Whats are the different theories on room acoustics to create a great sounding room?

Phelonious Ponk

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The best measuring loudspeaker I've heard was the Mackie HR824. It measures beautifully, even down to 1/12 octave smoothing with +/- 1.5dB throughout it's rated frequency range from 37Hz to 20kHz. It's got a beautiful dispersion pattern with the tweeter almost perfectly matching the woofer. Harmonic distortion is less than 0.5% from 100Hz to 20kHz. But yet, I can't stand listening to it.

Boy does that beg the question: What is wrong? What don't you like about the sound? What can't you stand?

Tim
 

caesar

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Gentlemen,

Good discussion so far. So if room design is about personal preferences as you say, I am wondering what the different approaches the experts use. Building a room is a bit different than trying gear. When Hernan Cortes set out to conquer the Aztec empire in Mexico, he ordered his men to burn all but one of his ships when they arrived from Cuba. By eliminating their method of retreat, Cortes forced his men to fight hard and win.

You can audition the gear and send it back (or sell it). But once you commit to a room built, it is a lot more costly and troublesome to tear the whole thing out. By understanding the philosophy behind the different room design alternatives, this possibly great expense can be eliminated.
 

AudioNMe

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There is the Science of Acoustics and the Art of Acoustics. At the two extemes of the spectrum you have:

1) Those that believe in measurements - You cannot have enough bass traps. If the reflectivity of surfaces is the same then it will measure the same so it will sound the same.

Or

2) Those that don't measure and use their ears - minimal absorption because you don't want to kill the sound. The harmonics of wood sounds better than laminate.

I started with (2) using wooden acoustical panels with a 2 inch backing of fluffy fiberglass. I ended up with a setup with a huge soundstage (a lot of ambience) and warmth from the wood products. The problem with this is it doesn't deal with bass resonance problems because this philosophy does not like to absorb too much of the sound away (no to bass traps).

I have heard plenty of (1) and don't like it. Sure no boomy bass but too dead sounding for my tastes.

Room acoustics is like food. Your favorite dish is another persons poison.

I am redoing my living room and still thinking about hiring an acoustician. But my fear is what I have read in this thread:

http://www.whatsbestforum.com/showthread.php?1836-Need-qualified-room-acoustician

I would hate to spend a lot of money on a design and construction to be dissapointed. So I may end up doing it myself in incremental stages by using the Science of Acoustics to guide me and the Art of Acoustics to decide if I like what I have added.
 

garylkoh

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Boy does that beg the question: What is wrong? What don't you like about the sound? What can't you stand?

Tim

It sounded like the musicians got bored of the session, and were just going through the motions to get to the end of the set. There is a lot I can forgive with music systems, and I can happily listen to a clock radio - but not something that makes the music boring. I don't know if rooms can do that... but there are some rooms that give me a headache.
 

JackD201

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Gentlemen,

Good discussion so far. So if room design is about personal preferences as you say, I am wondering what the different approaches the experts use. Building a room is a bit different than trying gear. When Hernan Cortes set out to conquer the Aztec empire in Mexico, he ordered his men to burn all but one of his ships when they arrived from Cuba. By eliminating their method of retreat, Cortes forced his men to fight hard and win.

You can audition the gear and send it back (or sell it). But once you commit to a room built, it is a lot more costly and troublesome to tear the whole thing out. By understanding the philosophy behind the different room design alternatives, this possibly great expense can be eliminated.

Well, first and foremost be wary of an acoustician that doesn't interview you extensively. It means he'll be leaving his preference stamped on your room and not your own. Frequency balance is pretty straight forward and I think most people if not all people want rooms that don't skew. I mean the room isn't meant to be used as some sort of EQ. Reverberation times however are really a matter of taste for the home enthusiast. Too short can be unhinging and too long totally annoying. So the owner has to ask himself what settings he has enjoyed music best. When I was being interviewed the basic question was whether I preferred the accuracy of a control room or the energy of the recording space. I said somewhere in between but leaning towards a control room. A control room is usually around .2 and recording spaces are variable going as high as .7 or .8. I asked for .4 and my acoustician gave me .35 so I'd have more play with my ambience drivers. The other thing is the noisefloor. I said I didn't want to hear my own breathing unless I was really trying to so he gave me 30dB with the HVAC running. With the HVAC off, I feel claustrophobic. It's like being in a cave. Being in a basement, I guess you can say my room really is one. I think if my room was above ground I could have asked for lower without coming unhinged. It's a psychological thing since I do live on the Pacific Ring of Fire.

So my figures wouldn't pass studio standards especially when it comes to sound transmission but puts me in my comfort zone. I'm just listening to the music and not working on it so my standards are lower. Setting the lower standards also saved me a lot of money. Getting mastering room figures takes A LOT of work and a lot of scratch to get that work done.
 

fas42

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It sounded like the musicians got bored of the session, and were just going through the motions to get to the end of the set. There is a lot I can forgive with music systems, and I can happily listen to a clock radio - but not something that makes the music boring. I don't know if rooms can do that... but there are some rooms that give me a headache.
No PRaT, eh?

(aside) PRaT is a bit of subjective mumbo jumbo, a nonsense ...

Shut up, you don't know a thing, you stupid prat !! :D:D

Frank
 

KlausR.

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Dec 13, 2010
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So what are there different theories to create a great sounding room?

The German acoustician Heinrich Kuttruff once wrote: "The traditional task of room acoustics is to create conditions which allow a good transmission of sound from the source to the listener. It should be pointed out that these conditions very much depend on whether speech or music is concerned. In the first case the best possible intelligibility is the citerion for the quality of the transmission, in the second case the success depends on the achievement of other, less quantifiable conditions and at last on the personal listening habits of the listener. In any case, a good acoustics as such of a room does not exist."

From Heckl, "Handbook of Technical Acoustics", Springer 1994 (in German)

To this you add the fact that different listeners will have different in-ear response curves (head-related transfer function) so that the same signal will be perceived differently both in timbral and imaging aspects.

As microstrip said, Toole's book will help to separate the chaff from the wheat, and there's tremendous lot of chaff in what's told in forums and web sites. A condensed version of that book is Toole's AES paper, which can be downloaded from: http://www.harman.com/EN-US/OurComp...tions.aspx?CategoryID=Scientific Publications (3rd from top)

And lastly, beware of acousticians who don't know psychoacoustics.


Klaus
 

JackD201

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Great post Klaus :)
 

garylkoh

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No PRaT, eh?

(aside) PRaT is a bit of subjective mumbo jumbo, a nonsense ...

Shut up, you don't know a thing, you stupid prat !! :D:D

Frank

Frank, you know I'll take digs at you, but I won't insult you. ;)

I didn't think that it was a total loss of PRaT. It had more than others - but it was boringly PRaT. Bit of subjective mumbo jumbo, but it was something I felt. When the system is singing right, you don't want to end a song even when you are doing critical listening. When the system is not, a couple of seconds on each track is more than enough.
 

FrantzM

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Hi

It seems to me that the notion of "preferences" is threatening to take over the world of Music Reproduction. The goal is to have your room behaving in such a way that it increase the sensation of real music playing in your listening place as simple as that. This is factual. Real music is very rapidly identified by most human beings whether they are audiophiles or not. If a room achieves that iti s a great room for most reasonable persons.
All solutions are not good. All treatments will not please all people but there are some basics treatment which would increase the enjoyment of any reasonable audiophile, statistics have shown that too:
Smoothness in bass response brings clarity and "texture" to music and speech reproduction. it even allows the ear to hear more of the treble frequencies... unmasking them if you will
Reduction of echoes increase intelligibility of speech and perception of small nuances
A certain amount of diffusion seems to bring an added impression of "live" to music reproduction. It adds a certain of "spaciousness"

How these are achieve is the crux of the matter. The science is known but not that well known. Acoustics , Small RoomAcoustics (that includes rooms as large as 70 feet long ) is immensely complicated and all the parameters that governs it have not been completely cataloged. Even the maths is complicated.. The smaller the room the more involve the maths and the fewest people actually understand let alone master it. That is where the Art comes in .. the better Acoustician plays with the parameters to come up with agreeable results in line with the (reasonable) listener expectations. If a listener insists on its bass always booming at a given frequency regardless of the music being played, there is not much room acoustics treatment can do for him in this regard .. it may be better off with an EQ to boost his favored frequency band ..although in retrospect a neutral room would have helped him get more from the EQ ..
I am not sure there is one solution for Room treatment but the goals to me are clear and quantifiable ... One may prefer a way to treat his/her/their rooms .. If the goal is to simulate Live music as closely as possible then the results are clear and quantifiable .. getting there is not simple and there are different roads .. The one you choose depends largely on the parameters you deem important to be fooled into thinking that live music is playing in front of you.
 

KlausR.

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The goal is to have your room behaving in such a way that it increase the sensation of real music playing in your listening place as simple as that. This is factual.

At least with 2-channel, that is a battle lost right from the start, because of the very different radiation patterns of musical instruments as compared to loudspeakers and because two channels cannot create stuff such as listener envelopment.

The science is known but not that well known. Acoustics, Small Room Acoustics (that includes rooms as large as 70 feet long ) is immensely complicated and all the parameters that governs it have not been completely cataloged. Even the maths is complicated. The smaller the room the more involve the maths and the fewest people actually understand let alone master it.

In small rooms the sound field is not diffuse so diffuse field concepts such as Schroeder-frequency or critical distance no longer apply. Some perception thresholds are different because things happen earlier than in a concert hall, but why would the maths be more involved? What maths and what does that actually mean: The smaller the room the more it involves the maths?

Klaus
 

FrantzM

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Hi

The battle is lost the second you try to replicate reality. You can however minimize the casualties. I am not siure I understand your point about the differences between the radiations patterns of real instrument they are bound to be different in reproduction... The goal is to simulate, I am not sure it is to replicate such is to be impossible with any number of speakers.

I never implied that in small room acoustics involve diffuse fields. I admit to not being clear in my wording. The maths indeed do NOT change with decrease in size. The problems however do as well as the solutions and that is what I wanted to convey. Point well taken.
 

JackD201

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In laymans terms, the logical extension of your position Frantz is how much help do you want from the room. The ratio of direct and reflected is a preference and so is the reverberant field. I think we can agree that nobody wants masking and also agree that FR if not totally flat should have a benign curve with no significant humps or suck outs. You and I share the same sentiments about taking relative subjectivism too far. While it is true that one man's real is one man's phony, if we look at this closely we're talking about small differences in narrow ranges in the area of (being quite generous) +/- 4dB between frequency extremes and tenths of milliseconds inside the misnomered reflection free zone.

The room's job in my opinion is to allow what's in it to perform as best it can and that includes the people. It is definitely not a simple task as you say. The silver lining is that it is possible at least to degrees that can be deemed satisfactory if not perfect. :)
 

fas42

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Frank, you know I'll take digs at you, but I won't insult you. ;)

I didn't think that it was a total loss of PRaT. It had more than others - but it was boringly PRaT. Bit of subjective mumbo jumbo, but it was something I felt. When the system is singing right, you don't want to end a song even when you are doing critical listening. When the system is not, a couple of seconds on each track is more than enough.
Gary, of course I wasn't having a go at you, rather at those who refuse to acknowledge the more subtle aspects of correct sound reproduction. But you knew that ...:)

This is a new one on me: "boringly PRaT", probably should be added to that vernacular thread! This to me again points to the real problem as expressed by FrantzM in the next post:

The goal is to have your room behaving in such a way that it increase the sensation of real music playing in your listening place as simple as that. This is factual. Real music is very rapidly identified by most human beings whether they are audiophiles or not. If a room achieves that iti s a great room for most reasonable persons
This is where I differ from seemingly most people here. I believe this is achieved by fixing the electronics, not the room. The latter solution to me is a classic "after the horse has bolted" technique.

At least with 2-channel, that is a battle lost right from the start, because of the very different radiation patterns of musical instruments as compared to loudspeakers and because two channels cannot create stuff such as listener envelopment.
This, luckily for all, is completely wrong. The few people who have experienced the counter to this know that it's wrong. The battle is still very much alive, it just has to be fought more intelligently ...

Frank
 

garylkoh

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At least with 2-channel, that is a battle lost right from the start, because of the very different radiation patterns of musical instruments as compared to loudspeakers and because two channels cannot create stuff such as listener envelopment.

Klaus

This, luckily for all, is completely wrong. The few people who have experienced the counter to this know that it's wrong. The battle is still very much alive, it just has to be fought more intelligently ...

Frank

Actually, you are both right and wrong. I need to find another couple of hours of writing time so that I can continue with my philosophy of sound thread. Klaus is correct from the distal theory of sound, but Frank is correct with the proximal theory of sound.
 

AudioNMe

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Can you restate this?

To clarify "If the reflectivity of surfaces is the same then it will measure the same so it will sound the same".

Let's say you have a room with wood laminate and replace it with a wood floor. The reflectivity of these two surfaces is so close that if you performed measurements there would be no significant difference. Some will then claim, it will sound the same. Others will say wood imparts a warmth to the sound. In my former house and current house I have replaced existing wood laminate with real wood. No other changes were made to the room. The same furniture and rugs in the same locations were put back in. Both times the sound became warmer and more full bodied. A couple of my friends made the same observation.

For me now, it is a combination of Science and Art. Your ears have to make and even override theoretical decisions if you like the results better. But I made the mistake of trusting my ears 100%.After I read about Acoustics theory, I borrowed some fiberglass batts from home depot; stuck them in the cornors and wow what a difference bass traps make. You don't know what you have missed if you have never had it before... That is why Science of Acoustics to guide but remember to use your ears as well (the Art of Acoustics).
 

microstrip

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(...) Those that believe in measurements (...)If the reflectivity of surfaces is the same then it will measure the same so it will sound the same.
(...)

As usual, the usually quoted single measurement for reflectivity (at normal incidence) does not describe the sound of the material in small rooms. In small rooms the large /medium angle reflections are critical and unless you have measured the angular dependence of the reflectivity coefficient versus frequency you can not compare two materials.

It is one of the reasons why some professionals use calibrated, more expensive sound diffusers and absorbers, that have been professionally measured - for these they have a full list of accurate parameters that they can enter in their simulations.

The so called "domestic materials", "non audio specific" or "pseudo acoustic" types need a lot of experiment, although some very talented people with large Knowledge (or just very, very lucky) can get good results with them. But the use of these materials can also kill the sound of your room.
 

garylkoh

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That's true. As usual, it's how comprehensive a set of measurements you can make - and also which set of measurements you choose. Even different wood, different size of panel, they will all make a difference. Whether the difference is sufficient that you want to rip out your oak floor and put in hard rock maple depends on the individual.

One reason very, very few loudspeaker manufacturers use an all solid-wood construction is that the wood you buy this year will sound different from the wood you bought last year. I could even argue that the wood from one tree on the South side of the hill will sound different from the wood from another tree on the North side of the hill.

I can believe that a wood floor will make a specific room sound warmer and more full-bodied, but I won't use that as a theory to treat every room.
 

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