So now that we've built the satellites (http://www.gedlee.com/Summa.htm) and subs (http://www.mehlau.net/audio/sub_peerless_sls-10/) that form the basis of a modern subwoofer/satellite concept the question is how to place them?
But first I would like to summarize the "why" and "how" of such a concept. If you need references to literature please let me know. A very good start is to read "Loudspeakers and Rooms for Sound Reproduction - A scientific Review" from Floyd E. Toole (JAES, Vol. 54, No. 6).
Reflections
The sound field in a small room like a domestic living room is not as diffuse as e.g. in a concert hall. It consists of several highly directional strong early reflections and a dimished late reflected sound field. These reflections have effects on localization of phantom sources, coloration, spaciousness and intelligibility. There's much literature on how reflections affect acoustic perception in a concert hall but there're virtually no studies on small room acoustics. So think twice before taking the various assumptions flying around as proven facts.
In most domestic rooms reflections are too loud - you hear your room and not the recording. This can be addressed with porous absorption at walls (at least 4" mineral wool mounted with a 4" air gap from wall) or with directional speakers. Furthermore these reflections arrive too early at the listeners position. Diffraction at enclosures or reflections from nearby furniture or walls arriving within 1 ms after the direct sound distract the perception of phantom images.
Furthermore the off-axis frequency response of a speaker can lead to coloration of sound perception if it's not flat.
Room modes
Every room has a unique pattern of modes. A mode results from two or more standing waves interfering with each other. Below about 100 Hz this leads to a "booming" or "one-note-bass" sound. Modes can be addressed with passive absorption which can become pretty expensive; or it's just not applicable at all because it consumes a lot of space that's normally needed by other persons living in your household. But there's also active absorption. A second modal field is actively generated and is overlaying the rooms modal field. This will not fix the bass in the whole room but it can fix the bass over a range of listening positions.
Resulting concept
As absorption is not a real alternative in a living room I've chosen to use directional speakers. When looking at the available concepts the best trade-off is to use a two way speaker with a horn and a large woofer. Only a horn can provide low distortion and constant directivity at the same time. The woofer has to be big to become as directional as possible. The Nathan's 10" woofer isn't the optimum – a 15" woofer like in the JBL 4430 is preferable.
The whole system is completed by 3 subwoofers that deliver the active absorption and low frequencies. The subwoofer signal is generated using a Behringer DCX2496. Every sub signal can be freely configured (gain, delay, HP, LP and EQ).
This is what my living room and the speaker setup looks like:
This setup has one big flaw: I'm sitting directly in front of the back wall which disrupts localization heavily. Hopefully a porous absorber will help.
Earl, feel free to add comments and additional information describing the process on how to integrate the subs.
Best, Markus
But first I would like to summarize the "why" and "how" of such a concept. If you need references to literature please let me know. A very good start is to read "Loudspeakers and Rooms for Sound Reproduction - A scientific Review" from Floyd E. Toole (JAES, Vol. 54, No. 6).
Reflections
The sound field in a small room like a domestic living room is not as diffuse as e.g. in a concert hall. It consists of several highly directional strong early reflections and a dimished late reflected sound field. These reflections have effects on localization of phantom sources, coloration, spaciousness and intelligibility. There's much literature on how reflections affect acoustic perception in a concert hall but there're virtually no studies on small room acoustics. So think twice before taking the various assumptions flying around as proven facts.
In most domestic rooms reflections are too loud - you hear your room and not the recording. This can be addressed with porous absorption at walls (at least 4" mineral wool mounted with a 4" air gap from wall) or with directional speakers. Furthermore these reflections arrive too early at the listeners position. Diffraction at enclosures or reflections from nearby furniture or walls arriving within 1 ms after the direct sound distract the perception of phantom images.
Furthermore the off-axis frequency response of a speaker can lead to coloration of sound perception if it's not flat.
Room modes
Every room has a unique pattern of modes. A mode results from two or more standing waves interfering with each other. Below about 100 Hz this leads to a "booming" or "one-note-bass" sound. Modes can be addressed with passive absorption which can become pretty expensive; or it's just not applicable at all because it consumes a lot of space that's normally needed by other persons living in your household. But there's also active absorption. A second modal field is actively generated and is overlaying the rooms modal field. This will not fix the bass in the whole room but it can fix the bass over a range of listening positions.
Resulting concept
As absorption is not a real alternative in a living room I've chosen to use directional speakers. When looking at the available concepts the best trade-off is to use a two way speaker with a horn and a large woofer. Only a horn can provide low distortion and constant directivity at the same time. The woofer has to be big to become as directional as possible. The Nathan's 10" woofer isn't the optimum – a 15" woofer like in the JBL 4430 is preferable.
The whole system is completed by 3 subwoofers that deliver the active absorption and low frequencies. The subwoofer signal is generated using a Behringer DCX2496. Every sub signal can be freely configured (gain, delay, HP, LP and EQ).
This is what my living room and the speaker setup looks like:
An externally hosted image should be here but it was not working when we last tested it.
This setup has one big flaw: I'm sitting directly in front of the back wall which disrupts localization heavily. Hopefully a porous absorber will help.
Earl, feel free to add comments and additional information describing the process on how to integrate the subs.
Best, Markus
Room size is 591 x 363 x 304 cm (width x length x height)
The pass-through to the kitchen:
The pass-through to the kitchen:
An externally hosted image should be here but it was not working when we last tested it.
Markus
Excellent start.
There isn't much that I can say about the setup, I can see that you options are quite limited. Sitting against the back wall is a very seriuos issue, but I don't see that you have many options. I might try using the legth of the room for the listening dimension, but with the furniture that you have shown this would be difficult. At some point you might want to try the longer dimension and see if it makes a big enough difference to make it considered as an option. Seems like you could move things arround temporarily just to give it a try.
The main thing that you have to do now is to balance the subs with the room and the mains. I'll describe how I do this.
The LF sound field in a small room has tro be considered as a steady state situation - there is no direct field in the time sense as the signals have arrived from multiple directions even before a few cycles of the LF signal have occured. The ear is simply going to react to this by considering this a steady state situation. Now in the steady state we have to deal with the random problem of sound measurements to get at the mean value of this steady state sound field. This is best done, or has to be done, by spatial averaging.
So first setup the mains and the nearest sub. Set your spectrum analyzer to a very low bandwidth but not less than 200 Hz. and fairly long averaging time. This will yield a very long average of the sound signal. Take your mic and move it through large spatial positions near but arround the prefered listening position. Be carefull as small bumps of the cable can generate large eroneous signals into the mic. The sweeping has to be smooth. When the analyzer has completed its run you will have a plot of the frequency and spatial averaged LF sound field. Try adjusting the sub - never adjust the mains - to see if you can get a better response by changing the gain, the low pass point, the phase and or delay if you have it. The bass should be sagging slightly at this point since you will be adding in two more subs.
Now add in the next closest sub and repeat the entire procedure again. You should be able to improve upon what you had before. If not try turning off the first sub and setting the second one optimal and then add in the first sub. If you still can't get a better response with two subs than with one then you will need to move one of them. You need to get an improvement from the second sub or something is wrong.
Now repeat this process with the third sub. The third sub, when you are close to it should barely be audible. It it is loud, then once again, something is wrong. It should only be filling in holes at this point and not adding any actual level. The level after two subs should be about flat or possibly a slight rise - based on preference. I find a few dB rise at the low end is desirable for best effect.
With the three subs things should be quite smooth when spatially averaged. You can now use any EQ that you have to make a final flattening of the response, but these bands should never be more than a few dB. When you are done, if things go as they usually do for me, your should have a spatial average of about +- 2-3 dB. This can take several hours so don't be impatient. But once you have it you will never change it. Make sure and write down all the settings!!
Two people helps - one to sweep the mic and another to run the analyzer. Sweep the mike vertically as well as horizontally, but in a wide ellipse. Its not necessary to repeat the same pattern, its only necessary to NOT leave the mic in a stationary position. You can try wider sweeps or narrower ones, but the bigger sweep will likely be better.
Hope this helps. Good luck.
Excellent start.
There isn't much that I can say about the setup, I can see that you options are quite limited. Sitting against the back wall is a very seriuos issue, but I don't see that you have many options. I might try using the legth of the room for the listening dimension, but with the furniture that you have shown this would be difficult. At some point you might want to try the longer dimension and see if it makes a big enough difference to make it considered as an option. Seems like you could move things arround temporarily just to give it a try.
The main thing that you have to do now is to balance the subs with the room and the mains. I'll describe how I do this.
The LF sound field in a small room has tro be considered as a steady state situation - there is no direct field in the time sense as the signals have arrived from multiple directions even before a few cycles of the LF signal have occured. The ear is simply going to react to this by considering this a steady state situation. Now in the steady state we have to deal with the random problem of sound measurements to get at the mean value of this steady state sound field. This is best done, or has to be done, by spatial averaging.
So first setup the mains and the nearest sub. Set your spectrum analyzer to a very low bandwidth but not less than 200 Hz. and fairly long averaging time. This will yield a very long average of the sound signal. Take your mic and move it through large spatial positions near but arround the prefered listening position. Be carefull as small bumps of the cable can generate large eroneous signals into the mic. The sweeping has to be smooth. When the analyzer has completed its run you will have a plot of the frequency and spatial averaged LF sound field. Try adjusting the sub - never adjust the mains - to see if you can get a better response by changing the gain, the low pass point, the phase and or delay if you have it. The bass should be sagging slightly at this point since you will be adding in two more subs.
Now add in the next closest sub and repeat the entire procedure again. You should be able to improve upon what you had before. If not try turning off the first sub and setting the second one optimal and then add in the first sub. If you still can't get a better response with two subs than with one then you will need to move one of them. You need to get an improvement from the second sub or something is wrong.
Now repeat this process with the third sub. The third sub, when you are close to it should barely be audible. It it is loud, then once again, something is wrong. It should only be filling in holes at this point and not adding any actual level. The level after two subs should be about flat or possibly a slight rise - based on preference. I find a few dB rise at the low end is desirable for best effect.
With the three subs things should be quite smooth when spatially averaged. You can now use any EQ that you have to make a final flattening of the response, but these bands should never be more than a few dB. When you are done, if things go as they usually do for me, your should have a spatial average of about +- 2-3 dB. This can take several hours so don't be impatient. But once you have it you will never change it. Make sure and write down all the settings!!
Two people helps - one to sweep the mic and another to run the analyzer. Sweep the mike vertically as well as horizontally, but in a wide ellipse. Its not necessary to repeat the same pattern, its only necessary to NOT leave the mic in a stationary position. You can try wider sweeps or narrower ones, but the bigger sweep will likely be better.
Hope this helps. Good luck.
hi markus
dunno if you have the latitude or authority from those that must be obeyed to play around with the room layout speakerwise, but I have very recently given the principle outlined in the link and found it to be of great benefit to my setup
http://www.decware.com/paper14.htm
there were associated issues with it, namely a loss of bass extension (I presume because both the speakers and chair are now 'in free space') which I'm now in the process of fixing by (strangely enough) adding distributed subs, exactly as you have outlined here. In fact I started a thread on it, didn't realise we were kinda asking the same stuff!
Which segues nicely into Earles response before. Earle, do you mind if I copy your response into my thread?? It is relevant and the kind of data I was after amongst other stuff. I'd like to ask a few questions and may do it there if you're fine on copying your post to the thread, else I'll ask here, no big deal.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=130472
I know I have mentioned this (the topic in my thread) before and I remember you kinda disputing my premise a bit. I have since starting the thread done a bit more fiddling, and what I have found is that I am coming around to your point of view.
I need to repeat that fiddling but this time without a few beers under my belt, (just to confirm) so will do that in the next few days and admit my mistake in the thread heh heh. anyway, your post was exactly what I was after so would like to put it there if you agree.
dunno if you have the latitude or authority from those that must be obeyed to play around with the room layout speakerwise, but I have very recently given the principle outlined in the link and found it to be of great benefit to my setup
http://www.decware.com/paper14.htm
there were associated issues with it, namely a loss of bass extension (I presume because both the speakers and chair are now 'in free space') which I'm now in the process of fixing by (strangely enough) adding distributed subs, exactly as you have outlined here. In fact I started a thread on it, didn't realise we were kinda asking the same stuff!
Which segues nicely into Earles response before. Earle, do you mind if I copy your response into my thread?? It is relevant and the kind of data I was after amongst other stuff. I'd like to ask a few questions and may do it there if you're fine on copying your post to the thread, else I'll ask here, no big deal.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=130472
I know I have mentioned this (the topic in my thread) before and I remember you kinda disputing my premise a bit. I have since starting the thread done a bit more fiddling, and what I have found is that I am coming around to your point of view.
I need to repeat that fiddling but this time without a few beers under my belt, (just to confirm) so will do that in the next few days and admit my mistake in the thread heh heh. anyway, your post was exactly what I was after so would like to put it there if you agree.
As far as I understand Steve Deckert tries to "group" the reflections of one speaker on walls near that speaker. But when I look at this picture that might be true for the left speaker but where would be the reflections of the right speaker?
An externally hosted image should be here but it was not working when we last tested it.
Best, Markus
Take some measurements while you're at it?
Hopefully you are not a total subjectivist and are willing to take some measurements during your set up and evaluation phase.
If you don't have anything already, I suggest you try Room Equalizer Wizard (REW).
http://www.hometheatershack.com/roomeq/
It's a powerful feeware program for checking out your room's response. Hometheatershack's website is a strong proponent of this program. There's tons of posts there about using it.
http://www.hometheatershack.com/forums/rew-forum/
Just trying to help....
Hopefully you are not a total subjectivist and are willing to take some measurements during your set up and evaluation phase.
If you don't have anything already, I suggest you try Room Equalizer Wizard (REW).
http://www.hometheatershack.com/roomeq/
It's a powerful feeware program for checking out your room's response. Hometheatershack's website is a strong proponent of this program. There's tons of posts there about using it.
http://www.hometheatershack.com/forums/rew-forum/
Just trying to help....I'm using FuzzMeasure
But for this special setup I'm looking for a high resolution RTA. Mac preferred – if you have any suggestions please let me know.
Best, Markus
But for this special setup I'm looking for a high resolution RTA. Mac preferred – if you have any suggestions please let me know.
Best, Markus
I also have a couch up against the back wall, and I have found that putting a large thick pillow on top of the back of the couch directly behind my head helps a lot. I have also done measurements that confirm this. You might want to try it.
A coffee table might be beneficial to the acoustic if it is placed right. It can stop the first reflection from the floor and reflections from the table might be at an angle that don't reach the listener.
A coffee table might be beneficial to the acoustic if it is placed right. It can stop the first reflection from the floor and reflections from the table might be at an angle that don't reach the listener.
reflections and such
Looks to me like Deckert's trying to hand-wave how he makes all the reflections he's showing coincide with the speaker they originated from, hence somehow minimizing "crosstalk" with this setup.
My line array dipoles image exceptionally well; I've found the source material to have a major impact on the quality and stability of the projected image in the room. Something impossible to fix if I want to listen to an artist recorded under pathetic conditions.
I wonder if anyone's working on an algorithm to somehow recover spatial cues and such from poorly recorded venues, or even if it can be done. Seems with all the artificial intelligence and information retrieval technology around, someone might be able to "reconstruct" the original sound from poor recordings.
Seeing as this "paper" is dated 2000, and we've heard little about it since then, one wonders how successful it really is. Deckert is nothing if not the epitome of self-professed hyperbole. His "articles" read like the worst of Stereopile, TAS, etc. wrt useless babble and excessive subjective "statement of opinions as facts" with little if any measurement or theory for justification.
As far as bass, using multiple subs has worked best for me for over 10 years now. With some measurements and experimentation, I've maintained excellent smooth bass response for more than a decade.
John L.
Looks to me like Deckert's trying to hand-wave how he makes all the reflections he's showing coincide with the speaker they originated from, hence somehow minimizing "crosstalk" with this setup.
My line array dipoles image exceptionally well; I've found the source material to have a major impact on the quality and stability of the projected image in the room. Something impossible to fix if I want to listen to an artist recorded under pathetic conditions.
I wonder if anyone's working on an algorithm to somehow recover spatial cues and such from poorly recorded venues, or even if it can be done. Seems with all the artificial intelligence and information retrieval technology around, someone might be able to "reconstruct" the original sound from poor recordings.
Seeing as this "paper" is dated 2000, and we've heard little about it since then, one wonders how successful it really is. Deckert is nothing if not the epitome of self-professed hyperbole. His "articles" read like the worst of Stereopile, TAS, etc. wrt useless babble and excessive subjective "statement of opinions as facts" with little if any measurement or theory for justification.
As far as bass, using multiple subs has worked best for me for over 10 years now. With some measurements and experimentation, I've maintained excellent smooth bass response for more than a decade.
John L.
re the deckert 'paper' all I can say is I like the results....for me and my system and my room.
Dunno about the right hand speaker..maybe draw out your own reflections and have a look-see.
Why do I like it? hey, it's a free try ain't it? Don't like it? whoa, put it back the way it was. no biggie.
all I saw in the earlier posts was 'I'm backed up solid against a wall and I know that's not good, and woe is me I simply cannot do anything about it as I'm a slave to my room'.
Heck, here is something to try for free.
your choice, take it or leave it.
(it won't affect me I got no horses in this race)
Dunno about the right hand speaker..maybe draw out your own reflections and have a look-see.
Why do I like it? hey, it's a free try ain't it? Don't like it? whoa, put it back the way it was. no biggie.
all I saw in the earlier posts was 'I'm backed up solid against a wall and I know that's not good, and woe is me I simply cannot do anything about it as I'm a slave to my room'.
Heck, here is something to try for free.
your choice, take it or leave it.
(it won't affect me
I got no horses in this race)markus76 said:I'm using FuzzMeasure
But for this special setup I'm looking for a high resolution RTA. Mac preferred – if you have any suggestions please let me know.
Best, Markus
I'm not sure how hi-res REW is but there are downloadable versions for Mac OS X zipped and Linux. Scroll down at the REW home page (my first link earlier).
I don't care if someone copies my comments to another post. but I wil probably only response within this one.
As to mapping reflections in a room, this is often seriously misleading because the loudspeakers polar response HAS to be taken into consideration. Then one has to de-weight the reflections with their number as they diminish in amplitude and tend to get difused in time and space - i.e. more incoherent.
So to me the better approach is to track only the first two reflection from within the +-6 dB points of the speakers directivity. Beyond two, I generally don't care, but the first two are critical: 1) they must not be to the same ear as the direct signal, 2) they should arrive as late as possible. For example, a speaker whose polar radiation "see's" the nearest side wall will violate both of the simple rules above. A directional source pointed away from its nearest wall towards the opposite one will obey both of these simple rules. A non-directional loudspeaker simply cannot be placed such that it is not sending sound off of the near wall.
As to mapping reflections in a room, this is often seriously misleading because the loudspeakers polar response HAS to be taken into consideration. Then one has to de-weight the reflections with their number as they diminish in amplitude and tend to get difused in time and space - i.e. more incoherent.
So to me the better approach is to track only the first two reflection from within the +-6 dB points of the speakers directivity. Beyond two, I generally don't care, but the first two are critical: 1) they must not be to the same ear as the direct signal, 2) they should arrive as late as possible. For example, a speaker whose polar radiation "see's" the nearest side wall will violate both of the simple rules above. A directional source pointed away from its nearest wall towards the opposite one will obey both of these simple rules. A non-directional loudspeaker simply cannot be placed such that it is not sending sound off of the near wall.
If you are using the DCX2496 you might want to look at doing the input/output buffer mod.
I have a DEQ2496 and the analogue in/out is far from audiophile, especially what it does to the bass. I only use mine with the digital in/out and leave the digital/analogue conversion to a separate DAC.
There is heaps of info in this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=15943&highlight=
col.
I have a DEQ2496 and the analogue in/out is far from audiophile, especially what it does to the bass. I only use mine with the digital in/out and leave the digital/analogue conversion to a separate DAC.
There is heaps of info in this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=15943&highlight=
col.
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