Posts Tagged sound stage
Setting the Soundstage: How to treat your home theater like a real theater
Posted by Acoustics First in Articles, Home Entertainment, Home Theater on March 14, 2013
Modern AVR’s include all kinds of wizardry for speaker setup, positioning and room equalization. Anyone in the know will tell you that room EQ hardware and software should be a last resort. Correct acoustical treatments will pay much bigger dividends.
If you are like many people, you have recently upgraded your home theater, or you’re getting ready to do so. During this process you’ve likely learned that the speakers in the TV are sub-par and you should upgrade your audio experience to include an external sound system. This has become common practice and common knowledge. What you haven’t learned, and which is probably even more important, is how to upgrade the room itself.
One of the things people overlook when trying to make a home theater, is that a real theater pays a lot of attention to the design and treatment of the theater environment. They have good left-right design symmetry (see the diagram for a sample home theater layout). A good theater also has acoustically treated the space so that people can hear everything that is happening, from anywhere in the theater. This article will teach you some of the tricks of getting that great big theater soundstage into your home theater.
Bass Traps – the low-down solution.
Low frequency problems are common to almost any room, regardless of size. The good news is that, most of the time, the solution is simple: put bass traps in the corners of the room. This is one place where it pays to put a little extra in the budget. Corners are defined as the intersection of two or more surfaces. There are not just corners at the end of each wall, but also along the floor and ceiling where the walls intersect them. The more corner you cover with a good trap, the better bass response you get – it’s that simple. Bass loves the corners, and by putting bass traps there, you keep the bass crisp and natural. If bass frequencies are allowed to build in the corners, it causes the bass frequencies to become muddy and undefined – trap them.
Some bass traps work double duty as broadband absorbers as well, which can keep your costs down when considering covering a bunch of square footage with absorbers. Bass traps alone can solve many problems in your room, and due to the simplicity of the implementation, I recommend you start with these first – at least fill the four main corners.
Foam works. But this is a theater, not a studio. Fabric wrapped absorbers look as good as they sound, and Geometrix™ by Acoustics First, fit the corners like a glove. Pick a fabric and get some quarter rounds to fill your corners – that’s it.
Broadband Absorption – tame the ring.
Another common problem in home environments can be easily verified with a clap test. Go into your room and clap your hands. Most likely you will hear more than just the initial clap. Depending on the severity of the problem, you will hear a flutter, ring, or echo after the initial *pop*. This is caused by the sound waves bouncing around off the hard surfaces of the room and returning to your ears after a delay – the more times they bounce without losing energy, the longer the delay. The best way to remove energy from these waves is to use broadband absorption, but where do you put them?
More than likely, your TV and sound system are going to be in a fixed position, and your listening position will also be fixed – so the early reflection surfaces should be easy to locate. You will need a friend for this activity, a mirror, and a pencil. Have your friend place the mirror flat against the side wall and move it around until you can see the speakers in the reflection from your seat – then mark the wall. This is where you are going to place the absorber. The diagram shows a good place to start looking for these reflection paths. Repeat this for all the walls from all the seats.
What you are looking to create is a reflection free zone, which basically means, wherever the sound could bounce off a surface and get to your ears, we are going to absorb energy from it. You can spend a good deal of time on this, but this is the only step that requires this time and effort, so make it count. Sound travels in all directions from the speaker, including behind it, so put absorbers behind it on the wall. Don’t forget the floors, ceiling, and the wall behind you – sound will bounce off those as well.
This simple process will show you where you need to treat. Hang broadband absorbers over all the early reflection points – left, right, front and back. Absorber clouds should be hung on the ceiling, and place a nice thick carpet on the floor. Placement is the first key to getting this reflection free zone. The second is the right choice of absorber.
To match your fabric wrapped bass traps, the simple choice is get some more panels wrapped in fabric. The Sonora® line of broadband absorbing panels coordinate with the bass traps, and come in a plethora of sizes and mounting options to work in your space. Need 2’x4’ behind the speakers, 4’x4’ on the sidewalls, 2’x6’ on the back wall, and a 2’x6’ ceiling cloud – all in material that match those bass traps? Done.
Finally, use broadband absorption with caution, specifically using too much. If you plan on covering more than 50% of your walls with this stuff, you’re going to notice a muffled almost claustrophobia inducing deadness. We are not trying to suck the life out of the room. We are just trying to take enough energy away from those early reflections to keep the focus on the initial sound produced by the speakers.
Diffusers – put life back into your space.
The steps we have taken up to this point have been using absorption to control excess energy that can have an adverse effect on the listening environment. We have removed the unwanted direct reflections and we have tamed the bass, but there is something more we can do to give life to this room – diffusion.
Diffusion will give us something we couldn’t attain through absorption – a sense of open space. Even after treating with absorbers, there are still areas of the room where sound waves will sit, because your room is a fixed box with fixed speakers. Diffusers scatter the energy, creating ambiance with residual energy, like sitting quietly in a forest – the energy around you being directionless, omni-present, and spacious. This simple step does not remove energy from your room, but redistributes it into a soundscape that can make you forget you are in a room at all.
There are many ways to diffuse the sound and coordinate with your room, from the fabric covered HiPer™ Panel and Double Duty Diffusers™, to the striking line of Art Diffusors® like the Model C, which can be painted to match your décor.
Advances in acoustic treatments are being made all the time, bridging form with function, creating products as visually stunning as they sound – and helping your theater, or any theater, be the best that it can be. So use these tips to set up your home theater like a real theater, and experience the difference a soundstage upgrade makes.
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Acoustics First Corporation supplies acoustical panels and soundproofing materials to control sound and eliminate noise in commercial, residential, government, and institutional applications worldwide. Products include the patented Art Diffusor®, sound absorbers, noise barriers, acoustical fabrics and accessories. Acoustics First® products are sold for O.E.M applications, direct, and through dealers. For more information on acoustical materials and their application, please visit www.AcousticsFirst.com or call Toll Free 1-888-765-2900 (US & Canada).
The complete article is posted at the following link: http://acousticsfirst.com/article-setting-the-sound-stage-how-to-treat-your-home-theater-like-a-real-theater.htm
Setting the Stage for Acoustics First
Posted by Acoustics First in Articles, Home Entertainment, Home Theater, Product Applications, Studio Control Room on February 28, 2013
Setting the Stage for Acoustics First
by Nick Colleran
Originally Published in Productions Magazine Sept/Oct 2012 issue.
Early acoustical theaters were just that – acoustic. The good news and the bad news are usually the same news when a venue sounds incredibly good at the start. An auditorium that projects natural sound well is most often over-powered and overloaded by modern musical performances and the line array sound systems that reinforce them. That’s the bad news in the good news. This type of good room will need to be modified to handle high-powered sound from modern music performances while keeping its sound-enhancing properties. All efforts can be directed into the “how” of doing the job when everyone has heard the “why” it needs to be done.
Re-engineering reinforcement – Modifications for “loud”
The hard back wall of the stage is a significant source for monitor splash-back into the performers’ microphones, reducing gain-before-feedback and enhancing opportunities for system squeals. This is in addition to promoting timing confusion due to slap-back that is usually out of sync with the music. This disturbance and annoyance can be overcome by using materials from the province of industrial noise control. A factory finish, that is a finish for the factory, is also both “roadie-proof” and “on-the-road” compatible. Yes, you can take it with you. This allows one set of materials to follow the performances from one venue to the next.
Curtain call – Reflecting on the stage
The industrial curtains called QFM for Quilted Fiberglass Materials accomplish multiple functions:
Bass control from an internal limp mass, Absorption from quilted fiberglass, and Resistance to abuse from a tough vinyl cover.
The covering is thin enough to avoid reduced effectiveness at all but the highest frequencies and strong enough to withstand stage and road wear. Hanging mass (at one time plywood) with an absorptive cover is a long-standing studio technique to control low frequencies. The newer, non-rigid barriers allow a curtain configuration that is invisible to the audience, while providing a clean sound source for the both the performers and the listeners.
Overhead, not overheard – Many are baffled
Above the stage, there is almost always a large cavity designed for lights and to accommodate rigging. This space can act as an unintended echo chamber. Being out of harms way, the area allows for a lighter and less costly sound treatment with acoustical baffles. Besides the obvious requirement that they work acoustically, they need only to be invisible (usually black) and pass the proper fire code. Acoustically, they have about twice the exposed sound absorbing surface as a wall-mounted panel, by hanging in free space. It’s more surface, less reverberation, out-of-sight and within budget. They are light enough and small enough to travel well if strung in a way that allows easy removal for relocation, such as threaded onto aircraft cable and hung in a line from side-to-side. Adding a fabric finish to the baffles, produces a more decorative product, suitable to the audience side of the auditorium when a more permanent ceiling solution is required.
Stage One – Separating Sound
Stage one of acoustical control often is the stage. Both on-stage and in-studio sound isolation usually begin with structure borne sound traveling through the floor. It is always wise to implement isolation between instruments from the beginning, where it is a “cheap” fix rather a costly solution. This can be accomplished by floating the stage surface, and doing it in several separate sections. As noted previously with the hanging back of stage curtains, mass matters. Mass can come from many different materials whose properties are heavy and dense. They can be common materials such as gypsum or sand as well as more acoustically specific items like sheet lead or mass loaded vinyl barrier. (BlockAid® is a readily available example.) Added mass damps the damage of vibration and reduces ringing resonance.
Once the stage goes “thud” when hit due to its added mass rather than a cartoonish “boing”, it is time to handle the hollow space beneath the stage and fill it with fluffy stuff. This can be whatever attic insulation that is on sale at the local home improvement store. It need only trap the air to prevent its becoming a big bass drum when stomped upon.
Way back in the days of Disco (or Disco daze), complications arose in the studio from the required “lead-foot” kick drum getting into the acoustical piano by traveling through the studio floor as vibration and transmitted up the piano legs. Although studio floors are usually isolated from other rooms, they can still connect within a room. This problem was solved by floating the drum booth independent of the common recording studio floor. At that time this author’s studio went so far as to construct a sand-filled floor set on nine truck tires. The sand provided mass and inertia while the tires created de-coupling from the common structure. Today it is accomplished with high mass materials and off-the-shelf vibration pads, at about the same cost. Independent and transportable compact structures can be created for the individual instruments and be moved with very little heavy lifting.
After stage resonance is reduced by adding a layer of mass loaded vinyl to its surface and the cavity below is stuffed with fiberglass to prevent its ringing or singing along with the music, a second stage may be layered on top of the original and floated on ribbed neoprene pads every 12 inches along standard, 16” on-center bracing. This keeps the guitar amp’s sound out of the vocal microphone stand, bass drum out of the piano legs, and so on, to create increased clarity and improved separation in the live performance.
Islands in the stage will stop transmission transit and are relatively cheap to build into the plan. Separate sections for drums, piano, singer, bassist and guitar amplifier can be buffered with half-inch strips of flexible resilient neoprene without being seen. Much like vocals can be modulated when source through the same speaker as the bass, surfing the bass wave in the stage floor can also add an undesirable tremolo (or vibrato) effect to voice or other wind instrument. (This effect can be demonstrated by auditioning a vocal through the bass player’s amplifier while playing.)
Dome details – Round and around
One technique used in early acoustical performance theaters was the overhead dome. This feature captured wasted sound energy and focused it back to the audience to reinforce sonic energy in areas where it had diminished with distance from the source. With new systems the level is electronically reinforced, not needing further enhancement, which confuses rather than clarifies. In addition, the dome creates a sonic racetrack where the sound moves around the edge in a swirling motion. Anyone who has been in a domed facility during a thunderstorm has heard how sound travels around the perimeter. The RCA dome in Indianapolis provided a good example to CEDIA attendees a few years ago . This phenomenon of raceway runaway can be abated with acoustical “speed bumps” of Melamine foam which easily bends to conform to curves*, keeping the look while truncating the travel of the fast moving sound waves. In this case being unfocused is a desirable trait.
To reduce sound getting into the dome from the line arrays and the like, hanging baffles can be placed around the front half of the perimeter of the ellipse. These may be fabric covered to blend with the décor of the audience area and made from two-inch, seven pound per cubic foot density acoustical fiberglass to extend its absorption range. Being hanging baffles they do not permanently change the original architecture, where that is a concern.
(Don’t Look) Behind the curtain – Unseen, Unheard
When acoustical treatments must be essentially permanent, high efficiency at low cost can be achieved with utility finishes that can be field-cut to fit spaces in cavities behind auditorium side curtains. Factory fit panels require precise measurements to install within curves. Field cutting skips this step as it is, by definition being, done in real time to as-built measurements rather than made to out-of-date plans. Savings derived from the unseen, utilitarian treatments can be applied to upscale finishes for panels in plain sight.
Balcony bounce-back
Another common problem for an older theater in the modern world is sound returning from the balcony face. These are usually concave surfaces that not only send sound back but focus it for feedback as well. Convex curves such as polycylindrical “barrel shapes or semi-reflective half-round, hollow traps can control concave characteristics when interspersed with thicker, flat acoustical wall panels to achieve a combined “Flat” curve.
Definition by Diffusion
Sound intensity can be reduced by the decision to destroy or diffuse. Absorption is the destructive choice, eliminating the problem by eliminating the sound. Care needs to be taken to use only what is necessary and no more.
The other alternative is to spread the sound over a larger area to reduce intensity. This can be likened to spreading peanut butter on bread – it becomes easier to swallow although it is the same quantity as the original lump from the jar. With diffusion, a little goes long way. A single barrel shaped diffuser can clear up the cacophony of a board room without the deadness of absorption required for the same amount sound clarification.
Check back After Launch
With venue retrofits, some tweaks can be made after opening. Covering all walls before there is an evaluation with performers and audience, is not always a good idea. While it may be theoretically possible to model and predict acoustical performance, it can be more economical and efficient to get the room in a reasonable range and polish to the real world result. An informed conclusion, upon hearing the room in use, can produce an optimum result.
*Contrary to popular belief, acoustical foam can be painted to match décor without affecting its performance. (The author has a copy of the independent lab report comparing painted to unpainted natural. Painted measured better, but not significantly.)
The Author
Nick Colleran is past-president of SPARS (Society of Professional Audio Recording Services), past president of the VPSA (Virginia Productions Services Association), a former recording artist and audio engineer.
Starting in 1978, his company began supplying unique acoustical materials. Nick now leads a “quiet life” as a principal of Acoustics First Corporation. The company holds patents for several innovative acoustical products.
Acoustics First designs, manufactures and distributes products to control sound and eliminate noise for commercial, residential and industrial uses.
Materials Mentioned:
Vib-X™ vibration pads | BlockAid® mass loaded vinyl noise barrier | Stratiquilt™ quilted industrial blankets | Cloudscape® Baffles hanging acoustical baffles | Sonora® acoustical wall and ceiling panels | Select Sound™ black fiberglass board | Geometrix™ half-round broadband absorbers
Download of article available here: http://acousticsfirst.com/article-setting-the-stage-for-acoustics-first-productions-mag.htm
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Acoustics First Corporation supplies acoustical panels and soundproofing materials to control sound and eliminate noise in commercial, residential, government, and institutional applications worldwide. Products include the patented Art Diffusor®, sound absorbers, noise barriers, acoustical fabrics and accessories. Acoustics First® products are sold for O.E.M applications, direct, and through dealers. For more information on acoustical materials and their application, please visit www.AcousticsFirst.com or call Toll Free 1-888-765-2900 (US & Canada).
Originally published by Home Toys.
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