• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Need some advice on DIY bass traps and their placement

Koeitje

Major Contributor
Joined
Oct 10, 2019
Messages
2,292
Likes
3,880
So I got big nulls in my room at 40hz and at about 80hz (mainly want to fix the 80hz). The image below is my listening room. Things to note is that at the far end of the room I cannot really place anything and the front wall is sloped (the green line indicates where the slope is) with a radiator on the right where I can't really put anything. Since I don't want my room to look like a studio I want to put bass traps in Ikea bookshelves etc. I also have no way to fix ceiling reflections.

In purple I've indicated possible places I can put stuff.
  • On the bottom you see a bookcase I can put trapping material in (its about 30cm deep). I can also stick something to the side, because that's nicely out of sight.
  • I can put a room divider such as Ikea Kallax behind my couch and fill it with material. This would be about 1.5m in height and can be about 30-40cm in depth.
  • I can also put a bookcase next to the couch and fill that.
I plan to use cotton based insulation material. I can choose between 45kg/m3 and 25kg/m3 material. Thickness for the heavier type is up to 45mm and for the lighter material up to 200mm. But will all of this have any effect at all, because I cannot really put them in the actual corners...

room.png
 

Inner Space

Major Contributor
Forum Donor
Joined
May 18, 2020
Messages
1,285
Likes
2,938
So I got big nulls in my room at 40hz and at about 80hz (mainly want to fix the 80hz). The image below is my listening room. Things to note is that at the far end of the room I cannot really place anything and the front wall is sloped (the green line indicates where the slope is) with a radiator on the right where I can't really put anything. Since I don't want my room to look like a studio I want to put bass traps in Ikea bookshelves etc. I also have no way to fix ceiling reflections.

In purple I've indicated possible places I can put stuff.
  • On the bottom you see a bookcase I can put trapping material in (its about 30cm deep). I can also stick something to the side, because that's nicely out of sight.
  • I can put a room divider such as Ikea Kallax behind my couch and fill it with material. This would be about 1.5m in height and can be about 30-40cm in depth.
  • I can also put a bookcase next to the couch and fill that.
I plan to use cotton based insulation material. I can choose between 45kg/m3 and 25kg/m3 material. Thickness for the heavier type is up to 45mm and for the lighter material up to 200mm. But will all of this have any effect at all, because I cannot really put them in the actual corners...

View attachment 69896

If you mean nulls, rather than peaks, then traps and absorption won't really help. You could try moving the sub, perhaps along with rotating the speakers and sofa through 45 degrees clockwise, so that the main axis becomes diagonal. If none of that helps, then you could try EQ.
 
OP
K

Koeitje

Major Contributor
Joined
Oct 10, 2019
Messages
2,292
Likes
3,880
If you mean nulls, rather than peaks, then traps and absorption won't really help. You could try moving the sub, perhaps along with rotating the speakers and sofa through 45 degrees clockwise, so that the main axis becomes diagonal. If none of that helps, then you could try EQ.
I guess I need absorption behind the source to stop the reflections from causing the nulls?
 

Vini darko

Major Contributor
Joined
Jun 1, 2020
Messages
2,280
Likes
3,395
Location
Dorset England
You could try reducing the distance between the speakers and listening position. Pull the speakers out a touch and move the couch forwards a touch. Getting further into near field will negate the room to some degree. Bass traps do thier best work at right angled spots in the room. Putting them on flat surfaces is likely to affect the mids and treble more than bass. That's my layman's understanding anyway.
 
OP
K

Koeitje

Major Contributor
Joined
Oct 10, 2019
Messages
2,292
Likes
3,880
You could try reducing the distance between the speakers and listening position. Pull the speakers out a touch and move the couch forwards a touch. Getting further into near field will negate the room to some degree. Bass traps do thier best work at right angled spots in the room. Putting them on flat surfaces is likely to affect the mids and treble more than bass. That's my layman's understanding anyway.
Moving the couch forward does help a bit, at least I think...because I also did a measurement with the mic on the table in front of my couch and that was slightly better. But there isn't much room and I can't get to the optimal position there, so I prefer to solve it a different way..
 

patate91

Active Member
Joined
Apr 14, 2019
Messages
253
Likes
137
Moving the couch forward does help a bit, at least I think...because I also did a measurement with the mic on the table in front of my couch and that was slightly better. But there isn't much room and I can't get to the optimal position there, so I prefer to solve it a different way..


Corner bass trap.

I put unpacked mineral wool in the corners behind speakers and the corner near my listening spot. I got improvement with bass dips.

Unpacked mineral wools are great to experiment. Alter you can do something that looks better.
 

patate91

Active Member
Joined
Apr 14, 2019
Messages
253
Likes
137
Moving the couch forward does help a bit, at least I think...because I also did a measurement with the mic on the table in front of my couch and that was slightly better. But there isn't much room and I can't get to the optimal position there, so I prefer to solve it a different way..


Your room looks like mine
 
OP
K

Koeitje

Major Contributor
Joined
Oct 10, 2019
Messages
2,292
Likes
3,880
Corner bass trap.

I put unpacked mineral wool in the corners behind speakers and the corner near my listening spot. I got improvement with bass dips.

Unpacked mineral wools are great to experiment. Alter you can do something that looks better.
There is no space except for the corner behind the left speaker, but even there its limited due to the slanted ceiling (starts from the floor).
 

Vini darko

Major Contributor
Joined
Jun 1, 2020
Messages
2,280
Likes
3,395
Location
Dorset England
Moving the couch forward does help a bit, at least I think...because I also did a measurement with the mic on the table in front of my couch and that was slightly better. But there isn't much room and I can't get to the optimal position there, so I prefer to solve it a different way..
Sorry I don't have any better suggestions. Hopefully one of the experts here can help with some maths based solutions.
 
OP
K

Koeitje

Major Contributor
Joined
Oct 10, 2019
Messages
2,292
Likes
3,880
Sorry I don't have any better suggestions. Hopefully one of the experts here can help with some maths based solutions.
Maybe a second sub will fix it, then I can put one behind the left speaker and one on the right of the couch.
 

Dj7675

Major Contributor
Forum Donor
Joined
Jan 12, 2019
Messages
2,116
Likes
2,782
Not sure what your electronics are or if it include room correction or not, but to have the greatest affect on room modes:
1-Go with 2 subs, maybe put one behind the left M106 Possibly? Even if you have to do 2 smaller ones
2-Use eq below 3-500hz

Also with the M106 do you need to absorb the first reflections at all? Their reflected sound and direct sound will be very similar which should just get it a nice sounding wide image. Just a thought.
 

tuga

Major Contributor
Joined
Feb 5, 2020
Messages
3,984
Likes
4,281
Location
Oxford, England
You could try hanging a very heavy curtain behind the listening spot / sofa (partitioning the listening room from the office) from a rail that you can slide to the short wall next to the door when not in use. Unless of course you enjoy the effect of the low end bouncing back from the back wall and arriving at a later date... Or maybe add absorption to the back wall? 11 metres is a long distance.
 
OP
K

Koeitje

Major Contributor
Joined
Oct 10, 2019
Messages
2,292
Likes
3,880
Not sure what your electronics are or if it include room correction or not, but to have the greatest affect on room modes:
1-Go with 2 subs, maybe put one behind the left M106 Possibly? Even if you have to do 2 smaller ones
2-Use eq below 3-500hz

Also with the M106 do you need to absorb the first reflections at all? Their reflected sound and direct sound will be very similar which should just get it a nice sounding wide image. Just a thought.
Yes, a second sub behind the left speaker is still part of the plan. I already have one SB2000, will be on the look-out for a second one. I'm trying to deal with <500hz, above that its fine. I would maybe want it to roll off a tiny bit more, but maybe that changes when I fix the issues below 500hz.

You could try hanging a very heavy curtain behind the listening spot / sofa (partitioning the listening room from the office) from a rail that you can slide to the short wall next to the door when not in use. Unless of course you enjoy the effect of the low end bouncing back from the back wall and arriving at a later date... Or maybe add absorption to the back wall? 11 metres is a long distance.
I'm not sure what impact the length of the room, but a curtain wont stop <500hz that's why I was thinking about a room divider stuffed with something that absorb lower frequencies. I can stuff about 1m3 worth of material in one of the top corners at the end of the room, but that's about it.
 

pozz

Слава Україні
Forum Donor
Editor
Joined
May 21, 2019
Messages
4,036
Likes
6,827
You could try reducing the distance between the speakers and listening position. Pull the speakers out a touch and move the couch forwards a touch. Getting further into near field will negate the room to some degree. Bass traps do thier best work at right angled spots in the room. Putting them on flat surfaces is likely to affect the mids and treble more than bass. That's my layman's understanding anyway.
To clarify vocabulary.
  • "Bass traps" should be reserved for pressure-based designs like membrane or Helmholtz type.
  • "Broadband traps" refer to velocity-based traps using insulation materials and so on which have no effectiveness <100Hz.
Pressure is greatest in rooms at walls, so a common bass trap mount is directly on the wall. In corners you have even greater pressure given that's multiple walls meet, which is why those traps are set there as well.

At bass frequencies you cannot negate the room in the sense you mean. Bass frequencies are modal in small rooms, which means they will cause different areas to be differently loud and soft. Speaker and listening position placement will help find the most even area.

When you move closer to the speakers you are increasing the direct sound vs. reverberant sound. This is most effective for frequencies above the transition region.
If you mean nulls, rather than peaks, then traps and absorption won't really help. You could try moving the sub, perhaps along with rotating the speakers and sofa through 45 degrees clockwise, so that the main axis becomes diagonal. If none of that helps, then you could try EQ.
Room treatment can help with nulls as well as dips. Standing waves are most affected, while room modes will show only slight improvements (room modes are peaks/nulls based on physical room dimensions... they are room resonant points; standing waves are peaks/nulls due to phase cancellations/additions from the speaker/room interaction).
I guess I need absorption behind the source to stop the reflections from causing the nulls?
@Koeitje in a large space like yours a few isolated traps won't do very much. You will need an incredible amount of treatment to stop SBIR effects.

Just from rough simulation, using 11m length and 3.6m width, your 40Hz/80Hz issue is modal in nature. You can't really get around it unless you reposition where you sit, and it seems like you are very constrained seeing where the doors are.

A second sub and EQ to pull down peaks after measuring using MMM will help, but no amount of added bass or EQ boost will make those modes disappear.
 
Last edited:

dasdoing

Major Contributor
Joined
May 20, 2020
Messages
4,209
Likes
2,674
Location
Salvador-Bahia-Brasil
the nulls are probably caused by http://arqen.com/acoustics-101/speaker-placement-boundary-interference/

the biggest mode is produced between front and backwall, so and absorbent room divider behind the couch could(!) have some effect.
placing material directly on the wall wont do much.

I never heard or meassured sound in a sloped ceiling room but I imagine there will build up lots of energy on the bottom "corner" where ceiling and floor are close. putting material there would be effective
 

pozz

Слава Україні
Forum Donor
Editor
Joined
May 21, 2019
Messages
4,036
Likes
6,827
In purple I've indicated possible places I can put stuff.
  • On the bottom you see a bookcase I can put trapping material in (its about 30cm deep). I can also stick something to the side, because that's nicely out of sight.
  • I can put a room divider such as Ikea Kallax behind my couch and fill it with material. This would be about 1.5m in height and can be about 30-40cm in depth.
  • I can also put a bookcase next to the couch and fill that.
About these I have no strong opinions other than the second, which should be avoided since having absorption immediately behind your head will ruin the sense of spaciousness.

The other thing to consider is the effect of late reflections from the far back wall. Perceptually these will be more bothersome than the early reflections from your living room/TV room area. Maybe a heavy curtain in front or behind the bunch of stuff might help, depending if the stuff is solidly stacked or loosely arranged. Or maybe a broadband hanging baffle. An ETC in REW will help gauge how strong those late reflections are and if you need to treat them.
 

Dj7675

Major Contributor
Forum Donor
Joined
Jan 12, 2019
Messages
2,116
Likes
2,782
A well designed speaker doesn’t need side wall reflections absorbed. Side wall reflections from a well designed speaker with wide even dispersion will actually enhance the soundstage. From the many reviews of speakers it does seem that absorbing ceiling reflections does help many speakers. I would think speakers where direct sound does not match reflected sound would benefit from absorbing side reflections. The need to absorb side wall reflections seems to be speaker dependent.
 

patate91

Active Member
Joined
Apr 14, 2019
Messages
253
Likes
137
A well designed speaker doesn’t need side wall reflections absorbed. Side wall reflections from a well designed speaker with wide even dispersion will actually enhance the soundstage. From the many reviews of speakers it does seem that absorbing ceiling reflections does help many speakers. I would think speakers where direct sound does not match reflected sound would benefit from absorbing side reflections. The need to absorb side wall reflections seems to be speaker dependent.


Wider sounstage it's just one part of music experience. In my listening room the soundstage is limited to room boundaries anyway.
 

patate91

Active Member
Joined
Apr 14, 2019
Messages
253
Likes
137
A well designed speaker doesn’t need side wall reflections absorbed. Side wall reflections from a well designed speaker with wide even dispersion will actually enhance the soundstage. From the many reviews of speakers it does seem that absorbing ceiling reflections does help many speakers. I would think speakers where direct sound does not match reflected sound would benefit from absorbing side reflections. The need to absorb side wall reflections seems to be speaker dependent.

I re-read your post and I'm not sur I follow you.

Once soundwaves are in the roo
A well designed speaker doesn’t need side wall reflections absorbed. Side wall reflections from a well designed speaker with wide even dispersion will actually enhance the soundstage. From the many reviews of speakers it does seem that absorbing ceiling reflections does help many speakers. I would think speakers where direct sound does not match reflected sound would benefit from absorbing side reflections. The need to absorb side wall reflections seems to be speaker dependent.

What kind of speakers eliminate SBIR effect?
 
Top Bottom