Need some advice on DIY bass traps and their placement

[patate91]

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.

And soundstage, imaging are dependant on how the instruments have been recorced and album produced.

 

[pozz]

And soundstage, imagine are dependant on how the instruments have bien recorced and produced.

In my little studio I have 6" broadband traps on the sidewalls and ceiling, and membrane traps mounted flat on the front corners and front wall. Back wall has one 8" broadband trap (no room for anything else; the trap is in the middle of the wall, with a closet door on one side and bookshelf on the other).

Too keep the room reverberant only the front half is treated with broadband absorption. The back half is mostly books aside from that one absorber. If I sit at the halfway point, I can lean backwards and forwards from the treated to untreated portion and back. At this exact spot I can make the soundstage expand and contract. It's really obvious with well-made recordings, but is evident even with mono.

 

[patate91]

In my little studio I have 6" broadband traps on the sidewalls and ceiling, and membrane traps mounted flat on the front corners and front wall. Back wall has one 8" broadband trap (no room for anything else; the trap is in the middle of the wall, with a closet door on one side and bookshelf on the other).

Too keep the room reverberant only the front half is treated with broadband absorption. The back half is mostly books aside from that one absorber. If I sit at the halfway point, I can lean backwards and forwards from the treated to untreated portion and back. At this exact spot I can make the soundstage expand and contract. It's really obvious with well-made recordings, but is evident even with mono.

Sure, by leaning forward and backward you change everything that's and effect of SBIR. The way your speakers are toed-in probably affect what you are hearing when you move.

 

[pozz]

Sure, by leaning forward and backward you change everything that's and effect of SBIR. The way your speakers are toed-in probably affect what you are hearing when you move.

This only works if I sit at the halfway point. The soundstage is stable if sitting squarely in the treated or untreated portion and leaning around.

Using the mirror method, the expansion starts right where the bare plaster wall begins.

 

[dasdoing]

why use dirty first reflections (left reflection from left speaker might be ok, but right reflection from left speaker is as dirty as it can get) if you can get closer in the stereo triangle to widen soundstage? when I started treating sidewalls I did that, but over the time I went back to regular equilateral triangle as I automaticly started to focus on ambience in the recording instead of room ambience

 

[Sonicears]

I built some triangulated bass traps out of Rockwool using a popular design of laying pieced cut in triangles one on top of each other in a triangular frame.

I placed these in the front corners of the room and I wasn't very pleased with the result in REW. Barely noticeable.

So I placed some bean bag couches I have vertically in the corners in their stead and they both measured and sounded better.

Has anyone else experimented with bean bag bass traps?

My suspicion is that my Rockwool ones are too dense.

 

[dasdoing]

My suspicion is that my Rockwool ones are too dense.

probably. superchunks need that "fluffy stuff"

 

[Sonicears]

The original corner bass traps I built were rubbish in my lounge for my systme. The design just used triangular pieces of the rockwool sheet layered on top of each other. I use a very similar design to this one on Youtube.

They made almost no improvement and measured worse than just using bean bags with REW.

I rebuilt them today using sheets of compressed 30mm thick sheets of Rockwool (Density 67 kg/m3) as the perimieter to triangular frames (held in place with builders strapping tape stapled to the frames I had made for the previous design and loosely stuffed the inside of them with low density rockwall ceiling installation. New ones operate like a diaphram. Very very pleased with the result and they were simpler, cheaper and faster to make. Haven't had a chance to measure them yet but evenwith out my Dirac MiniDSP unit retuned for them they sound a gizillion times better.

 

[Hipper]

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

What did you do in the end?

When you consider the sound you will hear you have to divide up the frequencies into those above and those below the Transition (or Schroeder) frequency, usual around 250Hz but variable depending on the room size and shape. The biggest problems will undoubtedly be in the bass region, say 0-300Hz. This is the most difficult to solve but get this right and it will free your music to sound more as it should.

As you can't use lots of bass traps it may well not be worth using any and concentrate on using subs and DSP/EQ to try and solve the issues. On subs I don't know much but it seems a case of moving these around to get the best results (this applies to your main speakers and listening chair too if you can do this). With DSP/EQ you can adjust individual peaks and nulls (often very narrow nulls have little impact on the sound - it is the wider ones that cause problems). Machines like MiniDSP with Dirac are worth considering.

For the higher frequencies, say 300Hz to 20kHz, symmetry is one of the factors in a balanced sound and you haven't got it! How you listen to your music - on your own sitting anywhere on the sofa, or with someone else so that you are off centre - will have a bearing on what you hear. If you sit on your own then it would be wise to have the speakers at least as part of an isosceles triangle with you at the apex. It's true that your left speaker is closer to the side wall then your right one and this will effect the balance of the higher frequencies that you will hear at your chair. You can solve this by placing a suitable absorber on the left wall, and a moveable absorber on feet by the right one, to be stored elsewhere when not listening. You can also buy (or make) them in the form of an image so they look more attractive.

You mention you have a coffee table. You should check if there are reflections coming off that which will distort the sound. On ceiling reflections, you may not suffer from them. It will depend on your speakers dispersion characteristics and how far you are from them. If it is an issue, you could put some sort of absorbent material (that absorbs from say 300Hz to 20kHz) on top of the speaker so it sticks out a bit forward enough to stop a sound 'ray' going to the ceiling and bouncing back down to your ears.

Apart from the frequency response, there care two other aspects that are sometimes considered - phase, and sound decay times. Absorbers seem to help with both these whereas DSP/EQ has a more limited effect. Of these, decay times are a big influence on quality of sound.

Overall you shouldn't get carried away with trying to get the perfectly flat frequency response. If you clear up the worst damage to the lower frequencies and generally smooth out the higher ones that should give you a good sound. Above all of course it is what you hear that counts.

 

[Koeitje]

What did you do in the end?

When you consider the sound you will hear you have to divide up the frequencies into those above and those below the Transition (or Schroeder) frequency, usual around 250Hz but variable depending on the room size and shape. The biggest problems will undoubtedly be in the bass region, say 0-300Hz. This is the most difficult to solve but get this right and it will free your music to sound more as it should.

As you can't use lots of bass traps it may well not be worth using any and concentrate on using subs and DSP/EQ to try and solve the issues. On subs I don't know much but it seems a case of moving these around to get the best results (this applies to your main speakers and listening chair too if you can do this). With DSP/EQ you can adjust individual peaks and nulls (often very narrow nulls have little impact on the sound - it is the wider ones that cause problems). Machines like MiniDSP with Dirac are worth considering.

For the higher frequencies, say 300Hz to 20kHz, symmetry is one of the factors in a balanced sound and you haven't got it! How you listen to your music - on your own sitting anywhere on the sofa, or with someone else so that you are off centre - will have a bearing on what you hear. If you sit on your own then it would be wise to have the speakers at least as part of an isosceles triangle with you at the apex. It's true that your left speaker is closer to the side wall then your right one and this will effect the balance of the higher frequencies that you will hear at your chair. You can solve this by placing a suitable absorber on the left wall, and a moveable absorber on feet by the right one, to be stored elsewhere when not listening. You can also buy (or make) them in the form of an image so they look more attractive.

You mention you have a coffee table. You should check if there are reflections coming off that which will distort the sound. On ceiling reflections, you may not suffer from them. It will depend on your speakers dispersion characteristics and how far you are from them. If it is an issue, you could put some sort of absorbent material (that absorbs from say 300Hz to 20kHz) on top of the speaker so it sticks out a bit forward enough to stop a sound 'ray' going to the ceiling and bouncing back down to your ears.

Apart from the frequency response, there care two other aspects that are sometimes considered - phase, and sound decay times. Absorbers seem to help with both these whereas DSP/EQ has a more limited effect. Of these, decay times are a big influence on quality of sound.

Overall you shouldn't get carried away with trying to get the perfectly flat frequency response. If you clear up the worst damage to the lower frequencies and generally smooth out the higher ones that should give you a good sound. Above all of course it is what you hear that counts.

I haven't gotten around to doing anything yet. All I did was move the sub around a bit more to come the conclusion I really need a second one. So I'm waiting for that before doing anything else.