The performance characteristics of the Home theater are critical to delivering a total theater environment to our clients. The artful combination of superior aesthetic design with performance-quality acoustics provides clients with the most realistic theater experience possible.
Theo Kalomirakis theaters can be acoustically designed from a theoretical and practical standpoint to provide the Customer with an architectural space that maintains and enhances the sound quality produced by the installed audio system. Thorough acoustic analysis has been performed on every design with respect to the following areas:
room sizing and shaping
room mode distribution
early reflection control
average room absorption
spatial enhancement location of diffusive treatments
isolation of sound between the Theater and adjacent spaces
ambient noise criteria
control of noise from HVAC (heating, ventilating & air-conditioning systems), audio/visual and electrical/lighting systems.
Where it has not been possible to accurately predict the existing conditions of each Customer, we have provided specific guidelines for a general contractor to follow for achieving the optimum acoustic quality. If a Customer is interested in having the acoustic design fine-tuned to his/her specific conditions or needs, Theo Kalomirakis Theaters can offer this as an additional service.
Frequently Asked Questions
ARCHITECTURAL ACOUSTIC DESIGN
The interior design of a theater is augmented with acoustic treatments that provide a high-quality stereo and surround sound imaging, enhanced spaciousness and localization of sound. Described below are the acoustic factors necessary to address in the design of a home theater along with the specific methods used to address them in the Signature design and the tested or predicted results. In order to explain the effect that the room size and shape has on the acoustic performance of the theater, we must first review the principles of room modes and modal distribution.
What are the basic definitions of sound?
Sound is made up of one or more pressure waves that cycle between high and low amplitude regions. The time period of each cycle is known as its frequency, expressed in terms of Hertz (Hz.). The physical length of each cycle is known as its wavelength. Lower frequencies have longer wavelengths. For instance, a sound with a frequency of 1000 Hz has a wavelength of one foot, while a 60 Hz sound has a wavelength of approximately 18 feet. The effect of the longer wavelengths in a small room (like a home theater) is a potential variation of loudness level dependant upon listener position in the room.
Do we have to worry about these frequencies at all?
Actually, this potential acoustic problem only occurs for frequencies below about the 250-300 Hz range, where the distance between the high and low amplitude portions of an individual wave are significant enough to produce the perceived variation in sound level. In order to minimize this effect, one must analyze the distribution of modal frequencies (modes) in the room.
What is a mode?
Given a distance, L, between any two planar surfaces (two walls or a floor & ceiling), there is a fundamental frequency equal to c/(2*L), where c is the speed of sound in air – 1170 feet per second. For example, a room with a length of 32 feet will have a fundamental frequency of about 18 Hz. The modes for this pair of surfaces are then defined as the fundamental and all of its multiples (e.g., 18 Hz, 36 Hz, 54 Hz, etc.). The modes between just two surfaces are referred to as axial modes. There are other types of modes that interact with four and even all six boundary surfaces of the room, known as tangential and oblique modes, respectively. Since the energy level of these types of modes, however, is much lower than that of the axials (through the impact on more surfaces), it is often necessary to evaluate only the axial modes.
Once all of the modes between the three pairs of surfaces (front/back wall, side walls and floor/ceiling) are calculated and listed together in ascending order, they must be evaluated to ensure that a: there are no two adjacent modes that occur at the same or within a 2 Hz frequency of each other and b: that the average spacing between all modes is no greater than 15 Hz.
Why are these criteria important?
The first criterion is important for two reasons. First, if two or more modes occur at the same frequency, the peaks and dips in the wave amplitude will sum together – thus resulting in even greater variation of sound at different listening positions. Second, if the modes are not exactly at the same frequency but still within a small differential, a phenomenon called beating occurs, where a listener can actually perceive a note sustained at one modal frequency shifting back and forth between that frequency and another closely spaced modal frequency.
What is the difference between a mode and a standing wave?
There is none. The term standing wave was developed due to the fact that, in rooms with strong individual modes or multiple modes occurring at the same frequency, the high pressure region of the wave (or note) almost appears to the ear like it is “standing” in place.
How does this apply to room shaping and sizing?
The Home theater design team has determined 3 recommended theater sizes for a given ceiling height that will achieve an excellent modal response. The size and proportions of the room directly influence the modal distribution. If either length, width or height are the same dimension or multiples of each other, than there will be modal overlaps.
Why aren’t the walls in the Home theater non-parallel to help eliminate the modal problems/standing waves?
This is a common misconception. Because of the long wavelengths in the low frequencies, slightly angling the walls will not break up, or diffuse, the room modes. Rather, it will take a modal condition that can be calculated (see worksheet above for example), and turn it into something much less predictable.
EARLY REFLECTION CONTROL
In any typical room, sound arrives at the listeners? ears via two main paths:
Direct, in (more or less) a straight line between the source and the listener.
Reflected, off of a multitude of surfaces in the room.
Because any reflected sound wave arrives at the listener’s ear slightly delayed in time from the direct sound, there is another phenomenon that occurs known as phase cancellation, or sometimes called comb filtering.
What is comb filtering?
Based on the delay time of the reflected sound which, in turn, is dependant upon the path length difference between the direct and any individual reflected path, the high amplitude region of the direct wave could arrive exactly at the same time as the low amplitude region of the reflected wave – thus canceling the frequency at the listener’s ears. This would occur at the frequency (and all its harmonics) whose wavelength relates to one-half of the path length difference.
Why is this important in the home theater?
The fundamental goal in designing a room for motion picture or music is to achieve the sound at the listeners ears that the producer intends. Assuming a flat response from the loudspeakers, this assumes that the room itself does not distort or otherwise alter the frequency response, the relative amplitude or the time arrival of any sound events. The comb filtering effect, if left untreated, would in fact cause a significant distortion of sound. The distortion would be different as well at every seat (or at least all seats on one side of the centerline of the room, if the room is completely symmetrical) due to varying reflection patterns and path length differences.
Another important reason to eliminate the early-arriving reflections is that a strong reflection can also cause a shifting of an image in the frontal sound-scape. For example, a strong reflection of a speaking voice playing through the center channel loudspeaker off of either side wall can make the voice seem like it coming more from the side of the screen rather than the center. This would be an obvious concern if the film director’s intent was to have the voice be located in line with the actor’s position on screen.
How have these issues been addressed in the Home theater?
In order to avoid the distortion, comb filtering effects and image shift problems, we have analyzed all surfaces that sound could reflect off of and reach the listeners’ ears within a very short time after the direct sound. These surfaces have been treated with sound absorbing materials that are highly efficient at all frequencies above 125 Hz. These materials serve to significantly reduce the energy level of the reflected sound so that it is well below the level of the direct sound. Some comb filtering might occur, but the impact will be so small that no distortion would be heard.
AVERAGE ROOM ABSORBTION AND REVERBERATION TIME
While evaluating surfaces on which to apply sound absorbing materials, we also evaluated the reverberation time, or decay time of the room. Often people make the mistake of applying sound absorbing materials to every possible surface in the room. Not only does this create an unnatural listening environment, but it also eliminates non-absorptive surfaces that can be beneficial for surround sound speakers to interact with (see discussion below on spatial enhancement).
What is reverberation time?
The reverberation time, abbreviated as RT60, is defined as the time it takes in seconds for a sound to decay 60 decibels (dB) in level once the sound source has been abruptly shut off. In most cases, the 60 dB reduction is equivalent to the time it takes for one to no longer hear the sound. To experience the RT of a room, clap you hands in a small office or conference room and hear how quickly the sound decays. Then go into a large atrium or lobby with all hard materials and do the same thing.
It is important to maintain a relatively low reverberation time in a home theater or listening room since this has a direct relation to the clarity and intelligibility of sound. It also allows any type of artificial environmental sound that is recorded onto the motion picture to be translated to the audience, and not masked by a longer decay in the listening room.
What is the reverberation time criteria for the Signature design?
The amount and location of sound absorbing materials have been chosen very carefully to arrive at a balance between reducing early sound reflections and achieving a target reverberation time goal of around 0.30-0.35 seconds at all frequencies between 250 Hz and 4 kHz, and 0.40-0.50 seconds at frequencies between 60 Hz and 250 Hz.
SPECIAL ENHANCEMENTS AND LOCATION OF DIFFUSION MATERIALS
As stated above, having too much sound-absorption in the room can create a difficult listening experience. Yet, having exposed flat and hard surfaces like drywall or wood in upper side wall or rear wall areas can result in several acoustic problems, including:
flutter echoes, or short repetitive echoes of mid- to high-frequencies between two parallel hard walls.
long delayed echoes off the rear wall that can actually shift localization of an image from in front of a listener to behind a listener.
Harshness of the reflected surround sound.
What has been incorporated into the Signature Design to alleviate these concerns?
On relevant areas of the walls, we have incorporated materials that reflect the sound in a diffused manner. That is, the sound is scattered in multiple directions. This eliminates any perceived echoes as well as enhances the surround sound quality by widening the apparent width of the theater.
To ensure that the listeners in the theater do not hear outside noise that could interfere with their enjoyment of movies, or that others who might be in the house are not disturbed at times by the incredibly loud sound that can be generated in the Theater, we have developed construction details to achieve a high level of sound isolation at most frequencies. These details deal not just with the basic wall, floor and ceiling partitions, but also all the critical details involving the sealing of penetrations, partition intersections and edge conditions that are essential to achieving maximum performance. Details for isolating doors and windows are provided as well.
Other companies claim to have materials or details that can achieve complete isolation of sound. These claims are almost never realized in the real world, since the materials do not significantly address low-frequency energy such as that from a subwoofer. Also, since the amount of sound heard on the other side of a room is dependant upon the level of the sound source in addition to the construction, it is impossible to say that no sound will be heard outside of the Theater, especially at the bass frequencies.
Therefore, our position is that the details developed are based on average listening levels and our experience in the use of these construction details in numerous real world project. Our criteria for the isolation performance of the walls and floor/ceiling are based on a single-number field measurement called the Noise Isolation Class, or NIC value. The results, provided that all details are followed precisely will be essentially a completely silent condition at most frequencies, with the potential for just a small degree of bass leakage. This is especially dependant upon the ability to get a good isolating door construction.
If a client intends to play their sound at extremely high volumes and wants total isolation, even at low frequencies, we can provide customized design details to achieve this for an additional fee.
AMBIENT NOISE CRITERIA
Having a noise free environment is extremely important to being able to experience a wide dynamic range of sound. There are many instances where an action scene in a movie builds to a climax of visual and sound level and then suddenly stops with dead silence in the film. To have this immediate contrast in sound level appreciated to its fullest, the theater needs to have a reasonably low background noise level.
How is background noise measured and rated?
The noise in the theater is measured with a special sound level meter that records the average decibel level over a short period of time throughout the seating area. The level is measured in ranges of frequencies call octave bands to allow for a more detailed analysis of the quality of noise in the theater. The measured octave bands are then compared to a set of plots that rate decibel level versus frequency. These are known as the Noise Criteria, or NC, curves.
Can you tell me more about the NC curves?
The NC curves were developed as a comparison of noise levels for different types of spaces. Each curve shown below has a number attached to it. The lower the number, the quieter the space. For any NC curve, the lower frequencies have a higher decibel level than the mid- and high-frequencies. This is because the human ear is less annoyed by the presence of low frequencies – thus, the low frequency level can be higher and still match the tolerance factor of the upper frequencies.
The lowest curves around NC 15 and NC 20 represent the goals for extremely critical spaces like concert halls and recording studios, while a higher level like NC 35 or NC 40 is typically found in office buildings.
What NC level is established for the Home theater?
The target goal for the Home theater is NC 20. Although, in many cases it will be possible to achieve even lower noise levels by following the guidelines included with the Signature documentation package.
The NC 20 curve corresponds to the following target noise levels in decibels:
NOISE CONTROL FROM HVAC, A/V, ELECTRIC AND LIGHTING SYSTEMS
The ambient noise in the theater is influenced by two factors – 1) outside noise sources infiltrating the theater’s boundary partitions, and 2) noise generated by systems that serve the theater.
The first group is addressed through the sound isolation construction described above. The second group is further broken down into categories of HVAC, audio/visual and electrical/lighting systems.
Guidelines for attenuating the noise from HVAC systems that serve the theater are included in the Signature documentation. Issues addressed include: proper selection of air-handling equipment, location of equipment rooms, ductwork sizing & routing, internal attenuation treatments, vibration isolation and proper specifying of registers and grilles.
Guidelines for audio/visual equipment include: containing noise and vibration of projectors, amplifiers & other fan-cooled equipment; vibration isolation and mounting of loudspeakers; and shielding of electrical noise interference into the audio-visual system.
Guidelines for electrical/lighting systems include: locating and attenuating noise of low-voltage lighting transformers and fixtures; electrical noise interference issues, dealing with refrigeration equipment from in-room bars; and selection of quiet dimming systems.
Theo Kalomirakis Theaters
For clients who desire a truly unique theater, Theo Kalomirakis Theaters offers custom theater design services. With a custom theater design, the sky?s the limit. We can create the ?theater of your dreams?, or we can design an entire entertainment complex complete with a host of recreational facilities like bowling alleys, restaurants, night clubs, swimming pools, wine cellars, cigar bars, etc. For clients who have the space available for an entertainment environment, we provide complete design and architectural services to make every dream a reality. As part of our specialized services to our clients, we offer the following:
When a new project is initiated, our first goal is to meet with the client to understand their objectives and to establish a design theme for the theater. We review the client’s requirements ? style, number of theater seats, lobby, ticket booth, etc. ? and the allocated space for the theater. Then, we begin to define circulation patterns and spatial relationships within the theater environment. The Schematic Design, which lacks refined details, serves as a template for the next phase of the process, Design Development. The Schematic Design serves to identify spatial requirements and design intent. At the conclusion of this phase, a presentation is given to the client for review, modification and approval before proceeding to the next phase.
In the Design Development phase, the layout becomes more defined and we begin to articulate surfaces and volumes with regard to form, materials and specific ornamental details. In this phase we produce a much more comprehensive design. For existing residences, we also visit the site to take field measurements of the space. In new construction, we work with the architect and/or the contractor of the project to coordinate our design with their plans. Our design development package includes complete floor and ceiling plans as well as all major elevations. Once approved by the client, it will serve as the framework for the next phase of our services, which is construction documentation.
We follow the design development with the following construction documentation package:
A complete set of construction documents and details to direct the contractor and others in the building of the theater.
A list of accessories, moldings and other fabrication elements that are required for its construction.
A lighting design diagram with appropriately selected light fixtures and a guide for developing a lighting control system scheme to accommodate dimming and pre-programmed theatrical lighting scenes.
Recommendations for acoustical treatments and materials that will deliver a superior listening environment for even the most demanding of sound sources.
Sight-line study to optimize screen viewing.
Aesthetic integration of the audio/video electronics and the HVAC system into the theater design.
Sight-line study to optimize screen viewing.
Aesthetic integration of the audio/video electronics and the HVAC system into the theater design.
The final product is a set of drawings, which takes the design from an abstract idea to buildable reality.
Theater accessories and supplies
Through our Home Theater Supply Division we will provide services required for or in connection with the selection and purchase of furniture, furnishings and related accessories to be used in the Project such as fabrics, carpets, light fixtures, chairs, motorized curtains, acoustic panels, etc.
Construction Management and Coordination
The involvement of Theo Kalomirakis and our project architects during the construction of a theater insures that the design is executed accurately and that a superior level of quality is maintained. We are available to the contractor of the project to answer any questions about the design either by phone or through periodic site visitations. We review and approve shop drawings and samples for specialty construction. We also oversee the selection of various subcontractors for items that require special construction such as millwork, metal, and plaster fabrication in order to secure acceptable bids and workmanship. Our goal is to assist the client and contractor where appropriate.
Theater Construction Cost
As a guideline, typical construction costs to build our designs can range from $200-$400+ per square foot, excluding audio/video electronics and our design fee. The actual per square foot cost will depend upon selected finishes, the level of design customization and fabrication, as well as regional construction costs. During the initial consultation with the client, the allocated space for the theater is determined and measured. Theo Kalomirakis and the client agree upon an initial per-square-foot cost. The project construction budget is calculated by multiplying the square footage of the theater by the cost per square foot. This serves as a benchmark for monitoring construction costs throughout the project.
Fee for Services
Our fee is a fixed amount based on the square footage of the project. Typical fees range from $50 – $80 per square foot. The fee covers the cost of our architectural and design services as well as the construction supervision. During the course of the project, we periodically visit the client and the site to supervise the work in progress.
Upon the request of the client, we will utilize our extensive network of suppliers to order accessories such as seating, fabrics, carpets, appliances, light fixtures, specialty moldings, marquee signs, curtain motors, etc. We will also arrange to have the materials shipped directly to the construction site.