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DIY Corner Bass Traps: Work In Progress
Old 6th April 2018
  #31
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🎧 10 years
John Sayers forum ALSO advocates the rigid fiberglass [similar 703] for Chunky Corner Bass Traps.
This is the same matterial used for Broadband absorbers, and Ceiling Clouds.

The 'fluffy' is an effective, cheaper, route for some.
Old 18th May 2018 | Show parent
  #32
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🎧 5 years
Quote:
Originally Posted by engin View Post
Come on, man!

REW after results!

I'm very curious to see how just absorber bass traps do the work.

Because I started to believe, they should not be effective on very low end as physics does not let them to be. A low frequency wavelength could be as large as 8 meters.

All my readings led me to believe a membrane bass trap is the only way to go to handle low end.
Hello engin,

Sorry for the late response. For some reason I didn't get email notifications and I'm haven't been on the site for a while.

Anyhow, yes, I'll try to get to REW results soon. Promised!

You're right about the very low freqs. I don't think my bass traps are taking care of them. The lows and mid-lows certainly seem more controlled.

I also concluded while I was doing my research that membrane traps are you best option. I just didn't feel the need to spend that much money at the time.

But I'm satisfied with the results.
Old 18th May 2018 | Show parent
  #33
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🎧 5 years
Quote:
Originally Posted by antireign View Post
I really like this design!! Do you find the foil on the 703 prevents all the highs from being sucked out by the roxul ?
Hello antireign,

Sorry for the late response. Well the foiled 703 was meant to do two things: keep the highs out and act as a membrane to absorb lows.

I mainly track classical and acoustic guitars in my studio and the highs are just fine. A friend who is a sound engineer says my recordings are fine. But I tend to do close miking recordings, so the room has less effect on them.

As for the membrane effect, not to sure. The bass sounds much tighter though. I'd have to do a REW test and compare it to the initial test without the bass traps.

I'll get to that test soon.
Old 18th May 2018 | Show parent
  #34
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🎧 5 years
Quote:
Originally Posted by AntonMcmillan View Post
Hey dramis,

Cool craftsmanship. I like how you put everything neatly.

I am about to build my own corner bass traps. Why arent you using less denser products for corners? Over at John Sayers forum they ar strong advocates of using as less dense products as possible for low frequencies. I have read Ethan Winers report on OC measurements and seen the graphs and waterfalls. But still guys over at Sayers forum keep their point.

As for the facric - I will be using locally produced flax. It is actually linen material and the guys here produce it in very different specifations. I would reccomend any good quality fabric that you can blow air through with your mouth without much effort.

ANother question for the SLUTZ:
What if one would also add wooden slats on the face of this type of corner bass trap at a sequence to reflect even more highs back into the room? Would it lower the effectiveness of the bass trap significantly? I guess since modes build up in the corners anyway - it would not do much harm and some liveness in the room is never a bad thing.

Thanks for your input.
Cheers,
AM
Hello AntonMcmillan,

Sorry for the late response.

I started doing my research almost 2 years ago so I don't remember all the details. But I did spend a lot of time comparing different materials' absorption capacity of low freqs and the OC703 and Roxul seemed at the time the best combination I could come up with.

I'm not a specialist but I would tend to say that a wooden slab would also reflect some low freqs. That's why I went with the foiled 703. It's very thin so it should reflect the highs while letting the lows being absorbed. It can also act a little like a membrane to absorb more bass.

Like I've written many times here, the only way to find out how effective they are is by doing a REW test. I haven't done it yet because I'm very good at procrastinating...

One sure thing is that my room sounds MUCH better with the bass traps.

Take care!

dramis
Old 18th May 2018 | Show parent
  #35
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🎧 5 years
Quote:
Originally Posted by RJHollins View Post
John Sayers forum ALSO advocates the rigid fiberglass [similar 703] for Chunky Corner Bass Traps.
This is the same matterial used for Broadband absorbers, and Ceiling Clouds.

The 'fluffy' is an effective, cheaper, route for some.
Agreed. And if I'm correct you would need a very thick amount of fluffy stuff to do the job right because the lows would go through it more easily than in a denser material and some would bounce back. I think...
Old 27th July 2018 | Show parent
  #36
Gear Head
 
🎧 5 years
REW Measurements

Quote:
Originally Posted by dramis View Post
...

Anyhow, yes, I'll try to get to REW results soon. Promised!

....
Were you able to get any REW measurements to share ???

TIA
Old 27th July 2018 | Show parent
  #37
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🎧 5 years
Quote:
Originally Posted by ths61 View Post
Were you able to get any REW measurements to share ???

TIA
Yes, on popular demand, I just did (see screenshot). Don't really know how to interpret this though...

Blue line before, red line after adding bass traps. Weird dip at 93 Hz...
Attached Thumbnails
DIY Corner Bass Traps: Work In Progress-before-after.jpg  
Old 27th July 2018 | Show parent
  #38
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🎧 5 years
Quote:
Originally Posted by dramis View Post
Yes, on popular demand, I just did (see screenshot). Don't really know how to interpret this though...

Blue line before, red line after adding bass traps. Weird dip at 93 Hz...
DRamis,

Did you move the microphone at all between measurements ?

Also, can you post the Impulse graphs ?

TIA
Old 27th July 2018 | Show parent
  #39
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🎧 5 years
Quote:
Originally Posted by ths61 View Post
DRamis,

Did you move the microphone at all between measurements ?

Also, can you post the Impulse graphs ?

TIA
Yes, first measurements were taken 2 years ago. So I put the mic basically where it was then, at the sweet spot where I sit. There is probably an inch or so difference between both tests.

Impulse before in green, after in red.
Attached Thumbnails
DIY Corner Bass Traps: Work In Progress-impulse-after.jpg   DIY Corner Bass Traps: Work In Progress-impulse-before.jpg  
Old 27th July 2018 | Show parent
  #40
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🎧 5 years
Quote:
Originally Posted by engin View Post
Come on, man!

REW after results!
Results are in, finally...
Old 27th July 2018
  #41
Gear Maniac
 
🎧 10 years
I hate to be "that guy", but these don't tell us much if the mic has been moved and the rest of the signal chain isn't exactly the same :/
Old 27th July 2018 | Show parent
  #42
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🎧 5 years
Quote:
Originally Posted by Eggsmack View Post
I hate to be "that guy", but these don't tell us much if the mic has been moved and the rest of the signal chain isn't exactly the same :/
Yes, you are "that guy". But I get it...

It wouldn't take long to take the bass traps out of the room, do a test, put them back, and do another.

I'll do it next weekend when I get back from vacation.
Old 7th August 2018
  #43
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🎧 5 years
OK, as promised.

Removed the bass traps, did 3 tests that yielded the exact same results.

Put the traps back in, didn't touch the mic or signal chain, did 3 tests that all produced the same results.

Don't really know how to interpret this, but it does look good!

Red before traps, blue after.

PS: let me know if you'd like to see the data formatted in a different way.
Attached Thumbnails
DIY Corner Bass Traps: Work In Progress-red-before-blue-after.jpg  
Old 7th August 2018 | Show parent
  #44
Gear Maniac
 
🎧 10 years
There's only so much we can tell from the snapshot you've uploaded, but it's looking good! It looks like you used Fuzzmeasure for this, would you mind uploading the file to your dropbox and throwing a link on here for us? I'm considering building some similar traps and I'd love to see what happened in your room.

Cheers,
Alex
Old 7th August 2018 | Show parent
  #45
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🎧 5 years
Quote:
Originally Posted by Eggsmack View Post
It looks like you used Fuzzmeasure for this, would you mind uploading the file to your dropbox and throwing a link on here for us? I'm considering building some similar traps and I'd love to see what happened in your room.
I used REW. Here's the link to the file. Let me know what you think of it. 3 first tests in the file without traps, 3 last with traps.

Dropbox - 3before3after.mdat
Old 8th August 2018 | Show parent
  #46
Gear Maniac
 
🎧 10 years
Ok, this is hasty and imperfect, but I thought I'd congratulate you

Here we can see how your room had some nasty standing waves at something like ~42Hz/84Hz/98Hz etc. Worst offender was ~42Hz at 500+ms for the random window that REW opened up for this. I didn't realize I didn't put any thought into the y axis of this, but it'll still basically show us what's still resonating in your room around 20dB quieter than what your imaginary "flat" response would be.

Imgur: The magic of the Internet

Here's the After. 42Hz is still a killer at 400, but your room now has nearly a consistently flat decay time of ~100ms all the way from 60Hz-20k for this small window. If I have more time later I'll fix it to give you more proper numbers (as far as I understand how to do so, at least ).

Imgur: The magic of the Internet

The SPL graph is essentially unchanged from 1k up, so I focused on below 1kHz and below, starting with the Bass (40-400Hz). This is smoothed at 1/48.

Imgur: The magic of the Internet

And here's 400Hz-1kHz:

Imgur: The magic of the Internet

Good stuff!
Old 8th August 2018 | Show parent
  #47
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🎧 5 years
Quote:
Originally Posted by Eggsmack View Post
Ok, this is hasty and imperfect, but I thought I'd congratulate you
Thank you Eggsmack.

Considering it cost me a little more than $600 USD to build, it think it was a darn good investment.

When I removed the bass traps to do the tests, the room sounded like crap, even if I have 8 other 3" thick absorbing panels for mids and highs.

Thanks for your input,

Dramis
Old 9th August 2018 | Show parent
  #48
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akebrake's Avatar
 
🎧 5 years
Switch Monitor Off

Quote:
Originally Posted by dramis View Post
I used REW. Here's the link to the file. Let me know what you think of it. 3 first tests in the file without traps, 3 last with traps.

Dropbox - 3before3after.mdat
Hi,
Just downloaded the latest REW (5.19 Beta12) and took a quick look at your files.
Noticed you've got feedback e.g Monitor"leekage" into the measurement.
(comb filter)

Make sure monitor (soundcard) function is off when running measurements.

Best
Attached Thumbnails
DIY Corner Bass Traps: Work In Progress-dramis-monitor-feedback.jpg  
Old 9th August 2018 | Show parent
  #49
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🎧 5 years
Quote:
Originally Posted by akebrake View Post
Make sure monitor (soundcard) function is off when running measurements.
Duly noted akebrake!

Hopefully it didn't screw up the results too much, because I'm not taking those big bass traps out of the room again.

Dramis
Old 9th August 2018 | Show parent
  #50
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Quote:
Originally Posted by dramis View Post
Duly noted akebrake!

Hopefully it didn't screw up the results too much, because I'm not taking those big bass traps out of the room again.

Dramis
OK. I think this is a good question for John PM (REW author).

I have some other questions for him anyway

Best
Old 14th June 2019
  #51
Gear Head
 
🎧 15 years
Quote:
Originally Posted by dramis View Post
Hello,

I asked for advice here in the past year about building my own bass traps and a lot of nice folks helped me out, so I figured it might be of interest to document this little project. Here are a few pics taken today. I used two 2'x4' sheets of OC 703, 2 inches thick, the first one facing the room is foil reinforced. Behind those two sheets, triangular layers of Roxul Safe and Sound.
Hey Dramis,

I'm in the process of acoustically treating and optimising a (small) room. Corner traps / Super Chunks are first on the agenda.

Can you explain why you put a piece of insulation in front of the triangles and why it has foil on it? What is the idea behind that? Any acoustical benefit to be gained versus just using triangles of glass fibre board?

I'd think intuitively that the foil would form a reflective surface for high frequencies. I'm new to all this, so please forgive my ignorance... I'm learning.

Thanks!

James.
Old 14th June 2019 | Show parent
  #52
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🎧 5 years
Quote:
Originally Posted by jamesblond View Post
I'd think intuitively that the foil would form a reflective surface for high frequencies. I'm new to all this, so please forgive my ignorance... I'm learning.
Hi jamesblond,

You're right, my hypothesis was that the foil would act as a membrane to reflect high and high-mid frequencies that are already absorbed by other 3" thick panels I have in the the room. And absorb mainly the mid-lows and and hopefully some part of the lows.

I read a lot about the absorption capacities of different materials and concluded a mix of Roxul and OC 703 would do the job pretty well. I also wanted to have no air gap in the corner traps and use the maximum depth available. If I remember correctly, from the apex of the triangle in the corner to the middle of the bass trap I have 16 inches deep.

I have posted the before/after results (REW software) in an earlier post in the thread and according to comments I got, the traps did a pretty good job. I'm not really good at interpreting these results.

But just by ear and I can tell that the room (ex-bedroom) is well balanced. I record my tracks and do pre-mixes in that room, then bring the session in a real studio. The guy who does my final mixes is always pleased with the work that I have done at home.

Hope this helps!

Cheers,

dramis
Old 25th June 2019
  #53
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🎧 5 years
And now "shameless plug" time. I released an instrumental album last January called Meadows, under the name Sun Under. All guitars, classical, acoustic and electric, as well as banjo and ukulele, were recorded in my home studio after installing the bass traps I built. The guy who mixed the album in his own studio says my tracks sounded great, especially since recorded in a converted bedroom.

Aside from the "shameless plug" part, this post can be interpreted as proof that a well acoustically treated bedroom can go a long way. Not in terms of sales, in terms of sound!

> Meadows on Bandcamp

> Meadows on Spotify
Old 13th August 2019
  #54
Here for the gear
 
Quote:
Originally Posted by dramis View Post
Hello,

I asked for advice here in the past year about building my own bass traps and a lot of nice folks helped me out, so I figured it might be of interest to document this little project. Here are a few pics taken today. I used two 2'x4' sheets of OC 703, 2 inches thick, the first one facing the room is foil reinforced. Behind those two sheets, triangular layers of Roxul Safe and Sound.

How does the trap absorb sound if the front face is aluminum foil?
Can someone explain to me please?
Old 13th August 2019 | Show parent
  #55
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🎧 10 years
Quote:
Originally Posted by Xteon View Post
How does the trap absorb sound if the front face is aluminum foil?
Can someone explain to me please?
The foil is thin and would only reflect high frequencies; but these are absorbed by the fabric used to finish the trap.
The foil eventually works as a membrane providing a little extra absorption at a relatively narrow frequency band.
Old 13th August 2019 | Show parent
  #56
Here for the gear
 
Quote:
Originally Posted by bert stoltenborg View Post
The foil is thin and would only reflect high frequencies; but these are absorbed by the fabric used to finish the trap.
The foil eventually works as a membrane providing a little extra absorption at a relatively narrow frequency band.

Thanks for the explanation, however I still don't understand..
The foil has no holes or openings, how can sound pass through it?

To my understanding, the foil can only reflect high frequencies and it will prevent other frequencies to pass through it and be absorbed by the mineral wool behind it.

Can you give some more details please?
Old 13th August 2019 | Show parent
  #57
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🎧 10 years
Quote:
Originally Posted by Xteon View Post
Thanks for the explanation, however I still don't understand..
The foil has no holes or openings, how can sound pass through it?

To my understanding, the foil can only reflect high frequencies and it will prevent other frequencies to pass through it and be absorbed by the mineral wool behind it.

Can you give some more details please?
Like sound goes through a wall.
The moving air particles exite the foil particles and make them move, the moving foil exites the air particles and the wool on the other side of the foil.
A heavy wall will reflect most of the frequencies above the resonant frequency of the wall thus preventing sound to pass, a foil is so light/has a high resonance frequency so it reflects only the highest frequencies and the rest will pass.
Old 13th August 2019 | Show parent
  #58
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🎧 10 years
I'll try to take some stress off Stuart .

Isolation works like this:

A construction like a wall is fixed to another construction, by gravity screws, glue... so that prevents it from moving. This is called isolation by stiffness.

Our constuction has a resonance frequency.
A swing that you push at the right moment will start to swing very easely. It is exited in Phase.
If you hit it at random some hits will accelarate it, others will stop it. The exitation is out of phase.

Sound hitting a wall in phase hits it at a frequency where the wall will swing very easily. Here the sound isolation is minimum as the wall will exite the air on the other side and the sound travels through it. When frequencies go up they become more and more out of phase and the wall will isolate at about 6 dB per octave, this is called the mass law.

The mass law works to the coincidence frequency.
Here the sound will generate shearing waves in the material; these waves have, in contradiction to sound waves in air, a frequency dependent speed.
When the shear wave has the same speed as the sound wave thwe construction will pass sound more easily, you recognise this as a dip in the sound isolation.
This phenomenon is important because when sound hits the construction at a certain angle it will pass through the construction.
A window at floor level will isolatie sound of trafiic, the same window on the 4th floor could be a problem because traffic noise is not reduced enough because it hits the construction at an angle exiting coincidence.
Making constructions double like a double wall or two window panes connected by a foil will reduce this dip.

Above this coincidence region the sound is isolated lineair again.
Old 13th August 2019
  #59
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🎧 5 years
Quote:
I'll try to take some stress off Stuart
Cool!

- Stuart -
Old 14th August 2019 | Show parent
  #60
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akebrake's Avatar
 
🎧 5 years
Quote:
Originally Posted by Xteon View Post
...The foil has no holes or openings, how can sound pass through it?
The sound energy is "passing".(Transmitted)
Vibrations in the air (sound) will vibrate the foil which in turn will vibrate the air behind the foil...

TEST this:
Put a plastic bag over the loudspeaker. Play some music and check what it sounds like.

Best
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