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I'm often asked by clients and A/V dealers for my recommendation for acoustical wall/ceiling treatments. The professional acousticians I've worked with in the past have various and often conflciting ideas on the subject. I'd be interested (and hopefully it would be a subject of interest to others as well) in what this group thinks is appropriate for-A) A "bells and whistles" home theater surround sound system or, alternately,
B) A typical two front speaker listening room...Thanks
Rob Lyons
Hi Rob,What is common to both the audio listening and video viewing room is the standardizing the acoustics of the room to a reference which should be established prior to even considering acoustical treatments. At the Soundstage Tweaks Talk Online forum, there is quite a discussion on the importance of establishing a "reference" for the acoustic signature of your room and how to do this. An article posted by MGD on how to create a musical reference and why its important is pasted below. Here's the article and the metholdology laid out is applicable to audio listening room, video rooms, recording studios, concert halls and performance centers among other venues:
The Making Of A Musical Reference -- Part IThere are many rest areas along the road of the musical reproduction highway at which one can stop. Each one of these areas is, in and of itself, an industry and sometimes becomes so focused on itself that it forgets that it's a part of the entire highway. You have the instrument, concert, recording, software, hi fi, music school, multimedia, manufacturing industries and, their respective industry critics, the reviewing industry. These different industries are all integral parts of one whole. They are interdependent upon each other and can in no way be separated. These parts have a common thread and a common goal -- making and preserving the music.
Where Do We Start?
In finding a reference, we must first look at the reference itself -- something that we can call the "absolute truth", to which, all the parts can relate. You must begin with sound and energy itself -- sound and energy as being one. Energy works off a simplistic set of rules. Energy, as we all know, is spherical in shape. Energy, as we know it on earth, affects all other energy. All energy forms stimulate other parts, or growing parts, of the same energy. This is an important factor and a factor that applies to all the parts of this highway. As we get into these individual parts, we must remember to rely on the thought that we are preserving energy and its effects. We spend so much time on energy and its support system because science has told us that without the support system, the balance of the sphere of energy is incomplete. This can be easily illustrated with the earth, the universe and the forms of energy found upon the earth. In sound, we talk of sound waves. These sound waves create what we call musical harmonics. It's kind of like taking a flat, malleable membrane that is flexible and pushing a ball against it. Now remove the ball and see that the membrane now has a round, concave dent in it. Now walk around the other side of the membrane and you will see the membrane does not have a dent, but a round, convex bump. Whenever energy is generated, it is automatically a three dimensional proposition. When a musical note is created, it is surrounded by a harmonic structure. This harmonic structure gives this sound its own individual signature. It is the harmonic structure that turns this sound into a musical note played by a particular instrument, in a particular place, as opposed to a musical note on a piece of paper. It is very important that we examine this to realize the delicate balance that we must preserve.
It was not long after the creation of the musical instrument that we found out that the instrument was not singular in its reproduction of a musical note, but actually had the capability to create not only harmonics but, by altering vibration control, was able to produce several notes. On top of this, most instruments were then designed to create a series of notes that could be played together from the same instrument, kept sonically intact by aligning fundamentals with harmonic structures. This allowed us, even though each instrument now has its own sonic characteristic, the ability to not only tune to itself, but to tune to the instruments around it and yet still maintain its individuality. Assume all of these instruments are now tuned. Take one of these instruments and put it out of tune with the others. You will hear immediately that the harmonics are now in discord. Put it back in tune and the sympathetic balance is back in place.
The Interaction of the Instrument and the Room
Let's move to the next stage -- the interaction between the instrument and the room. If you apply the same principles to the room that you have just applied to the musical instrument, you will be able to keep this balance in tact. This is a hard task to achieve. In fact, its like crawling inside of one of the musical instruments. A room brings many different factors into play that are different than the musical instrument, yet can be controlled the same way. The musical instrument plays from the inside "out". A room plays from the inside "in". If you were inside of a musical instrument, you would wonder how the sound inside the instrument could be used to create the beautiful energy outside of the instrument. Yet the air pressure and mechanics of the instrument were built, by design, to accomplish this goal of creating musical notes. The marriage of the instrument designer and the vibration of the materials he uses makes this possible. The room should be an extension of that creation.
How do we design a room to be that extension of the musical instrument? First, we must realize that the materials we use, in the building of this room, and the acoustical preserving of this room, must be sympathetic to the cause of preserving the sound of the musical instrument. When "referencing" a sound, it is important to take a look at the sound itself as it relates to the instrument. How does the instrument (or instruments) sound? Was the instrument designed in the outdoors, the outdoors with trees and buildings around it or perhaps indoors in a particular type and size of room in a particular area of the world? These are the important questions to ask, as well as what type of room will the instrument be played in, in order for us to establish our goal of creating a reference. We must remember that sound and energy are forever changing and cannot be equated with an absolute. Only a performance in a particular time and place can be equated and is the reference we seek to preserve. So, it is not the sound of the instrument itself, but it is the sound of the instrument in its environment that we wish to capture.
Creating the Sound
When thinking about creating the sound, you must think of the sound and its environment as a whole. For example, when in the individual practice room, you should be able to transport yourself mentally to the assembled practice room, the performance stage and the recording studio. The closer you make the similarities between these different rooms, and their functions, the better the reference you can make to your performance task Whether it be part of a live concert or a stored recording, the goals are the same and each one of your rooms should be able to give you a likeness of the other rooms in which you will be playing. In other words, the room now becomes a part of not only the musical performance, but also a part of the instruments themselves that are playing in that room. It is important to remember that you cannot remove the room from the equation at this stage. Creating a room's balance now becomes extremely important. For a conductor or arranger to accurately make judgment calls on the musical performance, in order to shape it into the desired results, (whether it be in the practice room, the musical hall or the recording studio) he or she must be able to hear localization of each instrument and the harmonic and tonal balance of each instrument, as well as the performance of the musicians themselves. How do we determine if this room is accurate enough to sustain the proper sonic values that are needed by the conductor or arranger? We do this by making the room an ever changing tunable instrument, able to receive and give back the desired sonic values.
This tunable instrument, or room, becomes a crucial part of the musical highway. When we achieve a balance between our respective rooms, we will grow closer to achieving our goal -- the reference. The room, no matter what environment in which it is placed or what part of the highway it chooses travel, must be able to reproduce harmonic structures which are crucial in keeping the tonal and tuned balance between the instruments. In essence, this room should be variable enough to simulate and maintain the chosen reference of any application in which it is asked to participate and, on its own and without the use of electronic effects or enhancements that we will get into later, should be able to always take on the form of a performance room -- meaning, you should be able to play a live instrument in this room and maintain the criteria of the instrument's sonic requirements which are tonal balance, harmonic structures, localization and the ability to tune with other instruments. This room should also be able to host a linear sonic performance. In other words, this room should have the ability to become void of the rise of note accentuation and the subtraction of note values. Either one of these areas affects the harmonic and fundamental integrity of the music.
A Lesson in Evaluating Your Reference Environment
Before moving any further, here is a common teaching tool I use to evaluate the environment in which I'm working when establishing a reference. I will take one of the musicians in the class or recording artists or engineers with me on a reference finding field trip. I may do this several times during a performance, practice session, recording session or a playback session. It's simple to do. Move the field trip to the outdoors and have the person playing the instrument simply walk around until they find the spot outdoors where they like the sound of the instrument. Let me give you an example. Let's say it's a guitar player and the studio is located in an industrial park. We follow the musician playing the instrument and ask the musician, as we back away from him, to play and close his eyes and to move in a circle (turn 360 degrees) until he finds the surface with the sound reflecting back to him that he prefers. If he does not find the sound pleasurable, he keeps walking until he hears the tonal balance he desires. When that sound is found by the musician, it is always greeted with a look of surprise on the musician's face and the following question. Why does it sound so much better standing here than it does in the other areas? The answer is simple. When you are building up air pressure, by being around objects, you are not hearing the sound of the guitar anymore, but the sound of the guitar as it interacts with the mechanics and the acoustics of nearby materials. Once we establish this "sound", we go back into the room to see if the room has the flexibility and the tonal qualities to reproduce the musician's reference.
"Time to Get Practical -- Within Your Acoustical Environment
We are spending so much time on the acoustical and mechanical side of creating a reference because we realize by now that there is no way to naturally alter the performance once it is captured or delivered outside of this realm. Finding the reference and preserving the acoustical signal is the key to restoring and maintaining musical integrity. Since the room is now a part of the musical performance, it is time for us to evaluate its ability to reproduce music. The most practical way to find out the reference and performance level of any room is not with test equipment, but with the human ear. Test equipment has not yet been developed to the standards needed to measure the emotional impact of music. The human ear is able to detect the value of the musical note as opposed to the test equipment which only gives you a numerical read-out of frequency responses. Musical notes created by individual instruments, based on their delicate harmonic balance, are far different than frequency responses in test equipment. Please feel free to refer to some of my other articles on this subject. Let's reference the acoustical value of any wall in your room. Once we've established the sound that we wish to duplicate, remembering our tour that we've just taken outside, we can now use that tool to reference our inside acoustics. I recommend using an acoustical instrument or your voice. Walk around the room and see if the room is able to reproduce the sound, that you are either playing or making, linearly -- meaning that you should not have any sucked out sounding areas or areas of "boominess" with your source. Remember this is an exercise to see if your room can become a reference for listening. It does not mean that you will or will not alter it per personal taste or effect. But, before we make personal taste judgment calls, we must first see if the room can do the basics. How do you establish or fix a room that is not linear or has suck outs or accentuated frequencies? Remember, your room is a tool, an instrument. It will tell you what it is hearing and what it is playing. Stand in the middle of the room, taking your guitar or your voice or whatever source you choose acoustically, and study the sound of your room by moving in a 360 degree circular motion. If your room is too "dead", you will hear many of the frequencies missing that you once heard in your reference outside. You may want to go back and forth from your favorite area of reference to your room until you are clear what is missing. If your room is too "live", you will hear a "loading" effect. This may sound like standing in a canyon with echoes all around you. To correct these problem, or to make your room closer to a reference, here are some easy instructions. In a dampened situation, begin removing the material from the room that is absorbing or sucking out the sound. In a live room, begin controlling the amount of buildup by strategically barricading pressure zone areas. Pressure zone areas are found in corners first, next in seams of a room where walls meet ceiling and in symmetrical areas of a room (meaning the distance between two objects on a flat wall). In other words, halfway between wall to wall or it can even mean halfway between one piece of furniture and another piece of furniture. These pressure zone controllers or acoustical devices primary job is to burn up just enough of the energy in these pressure zones and yet maintain the mechanical and acoustical values by using materials that are able to, when stimulated, reproduce the same sounds as the source or musical instrument that you are using as a reference. Remember to keep walking back to your outside reference or where ever your reference is, and then back into this room to use as a gauge to find out how close to the reference you are. There are many acoustical products available for you to choose from and many materials available for you to use to create an accurate reference. Pay close attention again to your harmonic structures and keep in mind that the room may already be built to stimulate enough of the tonal qualities you need to achieve your desired reference. You may only need to control the pressure zone areas.
Evaluating Pressure Zones In Your EnvironmentBefore applying pressure zone treatment, your instrument or voice will be disembodied and localization and tonal balance will be non intelligible. When pressure zone treatment is applied, localization is restored, along with tonal balance. This is best demonstrated with two people -- one standing back as the listener and one being the source, whether playing an instrument or speaking. Remember, if the room is over dampened, you have already lost crucial harmonic structures and will not be able to establish a reference for notes and their tonal balance. If a room is over dampened, you can still achieve some localization, but your source will sound dull and dampened (or sucked out) as compared to your live reference.
How To Measure The Sonic Value Of A WallOnce you have your room sounding like your musical reference, you should be able to stand in the middle of the room, facing any wall with your instrument or source playing, walk towards the wall and hear, as you walk towards the wall, the amplification of that source yet still maintaining tonal balance. This will tell you if your wall construction on your wall, or the fixtures on your wall, are able to reproduce the musical requirements to make a musical reference. All walls, ceilings and floors should have the ability to make the same value judgment. If not, and there is no desire to rebuild the wall and making it tunable out of the desired sonic materials, then place on the wall materials that give you the sonic values required. As a suggestion, wood holds a high amount of musical integrity.
Conclusion
In conclusion of part I of The Making Of A Musical Reference, it is important that we realize that "live", whether it be our voice or a musical instrument or any object that can make a sound, is our reference and it our responsibility, or challenge, to preserve and maintain this reference. When we design a room, regardless of size or use, to the design principles of a musical instrument while maintaining the same values of the musical instrument and controlling the characteristics of air pressure contained within the room, we have succeeded in making a musical reference."
Best wishes,
Jim
Room treatments are almost always appropriate regardless of the listening room acoustics and system goals. My personal recommendations involve RPG Profoam Level 2 and heavy use of tube traps. I also like the RPG Skyline diffusors, but for some they are too expensive.
Hope this was helpful.
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