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Just a simple/stupid Q about bass traps behind listening position
Old 4 weeks ago
  #1
Just a simple/stupid Q about bass traps behind listening position

So Im in the middle of building stuff for my new room which I have another thread with pictures.

I was just wondering...

If you put bass traps, say 1m, behind your listening position but the wall is maybe 2m further back.
How would this generally affect the room?

The idea is that, since my room is very unsymetrical and my listening position isnt even in the middle of the room, I would kind of bulid in my listening position so the soundwaves bounces more symetrical where I sit.
But maybe I need a real wall to do that?
Old 4 weeks ago
  #2
Gear Nut
 
Mark Alpine's Avatar
I've had that question asked here too. Bass trap/gobo open back or closed back. Didn't receive any answer from the experts yet. Maybe the question is stupid, or I'm to thick to understand why it won't work...
Old 4 weeks ago
  #3
Quote:
Originally Posted by Mark Alpine View Post
I've had that question asked here too. Bass trap/gobo open back or closed back. Didn't receive any answer from the experts yet. Maybe the question is stupid, or I'm to thick to understand why it won't work...
Its definitely so many factors that a simple answer isnt enough.....

The search goes on
Old 4 weeks ago
  #4
Lives for gear
 

lf refracts around obstacles as one can easily experience so bass traps become way less efficient if not positioned against walls/in corners.

large absorbers and/or diffusors behind the mixing position can help to contain the mids/hf in asymmetrical rooms though.
Old 4 weeks ago
  #5
Quote:
Originally Posted by deedeeyeah View Post
lf refracts around obstacles as one can easily experience so bass traps become way less efficient if not positioned against walls/in corners.

large absorbers and/or diffusors behind the mixing position can help to contain the mids/hf in asymmetrical rooms though.
Thank you.
Old 4 weeks ago
  #6
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Jason Foi's Avatar
 

If large enough vs wavelength, like if it made a faux back wall, it would be highly effective, although not the smoothest absorbtion acording to the PAC. Velocity traps placed 1/4 wavelength away from the wall is in theory perfect absorbtion.
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Just a simple/stupid Q about bass traps behind listening position-screenshot_20191114-091242_firefox.jpg  
Old 4 weeks ago
  #7
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Quote:
Originally Posted by Jason Foi View Post
If large enough vs wavelength, like if it made a faux back wall, it would be highly effective, although not the smoothest absorbtion acording to the PAC. Velocity traps placed 1/4 wavelength away from the wall is in theory perfect absorbtion.
trouble is that 'large enough' can become an issue in small places and that 'quarter wavelength' only works at a very specific frequency, so no broadband absorbtion. plus this position of absorbers often has limits for practical reasons and works better in theory than in reality: i get to experiment with absorbers on location quite often and results are mostly an improvement but far from ideal...
i find a rear sub in this position often to be equally or more efficient; add some dsp and things improve further.
Old 4 weeks ago
  #8
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Jason Foi's Avatar
 

Quote:
Originally Posted by deedeeyeah View Post
trouble is that 'large enough' can become an issue in small places and that 'quarter wavelength' only works at a very specific frequency, so no broadband absorbtion. plus this position of absorbers often has limits for practical reasons and works better in theory than in reality: i get to experiment with absorbers on location quite often and results are mostly an improvement but far from ideal...
i find a rear sub in this position often to be equally or more efficient; add some dsp and things improve further.
PAC shows its still very much broadband (.7 or higher from 20hz-20khz with exception to 80ishhz in my example), but i agree its not a very practical aproach for most circumstances.
Old 4 weeks ago
  #9
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akebrake's Avatar
 

Quote:
Originally Posted by mattias78 View Post
So Im in the middle of building stuff for my new room which I have another thread with pictures.
Is this the room?
Fake wall absorber


Quote:
... since my room is very unsymetrical and my listening position isnt even in the middle of the room, I would kind of bulid in my listening position so the soundwaves bounces more symetrical where I sit.
But maybe I need a real wall to do that?
Would you mind draw a rough sketch of the room with dimensions.

Best

PS Your monitors are meant to be positioned standing. (Not laying on it's side).
That will improve imaging.
Old 4 weeks ago
  #10
Quote:
Originally Posted by akebrake View Post
Is this the room?
Fake wall absorber




Would you mind draw a rough sketch of the room with dimensions.

Best

PS Your monitors are meant to be positioned standing. (Not laying on it's side).
That will improve imaging.
Thanks for the answers guys.
Yes thats the room.
But I changed it up again and the monitors are standing up now
new pictures below

335x510 cm is the dimensions.
But since the room is so weird I thought maybe it could help by putting some stuff around the listening position.

My next plan is to build a desk with angled rack.
Then I plan to build a faux wall to the left of the listening position to make it symetrical left to right.

But as a layman Im not so sure how much you gain on the different solutions Im thinking about.
Attached Thumbnails
Just a simple/stupid Q about bass traps behind listening position-img_20191114_221253.jpg   Just a simple/stupid Q about bass traps behind listening position-img_20191114_221223.jpg   Just a simple/stupid Q about bass traps behind listening position-img_20191114_221144.jpg   Just a simple/stupid Q about bass traps behind listening position-img_20191114_182549.jpg  
Old 4 weeks ago
  #11
Ok so I redid my room with my current stuff.
I have to wait a few weeks before building my own DIY desk.

But I did some testing today with the room empty from all acoustics from the front wall.
Then I added stuff and tried to move the desk and speakers in different positions approximately where it as now.

Since the setup still is unsymmetrical I tried to aim at getting the left and right speakers kind of the same.

The right and the left side has a broad and big peak around 143Hz.
It didn't change no matter what I did so I think it has to do with untreated roof and thick desk maybe?

The right side has a broad big null around 90-100Hz which the right side don't have in the same amount.

I put the speakers 45 cm(from the speakerdriver to wall) from the front wall with 8" and 4" bass traps behind.

Afterwards I went through with Sonarworks and I attached the measurements.
I used REW during the setup but the measurements dissapered unfortunately.


Anyone has ideas how to treat the room further.
I have a lot of ideas but most of them is just fill up with more bass traps
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Attached Images
Just a simple/stupid Q about bass traps behind listening position-image.png 
Old 4 weeks ago
  #12
Sitting and planning my studio desk build during my workbreak.

Got an crazy idea that I dont think I would do but really want to know if it works.

Say you build you desk with angled rack in front of speaker.
Then when the desk straighten out after 30 cm instead of woodenboard why not put some sort plate with small holes in and put fiberglass underneath wrapped in fabric?
So when the sound bounces of the desk it hits the plate/fiberglass instead.
I dont know how the plate is making the sound bounce and what kind of holes you'll be best of with.
Old 3 weeks ago
  #13
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akebrake's Avatar
 

Quote:
Originally Posted by mattias78 View Post
...The right and the left side has a broad and big peak around 143Hz.
Quote:
The right side has a broad big null around 90-100Hz which the right side don't have in the same amount.
Forget the desk for a while and start investigating the room.
Make it as good as ”possible” (e.g practical, effort, budget etc)
Measure with REW before and after, documenting every step.

When the room is ”OK” you have a reference and you can start building a desk or equipment racks that will ”ruin” your result as little as possible...


1. Total length of room is around 5.1m? From the Beatles photo to the walk in closet wall. (Just behind spkrs). Is that a rigid wall?

2. Stick to REW when communicating with this Forum. Upload mdats here.
SonarWorks only shows FR which will not help finding reflections, slow decaying modes or first reflection "holes".

3. To get an idea of the measured modal frequecies (as the room is unsymetrical) Place one speaker on the floor close to the Right front corner. Microphone in the diagonal opposite rear left ceiling corner. (Mic pos 1) Save mesurement. Watch out for overload as modes are strong.

4. Then check positions of modal nulls. I like Pink Periodic Noise (Pink PN) from REW Generator while watching the result on REW RTA (real time)
You can restrict it to the low end (to save your ears and tweeters).
Move the microphone around the listening area and estimated stereo speaker positions and observerve the modal nulls of the modes.
(Nulls are not good spkr or listening positions) To Save just press the disk ikon.

5. Close the doors while measuring.

6. Is a deep rear wall trap an option? Like a 40cm deep slat-covered mineral wool trap?

I draw a sketch of your room (approx to scale?). You can compare calculated modes peak/ nulls to measured (square room) with the Hunecke Calc. (or amroc)

Hope that helps a bit
Attached Thumbnails
Just a simple/stupid Q about bass traps behind listening position-mattias-simple2.jpg   Just a simple/stupid Q about bass traps behind listening position-mattias-hunecke.jpg  
Old 3 weeks ago
  #14
Quote:
Originally Posted by akebrake View Post
Forget the desk for a while and start investigating the room.
Make it as good as ”possible” (e.g practical, effort, budget etc)
Measure with REW before and after, documenting every step.

When the room is ”OK” you have a reference and you can start building a desk or equipment racks that will ”ruin” your result as little as possible...


1. Total length of room is around 5.1m? From the Beatles photo to the walk in closet wall. (Just behind spkrs). Is that a rigid wall?

2. Stick to REW when communicating with this Forum. Upload mdats here.
SonarWorks only shows FR which will not help finding reflections, slow decaying modes or first reflection "holes".

3. To get an idea of the measured modal frequecies (as the room is unsymetrical) Place one speaker on the floor close to the Right front corner. Microphone in the diagonal opposite rear left ceiling corner. (Mic pos 1) Save mesurement. Watch out for overload as modes are strong.

4. Then check positions of modal nulls. I like Pink Periodic Noise (Pink PN) from REW Generator while watching the result on REW RTA (real time)
You can restrict it to the low end (to save your ears and tweeters).
Move the microphone around the listening area and estimated stereo speaker positions and observerve the modal nulls of the modes.
(Nulls are not good spkr or listening positions) To Save just press the disk ikon.

5. Close the doors while measuring.

6. Is a deep rear wall trap an option? Like a 40cm deep slat-covered mineral wool trap?

I draw a sketch of your room (approx to scale?). You can compare calculated modes peak/ nulls to measured (square room) with the Hunecke Calc. (or amroc)

Hope that helps a bit
Thank you so much for the answers.
I will get to it eventually.
I have alot of building plans.
And as you said the desk is not the next step.
Im gonna build one or two walls that I can move around and those will be set on the left and right side of my listening position. To get the listening position more symmetrical.
In those walls I will put insulation with a wood backdrop.


And yes all the walls are rigid.

A 40cm bass traps on the backwall would eventually work.
I will take away the big sofa in the corner and replace with a 2 piece sofa.
Then I will have more room to fit alot of things to the back wall.

Thanks again for the support. It means alot.
I will do some tests next week and post as quickly as I can.
Have a good weekend.
Best regard mattias
Old 3 weeks ago
  #15
Gear Addict
 

In fact a velocity absorber like mineral wool is most effective in het middle of the room where the velocity is max and the pressure is minimum.
In practice you'll probably encouter problems, but in for example a loudspreker enclosure this works well.
Old 3 weeks ago
  #16
Quote:
Originally Posted by bert stoltenborg View Post
In fact a velocity absorber like mineral wool is most effective in het middle of the room where the velocity is max and the pressure is minimum.
In practice you'll probably encouter problems, but in for example a loudspreker enclosure this works well.
You can't have enough bass traps right
I'm building a bookshelf with rock wool hidden in the shelf 30cm thick. Nice small bass trap/fake diffusor.
Old 3 weeks ago
  #17
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akebrake's Avatar
 

Quote:
Originally Posted by mattias78 View Post
You can't have enough bass traps right
Yes, that's a fairly safe claim. The flat FR speaker salesdept (sometimes) show in advertising is measured without reflections.

Quote:
I'm building a bookshelf with rock wool hidden in the shelf 30cm thick. Nice small bass trap/fake diffusor.
(Bolded mine) Small bass trap? Pls explain!
Old 3 weeks ago
  #18
Quote:
Originally Posted by akebrake View Post
Yes, that's a fairly safe claim. The flat FR speaker salesdept (sometimes) show in advertising is measured without reflections.



(Bolded mine) Small bass trap? Pls explain!
In the same time as I'm trying to fix my studio space I also want to divide the room from the "Xbox corner" and still maintain a nice look.
So I'm building a bookshelf which is gonna be behind me in the middle of the room.
It gonna have books and Lp's in it but the middle shelf will consist of rockwool with fabric around so it can contain stuff(fake diffusion) and bass trap at the same time.
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