I have tested with the sub moved to the rear, and it's not looking very good either.. Sub is placed just behind the listening position, cone facing the rear wall (window) at abt 20cm distance. I can upload a picture soon.
For some reason it does not seem to do anything about the standing wave, except reduce the SPL.
So this is what I did for the quick test:
I tuned the sub delay for max cancellation at 32Hz by ear, and then muted the sub and ran a measurement with just the fronts, and again unmuted the sub and measured with fronts and the sub.
There is abt -14dB at 32Hz with the sub unmuted, but the decay looks the same anyway, it just starts out on a lower level. So the level is lower, but the ringing/standing wave reverbs the same.
When I think about it, as a 'pulse/step' It kind of makes sense, since the first reflection is partially 'eaten' by the inverted sub at the rear wall, but whatever remains of that 'pulse' will keep bouncing back and forth in the room without any additional cancelation/extra damping, just as before, since it was only reduced in level once, when hitting the rear wall (with sub) sub the first time and getting the inverted pulse. When it reaches the front wall, there is no damping/cancellation, and so on
Feel free to have a look at the measurements attached
For some reason it does not seem to do anything about the standing wave, except reduce the SPL.
So this is what I did for the quick test:
I tuned the sub delay for max cancellation at 32Hz by ear, and then muted the sub and ran a measurement with just the fronts, and again unmuted the sub and measured with fronts and the sub.
There is abt -14dB at 32Hz with the sub unmuted, but the decay looks the same anyway, it just starts out on a lower level. So the level is lower, but the ringing/standing wave reverbs the same.
When I think about it, as a 'pulse/step' It kind of makes sense, since the first reflection is partially 'eaten' by the inverted sub at the rear wall, but whatever remains of that 'pulse' will keep bouncing back and forth in the room without any additional cancelation/extra damping, just as before, since it was only reduced in level once, when hitting the rear wall (with sub) sub the first time and getting the inverted pulse. When it reaches the front wall, there is no damping/cancellation, and so on
Feel free to have a look at the measurements attached
I was able to order four more of the denim-insulation. They (Eurokustik) had these as 'B-stock' that they offered for a reduced price. They were not planning on re-stocking since they had to buy large quantities, and did not sell very much of it.
I also ordered four 50mm basotect panels to put in the ceiling around the first reflection point. The basotect was not in stock, so I suspect it will take some time to get the delivery with the holidays coming up etc.
I'm still thinking about what to use for 'bass traps'. Maybe I will try the ones I'm making in the corners to see what it does, could help to get a clue..
I also ordered four 50mm basotect panels to put in the ceiling around the first reflection point. The basotect was not in stock, so I suspect it will take some time to get the delivery with the holidays coming up etc.
I'm still thinking about what to use for 'bass traps'. Maybe I will try the ones I'm making in the corners to see what it does, could help to get a clue..
I took the high panel home today and placed it on the rear wall behind my 'cosy corner' in the sofa. I could instantly notice the effect when sitting in the corner.
I have not made any measurements yet, but I can tell by ear that it's an improvement when sitting in the corner. Probably not so much in the main listening position though. I do spend a lot of time in the corner though, watching tv or listening to music in the background, I'm always sitting in the corner, so in total it's maybe 80% of the time.. So, the corner should get some attention too.
As I mentioned before, I made some experiments with some simple panels in the first reflection points on the side walls. The conclusion is that they seem to work better when angled so they are facing towards the speakers a bit. If I put them flat against the wall, they seem to have less effect. This got me thinking that since it looks too awkward to have them at an angle like that, maybe the ones I make should have a rounded shape to be more effective than a flat absorber against the wall?
So what I'm thinking at the moment is some sturdy metal net in a rounded shape (half cylindrical?) as backing, and the absorbent and some fabric wrapped around that. Maybe put a few small shelfs on it to make it look and function like furniture too.
I'm thinking this could help with the varying listening positions and their reflection points too. When I sit in the corner, the reflection point is further back in the room, but the angle is more shallow, so a rounded absorber sticking out a bit from the wall should 'shadow' this second reflection point better than a flat one. Some added depth should give it some absorption lower down as well.
Comments welcome!
I have not made any measurements yet, but I can tell by ear that it's an improvement when sitting in the corner. Probably not so much in the main listening position though. I do spend a lot of time in the corner though, watching tv or listening to music in the background, I'm always sitting in the corner, so in total it's maybe 80% of the time.. So, the corner should get some attention too.
As I mentioned before, I made some experiments with some simple panels in the first reflection points on the side walls. The conclusion is that they seem to work better when angled so they are facing towards the speakers a bit. If I put them flat against the wall, they seem to have less effect. This got me thinking that since it looks too awkward to have them at an angle like that, maybe the ones I make should have a rounded shape to be more effective than a flat absorber against the wall?
So what I'm thinking at the moment is some sturdy metal net in a rounded shape (half cylindrical?) as backing, and the absorbent and some fabric wrapped around that. Maybe put a few small shelfs on it to make it look and function like furniture too.
I'm thinking this could help with the varying listening positions and their reflection points too. When I sit in the corner, the reflection point is further back in the room, but the angle is more shallow, so a rounded absorber sticking out a bit from the wall should 'shadow' this second reflection point better than a flat one. Some added depth should give it some absorption lower down as well.
Comments welcome!
A small step forward, I just put an absorber in the front right corner. Still not finished, I need to make a 'cover' for it that can be used as a shelf and also to seal the top. There is a small piece on top now just as a temporary fix. Need to buy more wood to make one for the front left corner too.
I have not figured out how to hang the basotect panels in the ceiling yet.. Would be easy with double sided tape, but might be hell the day I move and should remove them..
I have not figured out how to hang the basotect panels in the ceiling yet.. Would be easy with double sided tape, but might be hell the day I move and should remove them..
A friend came by to audition the speakers today. I sometimes call him Ernst (Swedish TV decorator) because he's a perfectionist when it comes to interior decorating, and most other things too 
Anyway, his suggestion was to rotate everything in the living room 90deg counter clockwise, so the sofa would be between the bedroom door and terrace door. TV and speakers on the opposite wall.
We made some measurements, and it should be possible, but I would have to remove/modify an armrest on the sofa to make it slightly shorter to fit between the doors. Accessing the terrace door would probably be a bit awkward, since it would be 'behind the sofa'.
The listening triangle would be more correct like this, and sitting in the sofa, one would have a view out the window. The sofa and speakers would have to be up against the walls though, and speakers more or less in the corners still. No chance of adding a sub behind the sofa in that configuration.
I'm thinking I could make some extension for one speaker and move just the speakers and sofa to try what it does to the sound. Maybe make some measurements too.
Re-posting the room layout as it is just for reference. Does it sound like a good or bad idea?
Anyway, his suggestion was to rotate everything in the living room 90deg counter clockwise, so the sofa would be between the bedroom door and terrace door. TV and speakers on the opposite wall.
We made some measurements, and it should be possible, but I would have to remove/modify an armrest on the sofa to make it slightly shorter to fit between the doors. Accessing the terrace door would probably be a bit awkward, since it would be 'behind the sofa'.
The listening triangle would be more correct like this, and sitting in the sofa, one would have a view out the window. The sofa and speakers would have to be up against the walls though, and speakers more or less in the corners still. No chance of adding a sub behind the sofa in that configuration.
I'm thinking I could make some extension for one speaker and move just the speakers and sofa to try what it does to the sound. Maybe make some measurements too.
Re-posting the room layout as it is just for reference. Does it sound like a good or bad idea?
I made one more corner absorber for the other front corner, and also finished the first side wall absorber today.
It's just meant to lean against the wall, and a small 'shelf' to put some stuff on. It's light and easy to move around, but needs a wall to lean against, or it will fall over. Total height abt 130cm just like the corner absorbers.
Back side
Front
I skipped the idea about re-arranging the living room after consulting with the better half, -she did not like the idea at all..
It's just meant to lean against the wall, and a small 'shelf' to put some stuff on. It's light and easy to move around, but needs a wall to lean against, or it will fall over. Total height abt 130cm just like the corner absorbers.
Back side
Front
I skipped the idea about re-arranging the living room after consulting with the better half, -she did not like the idea at all..
The best results I've gotten so far with EQ'ing room modes is by doing it "musician style", e.g:
1) generating sine sweeps with a keyboard,
2) homing in on problem areas,
3) calculating the exact frequencies mathematically from the notes being played,
4) using parametric EQ (with independently settable gain, Q, and frequency for each knob) for to create notch filters.
5) verify with mic measurements. I generally don't like FFT plots at low frequencies as they usually don't have enough samples for good-enough resolution. However, looking directly at sine sweeps in the time domain can easily show subtle variations in SPL. Nevertheless, I'm inclined to trust my ears, because if there's a peak in harmonic distortion, that could also require EQ even if it looks flat on a graph.
6) going back and doing multiple passes until I'm happy. It can be tricky to get the right Q for the filter, producing double nulls or double peaks once the main peak has been flattened.
1) generating sine sweeps with a keyboard,
2) homing in on problem areas,
3) calculating the exact frequencies mathematically from the notes being played,
4) using parametric EQ (with independently settable gain, Q, and frequency for each knob) for to create notch filters.
5) verify with mic measurements. I generally don't like FFT plots at low frequencies as they usually don't have enough samples for good-enough resolution. However, looking directly at sine sweeps in the time domain can easily show subtle variations in SPL. Nevertheless, I'm inclined to trust my ears, because if there's a peak in harmonic distortion, that could also require EQ even if it looks flat on a graph.
6) going back and doing multiple passes until I'm happy. It can be tricky to get the right Q for the filter, producing double nulls or double peaks once the main peak has been flattened.
Interesting approach! I have only done EQ based on sweeps and response curves..
Usually I have not liked the results so much, so I try to EQ as little as possible. I found transients start to sound weird in the bass when I try to EQ for the room. Moderate EQ to tame standing waves a bit seem like a better compromise, just to reduce the 'booming' at some low bass notes, but still get decent transients.
This is my first real attempt at taming a room, and it's quite a challenge with the room being what it is..
I'm not trying to make it a studio, just improve it to something I can live with. I think there is audible improvement already, but I still need to finish the second side absorber, put lids on the corner absorbers and mount the basotect in the ceiling. After that I should run some measurements again to see where I am, and try to do some EQ based on the 'new room'.
Maybe I'll try your method and see what I come up with compared to REW sweeps. I think I have some midi keyboard in storage from past 'recording experiments', but I guess there should be an easier way to play musical tones from PC or an Android phone without the actual hardware? I think Windows XP (?) had a 'piano/keyboard' that could be played with the keyboard or mouse back in the day? Did not find anything on this Win10 laptop though.
Usually I have not liked the results so much, so I try to EQ as little as possible. I found transients start to sound weird in the bass when I try to EQ for the room. Moderate EQ to tame standing waves a bit seem like a better compromise, just to reduce the 'booming' at some low bass notes, but still get decent transients.
This is my first real attempt at taming a room, and it's quite a challenge with the room being what it is..
I'm not trying to make it a studio, just improve it to something I can live with. I think there is audible improvement already, but I still need to finish the second side absorber, put lids on the corner absorbers and mount the basotect in the ceiling. After that I should run some measurements again to see where I am, and try to do some EQ based on the 'new room'.
Maybe I'll try your method and see what I come up with compared to REW sweeps. I think I have some midi keyboard in storage from past 'recording experiments', but I guess there should be an easier way to play musical tones from PC or an Android phone without the actual hardware? I think Windows XP (?) had a 'piano/keyboard' that could be played with the keyboard or mouse back in the day? Did not find anything on this Win10 laptop though.
I cut some pieces of wood to cover the corner absorbers today, so now they are considered finished. Not too proud of the craftmanship though, but it is what it is.. They are stuck in the corners behind the speakers, so they are not that visible.
I also used some of the hemp insulation to fill up the small (old) absorbers behind the speakers. They are not the greatest at absorption, but at least it should be a small improvement compared to just towels which was what I used from the start.. Did almost nothing.
I still have to buy some wood for the other side wall absorber, and figure out how to hang the basotect in the ceiling. Thinking of using double sided tape on the basotect + masking tape to the ceiling. I'm afraid double sided tape could rip the paint or be hard to remove from the ceiling. If I use a quality masking tape, it should be removable without major problems even if they stick well enough to stay there for years.
I also used some of the hemp insulation to fill up the small (old) absorbers behind the speakers. They are not the greatest at absorption, but at least it should be a small improvement compared to just towels which was what I used from the start.. Did almost nothing.
I still have to buy some wood for the other side wall absorber, and figure out how to hang the basotect in the ceiling. Thinking of using double sided tape on the basotect + masking tape to the ceiling. I'm afraid double sided tape could rip the paint or be hard to remove from the ceiling. If I use a quality masking tape, it should be removable without major problems even if they stick well enough to stay there for years.
i have a concrete bunker myself and have made some mid size tower traps type of corner traps, 12 traps that is 45x45x120cm in size. they damp a lot of sound, almost to much, but did not do much for some problem frequencies i got, so i went for a multiple subs setup, one sub at the mid point on each wall, that goes for the height too. using less then four subs gave me a too small sweet spot.
I might end up adding subs, or just accepting the situation. Subjectively the situation has improved with the stuff I have done, but I still have not figured out how to hang the basotect in the ceiling. Once I have it in place, I would be ready to do some measurements to get an objective view of the situation.
I have been trying to figure out some nice way to mount the absorbers in the ceiling, but today I just slapped them there using some latex glue. I did a quick test in the garage first, and the glue seems fairly easy to remove, but the basotect still sticks well enough to it. Hope they stay up until the glue has dried.. Seems the sizes of the pieces was not perfect, so I ended up leaving some small gaps to get them to line up.
They are offset to the left side of the room since my listening position is either in the middle or to the left.
Time to listen to some music!
They are offset to the left side of the room since my listening position is either in the middle or to the left.
Time to listen to some music!
Yesterdays listening impression was that the treble 'clarity' was improved from the basotect in the ceiling. I got one comment from the boss last night when she saw yet more absorbers '-You're crazy'. Maybe that means it's time to stop adding absorbers?
Today I ran some sweeps with REW to try to compare to before the treatments, but honestly I can't see any obvious changes, well except the 'clarity' curves that were more even than before.
I'm not really into REW, I prefer ARTA, where I can look at the impulse/step response and understand (well, I hope.. ) what I'm seeing, looking at the impulse window in REW just makes me confused.
Subjectively I'm convinced of improvements. Objectively, I don't know how to verify them properly. For sure the constantly changing DSP-settings I've been doing will also influence the comparisons with old measurements, the microphone and speaker positions etc..
I think I'm going to just leave it that, and conclude it sounds less as a concrete bunker now than before, I'm convinced about that, maybe it's resembling more of a 'normal room'. I have found I prefer the corner position, so that is my 'main listening position' now. Partially for the comfort of sitting there, but with some tuning of the DSP with delays and levels etc, the stereo image is actually pretty good, and the bass is more even.
Today I ran some sweeps with REW to try to compare to before the treatments, but honestly I can't see any obvious changes, well except the 'clarity' curves that were more even than before.
I'm not really into REW, I prefer ARTA, where I can look at the impulse/step response and understand (well, I hope..
) what I'm seeing, looking at the impulse window in REW just makes me confused.Subjectively I'm convinced of improvements. Objectively, I don't know how to verify them properly. For sure the constantly changing DSP-settings I've been doing will also influence the comparisons with old measurements, the microphone and speaker positions etc..
I think I'm going to just leave it that, and conclude it sounds less as a concrete bunker now than before, I'm convinced about that, maybe it's resembling more of a 'normal room'. I have found I prefer the corner position, so that is my 'main listening position' now. Partially for the comfort of sitting there, but with some tuning of the DSP with delays and levels etc, the stereo image is actually pretty good, and the bass is more even.
Dear Rallyfinnen,
I am solving another noise suppression problem, totally unrelated to yours, but stumbled on this thread and... I have a feeling, that you are desperate and solving the problem the exact opposite way you should. I am no expert, but you miss some of the basic principles of "normal living room sound" and do some of the tricks of the studio, but totally miss the others which should be in standard room.
What you want to achieve? A bit of studio sound? A bit of normal room + studio sound? Normal room sound? Normal treated room sound? Just remove concrete wall echoes? There is nothing bad in any of those directions. But if you say the direction - then it will be easier and cheaper, because now you do random stuff. Forget the measurements for the moment.
So:
1. The planning of the room is very bad for music and imho not ergonomic at all. Here is why:
1a. You have a room, which is far from perfect square - a rectangle, and speakers-listening position is on the long ends. You get some of the horn effect, many echoes and so on.
1b. Window on the back of current listening location - nightmare. The back wall from listening position is the one I would try to treat first and maybe the only surface I treat. Massive skyline type diffuser or massive absorber on the back from listening position or nothing, as you sit in pretty big sofa which acts itself as an absorber and bass trap.
1c. The current position is not symmetric, terrace door and its arc on the right is untreatable. You cannot improve or change much accoustics of it.
1d. You have TWO door arcs near speakers: 4 extra corners (we can also count as 8?). This is probably the worst you can have near speakers, as now you get many reflections form the arc surfaces, corners, from another room surfaces and so on
1e. You loose a lot of the first order reflection of sound, as it goes into another rooms. I think around of 20-30% of the direct speaker radiation goes through the doors if I can say in such terms.
1f. Bonus. People go from entrance to bedroom... They definitely obstruct sound. A small thing but still...
1g. Bonus. You cannot listen to the music without bothering others in the bedroom and kitchen...
How to solve everything in "1"? Just move speakers + TV to the right (or left) wall!!! I think sofa can be rotated or you can just sit on the other side of it, right? The only thing you will lose some of the distance between speakers as the doors limit (no such problem on the left wall) but gain a lot.
2. Somebody gave idea about sub under sofa idea - brilliant thing! In my room sofa is in the middle of the room, if I had it near the wall the first thing I build the narrow transmission line sub to put under it. Volume knob will solve all the doubts about it being too loud. As a bonus - if you have sub ~1m from listening position, most likely it will have the phase you need and sound exactly the way you want. It is a half day work with beer bottle in hand to put wires behind skirting boards.
3. I cannot understand the size of the table. Is it big? Massive? Does it obstruct speaker drivers directly? Now it is as an additional surface which needs to be accounted for. I really doubt that it makes positive impact. Smaller table between listening position and speakers - better.
4. You have too little big dimension massive objects in room. I can count just 2: sofa and TV table with stuff in it. Absolutelly a cool thing you did with making sofa more massive and absorbant! No way you will make or want to make artificial sound absorbing panels of this size and weight, so Ikea bookshelf with books and random stuff on the current wall where now speakers are, could act as a diffuser and bass trap. Can be closed with some doors or open - does not matter much. Also for example a big pot (20+ liters, the more the betters) with plant in it could help on the corner near terrace door. If we assume rule of thumb that we need at least 1/4 of the wavelength size objects in corners to deal with reflections, then for 100Hz it is ~85cm, for 200Hz it is ~43cm. Imagine the face of your darling when you put acoustic panel of 40cm thickness on the wall... As a bonus: exacly on the opposite side is window, which also lets some low-mid freq sound out of the room - so you may gain some symmetry.
5. You already are putting some acoustic traps behind the speakers. Remove them! In this configuration it is the ONLY normal wall you have in entire room and you are ruining the reflections from it. In this configuration I would try to put them on the ceiling corners near terrace door and another corner behind listening position.
REW is a nice tool... I measured my own room... It is a nightmare, more than yours, but for different reasons, but I also have many arcs of windows, many corners, also big coffee table and so on. In your case just 1 move could solve the biggest problems, I don't have such opportunity. If you have doubts about my suggestions - you could paint with pencil arrows of "sound" every lets say 30 degrees from speakers with 3-4 reflections. In 3D - with imagination probably. Be honest: reflections form arc corners near sound source and windows not work well.
Wish you success!
I am solving another noise suppression problem, totally unrelated to yours, but stumbled on this thread and... I have a feeling, that you are desperate and solving the problem the exact opposite way you should. I am no expert, but you miss some of the basic principles of "normal living room sound" and do some of the tricks of the studio, but totally miss the others which should be in standard room.
What you want to achieve? A bit of studio sound? A bit of normal room + studio sound? Normal room sound? Normal treated room sound? Just remove concrete wall echoes? There is nothing bad in any of those directions. But if you say the direction - then it will be easier and cheaper, because now you do random stuff. Forget the measurements for the moment.
So:
1. The planning of the room is very bad for music and imho not ergonomic at all. Here is why:
1a. You have a room, which is far from perfect square - a rectangle, and speakers-listening position is on the long ends. You get some of the horn effect, many echoes and so on.
1b. Window on the back of current listening location - nightmare. The back wall from listening position is the one I would try to treat first and maybe the only surface I treat. Massive skyline type diffuser or massive absorber on the back from listening position or nothing, as you sit in pretty big sofa which acts itself as an absorber and bass trap.
1c. The current position is not symmetric, terrace door and its arc on the right is untreatable. You cannot improve or change much accoustics of it.
1d. You have TWO door arcs near speakers: 4 extra corners (we can also count as 8?). This is probably the worst you can have near speakers, as now you get many reflections form the arc surfaces, corners, from another room surfaces and so on
1e. You loose a lot of the first order reflection of sound, as it goes into another rooms. I think around of 20-30% of the direct speaker radiation goes through the doors if I can say in such terms.
1f. Bonus. People go from entrance to bedroom... They definitely obstruct sound. A small thing but still...
1g. Bonus. You cannot listen to the music without bothering others in the bedroom and kitchen...
How to solve everything in "1"? Just move speakers + TV to the right (or left) wall!!! I think sofa can be rotated or you can just sit on the other side of it, right? The only thing you will lose some of the distance between speakers as the doors limit (no such problem on the left wall) but gain a lot.
2. Somebody gave idea about sub under sofa idea - brilliant thing! In my room sofa is in the middle of the room, if I had it near the wall the first thing I build the narrow transmission line sub to put under it. Volume knob will solve all the doubts about it being too loud. As a bonus - if you have sub ~1m from listening position, most likely it will have the phase you need and sound exactly the way you want. It is a half day work with beer bottle in hand to put wires behind skirting boards.
3. I cannot understand the size of the table. Is it big? Massive? Does it obstruct speaker drivers directly? Now it is as an additional surface which needs to be accounted for. I really doubt that it makes positive impact. Smaller table between listening position and speakers - better.
4. You have too little big dimension massive objects in room. I can count just 2: sofa and TV table with stuff in it. Absolutelly a cool thing you did with making sofa more massive and absorbant! No way you will make or want to make artificial sound absorbing panels of this size and weight, so Ikea bookshelf with books and random stuff on the current wall where now speakers are, could act as a diffuser and bass trap. Can be closed with some doors or open - does not matter much. Also for example a big pot (20+ liters, the more the betters) with plant in it could help on the corner near terrace door. If we assume rule of thumb that we need at least 1/4 of the wavelength size objects in corners to deal with reflections, then for 100Hz it is ~85cm, for 200Hz it is ~43cm. Imagine the face of your darling when you put acoustic panel of 40cm thickness on the wall... As a bonus: exacly on the opposite side is window, which also lets some low-mid freq sound out of the room - so you may gain some symmetry.
5. You already are putting some acoustic traps behind the speakers. Remove them! In this configuration it is the ONLY normal wall you have in entire room and you are ruining the reflections from it. In this configuration I would try to put them on the ceiling corners near terrace door and another corner behind listening position.
REW is a nice tool... I measured my own room... It is a nightmare, more than yours, but for different reasons, but I also have many arcs of windows, many corners, also big coffee table and so on. In your case just 1 move could solve the biggest problems, I don't have such opportunity. If you have doubts about my suggestions - you could paint with pencil arrows of "sound" every lets say 30 degrees from speakers with 3-4 reflections. In 3D - with imagination probably. Be honest: reflections form arc corners near sound source and windows not work well.
Wish you success!
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