Loudspeakers, A complete illustrated guide to stereo speakers
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Definition
Loudspeakers are electro-mechanical-acoustic systems. Another word for speaker is transducer. A transducer is a device that converts one type of energy or signal into another. While there are many types of transducers the ones most common to music lovers are the microphone and the speaker. The microphone is at the beginning of the process and converts sound waves into electrical impulses. A speaker is at the end of the process and converts electrical impulses from the amp into acoustic energy (sound.) A loudspeaker typically accomplishes this conversion by causing a diaphragm to vibrate and send vibrations through the air, thereby propagating acoustic waves.
What Kind of Speakers Do I Need?
Your AV professional can help you with your choice. An appropriate speaker system for a particular application would be one that fits the budget, interfaces well with the room size, design and acoustical properties. In addition, it should have sufficient headroom (question: does everyone know what “headroom” means?) for the demands made upon it with flat frequency response, low distortion and freedom from compression. It must accurately reproduce the audio signal sent to it.
Stereo Playback Diagram
Bravo AV Design Philosophy
In the Audiophile press and on various websites you see people arguing about which component is the most important and often people claim it’s the speakers. We have a different belief. We believe everything in the signal path is important. Therefore our designs focus from the source to the speakers and everything in between. Having said all that the three most significant aspects of a system are: room acoustics, speakers, and source material.
At Bravo AV Consulting we take a holistic approach to the design of audio and video systems. We do this by carefully listening to the client’s wants and needs. We then develop a solution that contains the features and benefits that best fit the client’s lifestyle. Since we carry no inventory and have over 50 brands to choose from we can use our creativity and years of experience to craft a system that offers tremendous performance and value for a given budget. During our holistic design process we select components of a similar performance level. We know that the weakest link will be the limiting factor in the systems performance. Therefore, we pay attention to every facet of the AV system: the things you see and the things you don’t see. We also look towards the future and make sure the system has the ability to evolve as new technologies emerge.
The Myth of the Golden Ear and Audio
An audio/video system is a vehicle for conveying the vast emotional and intellectual potential of music. The higher the quality of reproduction the deeper our connection with the music. Bravo AV Consulting sells products in which you can definitely hear the difference. It does not take a trained or “Golden Ear” to know what sounds good. If you have ever seen quality high definition TV you don’t want standard definition anymore. It’s the same way with a good audio system. Once you have heard quality audio and are moved by the music you don’t want to go back to mediocre sound. Because music is important, re-creating it with the highest possible fidelity is important. Many of us have a practical knowledge of things we like and can communicate our preference without possessing the technical knowledge or specific vocabulary of the true expert. We talk with you using straight forward non-technical vocabulary. Come in and have a listen.
Speaker Types
Freestanding
Freestanding speakers do not go in or on a wall but “stand” on the floor. While free standing speakers are most often associated with traditional 2-channel stereo they can be used in surround sound environments.
Architectural
Architectural speakers can be classified by placement: on wall, in wall, in ceiling and outdoor.
● In Wall Are located in the walls. Speakers in this category must usually be less than 4” deep because the wall depth is usually 4”. However some stud depths are 6” allowing speaker manufacturers more freedom to design really great speakers.
● In Ceiling Are located in the ceiling. Because the joist depth is often 8 or more inches deep, in ceiling speaker designers have more depth to work with and that lets them create a wide variety of speakers.
● In wall and In ceiling characteristics
o Shape Round, rectangular or invisible.
o Quality The quality of in wall and in ceiling speakers can be as outstanding as your budget allows. Long gone are the days when you had to sacrifice sound quality moving from a freestanding speaker to an architectural speaker.
o Invisible Modern invisible speakers sound as good as visible speakers in a similar price range and are very reliable. Invisible speakers are installed to mate seamlessly with the adjoining wall or ceiling and can be finished using the same materials as the surrounding surface including paint, texture, wallpaper or even wood veneers.
o Open baffle vs. sealed enclosure Architectural speakers with open backs are usually less costly, and they can work well for background music in non-critical listening areas. Because there is no enclosure, sound can bleed into adjacent areas and become an annoyance. This result from the fact that as the cone (diaphragm) moves back to its neutral position it is putting sound energy into the wall stud-bay. This is very problematic if the common wall is shared with a bedroom or other room where sound leakage is a major concern. Also, open-baffle ceiling speakers can fall victim to settling construction materials, moisture, and critters. Sealed in-wall and in-ceiling speakers are generally more expensive, and they keep the sound in the intended room. They can also sound better due to the engineered enclosure, which eliminates the arbitrary nature of an open-back speaker. A sealed in-wall that is comparable quality to a freestanding speaker can sound as good if not better. The reflection off the wall behind a freestanding speaker does not exist in an in-wall, plus the in-wall can have a few dB more bass extension.
o Cost A pair of speakers for multi-room application can run from $250 – $7000 a pair.
● On Wall On wall speakers are designed to be mounted on the wall not in the wall. On wall speakers are useful when there is already something in the wall (like a pipe or HVAC duct) where you need to place the speakers.
● Outdoor There are two classes of outdoor speakers: rocks and on wall. Rock speakers look like rocks – they come in many shapes and sizes and are designed to be placed on the ground. On wall speakers are typically mounted on the side of the house.
The Myth of Wireless Speakers
There is no such thing as wireless speakers in the truest sense of the word. Today what is typically referred to as a wireless speaker is an active speaker that requires an AC power cord plugged in to receive its musical information wirelessly. [The exception is relatively inexpensive battery operated speakers, but these speakers are typically poor sounding and chew through batteries.]
Active vs. passive loudspeakers
A passive loudspeaker has no dedicated amplifier, and almost any receiver or amplifier can drive it. An active loudspeaker is mated to an amplifier that is optimized to the speaker -- and that may mean bi- or tri-amplification, protection and/or equalization. The cost of a comparable passive speaker and amplification compared to an active speaker system is usually a wash.
Uses and Broad Applications
One way to characterize the use of speakers is whether they will be used for multiroom audio or for surround sound audio.
1. Multi Room Audio Speakers used for multi room audio are placed in many rooms throughout the house in order to listen to music.
2. Surround Sound Speakers used for surround sound are placed in specific locations in one room and are used to recreate the sound track of a movie. Typically a media room has at least five (5) speakers plus a subwoofer. This speaker configuration is often referred to as 5.1 surround sound. These speakers are called: Left, Center, Right, and two side-surround speakers. In a theater two additional rear speakers are added on the back wall. This speaker configuration is referred to as 7.1 surround sound. In components and speaker systems, a channel is a separate signal path made up of the following: Center Channel: The center speaker in a home theater setup carries the primary amount of information and all the dialogue. Ideally, center speakers are placed within one or two feet above or below the horizontal plane of the left and right speakers and above or below the display device, unless placed behind a perforated screen. Left Channel: The left speaker carries the left audio channel information. Right Channel: The right speaker carries the right channel audio information. Side Surround Speakers: Speakers located beside the listener which reproduce the surround sound channels of surround-sound-encoded audio programs. Rear Surround Speakers: Speakers located behind the listener which reproduce the surround sound channels of surround-sound-encoded audio programs. Subwoofer: A loudspeaker dedicated to reproducing bass (sound with low frequencies.) Subwoofers typically add that shake and rumble to your home theater.
3. Speaker Placement a. Multi Room Typically multi room audio is delivered through one pair of speakers located in either the wall or the ceiling. Aesthetically we prefer to have speakers in the ceiling for the simple fact that people rarely look up. In a big room, two or more pairs of speakers are used in order to achieve a uniform sound field within the room. b. Stereo See Typical Stereo Speaker Setup diagram at the end of this article. c. Surround Sound See Typical Surround Sound Speaker Setup diagram at the end of this article.
Anatomy
Overview
A speaker is composed of drivers, a crossover and an enclosure or cabinet. A raw dynamic driver consists of a basket, cone, suspension (which incorporates components called a spider and surround), a permanent magnet and a voice coil. The drivers are mounted in a cabinet. The voice coil interacts electromagnetically with the permanent magnet, which causes the cone to move in and out. This produces a replication of the input signal. A crossover or dividing network channels bands of frequencies to the appropriate woofer, midrange or tweeter.
Drivers
Speaker drivers include a diaphragm that moves back and forth to create pressure waves in the air. The diaphragm is typically in the shape of a cone or for tweeters a dome, and is usually made of coated or uncoated paper or polypropylene plastic. Of course high-end speakers use other more expensive materials such as Kevlar, aluminum and titanium, although some of the very best drivers use paper cones. Invisible speakers also use special carbon fiber elements to allow sound to radiate through wall finishing materials. All speaker drivers have a means of electrically inducing back-and-forth motion. Typically there is a tightly wound coil of insulated wire (known as a voice coil) attached to the neck of the driver's cone. This cone, dome or other radiator is mounted to a rigid chassis which supports a permanent magnet in close proximity to the voice coil. For the sake of efficiency the relatively lightweight voice coil and cone are the moving parts of the driver, whereas the much heavier magnet remains stationary. Other typical components are a spider or damper, used as the rear suspension element, simple terminals or binding posts to connect the audio signal, and possibly a compliant gasket to seal the joint between the chassis and enclosure. Drivers are almost universally mounted into a rigid enclosure of wood, plastic, or occasionally metal. In operation, a signal is delivered to the voice coil by means of electrical wires. The current creates a magnetic field that causes the diaphragm to be alternately attracted to, and repelled by, the fixed magnet as the electrical signal varies. The resulting back-and-forth motion drives the air in front of the diaphragm, resulting in pressure differentials that travel away as sound waves. Speaker drivers may be designed to operate within a broad or narrow frequency range. Small diaphragms are not well suited to moving the large volume of air that is required for satisfying low frequency response. Conversely, large drivers may have heavy voice coils and cones that limit their ability to move at very high frequencies. Drivers pressed beyond their design limits may have high distortion. In a multi-way loudspeaker system, specialized drivers are provided to produce specific frequency ranges, and the incoming signal is split by a crossover. Drivers can be categorized into several types: full-range, tweeters, mid-range drivers, woofers, and subwoofers.
Crossovers
Crossovers – A Crossover is a frequency dividing network. A crossover is required because no loudspeaker drive unit suitable for serious listening can provide a flat response over the entire musical frequency range. Therefore loudspeakers require multiple drive units in a single cabinet. Theses drive units must be feed (receive and input signal) which is appropriate for their design performance. A crossover, sometimes referred to as a filter network, separates the incoming signal into different frequency ranges, and routes them to the appropriate driver. A loudspeaker system with n separate frequency bands is described as "n-way speakers": a 2-way system will have woofer and tweeter speakers; a 3-way system is either a combination of woofer, mid-range and tweeter or subwoofer, woofer and tweeter. Passive and Active Crossovers. Consumer speakers use passive crossovers. That is, the operational parameters are established at the time of design and do not change. Some consumer speakers allow slight adjustment in the cross over by means of a switch or deal in the back of the speaker that can adjust to tonal balance of the speaker to compensate for the room they are placed in. Pro or live sound speakers use active crossovers which lets the sound technician adjust the speakers to better suit the venue and the bands needs.
Cabinets
You want the cabinet to be inert in that it will not resonate and thereby “color” or distort the music. To achieve this speaker designers create rigid internally braced cabinets typically lined with sound absorbing material. With in-wall speakers, the wall cavity can create the cabinet, or a back box may be utilized. Back boxes help with maintaining consistent performance and help minimize sound transmission between spaces when using in-wall or in-ceiling speakers. The better in wall speakers have extensively braced and dead enclosures, just like the best freestanding speakers.
The Difference with Invisible Speakers
The best invisible speakers use the same types of crossovers and drivers as visible versions, but the components are over-provisioned for added reliability and they are enclosed behind a flat-front radiating panel face that installs into walls or ceilings. They can be used comfortably anywhere you would use a visible in-wall or in-ceiling speaker and include subwoofer capabilities. Due to their unique radiating characteristics, invisible speakers also offer wider coverage angles than most visible speakers allowing for added flexibility in placement and typically a smoother and broader sound field within the listening area. Since they can’t be seen after installation, invisible speakers also solve visual symmetry issues or other aesthetic challenges.
Anatomy Summary
To work best, crossover and driver components must be of high quality and properly implemented. The enclosure must also be properly designed and it must be acoustically inert as not to add any spurious distortions. See “Speaker Anatomy Figures” at the end of this article.
Speakers and the Room
The room has a major impact on how the system will sound. Each room needs a mix of reflective, absorptive and diffusive surfaces. A full discussion of room acoustic is not practical in the article. For more information you can read our article on Home Theater Acoustics or call us. As Home Acoustic alliance Level 1 acousticians we can help you get the most out of your speakers.
Speaker Type Figures
Speaker Anatomy Figures
For additional resources, please visit our page on Home Audio with articles like this on everything you need to know about speakers and surround sound. Additionally, you can check out our photo gallery on the same page to explore our previous work.
Bravo AV is proud to be an HTA (Home Technology Association) Certified Installation Firm and professional A/V experts. Tom Curnin, the owner of Bravo AV, is a CEDIA Professional Designer, a certified THX Level 1 home theater professional and a member of the Home Acoustic Alliance trained to Level II. You can contact Tom directly at (908) 953-0555 or through email at Tom@BravoAV.com.