Room Reflections & Human Adaptation for Small Room Acoustics

[gene]

Dealing with acoustics in small rooms is no trivial matter. The quest for the “perfect” room all depends on your expectations, why you are listening (business or pleasure), what program you are listening to, and the condition of the ears you are listening through.

This article focuses on the topic of early reflections in small room acoustics and how to deal with them based on listening preferences and the accuracy of your loudspeakers. The portions of side walls responsible for first lateral reflections are specified as “optional areas: absorb, diffuse, reflect.” It is a decision to be made by the customer and/or the installer.

Read: Room Reflections & Human Adaptation for Small Room Acoustics

Tell us how you treated the the early reflection points in your listening space. Please show pictures.

 

[ChicagoLR3]

Soooo, I guess everyone is playing nice on the Youtube front now?

 

[shadyJ]

Another great article by Floyd. I like the emphasis on how the ears and our perceptual processes can adjust to different room acoustics. In all the publications in hi-fi audio, the ear and our perception of sound is given far too little attention, yet it is the most important component of any hi-fi system (unless you are only buying the system for looks or status symbols instead of performance, which happens a great deal). The part about the less-than-stellar hearing of these sound engineers would have me worrying, were I worried about getting the most pristine sound recordings. That isn't my priority, however. One thing I would love to see is audiophiles demanding is audiometric test results of the sound engineers listed on the back of recordings, that would be hilarious.

 

[nathan_h]

So for music there isnt a perfect room. And the best room for each recording changes depending on what the recording is -- though themes emerge, often tied to genres.

Seems like movies, on the other hand, are mixed in more consistent environments which holds out some hope for home theater reproduction being less variable.

Good stuff.

 

[Floyd Toole]

Thanks nathan_h. Audio purists have long adhered to the belief that music was the "perfectionist" content, and movies, and home theaters, were somehow inherently inferior. Rubbish! It was movies that motivated the development of stereo, and then multichannel. The music world would have been content with mono. I am old enough to remember when stereo was introduced that a lot of music lovers said, basically, "who needs it?". It is clear in my last AES paper that movies can stand some improvement, but they are much more uniform than music, and they are multichannel. Movie mixers have long ago learned how to work with multichannel and some excerpts of music in movies are quite impressively good. In contrast, some of the efforts of the music side have been, to me, colossal failures because they were mixed by "stereo" engineers. When a multichannel music recording appears and there is no center channel . . . gimme a break! It has happened on some "audiophile" recordings. Play the test signals and all channels are present. Play the music and nothing is coming from the center speaker. Unfortunately this also happens in some otherwise entertaining music videos.

Sound is sound, good sound is good sound, and then there is content: I would not argue that the latest superhero movie is equivalent to the great classical, jazz or pop music - they are just different. Each one benefits from respectful treatment in the playback process. However, the fact that the music domain has been stuck in the stereo groove for decades is, to me, evidence that direction and space in music has lost out to rhythm, melody and timbre, all of which are audible in mono, or "headphone stereo" which is not real stereo. Too bad . . .

These days it is possible to have a multichannel home theater that can do it all, and do it at levels of excellence that would satisfy the fussiest of listeners. Just replace the crummy surround speakers with good ones (not dipoles, please!) and try it. All loudspeakers in a surround system need to be comparably good from a timbral perspective, and, if it is affordable, all the same.

 

[j_garcia]

Of course there is no perfect room in the typical use case of a non-dedicated home theater. There are always things you can do to maximize your listening experience in any given room though. There will be trade-offs which will vary by the tolerance of an individual and potentially the presence of a significant other who may have requirements that have nothing to do with sound. Proper placement and treatments may not be the most aesthetic in such a case, so you have to pick your battles and compromise. I configure things around how I can get the best sound within reason for that room while still making it a place to "live" also.

I also geared the system toward my music listening. Though I used to be 70% music, 30% movies, lately I have been more like 50/50. I find movie soundtracks more demanding of the system, but music to be more critical of the speakers themselves. The whole audio chain has to support the speaker obviously, but the speaker becomes more important for critical listening to me. While a movie soundtrack can be very dynamic, I rarely listen critically simply because the involvement with a film tends to be quite different than with music only. To that end though, a system that is good with music will usually have only benefits for movies IMO.

 

[Floyd Toole]

j_garcia I hear you about compromise. The good news is that good loudspeakers are very tolerant of room variations. Bass is the challenge.

Years ago I became aware of a difference between movie sound and music recordings. Once in a while, after watching a movie that I thought was less than pristine I would play a good CD for comparison. Sometimes the difference was simply dramatic. Even now, I occasionally am aware of what I call "movie sound". In the course of following the plot one adapts and it is not noticed, but it is there. But then, once in a while, there is a really good sounding movie. Some of us are working to make things better. Getting rid of the X-curve used to calibrate film sound facilities would be a good place to start. With cinemas having trouble making money, it is reasonable to think of having music concert playback events for those who can't or didn't get to the real thing, or who can't play things at high levels at home. For that one needs "hi-fi" in the cinema. Some reports I have heard from some of these events indicate that the picture was fantastic, but the sound was mediocre. I have heard a recording of Beethoven's 9th played over a neutrally balanced good cinema system - it was very enjoyable - not what many would expect. The potential exists for more than impressive explosions and 3D/immersive sound effects.

 

[gene]

j_garcia I hear you about compromise. The good news is that good loudspeakers are very tolerant of room variations. Bass is the challenge.

Years ago I became aware of a difference between movie sound and music recordings. Once in a while, after watching a movie that I thought was less than pristine I would play a good CD for comparison. Sometimes the difference was simply dramatic. Even now, I occasionally am aware of what I call "movie sound". In the course of following the plot one adapts and it is not noticed, but it is there. But then, once in a while, there is a really good sounding movie. Some of us are working to make things better. Getting rid of the X-curve used to calibrate film sound facilities would be a good place to start. With cinemas having trouble making money, it is reasonable to think of having music concert playback events for those who can't or didn't get to the real thing, or who can't play things at high levels at home. For that one needs "hi-fi" in the cinema. Some reports I have heard from some of these events indicate that the picture was fantastic, but the sound was mediocre. I have heard a recording of Beethoven's 9th played over a neutrally balanced good cinema system - it was very enjoyable - not what many would expect. The potential exists for more than impressive explosions and 3D/immersive sound effects.

Floyd;

What about the trend I'm seeing now where most "blockbuster" films these days deploy the same CGI effects and NON STOP boom of bass? The latest Batman v Superman movie is a prime example of a movie that is NOT only being played back too loudly but also with too much bass. I complained to the General Manager of the theater I was at and his response was the Corporate owner touts that their theater has the most speakers and wants it to be known as the loudest on the block. He then commented that they've blown 4 subwoofers since the premier of the BvS movie. Hopefully this won't be a sustainable business model for them

 

[nathan_h]

Floyd;

What about the trend I'm seeing now where most "blockbuster" films these days deploy the same CGI effects and NON STOP boom of bass? The latest Batman v Superman movie is a prime example of a movie that is NOT only being played back too loudly but also with too much bass. I complained to the General Manager of the theater I was at and his response was the Corporate owner touts that their theater has the most speakers and wants it to be known as the loudest on the block. He then commented that they've blown 4 subwoofers since the premier of the BvS movie. Hopefully this won't be a sustainable business model for them

I may be wrong but it sure seems like the only theater chain/brand that has reasonable (okay, it's loud but it's balanced and reference level) calibration and setup are the IMAX branded rooms. I know people complain about FauxMAX or whatever, when a small multiplex converts a room to "IMAX" but even then it seems like things are intelligently dialed in from both an audio and video perspective.

Not perfect, but the safest bet where I live (if for some reason I cannot wait for the content to be available on blu-ray).

 

[DD66000]

These days it is possible to have a multichannel home theater that can do it all, and do it at levels of excellence that would satisfy the fussiest of listeners. Just replace the crummy surround speakers with good ones (not dipoles, please!) and try it. All loudspeakers in a surround system need to be comparably good from a timbral perspective, and, if it is affordable, all the same.

Floyd, my exact thoughts for quite some time.
When setting up a multi-channel system, don't skimp on the surround speakers, and use mono-pole.
Anyone who will say "it makes no difference what surrounds you use" is totally clueless.
I actually prefer using identical speakers all around...I basically do, five JBL PT800's for center, four surrounds; and a pair of custom, highly upgraded speakers for the mains, based on L212, which for all practical purposes is the PT800 forerunner.

But I don't prefer a hard center over a phantom center for music. I can go either way on the center.

 

[ski2xblack]

I kind of rely on our hearing's ability to listen past the room (no room treatments, just the normal clutter, art, plants, etc), but none of my rigs fail to reflect some sort of consideration and management of room interactions. I'm pretty sure it wouldn't be that way if I didn't have a copy of Toole's book, at least not as purposefully. Most importantly, SWMBO puts up with some room-acoustic necessitated, idiosyncratic arrangements of stuff, and the various systems all sound quite good.

 

[gene]

I may be wrong but it sure seems like the only theater chain/brand that has reasonable (okay, it's loud but it's balanced and reference level) calibration and setup are the IMAX branded rooms. I know people complain about FauxMAX or whatever, when a small multiplex converts a room to "IMAX" but even then it seems like things are intelligently dialed in from both an audio and video perspective.

Not perfect, but the safest bet where I live (if for some reason I cannot wait for the content to be available on blu-ray).

I agree the IMAX at AMC within an hour drive from my house is pretty excellent actually. It is loud but the sound is good and balanced.

This place however is a different story:
http://www.fandango.com/studiomoviegrilltampa_aaxjb/theaterpage

Some of the worst sound I've ever heard in a theater. I hope they keep blowing subs and eventually can't afford to replace them

 

[Floyd Toole]

DD66000, Re: center channel for music.
Several years ago I attended an AES presentation on multichannel recording. The presentations were by, as I recall, three "famous" pop/rock engineers and a senior engineer from NHK, the Japanese organization that has done a lot of research in sound reproduction. All of the pop/rock guys were less than enthusiastic about using the center channel, and two of them avoided it in their mixes. I was sitting at the edge of the center aisle of the venue and for their demos, the featured artist joined the part of the band in the front right loudspeaker that was on my side of aisle. I moved a few feet into the aisle and naturally center was restored. To them multichannel audio was about adding reflections and reverb in the surround channels - or the backing vocalists: ugh!

So stable and correct localization is part of the advantage of a real center channel. If that doesn't matter to you, and you sit in the sweet spot, you grapple with the acoustical crosstalk cancellation I discussed.

The one pop/rock guy who used the center channel obviously did not know how to add signal processing to make it fit into the overall soundstage, and the close-miked vocalist was not well integrated into the band - too isolated, not nice, but she was correctly located between the L & R speakers.

The NHK guy had it nailed. He started off with an opera in which the orchestra was conventionally miked, big open and spacious sounding. The vocalist had been close miked, and he gave a sample of what that sounded like when combined with the spacious orchestra - awful. Then he played it again with synthesized "reflections" around her, compatible with the orchestra setting. It was superb, she was among the musicians in an extensive soundstage where she belonged, and was correctly localized wherever one sat in the audience. Impressive. He then did some other examples, jazz and pop. All sounded very nice - no obvious problems. Conclusion: it can be done if you know how.

I discussed this with my friend John Eargle, a multi-talented musician, recording engineer and loudspeaker engineer (RIP), and he told me that what I heard from NHK was what he and other skilled classical recording engineers have been doing all along. When a feeble voice or instrument is close miked, before they add it to the mix they embellish it with synthesized reflections and reverb to allow it to be perceptually compatible with the rest of the orchestra. This is routine, he says, and routinely not known about, or detected by listeners. "Purists would cringe if they knew", he said with a wry grin . . .

As I said, when stereo engineers do multichannel mixes, they don't aways get it right. None of this may have been in their training or previous experience. It is different from just adding reverb. When I visited McGill University last year on the occasion of my lecture (and now YouTube video) it was impressive to see that all of the trainee tonmeisters were doing multichannel recordings, up to 20.2 channels. I heard some impressive stuff. So, maybe the future will be better.

Then again, you may not be perceptually programmed for center channel music Just kidding. So when I complain about a missing center channel in a multichannel playback, I might be complaining about something that the recording engineer was simply not able to get right and skipped it.

 

[DD66000]

Floyd,
Yes I do have at least one DVD-A disc that does not use the center...irritates me to no end.
But when I listen to music it's usually via a Parasound P7 pre-amp, so stereo, except playing DVD-A/SACD.

I prefer the ease of use of the P7 over the HK AVR.
Plus the L7 music option on the AVR 3600 just does not seem as good as the old HK AVR 635, unfortunately. I think it has to do with the chip used in the newer AVR 3600 not being a TI chip, as was the case with 635. So I tend to stick with stereo playback now.

But these custom speakers provide excellent soundstage, especially with a quality recording like last year's "If I Can Dream" Elvis with the Royal Philharmonic Orchestra.

 

[Floyd Toole]

DD66000 Logic 7 is a variable algorithm. It is not the same in all products - unfortunately - even in the old Lexicon processors it would change with time as its inventor thought of "improvements". Nevertheless, it was normally preferable to the alternatives.

 

[highfigh]

DD66000 Logic 7 is a variable algorithm. It is not the same in all products - unfortunately - even in the old Lexicon processors it would change with time as its inventor thought of "improvements". Nevertheless, it was normally preferable to the alternatives.

I may not be remembering correctly, but I thought TC Electronic had real-time equalizers for live sound applications which could be programmed for specific target curves, depending on the venue. Obviously, this would be for larger spaces than residential, but if the room's characteristics can change with furniture placement, occupancy, opening/closing windows and doors, it would seem to be a decent way to provide relief from some of the problems that affect the low end, as long as it can react quickly enough to remain sonically transparent.

 

[Floyd Toole]

I suspect that the live sound (i.e. large venue, large audience) equalization would be to maintain a relatively constant overall broadband "house curve" when the audience density changes and the air heats up and becomes more humid during a concert. It would not be able to cope with room mode problems in small rooms. Now, if you are in the habit of having crowded, steamy, dance parties, maybe . . .

 

[DD66000]

DD66000 Logic 7 is a variable algorithm. It is not the same in all products - unfortunately - even in the old Lexicon processors it would change with time as its inventor thought of "improvements". Nevertheless, it was normally preferable to the alternatives.

Right now I am listening to Linda Ronstadt via iTunes on ATV, which is HDMI connected to the AVR, with L7 music on.
Does sound good, but really nothing more than 3 channel stereo. Nothing from the surrounds to get excited about.

But as I said, the AVR 635 was superior in every way, with exception of not having HDMI.

 

[Floyd Toole]

Yes, when you upmix a stereo recording what you get is a lottery because they were never mixed with that in mind. The lack of output from the surrounds is an indication that there is little uncorrelated (difference) information in the stereo signal - most of it is pan-potted mono. BTW, I think Linda R. is great, and the engineer, George Massenberg has been responsible for a lot of recordings I enjoy greatly. He is now a teacher in the tonmeister program at McGill University.

 

[DD66000]

Yes, when you upmix a stereo recording what you get is a lottery because they were never mixed with that in mind. The lack of output from the surrounds is an indication that there is little uncorrelated (difference) information in the stereo signal - most of it is pan-potted mono. BTW, I think Linda R. is great, and the engineer, George Massenberg has been responsible for a lot of recordings I enjoy greatly. He is now a teacher in the tonmeister program at McGill University.

In my old age, I find I appreciate Linda's voice more than I did back in the '70's. And just the opposite of ONJ's voice.

And if you want to hear a superior female voice (imo) German singer Helene Fischer. That sweet woman can sing most anything. And do it better, no matter the language she maybe singing in. German, English, Russian, Spanish.