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Building bass traps & panels from room mode calculations

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Building bass traps & panels from room mode calculations

Postby DelOro » Wed Jan 27, 2021 6:54 pm

Hi, first time posting here! I have currently been working on a new space to use for production/ vocal recording. I have installed padding and a carpet (on tile floor) within the room. From there I set up my monitors and ran some room acoustic tests on REW. There was a trough around 110 hz. Which gives the room a mode of 55 HZ. 1130/55= 20 ½ feet for the wavelength. This means I have to make a bass trap rated for 55 Hz. Would love advice in finding DIY ideas in creating bass traps that help me fix this problem.

I will also add the frequency response of the room so that if anyone has advice in working on DIY panels to help with the other peaks and troughs of the graphs. I was also told I could fix this with EQ my speakers, how do I do this?

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Thanks!
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Re: Building bass traps & panels from room mode calculations

Postby RichardT » Wed Jan 27, 2021 7:25 pm

Hi Deloro,

I would suggest getting broadband trapping to start with, and only consider building a tuned trap if you still have a serious problem after you’ve installed the broadband traps.

Yes, you can use EQ to even out the frequency response - for example you can use Sonarworks Reference 4 - but if you have budget constraints I’d get room treatment first.
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Re: Building bass traps & panels from room mode calculations

Postby Sam Spoons » Wed Jan 27, 2021 8:11 pm

How big is your room?

I agree with Richard, get some decent (i.e. thick enough, 50mm spaced 50mm off the walls) broadband absorbers* at the mirror points for the speakers/mix position (including ceiling and back wall) and, if you have a specific spot in mind for the vocal recording position then do similar in respect of that, basically in a small room absorption needs to be balanced across the vocal range, say 100Hz up but otherwise the drier the better.

Bass traps need to be big and deep to work

WRT Sonorworks, I haven't tried it but most dips and peaks in the low and low mid ranges will vary radically depending on your position in the room so what is right at the mix position won't be right elsewhere. Bear this in mind when choosing where to record vocals too.

IIRC the optimum position to mix is 40% from the wall behind the monitors

* You say you have installed 'padding' on the walls, a bit more detail might be useful as a lot of thin padding will make the room sound boxy and lacking in 'sparkle'?
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Re: Building bass traps & panels from room mode calculations

Postby DelOro » Thu Jan 28, 2021 1:28 am

Sam Spoons wrote:How big is your room?

Here is the layout, height of the room is on the top right. Image
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Re: Building bass traps & panels from room mode calculations

Postby DelOro » Thu Jan 28, 2021 1:38 am

Also, and sorry for the multiple post still new to this, regarding richard's statement its not bass absorbers but panel absorbers? these would need to be at the reflection points and not the corners. How thick would the frames have to be? and for the vocal placement I was thinking of making the position in the middle with a mic shield as well as removing panels to create a roomier sound. If that makes sense.

For the bass absorbers they would be too big for the room? I'm guessing at least 5 feet deep right?
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Re: Building bass traps & panels from room mode calculations

Postby RichardT » Thu Jan 28, 2021 9:55 am

DelOro wrote:Also, and sorry for the multiple post still new to this, regarding richard's statement its not bass absorbers but panel absorbers? these would need to be at the reflection points and not the corners. How thick would the frames have to be? and for the vocal placement I was thinking of making the position in the middle with a mic shield as well as removing panels to create a roomier sound. If that makes sense.

For the bass absorbers they would be too big for the room? I'm guessing at least 5 feet deep right?

Have a read of some articles here. https://gikacoustics.co.uk. You can also see what professionally-made traps look like. It’s quite easy to make your own also.
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Re: Building bass traps & panels from room mode calculations

Postby Sam Spoons » Thu Jan 28, 2021 3:18 pm

In a small room (like yours and mine) 'Normal' bass traps just need to be as big as is practical. Tuned bass traps can be smaller to deal with a specific frequency but still may take up too much space in a small room (I don't have any on my room). A better (probably) plan is to include some 'limp mass' panels in front of or internal to your bass traps. Hugh did as 'proper job' in his studio recently, detailed in this article https://www.soundonsound.com/techniques/studio-sos-making-small-room-sound-good
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Re: Building bass traps & panels from room mode calculations

Postby Martin Walker » Sat Jan 30, 2021 2:16 am

Sam Spoons wrote:A better (probably) plan is to include some 'limp mass' panels in front of or internal to your bass traps. Hugh did as 'proper job' in his studio recently, detailed in this article https://www.soundonsound.com/techniques/studio-sos-making-small-room-sound-good

+1 for this advice from Sam, and also a +1 for broadband absorbers first of all. to help flatten out all the other room modes.

However, even 100mm thick absorbers placeed across the corners won't really affect much below 100Hz, so if you really expect a big problem at 55Hz you'll require seriously big treatment, placed carefully for maximum effect.

Oh, and welcome to the SOS Forums DelOro! 8-)


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Re: Building bass traps & panels from room mode calculations

Postby DelOro » Sat Jan 30, 2021 8:04 pm

Martin Walker wrote:
Sam Spoons wrote:A better (probably) plan is to include some 'limp mass' panels in front of or internal to your bass traps. Hugh did as 'proper job' in his studio recently, detailed in this article https://www.soundonsound.com/techniques/studio-sos-making-small-room-sound-good

+1 for this advice from Sam, and also a +1 for broadband absorbers first of all. to help flatten out all the other room modes.

However, even 100mm thick absorbers placeed across the corners won't really affect much below 100Hz, so if you really expect a big problem at 55Hz you'll require seriously big treatment, placed carefully for maximum effect.

Oh, and welcome to the SOS Forums DelOro! 8-)


Martin

Hey Martin (and others!)

I have done a bit of research and realize that, yes, filling the corners it would require a lot of space which I unfortunately don't have. One idea I have found was adjusting my monitors closer to the walls. This has to do with the Speaker-Boundary Interference. Right now I have it like a foot and a half off the wall. What if I put the speakers closer to walls with absorption panels right behind it. I am just trying to figure out how thick the panels should be.
Please let me know if this is a possibility
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Re: Building bass traps & panels from room mode calculations

Postby Sam Spoons » Sat Jan 30, 2021 9:02 pm

You really do need some deep traps to help control the bass, the corners are the most space efficient places to put them, 50mm or 100mm traps placed across the corners, preferably infilled with rockwool of some kind, will be more effective than similar thickness traps flat against the wall. Supplimented with broad band absorbers 50-100mm thick spaced off the surface at the wall and ceiling mirror points you can achieve a decent sounding space. A small room won't ever be perfect but, if you've read Hugh article I linked to, you'll see that good results are possible. My bass traps are smaller than Hugh's (and yes, size does matter) but I'm happy with the result, my room is way better than it was before I fitted the treatment. Abbey Road it ain't but it serves me well enough.

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Re: Building bass traps & panels from room mode calculations

Postby Martin Walker » Sat Jan 30, 2021 11:49 pm

DelOro wrote:I have done a bit of research and realize that, yes, filling the corners it would require a lot of space which I unfortunately don't have. One idea I have found was adjusting my monitors closer to the walls. This has to do with the Speaker-Boundary Interference. Right now I have it like a foot and a half off the wall. What if I put the speakers closer to walls with absorption panels right behind it. I am just trying to figure out how thick the panels should be.
Please let me know if this is a possibility

It's impossible to say with certainty, as each room tends to be at least slightly different. However, I've certainly done this in my tiny studio, because you do largely avoid the SBIR problems if your loudspeakers are very close to the wall.

It works particularly well for me because my loudspeaker cabinets are sealed rather than ported, so their bass end naturally falls off smoothly from a slightly higher frequency, and by placing them with their backs a couple of inches from the wall the reflection from this wall simply boosts their low end response to provide an overall smooth bass extension.

If on the other hand your loudspeakers are already voiced with a more reinforced bass end, they could end up sounding bottom-heavy and boomy when placed against the wall.


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Re: Building bass traps & panels from room mode calculations

Postby DelOro » Sun Jan 31, 2021 5:33 pm

Martin Walker wrote:It's impossible to say with certainty, as each room tends to be at least slightly different. However, I've certainly done this in my tiny studio, because you do largely avoid the SBIR problems if your loudspeakers are very close to the wall.

It works particularly well for me because my loudspeaker cabinets are sealed rather than ported, so their bass end naturally falls off smoothly from a slightly higher frequency, and by placing them with their backs a couple of inches from the wall the reflection from this wall simply boosts their low end response to provide an overall smooth bass extension.

If on the other hand your loudspeakers are already voiced with a more reinforced bass end, they could end up sounding bottom-heavy and boomy when placed against the wall.


Martin

I see, I have the SPL MKII Series 3 speaker monitors. They do have a port located in the back. So I'm assuming this is probably not the best idea then.
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