than not.

Velocity absorbers depend on thickness and the air gap from the wall, it needs to be 1/4 wavelength of the lowest frequency desired to be effective, and it rapidly loses efficiency under that. At least, that is my understanding.

The rules of thumbs are good but not entirely on the money with velocity absorption. One thing to remember is velocity absorption absorbs all kinetic energy but never completely. None of it is all or nothing. Wavelength matters. But it’s all in degrees.

 

[Blumlein 88]

This info is reasonably good.

 

[HiMu]

However, what has not yet been discussed is whether a panel trap works better on the wall or in the corner. Is there a comparison between the effectiveness of the two, in terms of attenuation and size?

This video by John Brandt and Richard Lenz of Real Acoustix explains problems and findings of testing diaphragmatic absorbers with the ASTM C423 standards and effects of positioning:

Some more info bits in this post by R. Lenz: https://realacoustix.com/news/news-full-article/understanding-diaphragmatic-bass-trap-testing

I’d avoid the Helmholtz. By everything I have read and heard they are so specific that they miss the mark more often than not.

I had 4 commercial helmholtz resonators to try in my room before buying, they kind of worked but very unpredictably. Didn't buy them.

 

[Elder]

I built some 550mm deep, square velocity based traps for my room that run floor to ceiling in the corners of the room.

Had a huge effect on the decay times underneath 250Hz.

 

[Randolf]

Building and tuning a Helmholtz resonator is cheap, easy and was very effective in my use case (strong 45Hz room mode). You can get a similar result with a good room EQ like Dirac Live from the amplitude perspective. But often also very long reverberation is an issue which can be handled better by a Helmholtz resonator. https://homeaudio.jimdofree.com/ describes how I build and tuned it and the initial result. In https://homeaudio.jimdofree.com/dirac-live/ I added Dirac Live and compared the results.

 

[Mr. Haelscheir]

What about the case of having something the size of a 2' by 4' GIK Monster bass trap "straddling" a corner? Is the argument here only about the placement of something like a velocity-absorbing soffit or triangular trap right into a corner dominated by pressure? Is "straddling" a thick velocity-absorbing panel across a corner with sufficient air gap still useful, or is this thread debunking that common recommendation?

 

[MRC01]

Years ago I built big tube traps, 24" diameter, 7' tall, put them in the corners and they made a big difference, both measured and audible.
Is the gist of this discussion that they could make even more difference if I moved them out of the corners into the middle of the walls?

 

[Tim Link]

I sell TubeTraps, and we recommend putting them in the corners. They are fibrous but they need to be in high pressure zones because they have a volume inside, and when the pressure rises or falls outside the trap, the air tries to move in and out of the trap's center void, forcing motion through the fiber. We took a bunch of these up to NWAA labs to be tested in the corners of their big reveb chamber. Ron Sauro generously offered to do an extra test with them distributed around the room in other locations to see if they work as well. He thought they might, and was curious to find out. They didn't.

 

[Mr. Haelscheir]

Years ago I built big tube traps, 24" diameter, 7' tall, put them in the corners and they made a big difference, both measured and audible.
Is the gist of this discussion that they could make even more difference if I moved them out of the corners into the middle of the walls?

I believe that differs from my question in that tube traps are pressure-absorbers, whereby this thread seems to have established that corners are points of maximum pressure and are best treated with said pressure-absorbers such as tube traps.

 

[Justdafactsmaam]

What about the case of having something the size of a 2' by 4' GIK Monster bass trap "straddling" a corner? Is the argument here only about the placement of something like a velocity-absorbing soffit or triangular trap right into a corner dominated by pressure? Is "straddling" a thick velocity-absorbing panel across a corner with sufficient air gap still useful, or is this thread debunking that common recommendation?

It’s useful. Just not very useful. Ironically just like my answer.

 

[Justdafactsmaam]

I believe that differs from my question in that tube traps are pressure-absorbers, whereby this thread seems to have established that corners are points of maximum pressure and are best treated with said pressure-absorbers such as tube traps.

I thought they were velocity absorbers

 

[Tim Link]

I thought they were velocity absorbers

Yes, TubeTraps are velocity absorbers. And, the work in high pressure zones because they force velocity to happen when they are exposed to rapid pressure changes. The whole concept of separating trap designs this way is not particularly useful. Almost all traps are designed to work in pressure zones. A velocity zone trap could be made, but I don't think that many of them are out there, especially for bass use.

 

[Mr. Haelscheir]

Now, are products like https://www.gikacoustics.com/product/gik-acoustics-monster-bass-trap-flexrange-technology/ which purportedly reach down to 80 Hz (I suppose so long as they are actually positioned at a velocity peak for said frequency) useless in the sense of one's being better off solely using thinner broadband panels for midrange to treble absorption, or is it just a matter of positioning?