You can use that absorber and move it around to different positions and see the effect. If you have more than one use them in combinations. Also don't be afraid to listen to the speaker by itself to hear what effect it has on your perception. Listening before measuring can help with your own expectation bias. Is the strong reflection at 3ms really the floor? it is really prominent in the ETC, with another around 5ms. Perception and measurement are not the same, this is where Floyd Toole's two ear's and brain vs an omnidirectional microphone comes in. The mic tells you what is there but not what you hear. Fraunhofer did an experiment to remove the floor reflection completely and no one liked it. A floor is part of how you hear the world from before you can walk.
You might also want to try turning the rear facing woofer around to the front and using it in a .5 arrangement to see what effect that has on the in room measurement and sound to you.
The in room response is kind of flat with a bass boost and high treble dip. A Moving mic measurement is good for tonal balance, using shelving filters spaced an octave apart on the output is a good way of being able to adjust the tilt and hear how the response changes. Just don't get lost changing too many things all at once 🙂
You might also want to try turning the rear facing woofer around to the front and using it in a .5 arrangement to see what effect that has on the in room measurement and sound to you.
The in room response is kind of flat with a bass boost and high treble dip. A Moving mic measurement is good for tonal balance, using shelving filters spaced an octave apart on the output is a good way of being able to adjust the tilt and hear how the response changes. Just don't get lost changing too many things all at once 🙂
Thanks @Bill Brown, @HeadShake, @fluid for the suggestions So I have quite a few things more to try out.. 🙂
And the context of all this is to (hopefully) take this system performance to even better levels. Subjectively I already have been liking most of what I have been hearing (except for that tiny bit of bass problem and the slightly less "refined treble" thing that I had mentioned earlier). Maybe I am splitting hairs try to do this.. but still.. 🙂
I started listening to 2-3 songs with the new system placement today (with the absorber in place as in above pics).. In general, I like it even better than before.. Clarity and "envelopment" have increased further.. I am guessing it is because of the reduced listening distance, causing more direct sound to "wash over me" 😀 The treble perception has also improved ever so slightly.
I need to listen more to make a decision about what improvements have occured to the specific problems that I have been trying to address.
@Bill Brown
My suwoofer dustcap (currently turned to the backside under the main woofer) is 25cm up from the floor. The front facing 15pr400 woofer's dustcap is 70ish cm up from the floor. I can try out a 2.5 way configuration by just turning the suwoofer to the front side and changing the crossover settings as fluid has pointed out above.. Will try it out once I have identified the changes that have happened now.
@HeadShake: I did have a downward tilted response earlier. But I didn't like it on all songs initially.. Now that the settings have changed I will try the tilt again.
And the context of all this is to (hopefully) take this system performance to even better levels. Subjectively I already have been liking most of what I have been hearing (except for that tiny bit of bass problem and the slightly less "refined treble" thing that I had mentioned earlier). Maybe I am splitting hairs try to do this.. but still.. 🙂
I started listening to 2-3 songs with the new system placement today (with the absorber in place as in above pics).. In general, I like it even better than before.. Clarity and "envelopment" have increased further.. I am guessing it is because of the reduced listening distance, causing more direct sound to "wash over me" 😀 The treble perception has also improved ever so slightly.
I need to listen more to make a decision about what improvements have occured to the specific problems that I have been trying to address.
@Bill Brown
My suwoofer dustcap (currently turned to the backside under the main woofer) is 25cm up from the floor. The front facing 15pr400 woofer's dustcap is 70ish cm up from the floor. I can try out a 2.5 way configuration by just turning the suwoofer to the front side and changing the crossover settings as fluid has pointed out above.. Will try it out once I have identified the changes that have happened now.
@HeadShake: I did have a downward tilted response earlier. But I didn't like it on all songs initially.. Now that the settings have changed I will try the tilt again.
You can also re-jig the crossover to make the two woofers have a traditional crossover rather than interfere to create directivity and still leave the woofer facing backwards. Many reports of people liking the Genelec W371A configured like that instead of in directivity mode. Just in case you didn't have enough options 🙂
We must differentiate reflections and room modes. Remember also psychoacoustics
In your Left speaker wavelet Peak energy of bass below 100Hz is roughly 30ms late and 250Hz is pulsating after that, up to 150ms. Fortunately important octave 120-240Hz is pretty clean! Absorber panels did reduce pulsation of 250Hz quite well yes.
So, absorbing panels just at first reflection points won't help much for bass, only upper midrange and treble (which has very short decay because of high directiviy horn anyway)
Different positioning of speakers or seat will just change/distribute reflections and mode effects (peak energy) differently. Only wide area thick absorbers on two walls and ceiling would really help for bass.
Wavelet without absorbers, close-up
For comparison, my room with dipoles has much shorter RT above 200Hz, but still L and R have very different decays/modes in bass which is monopole below 150Hz
- your first reflections arrive mostly at 2,8 and 5,6ms (peaks in impulse envelope)
- below 3-400Hz we sense total sound power within at least 300ms of a sweep (much longer than 5 cycles as you used)
- room modes dominate perception below 3-400Hz , there first reflections have minor effect (except perhaps transients?)
In your Left speaker wavelet Peak energy of bass below 100Hz is roughly 30ms late and 250Hz is pulsating after that, up to 150ms. Fortunately important octave 120-240Hz is pretty clean! Absorber panels did reduce pulsation of 250Hz quite well yes.
So, absorbing panels just at first reflection points won't help much for bass, only upper midrange and treble (which has very short decay because of high directiviy horn anyway)
Different positioning of speakers or seat will just change/distribute reflections and mode effects (peak energy) differently. Only wide area thick absorbers on two walls and ceiling would really help for bass.
Wavelet without absorbers, close-up
For comparison, my room with dipoles has much shorter RT above 200Hz, but still L and R have very different decays/modes in bass which is monopole below 150Hz
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There's evidence in the Fazenda papers I sent you that at low frequencies decay time is more important to perceived quality than frequency response measured in any way.
First you have to consider wavelength and from there how reflections occurs.
Let's take 1khz as example.
343m/1000= 34,3cm.
Wl at 1k is circa 30cm. If you want to reflect/redirect this freq you need an obstacle 3x the size, so circa 1m reflector.
( Aside: this 3 time factor will be used for diffusion too as it is the minimal distance to a diffusor if you want coherent results ( otherwise you are into range where the idyiosyncratic pattern of artificial algorythm used to perform diffusion duty make it still stand out). )
From there it's easy to see that for 500hz you need a 2m reflector, for 250hz a 4m reflector, 125hz an 8m, etc,etc,...
The other point to consider is time: at 1khz a wl is 1ms, at 500hz 2ms, 250hz 4ms, 125hz 8ms,...
The fact is that below 5ms our brain is unable to differenciate things clearly, comb filtering happen ( coloration) but we can't differenciate direct/reflected sound as is.
So the most efficient approach is to try to modify the direct/reflected sound ratio through absorbing. ( shortcut but you got the primary idea).
This is what set a limit for Early Reflection management through redirection/shape of room wrt absorbing. Only large or very large room can manage this trick to frequency down to 500hz (at max 250hz) in practice.
In fact this isn't this much an issue as our auditory system switch from phase to intensity difference to identify directionality circa 1/1,5khz in practice, so using reflector panels of circa 1m is not a bad compromise as Bob Walker shown into his BBC's C.I.D. ( Controlled Image Design) paper.
The range you define 300/400hz, is in the vicinity of Schroeder frequency for a small to medium room. Above Schroeder freq, your loudspeakers characteristics define what happen, below it's your room which define what is happening.
Of course the border is not on/off, there is grey area where modal behaviour still have influence as well as early reflections. The 200/400hz range is like that. In practice it's easier to try to damp what happen trough absorbing in there as it's still possible to have not so bad bulkyness/efficiency ratio by passive means and it can be doubled as first reflection treatments too.
If you want more info about what hapen below Schroeder freq, Earl Geddes work is not a bad read imho.
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Not sure I've seen anyone mention that one is ~1/8-space and one is ~1/4-space, in the middle of all this.
This article may be the first place to start. It is written in support of a multi-sub approach, but the background acoustical theories are worthy of consideration and greatly informed my efforts:
http://www.gedlee.com/Papers/multiple subs.pdf
I'm in the same situation, but I used some latex glue to hang some basotect panels in the roof. I think they should come off without any damage (I did some test with the glue first), but it there is some paint chips the day I move out, I plan to fill them in by hand. I might even leave them in place the day I move out.
Audioholics.com is a very good site and resource for scientific info in popular sense
https://www.audioholics.com/room-acoustics/room-reflections-human-adaptation by Toole
https://www.audioholics.com/room-ac...ions-in-home-theaters-a-different-perspective by Szymanski
AkuTEK is one of leading acoustic design companies
https://www.akutek.info/research_files/small_room_acoustics.htm
Schroeder region is based on 4 times T60 (-60dB attenuation) and room volume, but transition is not sharp. Typically 200-300Hz
https://www.akutek.info/Papers/MS_Schroeder_Revisited.pdf
"A major problem is the fact that the Schroeder Frequency fc=2000·(T/V)*0.5 can not be detected directly by measurements."
https://www.audioholics.com/room-acoustics/room-reflections-human-adaptation by Toole
https://www.audioholics.com/room-ac...ions-in-home-theaters-a-different-perspective by Szymanski
AkuTEK is one of leading acoustic design companies
https://www.akutek.info/research_files/small_room_acoustics.htm
Schroeder region is based on 4 times T60 (-60dB attenuation) and room volume, but transition is not sharp. Typically 200-300Hz
https://www.akutek.info/Papers/MS_Schroeder_Revisited.pdf
"A major problem is the fact that the Schroeder Frequency fc=2000·(T/V)*0.5 can not be detected directly by measurements."
Or double sided tape it works too as basotect isn't this heavy material.
If you can drill on walls it is possible to use rope to hang things too. Like for this spotlight:
https://www.luminaire.fr/p/systeme-...vNDejCsLj6zxy3kTxlLqIjGE_KjQTLXAaAhbkEALw_wcB
I've seen same kind of arrangement used for a 'cloud' in a control room.
In the Netherlands there is akoestiekwinkel and they show a variété of solutions:
https://www.akoestiekwinkel.nl/akoestiek-verbeteren
https://www.akoestiekwinkel.nl/akoestiek-verbeteren
Yes, I bought some basotect with double sided tape already on it too, but the tape was so strong, so it would most likely rip the paint or be very hard to remove. It came off from the basotect pretty easily, but from a painted surface.. not so easy. It seemed the latex 'glue' was easier to remove from the painted ceiling.
I tried using 50mm thick absorption panels (https://www.auralexchange.com/product/nankarrow-geofill-premium-fireproof-acoustic-infill-boards/) at various places in the room, made some measurements, recorded a video clip and got rid of all that from the room before my wife caught me doing this kind of torture to the living room.. 🤣 🤣
Anyway, these absorption material are not targeted towards the low frequencies and are mostly for upper mids and highs from their specifications. I just used it because I had them lying around.. 🙂
Here are some results before and after using the absorption material
That ceiling reflection related area around 900Hz improved ever so slightly I guess.
I found that the close to 3ms secondary peak in above plot comes from the reflection from the sofa to that reaches the mic.
When I pulled out the mic towards the speakers by about 20cm out, it went away as shown in below pic
Spectrogram before "acoustic treatment"
Spectrogram after "acoustic treatment"
EDT & Topt before & after "acoustic treatment"
I recorded the same song before & after doing this (there is a bit of volume not matching issue as I changed the minidsp volume level between the two recordings one taken yesterday and one today). Surprisingly, differences in the vocal range are easily identifiable even in these videos.
Recording before "acoustic treatment"
Recording from after "acoustic treatment"
Subjectively, listening to the same song before and after, I feel that the vocals have relaxed a bit.. It is slightly more easier to notice fine details in the songs.. I feel like this is an improvement in the overall listening experience.. So I feel motivated to do something more about this.. 🙂
I think I need atleast 100mm thick panels a bit more "health-friendly" but more with more absorption capabilities at the back of the sofa put inside some nice acosutically transparent fabric with some pattern/picture like @wesayso has in his room, some behind the TV screen some in the corners, some attached to the ceiling with some double sided tape (hopefully) etc..
Now, how to do all this without making the living room a cave is the next question.. 😀
Anyway, these absorption material are not targeted towards the low frequencies and are mostly for upper mids and highs from their specifications. I just used it because I had them lying around.. 🙂
Here are some results before and after using the absorption material
That ceiling reflection related area around 900Hz improved ever so slightly I guess.
I found that the close to 3ms secondary peak in above plot comes from the reflection from the sofa to that reaches the mic.
When I pulled out the mic towards the speakers by about 20cm out, it went away as shown in below pic
Spectrogram before "acoustic treatment"
Spectrogram after "acoustic treatment"
EDT & Topt before & after "acoustic treatment"
I recorded the same song before & after doing this (there is a bit of volume not matching issue as I changed the minidsp volume level between the two recordings one taken yesterday and one today). Surprisingly, differences in the vocal range are easily identifiable even in these videos.
Recording before "acoustic treatment"
Recording from after "acoustic treatment"
Subjectively, listening to the same song before and after, I feel that the vocals have relaxed a bit.. It is slightly more easier to notice fine details in the songs.. I feel like this is an improvement in the overall listening experience.. So I feel motivated to do something more about this.. 🙂
I think I need atleast 100mm thick panels a bit more "health-friendly" but more with more absorption capabilities at the back of the sofa put inside some nice acosutically transparent fabric with some pattern/picture like @wesayso has in his room, some behind the TV screen some in the corners, some attached to the ceiling with some double sided tape (hopefully) etc..
Now, how to do all this without making the living room a cave is the next question.. 😀
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How does your wife like the decor now? 🙂
maybe a sub hidden behind the couch to even out the bass; a dressed-up absorber on the wall behind the couch, and some room eq to knock the sub-bass down to size, also to make the two channels match each other.
maybe a sub hidden behind the couch to even out the bass; a dressed-up absorber on the wall behind the couch, and some room eq to knock the sub-bass down to size, also to make the two channels match each other.
@nc535: I am testing the limits of her patience now.. : 🤣 🤣
I have those 4x Satori WO24P woofers in their sealed boxes lying around. I am planning to do something with it, like a double bass array or a multi-sub arrangement. 🙂
I am still trying to figure out the double bass array setup after reading Bruno Fazenda's papers (which @fluid had given to me) about controlling decay at low frequencies . Very slowly building up an understanding about it and reading through all those materials about room treatment everyone has posted in above posts..
I have those 4x Satori WO24P woofers in their sealed boxes lying around. I am planning to do something with it, like a double bass array or a multi-sub arrangement. 🙂
I am still trying to figure out the double bass array setup after reading Bruno Fazenda's papers (which @fluid had given to me) about controlling decay at low frequencies . Very slowly building up an understanding about it and reading through all those materials about room treatment everyone has posted in above posts..
I don't think DBA makes sense in your limited space. multi-sub seems a better fit. Dr. Geddes PhD thesis proved with 4 subs, placement hardly matters. He had some kind of frequency by frequency, least mean square error summation algorith that should be right up your alley. There is a multi-sub optimizer you can download and use. I don't know if its his algorithm or independently developed but here is a link:
multi-sub optimizer/
multi-sub optimizer/
I have found that asymmetry in the listening position vs speakers/room can improve the bass too. For example if you move the listening position to one side, re-aim the speakers and adjust delays in the DSP to get the correct time arrival (stereo image) from both channels at LP, bass can even out. Maybe just add a couple of ms delay to one channel and move to one side in the sofa where you get the center image. To do it properly you should adjust levels and FR too, but for a quick test of the bass quality, delay should be enough. Another alternative is to rotate the speakers & listening position triangle vs the room, for example 45deg without touching the DSP. My guess is that with asymmetry, the modes of the room can be excited less, and/or you might sit in a less 'symmetrical' listening position in relation to the modes too.
@vineethkumar01 Have you done simple hand clap test to hear if there is flutter echo? This is likely between your front and back wall, and will definitely help to cut as much as possible. So absorption behind the sofa would already help if there is flutter echo. The samples kinda sound like that, quick listen on laptop internal speakers 😀 If you can do loud hand claps they really trigger flutter echo and it's really easy to hear it.