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In assessing Klaus' views on reflections…

Posted by David Aiken (A) on January 19, 2008 at 15:18:33

In Reply to: You don't need to treat reflections!!! posted by KlausR. on January 18, 2008 at 21:52:36:

You need to be aware of several things:

1- the bit on Toole's views that is contained in the document he links to says in full:

"Toole has concluded that normal reflections in a typical small living room seem not to interfere with perception of the recorded space. He has also determined that early lateral reflections (<50ms) have a beneficial effect on intelligibility similar to raising the dialog level, and that the reflection pattern is more important than reverberation.

This has led to Toole’s recommendation that too many or too few reflections can be a problem. In particular, acoustic absorption, diffusion, and reflection must be broadband, ideally starting below 200Hz. He pointed out that the typical 1˝ or 2˝ sound panel most often affixed to walls works only at relatively high frequencies, and acts to effectively turn down the tweeter with no effect on the midrange or upper bass, thus unbalancing the sound.

Toole reminded us that many of the practices to deaden a room’s acoustics came from standards for broadcast and recording control rooms, where sound details must be heard more clearly, not for general listening rooms."

Klaus interprets the first paragraph of that section as saying that reflections aren't a problem, period. It doesn't go quite that far and the second paragraph points out that too many or too few reflections can be a problem. What is the situation in your room as opposed to Klaus ignoring that part of the discussion and saying they're never a problem? Do you have too few or too many reflections? Bear in mind that there isn't a fixed amount of reflection you should have but rather there's a range and different people can and do prefer different points on that range. Your room may fall within the range but at the other end of the range to your preference, or your room may fall outside the range. Klaus doesn't know or care about that. He just says there's no need to treat reflections and totally ignores the qualifications inherent in that quoted passage.

Note also that the quote is Linkwitz's take on what Toole said and not what Toole himself said. It's a summary and summaries always gloss over the fine detail. Klaus's statement that Toole says that reflections are not a problem is also a summary which drops out all of the fine detail and every qualification Toole makes. That kind of summary is absolutely the worst summary you can get. You can't assume that such a simplistic summary will apply to your situation. Linkwitz's summary is better and raises questions which should tell you that you shouldn't rely on Klaus's more extreme summary.

2- Next, treating first reflections does make a difference and it certainly improves imaging, soundstage, and the sense of the acoustic of the recorded venue in my room and in the one other room where I've seen first reflections treated. Other people who have done it report the same and at least one author, Everest, recommends treating of first reflections for that purpose. Note that Everest is a professional acoustician and author whilst Klaus is not. He's widely read but he hasn't conducted research and does not appear to work in the field of acoustics.

3- Klaus always conducts this debate in terms of "need". Do you NEED to treat first reflections? The answer is no because you can get quite enjoyable sound without such treatment and, in fact, without any treatment of your room. Can you get sound that you will enjoy more if you treat your room? Yes, most certainly and all you need to do to prove that for yourself is to try listening in a few treated rooms. You will probably like the results more in some rooms than in others depending on how well the treatment was done and what goal the person treating the room had for their results. If you're not interested in refining imaging and soundstage, don't treat first reflections with absorption but rather consider diffusion in those locations and at the speaker end of the room. There's more than one way to treat a room and you can certainly make your room deliver more of what you like in terms of sound quality than you get in an untreated room.

If you're thinking about room treatments then there must be some aspect of the sound you're currently getting that doesn't satisfy you and that you want to improve so the question is can room treatment do that for you. It can't fix every problem and it may take more treatment than you can afford or want to have in your room to fix some problems, but it can make a positive difference with many problems and there's more than enough people who've experienced the benefits to prove that claim. Klaus views their 'evidence' as anecdotal and chooses to ignore it but there's a lot of that evidence, it's consistent in its nature, and it agrees with the treatment recommendations of a number of professionals. You certainly don't NEED acoustic treatment in most cases but it certainly makes an improvement in most cases and, when it doesn't make an improvement, the reason is often because people ignored the recommendation of Toole and other knowledgeable people that absorption should always be broad band.

Its your room and your decision so you're free to choose to do what you want. Certainly consider Klaus' view but also consider those of others and decide on balance which side you agree with. If you're going to read references, certainly read those Klaus refers to but chase a few more as well and do include Everest's book, the Master Handbook of Acoustics, which just happened to be written to provide sensible advice on room treatment for people wanting to treat listening rooms and build their own recording studios.




David Aiken

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