Originally Posted by omholt
I mentioned at a another forum that Toole (or probably his followers to be accurate) has basically brought confusion. I believe this thread shows that exactly. But here the problem also lies in misinterpration of what Toole actually has conveyed.
I appreciate you chiming in. I really do
. But don't you think part of the confusion comes from the fact the people constantly try to parse his few words online rather than spending a few minutes with him in person? If anyone has, you will see that the views that I have expressed on his behalf are expressed even more strongly. Further, it is not just him. But a number of researchers who have worked with him. The first time I actually heard about the beneficial aspects of reflections didn't come from him but Alan Devantier. During this thread, I have quoted research by many other experts pointing to the same view.
Have you read his 17 page AES paper on reflections? Have you read both revisions and how they are both the same view even though it is distanced by many years and more updates in research? You see a consistent view in this area. Here is the summary of the section that deals with speech and reflections:
” 5 EFFECTS OF REFLECTIONS—A SUMMARY
Readers who have been keeping score will have noted a distinct absence of negative effects from reflections on any aspect of speech perception we have looked at. In fact, the effects range from neutral to positive. No single reflection has been shown to be a problem for speech reproduction in small rooms (see Table 1).
Multiple early reflections contribute even more to intelligibility.” Here is the table he shows:
The reason people are confused about his views is that they have not read sum total of what he has written and importantly all the research he cites from his team and others. If you read all of that, and spend time with him in person, you see that a strong point of view that emerges. One that is anything but confusing. It is logical from start to finish. It has a beginning and an end. This is what I really like about his teachings. It is not a random chapter that says, "run this tool and then you decide what to do next." He shows conviction in his point of view. He might be wrong but it takes a hell of a lot to prove it than folks show
Something worth mentioning when it comes to the so called favored Toole side-reflections are the following:
- It requires speakers with excellent polar respons. Most don't have that.
We have covered this point before. Why do you think it is better to keep them and spend hundreds of dollars/time and energy on acosutic products and uglify your listening spaces with them? And where is the evidence that points to people liking absorption there even with those flaws? Earlier I post this research from someone who designs pro spaces: From AES paper titled, LOUDSPEAKERS IN CONTROL ROOMS AND LIVING ROOMS, by George Augspurger:” Third, I did a lot of listening with various amounts of absorptive treatment in the comers behind the speakers. When first-order reflections were largely absorbed I noted that locations of individual sound sources were more precise, that the timbre of individual instruments was more natural, and that the overall stereo picture was more tightly focused. These observations agree well with other reported listening tests.”” Nonetheless, after extensive listening to classical and pop recordings I went back to the hard, untreated wall surfaces. To my ears the more spacious stereo image more than offset the negative side effects. Other listeners, including many recording engineers, would have preferred the flatter, more tightly focused sound picture.”
Is your theory that George's analysis was also limited to speakers with such good characteristics? How about the Clark study earlier where he clearly stipulates the benefits of side reflections?
Yes, it is true that if you leave the side reflections be and you have crummy off-axis speaker response you will hear that flaw more. That should be fodder to go and upgrade that speaker to something better than to spend years on these forums trying to determine what contraption to stick on the side wall with a hope and a prayer that it somehow mitigates that problem. Earlier I post examples of such poor speaker response and I asked what treatment fixes dips in directivity for example. Nothing came back as an answer: http://www.avsforum.com/t/1413173/does-sound-sounds-better-in-a-room-full-of-furniture-and-stuff-or-without/660#post_22246989
There is a good reason as no answer exists. Acoustic products are not tuned to compensate for a range of frequencies where you woofer starts to beam and with 100% precision. These problems cannot be fixed. Can you get lucky and improve the situation? Maybe. Will that agree with what your ears say was an improvement? Not likely. If your point is that some chance exists for this, then fine. This point of view is not about 100% absolutes but what the preponderance of evidence tells us.
- Does Toole say at what time and gain they turn to be beneficial? The arrival in both time and gain are crucial. And from what I've heard from close peers to Toole, he never meant that very early sidewall reflections were something positive. More when they were arriving at late as perhaps 15 ms.
From what you have heard of close peers? Why not read his work where this is clearly documented instead of relying on hearsay from unknown sources no less? It is not like this topic is one or two sentences in Dr. Toole’s work. He goes on for 100+ pages (my estimate) in his book alone if you ignore just as much written in his research and that of others referenced. There is no stone unturned. Here is the data you seek as cited from Alan Devantier *from Dr. Toole’s book*:
We see that reflection paths fall in the delay period of under 10 msec. If you think about it, it takes a pretty large room for the delay path to be longer than 10 feet from the direct sound. Such region and gain says that there is some perception of reflections being there and that it contributes to broadening of the source -- a property that is shown time and time again to be beneficial. Some choice quotes from Dr. Toole:"When listening tests were done in the two versions of the room, it was found that the condition with absorbing side walls was preferred for monitoring of the recording process and examining audio products, whereas reflective side walls (which reduced IACC) were preferred when listeners were simply “enjoying the music.” As might be expected, reflective side walls resulted in a “broadening of the sound image.”
And just yesterday I quoted this from him:"It was in this room that experience was gained in understanding the role of first reflections from the side walls. The drapes were on tracks, permitting them to easily be brought forward toward the listening area so listeners could compare impressions with natural and attenuated lateral reflections (see Figures 4.10a and 8.8). In stereo listening, the effect would be considered by most as being subtle, but to the extent that there was a preference in terms of sound and imaging quality, the votes favored having the side walls left in a reflective state. In mono listening, the voting definitely favored having the side walls reflective."
And:"See the discussions in Chapter 8, and Figures 8.1 and 8.2, which show that attenuating first reflections seriously compromises the diffusivity of the sound field and the sense of ASW/image broadening. One of the problems with both music and movies is that sounds that in real life occupy substantial space—multiple musicians or crowds of people, for example—end up being delivered through a single loudspeaker—a tiny, highly localizable source. The precision of the localization is the problem. Most of what we hear in movies and television is monophonic, delivered by the center channel, so a certain amount of locally added room sound may be benefical; this is definitely a case where a personal opinion is permitted."
There is no ambiguity here regarding his point of view.
- The researches seem to be conducted in rooms with very little spaciousness. Would the outcome be different if the room was treated differently and especially with the spaciousness arriving form lateral diffusion?
Seems to? Why not be specific here? The research and data cited is extensive in support of above views. It covers all manner of situations from single reflection to many. In speech and music. In real rooms and anechoic. But sure, let's have you quote such research and I can comment further.
- Absorption is not the only way to attenuate sidewall-reflections. There are other ways that will not only retain more energy, but actually attenuate reflections even more. It's been used for decades and is something Toole doesn't even seem to mention.
If you don't say what that is, I can't tell you if he has or has not mentioned it
. If you mean diffuison by "retaining more energy" then he extensively talks about that and actually recommends it as a method to enhance side reflections. If it is something else, you need to explain it.
- Amir tries to make this black and white. The fact is however that Toole researches were not very conclusive. Whether sidewall reflections were experienced as pleasing or not dependent on the music material. It actually varied quite a bit.
As I answered Dragon yesterday, it is a campaign slogan to say that a black and white position is taken. What I am black and white about is what Dr. Toole is black and white about. Which is the fact that there is considerable amount of research that points to the right direction here. It is not a wishy-washy thing of running a tool and then flipping a coin as to which direction may be right to take. The mountain of data that points to most people having certain preference is quite strong. It is not 100% and we have already talked about musicians and possibly others not having the same preference. That fact cannot be inverted to say that since the data does not apply to 100% of people, therefore it is a confusing situation and people should sign up for complicated and practically impossible tests to determine their own preference. To wit, none of the vocal posters in this thread have expressed any preference in this regard. If they are so sure of this reality how come no such data has been put forward?
But sure, there is no one here saying you may not have the other preference. Some guys do get to marry super models
. Go ahead and run the tests and report back. But please don’t say that just because the possibility exists that the research must not have been good, or confusing, or that the probability is equal for both outcomes. None of this is supported given what we know.
Not to mention that this was based on preferences and never accuracy. Here's Toole's own comments on this:
So we see that whether side-wall reflections are something positive or not greatly depends on many factors. Music material, taste, speakers, time of arrival and gain in db, how the rest of the room has been treated etc.
There is no way you can conclude that from what you quoted from him. Indeed just about everything is in defense of the point of view I have been presenting. The only thing you can hang your hat on is this: ” coincident-mic recordings may benefit from a lack of reflections”
. He says “may” benefit in that very narrow case. He goes to talk about his room at NRC with that curtain which I have quoted in more detail above. No one reading that quote will walk away thinking “it all depends.”
The best way to find out is simply to try it out yourself. Most people who try dampening early reflections from sidewalls seem to favor it.
Who are those people and how do you know that they are not liking the fact that they reduced late reflections which must be done as otherwise the room is too live? An empty listening room is too live and you must have some amount of absorption added to it. When you put a panel at first reflection, you are not just absorbing the first reflection but also all the later ones. You can’t disambiguate those cases. And this assumes your general assertion here is true with no specific and no protocol in gathering such data.
Or if the plan is to use diffusion in the rear of the room, one could redirect sidewall reflections instead of dampening.
Why would you want diffusion in the back?
But this is certaintly something you would need to use ETC for. Besides waterfall, ETC is the most useful and important tool to treat small rooms with. Well known in serious acoustic circles for decades. Don't let someone try to persuade you differently.
You mean don’t let Dr. Toole do that? Here he is again:” The message is that we need to know the spectrum level of reflections to be able to gauge their relative audible effects. This can be done using time-domain representations, like ETC or impulse responses, but it must be done using a method that equates the spectra in all of the spikes in the display, such as bandpass filtering. Examining the “slices” of a waterfall would also be to the point, as would performing FFTs on individual reflections isolated by time windowing of an impulse response. Such processes need to be done with care because of the trade-off between time and frequency resolution, as explained in Section 13.5. It is quite possible to generate meaningless data. All of this is especially relevant in room acoustics because acoustical materials, absorbers, and diffusers routinely modify the spectra of reflected sounds. Whenever the direct and reflected sounds have different spectra, simple broadband ETCs or impulse responses are not trustworthy indicators of audible effects"
I can’t get Dragon or Local to do this. So it would be great if you could tell me once and for all if we should or should not listen to Dr. Toole. He can’t be clearer here about the tool generating "meaningless data.” This proof point has been backed extensively with mathematics of it and experimentation into how we hear. Will you demonstrate why your view and the nameless people in acoustic circles are more right than his?