Gearslutz.com - View Single Post - Above the Schroeder Frequency. Diffraction.

SAC · 11th February 2010

Lupo, it is easy to verbally jump from analyzing a response (i.e. identifying individual reflections and their attributes) - of which one stated that the frequency response and RT60s should be sufficient for analysis and refused to generate ETCs!

- to treating a room! Of course, others have complained that the ETCs do not cure room modes. A case of using the right tool for the job. And the process has been curtailed in large measure as some individuals have either been unable to generate the ETCs, or unwilling to pursue the methods of evaluating the individual reflections. One has. But to my knowledge, I am not sure what options they have decided to pursue in addressing identified issues.

But in any regards, identifying individual reflection behavior and subsequent 'room tuning' are TWO different processes! Related? Sure! But not necessarily the same. Just as taking the temperature and performing open heart surgery are related, but simply having a tool does not imply that one can simply demand "the answer" and perform the other. One is a step in the process of learning more in order to do the other.

And its been like pulling teeth to simply get many to become aware of the ETC and that it is useful. And also that it implies a VERY different point of view on the world of acoustics from what many have ALWAYS been accustomed! We are no longer in the Flatland of the frequency response.

And this has been a recurrent problem here!

We are dealing with what is necessarily a process, not some static one size fits all solution that you simply order in red or blue. And while part of that process may involve discussing and referring to General models, but it also necessarily involves evaluating each space individually to see how each particular space behaves relative to the generalization. And from this, one may determine the best set of options to achieve a desired end.

The thinking process must change.

Once an ETC is generated, the interest in doing the mundane trivial work of evaluating each reflection (which, granted is not glamorous!) is quickly abandoned and the demands quickly change to - well, you didn't tell them exactly how to treat their room - as in "what is THE answer" - so the measurement and process are quickly determined to be invalid.

Identifying and addressing early reflections that result from enclosure or speaker shelf mount diffraction is 'easy'. But so is the mantra of "MORE ABSORPTION" which has become an automatic conditioned response here, although it presents a potentially conflicting scenario that is not necessarily optimal. A more tempered response is in order.

And for those who will jump in to say they don't want or need more - hey, then by all means go about your business and don't bother those who do. Aside from simply making others aware that more is possible if they so desire it, the two 'approaches' need not conflict or bother each other at all.

What has not been adequately addressed are the acoustical room models. The templates used as guides for 'tuning' the room. These serve as blueprints for the response. And in one sense, they can be very complex if one is going to understand all of the psycho-acoustical and acoustical underpinnings of the concept; yet they can be quite simple IF you are using the ETC to match the responses to the template. But lest anyone misunderstand - it is 'easy' partly if one understands or has experience as to how to effect response changes such that the ETC response actually achieves the changes necessary - which almost begs the original question!

To relate...I can pretty much look at the TC and tell you what needs to be done and to suggest specific treatments without seeing the room. Now, there will probably be few variations in that the particular reflection indicated might be switched between say, ceiling and floor and side walls - depending upon the orientation of the room (realizing few have any idea of that to which I refer - if the room is very wide, the floor ceiling reflections may appear first, while if the room is very narrow, the side wall reflections may appear first...)

I can do this as I have a template - a particular room response to which I am using as a goal.

Many here do not. And that is a problem in several ways. If one is not prepared to complete the project and to do what is required, you can fix a few anomalies that affect imaging and intelligibility, etc., but you will not have the fully tuned room that you might desire. But that might be enough.

I personally prefer the LEDE/RFZ concept as developed by Don Davis, Chips Davis, Russ Berger, Bob Todrank, P. D'Antonio and so many others - as a few already know who have referenced the resources. And one will note that the specifics are NOT what many find in the MANY erroneous and nonsensical write-ups regarding the model on the web - and of which many here have categorically stated is a flawed and dead model that began and died some 35 years ago!!! But that to which I refer is a refined model that is VERY much current and WIDELY used and assumed by many of he top professionals, including the names mentioned. Additionally, there are variants and options for particular applications!

But the details of this extend far beyond the scope of a thread where the intent was simply to get folks to understand the where and hows of the base ETC tool. And an understanding of the ETC tool is a pre-requisite to looking at this, as that is the 'language' that will be used.

Additionally, to fully treat the room in the manner many demand, may require quite a bit of time and effort, as is illustrated in your fine efforts with respect to diffusion. And then it will require a bit more followup to define additional factors such as an optimal and well defined ISD gap, and this MAY (read PROBABLY - in a very small space) include the use a technique called a Haas kicker, as you cannot go to a catalog and simply order one! And then there will be the necessity to employ techniques to increase the density of the later arriving diffuse sound field.

So, without wandering too far afield, it is important to note that one cannot simply "tell someone how to treat their room", as it requires a base understanding of the goal, the trade-offs and their effects, and what is involved before one simply thinks that tuning their room involves just moving an absorptive panel from one spot to another.

But that being said, the tool can be used quite effectively to address specific anomalies that DO impact the practical and real response to a positive end in almost any space by addressing basic fundamental issues - perhaps most common being he effects of early reflections from the speaker mounting, and work surfaces as so many seem to want to place their monitors directly on the desk. (With a bit of luck and arm twisting, maybe we can change this to encourage a more beneficial arrangement.)

But the larger point is, that each room will have its own idiosyncrasies based upon the gear and the arrangement of it in the room. Thus the point of learning HOW to use the ETC to identify the specific sources of issues in each room.

Standard general rules are great, but they do not resolve the specifics of your room. So it will require a bit of detective work to identify the real issues in YOUR room. So one cannot get hung up with the necessary dichotomy between general guidelines and the specifics of their room.

And another topic which will quickly become an issue - which I have tried to avoid here as long as possible, is the use of massive porous bass traps. There is a very real possibility that you will quickly reach point of conflicting purposes with very real conflicts. By this I mean, that in the desire to address modal issues, it is very easy to absorb the critical and easily absorbed energy above the critical frequency - where modes are no longer and issue and where we deal with specular reflections.

This is a PROBLEM with massive porous absorbers. In the process of dealing with one problem, they create another which many have been content to simply ignore.

There are some workarounds - of various complexity. And thus far the majority of those posting here been quite adamant in their frustration with having others provide a SPECIFIC solution to their inability to determine practical alternatives to THEIR specific situation. This mindset must change.

As is noted in many respected sources, this issue is almost a non-starter in many environments. But it will result in some becoming very upset here - for a fascinating array of reasons.

So, to wrap this up, what will be required is a more holistic approach to the system. If one is going to be preoccupied with simply one aspect then they need to be aware of this up front and avoid the issue, as the resulting debates as to whether one should eat or breath is probably not a fruitful one. Both are possible and beneficial. But they may require bit of an adjustment in comfortable preconceptions in order to accommodate a more balanced treatment of the room response.

----------------------------------------

(Addendum. Another prerequisite topic of several that needs to be addressed at some point that is often ignored or treated as a separate unrelated subject are the monitors!!!! Little regard is taken for their Q/dispersion pattern - which is a MAJOR cause of room problems. While i will not address it fully here, the speakers response cannot be made independent of the environment in which it will be used without potentially disastrous consequences!

Already we have many threads simply addressing SBIR issue with speakers designed for anechoic free field response that are utterly inappropriate for surface and surface wall mounting! And this does not even begin to address the dispersive qualities of the speakers and how they directly impact the reflections in a small space! And much of this is the fault of speaker manufacturers who are clueless - or more often - lazy who are too busy pushing meaningless free field anechoic frequency response curves than they are in designing speakers for tailored application environments! but the other responsibility is for end users to become more cognizant of the REAL actors and of their own intended environment and make better choices, rather than simply buying so 'hot' band name and then complaining that they work poorly in their room where the problem is in effect one of their own making due to the poor choice of tools... The moral: It is easier to avoid problems from inception through good choices than it is to remediate them reactively.)

11th February 2010	#225
SAC Registered User Joined: Dec 2009 Posts: 2,622	Lupo, it is easy to verbally jump from analyzing a response (i.e. identifying individual reflections and their attributes) - of which one stated that the frequency response and RT60s should be sufficient for analysis and refused to generate ETCs! - to treating a room! Of course, others have complained that the ETCs do not cure room modes. A case of using the right tool for the job. And the process has been curtailed in large measure as some individuals have either been unable to generate the ETCs, or unwilling to pursue the methods of evaluating the individual reflections. One has. But to my knowledge, I am not sure what options they have decided to pursue in addressing identified issues. But in any regards, identifying individual reflection behavior and subsequent 'room tuning' are TWO different processes! Related? Sure! But not necessarily the same. Just as taking the temperature and performing open heart surgery are related, but simply having a tool does not imply that one can simply demand "the answer" and perform the other. One is a step in the process of learning more in order to do the other. And its been like pulling teeth to simply get many to become aware of the ETC and that it is useful. And also that it implies a VERY different point of view on the world of acoustics from what many have ALWAYS been accustomed! We are no longer in the Flatland of the frequency response. And this has been a recurrent problem here! We are dealing with what is necessarily a process, not some static one size fits all solution that you simply order in red or blue. And while part of that process may involve discussing and referring to General models, but it also necessarily involves evaluating each space individually to see how each particular space behaves relative to the generalization. And from this, one may determine the best set of options to achieve a desired end. The thinking process must change. Once an ETC is generated, the interest in doing the mundane trivial work of evaluating each reflection (which, granted is not glamorous!) is quickly abandoned and the demands quickly change to - well, you didn't tell them exactly how to treat their room - as in "what is THE answer" - so the measurement and process are quickly determined to be invalid. Identifying and addressing early reflections that result from enclosure or speaker shelf mount diffraction is 'easy'. But so is the mantra of "MORE ABSORPTION" which has become an automatic conditioned response here, although it presents a potentially conflicting scenario that is not necessarily optimal. A more tempered response is in order. And for those who will jump in to say they don't want or need more - hey, then by all means go about your business and don't bother those who do. Aside from simply making others aware that more is possible if they so desire it, the two 'approaches' need not conflict or bother each other at all. What has not been adequately addressed are the acoustical room models. The templates used as guides for 'tuning' the room. These serve as blueprints for the response. And in one sense, they can be very complex if one is going to understand all of the psycho-acoustical and acoustical underpinnings of the concept; yet they can be quite simple IF you are using the ETC to match the responses to the template. But lest anyone misunderstand - it is 'easy' partly if one understands or has experience as to how to effect response changes such that the ETC response actually achieves the changes necessary - which almost begs the original question! To relate...I can pretty much look at the TC and tell you what needs to be done and to suggest specific treatments without seeing the room. Now, there will probably be few variations in that the particular reflection indicated might be switched between say, ceiling and floor and side walls - depending upon the orientation of the room (realizing few have any idea of that to which I refer - if the room is very wide, the floor ceiling reflections may appear first, while if the room is very narrow, the side wall reflections may appear first...) I can do this as I have a template - a particular room response to which I am using as a goal. Many here do not. And that is a problem in several ways. If one is not prepared to complete the project and to do what is required, you can fix a few anomalies that affect imaging and intelligibility, etc., but you will not have the fully tuned room that you might desire. But that might be enough. I personally prefer the LEDE/RFZ concept as developed by Don Davis, Chips Davis, Russ Berger, Bob Todrank, P. D'Antonio and so many others - as a few already know who have referenced the resources. And one will note that the specifics are NOT what many find in the MANY erroneous and nonsensical write-ups regarding the model on the web - and of which many here have categorically stated is a flawed and dead model that began and died some 35 years ago!!! But that to which I refer is a refined model that is VERY much current and WIDELY used and assumed by many of he top professionals, including the names mentioned. Additionally, there are variants and options for particular applications! But the details of this extend far beyond the scope of a thread where the intent was simply to get folks to understand the where and hows of the base ETC tool. And an understanding of the ETC tool is a pre-requisite to looking at this, as that is the 'language' that will be used. Additionally, to fully treat the room in the manner many demand, may require quite a bit of time and effort, as is illustrated in your fine efforts with respect to diffusion. And then it will require a bit more followup to define additional factors such as an optimal and well defined ISD gap, and this MAY (read PROBABLY - in a very small space) include the use a technique called a Haas kicker, as you cannot go to a catalog and simply order one! And then there will be the necessity to employ techniques to increase the density of the later arriving diffuse sound field. So, without wandering too far afield, it is important to note that one cannot simply "tell someone how to treat their room", as it requires a base understanding of the goal, the trade-offs and their effects, and what is involved before one simply thinks that tuning their room involves just moving an absorptive panel from one spot to another. But that being said, the tool can be used quite effectively to address specific anomalies that DO impact the practical and real response to a positive end in almost any space by addressing basic fundamental issues - perhaps most common being he effects of early reflections from the speaker mounting, and work surfaces as so many seem to want to place their monitors directly on the desk. (With a bit of luck and arm twisting, maybe we can change this to encourage a more beneficial arrangement.) But the larger point is, that each room will have its own idiosyncrasies based upon the gear and the arrangement of it in the room. Thus the point of learning HOW to use the ETC to identify the specific sources of issues in each room. Standard general rules are great, but they do not resolve the specifics of your room. So it will require a bit of detective work to identify the real issues in YOUR room. So one cannot get hung up with the necessary dichotomy between general guidelines and the specifics of their room. And another topic which will quickly become an issue - which I have tried to avoid here as long as possible, is the use of massive porous bass traps. There is a very real possibility that you will quickly reach point of conflicting purposes with very real conflicts. By this I mean, that in the desire to address modal issues, it is very easy to absorb the critical and easily absorbed energy above the critical frequency - where modes are no longer and issue and where we deal with specular reflections. This is a PROBLEM with massive porous absorbers. In the process of dealing with one problem, they create another which many have been content to simply ignore. There are some workarounds - of various complexity. And thus far the majority of those posting here been quite adamant in their frustration with having others provide a SPECIFIC solution to their inability to determine practical alternatives to THEIR specific situation. This mindset must change. As is noted in many respected sources, this issue is almost a non-starter in many environments. But it will result in some becoming very upset here - for a fascinating array of reasons. So, to wrap this up, what will be required is a more holistic approach to the system. If one is going to be preoccupied with simply one aspect then they need to be aware of this up front and avoid the issue, as the resulting debates as to whether one should eat or breath is probably not a fruitful one. Both are possible and beneficial. But they may require bit of an adjustment in comfortable preconceptions in order to accommodate a more balanced treatment of the room response. ---------------------------------------- (Addendum. Another prerequisite topic of several that needs to be addressed at some point that is often ignored or treated as a separate unrelated subject are the monitors!!!! Little regard is taken for their Q/dispersion pattern - which is a MAJOR cause of room problems. While i will not address it fully here, the speakers response cannot be made independent of the environment in which it will be used without potentially disastrous consequences! Already we have many threads simply addressing SBIR issue with speakers designed for anechoic free field response that are utterly inappropriate for surface and surface wall mounting! And this does not even begin to address the dispersive qualities of the speakers and how they directly impact the reflections in a small space! And much of this is the fault of speaker manufacturers who are clueless - or more often - lazy who are too busy pushing meaningless free field anechoic frequency response curves than they are in designing speakers for tailored application environments! but the other responsibility is for end users to become more cognizant of the REAL actors and of their own intended environment and make better choices, rather than simply buying so 'hot' band name and then complaining that they work poorly in their room where the problem is in effect one of their own making due to the poor choice of tools... The moral: It is easier to avoid problems from inception through good choices than it is to remediate them reactively.)