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Home Audio Tips

Home Audio Tips from Speaker Shop

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Are you listening to TV and movies through those tiny speakers built into the TV? If so, you're only getting half of the home theater experience.

Home theater is all about surround sound and the way that your audio system interacts with your TV and DVD player to create a realistic cinema environment. With the help of our friends at Speaker Shop we have gathered all of the information you need to understand the terminology and how it all works.

After you read through all of this information below, you should have a decent understanding of how it all works. If you have any questions or if you are looking for the perfect solution for your living room talk to our friends at Speaker Shop.

Preparing the Room
One goal of a home theater is to re-create the same sounds and effects that the audio director heard when the soundtrack was recorded. But every room adds its own characteristics to a given sound, and the same speaker can sound differently from room to room. A square room, or room with parallel walls, is likely to cause problems because sound waves will bounce back at themselves and, depending on their wavelength, can amplify or cancel themselves out. Basically, all bare surfaces in a room can be problematic for home theater sound.

Oddly shaped rooms with walls of different lengths often make the best home theaters. Reality, however, is that the room you choose- a living room, bedroom, etc.- was built long before you decided to turn it into a home theater. So you make do with what you've got. Variations in speaker placement and efforts to "deaden" the room will make a difference. Adding carpeting, furniture, and hanging things on the walls will help minimize acoustic anomalies.

Another way to correct for a room's natural acoustics is to add an electronic equalizer to your system. Equalizers allow you to increase or decrease specific frequencies of the audio signal. Some equalizers include a pink noise generator, microphone, and spectrum analyzer. With these features, the equalizer helps guide you electronically through the process of "flattening" the room's response.

Speaker Placement
All three of the front speakers- left front, center, and right front are intended to be directional and should be placed at approximately the same height and distance from the ideal listening spot. The center speaker should be placed as close to the Television as possible so that the audio appears to come straight out of the picture. The front left and right speakers should be placed far enough from the TV to ensure that you can distinguish sounds coming from the left and right. Audio purists recommend placing the speakers at a 45 degree angle to mimic the conditions set by the mixer at the film studio. For many rooms, the combination of the screen placement rule with this 45 degree rule means spreading the front left and front right speakers as far apart as the room will allow.

The rear speakers are provided with signals intended to simulate the surroundings of what is occurring on the screen. If you are primarily using Dolby Prologic, the speakers do not need to be pointed at the ideal listening spot. Instead, they should be placed so as to diffuse the sound throughout the room. Remember, the two surround speakers are receiving the exact same signal. The best spot is usually above and slightly behind the listening area. Often, facing the speakers at one another from either of the side walls achieves the desired affect.

For Dolby Digital and DTS applications, there are differing opinions on surround speaker placement and type. Bi-pole and Dipole speakers were popularized with the advent of home theater when the rear (surround) speakers were sent the same signal. It made sense to diffuse the audio track when both speakers were being sent the same signal. Bi-pole speakers diffuse the sound by sending the same signal at the same time in opposite directions, usually toward the front and the rear. Dipole speakers send two signals 180 degrees out of phase. This means that while one speaker driver is "pushing out" the other driver is "sucking in". Both of these configurations are designed to spread the rear signals in such a way as to make the exact location of the signal source difficult to pinpoint.

But now, with discrete signals being sent to all five speakers, the recording engineer has the option of localizing rear signals or combining them with any of the other speakers. Just as with stereo panning and imaging, the engineer can now create incredible effects between the rear right and front left, the rear left and front center, the front right and rear right, the rear right and rear left and front center, etc. to better match the activity occurring on screen. The multiple combinations are endless, providing plenty of opportunity to create a diffuse sound field when needed, but also more localized and identifiable sound patterns when desired.

A matched set of speakers all around means a smooth transition of audio signals moving seamlessly from one part of the room to another. Using bi-pole or di-pole speakers to intentionally disguise the source of the audio, simply reduces the optimum effect. They were great for Dolby ProLogic, but they are no longer enhancing the movie viewing experience. You will read and hear differing opinions on this, but they usually come from the same people who have already invested in bi-pole or dipole speakers when ProLogic was king.

All of this has produced a growing trend among audiophiles, with which we happen to agree. This philosophy is to use the same mono-pole speakers in the front and the back. This has always allowed for the best system for audio-only applications and now, with 5.1 discreet channel separation, home theater applications as well. Place the rear speakers at about the same distance from the ideal listening spot as you did the front left and right speakers, and about the same height or slightly higher. Then aim the speakers directly back toward the listening area. This will help produce the best sound field for Dolby Digital and DTS applications. The rear (surround) speakers might be a bit more noticeable with Dolby ProLogic recordings, but hey, the future is digital. All HTD speakers utilize a mono-pole design.

The powered subwoofer can be placed just about anywhere in the room. This is because the human ear has a great deal of trouble localizing frequencies below 100 Hz. This is especially true indoors where the reflections, standing waves, and boundary effects make it nearly impossible to identify the source. In fact, low frequency effects (LFE) are more often felt than heard. You should be aware that corners tend to amplify the bass frequencies. This can sometimes cause distortion in the bass frequencies that "muddy" the sound. However, if you're not getting the rumble you were expecting, experiment placing the subwoofer nearer a corner before you invest in a bigger, more powerful sub.

Today, there are four primary ways an audio signal can be processed, all of which are determined by how the signal was originally encoded:

Stereo - a separate left and right channel. This is available as long as the recording was made with two separate channels.

Dolby ProLogic - separates a Dolby Surround Sound encoded stereo signal (two channels) into four separate channels- One for the Front Right, One for the Front Left, One for the Center, and one for the Rear (both rear speakers get the same signal).   While Dolby ProLogic does not provide a separate channel for Low Frequency Effects (LFE), a powered subwoofer can, and should, still be added for separate amplification of the bass frequencies.

Dolby Digital and DTS - include 6 separate audio channels.   Five of these signals carry the full range of frequencies audible to the human ear (Front Right, Front Left, Center, Right Surround, Left Surround) and one signal carries only low end, or bass frequencies for special effects (sometimes referred to as the LFE channel- "Low Frequency Effect"). You will often hear the term "5.1" or "Five Point One" to describe this concept.

NOTE: Dolby Digital for home theater was originally referred to as AC-3 to distinguish it from the Dolby Digital intended for a regular movie theater. The difference is so slight that Dolby now prefers to simply call them both "Dolby Digital".

Only a digital source (DVD, Laser Disc, digital satellite or digital broadcast) can include these 6 separate channels. Dolby Digital and DTS are competing technologies based on the 5.1 concept. To learn more about Dolby Digital, go directly to the source, Dolby Laboratories.

DTS
Lately, there has been a great deal of confusion about the digital audio format known as DTS. DTS is similar to Dolby Digital in that it provides 5.1 separation.   DTS is not a Dolby technology and is in fact a competitor. Both technologies use digital compression when recording the 5.1 information. The main difference between the two formats is that DTS utilizes less compression than Dolby Digital. Some say that this results in a "fuller" sound, while others say the difference is insignificant.

Many movies have been recorded in DTS and are played back in theaters which include DTS decoding. For home audio, however, Dolby Digital is more prominent for DVD's, although more and more DVD's are being produced with DTS   Most hi end processors already include both Dolby Digital and DTS decoding.

DVD's have the capability of including up to eight audio tracks and according to Dolby Laboratories, Dolby Digital or PCM will always be provided on one track as the standard. This leaves the remaining tracks for additional languages, or other technology formats such as DTS.

Most receivers include amplifiers to drive at least two channels, with a growing majority of receivers now offering five channel amplification. Amplifiers are designed to handle a certain level of impedance placed on them as a result of the speakers connected to them. In general, you want to match the impedance from the speakers to the impedance rating of the amplifier. Most amplifiers (and receivers) are rated at 8 ohms, but they can typically handle anywhere from 4 ohms to 10 ohms without difficulty (check with the manufacturer of the receiver to be certain). A majority of speakers, including all HTD speakers, are rated at 8 ohms so they can safely be connected to an amplifier rated at 8 ohms.

If you are using a speaker selector box, this device is wired to automatically connect all of the speakers in parallel. Most speaker selector boxes offer impedance "protection" by including resistors that prevent the impedance level from ever dropping below a certain level. This is NOT the same as impedance matching. And while you do not have to use impedance matching volume controls when using these impedance "protection" devices, the result is that the sound level is greatly reduced. Impedance "matching" allows for the best performance from both your amp and speakers.

If you connected all five pairs of these speakers to a single impedance matching volume control that was set to x4, the impedance seen by the amplifier would be 1.6 x 4 = 6.4 ohms which is well inside the acceptable range of most amplifiers. If you set the volume control to x2, the ultimate impedance would be 3.2 ohms which is outside of the acceptable range. If you set the volume control to x8, the impedance would be 12.8 which is also outside the acceptable range.

The Components

Big Screen Television (or projector and screen)- We recommend spending the majority of your home theater budget on the Television.   While the signal source- cable, DVD, VHS, etc.- will have an effect on your video enjoyment, the resolution, functionality, and size of the TV will have by far the greatest impact. HDTV (High Definition Television) capable sets are now very affordable as rear projection technology has gotten much better. "Regular" analog big screen TV's now only offer a slightly better bang for the buck. We go into more detail about HDTV at the bottom of this page.

Speakers - Every article you read seems to agree that the most significant impact on audio is the speakers- not the receiver, not the amplifier, and not the signal source. Choose wisely. With HTD speakers, you get the quality and fidelity of speakers costing twice as much at retail by buying direct.   1/4 of your budget can be applied toward speakers instead of 1/2. Put your savings toward a bigger TV or new DVD player.

HiFi VCR - The VCR is a relatively old technology and as a result, even the most feature-packed units are now very affordable.   Your VCR must include HiFi stereo outputs in order to enjoy surround sound from a VHS tape. If you are buying a new VCR, you should also make sure it includes 4 video heads. 4-head VCR's provide cleaner looking slow motion play and freeze frames.   Super VHS (S-VHS) is a nice-to-have feature that provides 60% better picture quality than regular VHS. Super VHS is great for recording from digital sources. The only downside to Super VHS is the cost. This feature typically adds another $200-$300. We recommend VCR's with and without this feature.

The versatility of the HiFi VCR for playing old movies and home recordings makes it a must-have for any home theater. A high quality, highly functional, HiFi VCR can be purchased for around $150.

DVD Player - To date, this is the greatest movie machine for the home. DVD's offer 345,000 video pixels per frame. By comparison, S-VHS provides 250,000 and regular VHS 150,000. DVD's also offer as many as 8 tracks of audio. Don't confuse audio "tracks" with "channels". One audio track can contain the entire digital bit stream of Dolby Digital or DTS which includes six audio channels.

DVD Players also play CD's, so if you're still in the market for a CD player, consolidate your money for a better DVD player. A good DVD player costs about twice as much as a VCR. If you've got an HDTV, be sure to get a DVD player with progressive scan capability in order take advantage of the extra resolution.

Laser Disc(LD) - The first real high end video source. If you don't have one currently, we don't recommend buying one. With the advent of DVD, the Laser Disc is on the verge of extinction. Some manufacturers offer a combo DVD/Laser Disc player for those of you who own Laser Discs and are looking to add DVD but don't want two players, but these players are getting more and more difficult to find.

Satellite and Cable Broadcasts - Offer the most programming choices. With satellite, like cable, you subscribe to a service of your choice for a monthly fee. Unlike cable, a satellite dish and receiver are not usually free of charge. You buy and keep the equipment. Local TV stations are not always available and when they are, there is usually an extra fee to get them.

For satellite broadcasts, we recommend DSS which is a standardized system. This means you can mix and match DSS dishes and receivers made by different manufacturers- although if you are starting from scratch it is best to select a dish and receiver from the same manufacturer. DSS systems allow you to subscribe to the popular DIRECTV and USSB programs. These programs offer the most popular movie channels like HBO and Cinemax as well as special sports packages and pay-per-view movies and specials.

DSS systems are fairly easy to install (some easier than others, so check out the "install" features provided with your satellite dish and receiver).   It is estimated that 80% of DSS users install their own systems. Custom installation will usually cost you between $50 and $100 dollars although packaged deals with equipment, installation, and a year's subscription are often available for a smaller up-front charge. All satellite dishes require a clear view of the sky although bad weather, clouds, etc. rarely interfere with your reception.

For the moment, we do not make manufacturer recommendations for DSS products. This is primarily because "deals" are always being offered, by region of the country, for combinations of systems and subscriptions. We recommend checking your local paper for current specials.

Audio/Video Receiver - Think of the A/V Receiver as the hub which determines which source (CD player, Radio, DVD player, VCR, Tape Deck, etc.) will send the audio (and often video) signal to the speakers and Television. By definition, a receiver includes a tuner for listening to AM and FM stations. "Home theater" receivers include an audio processor and decoder for reproducing the surround sound experience. Most AV receivers now include the ability to decode both Dolby Digital and DTS encoded material. (see PROCESSORS below). While you can buy decoders and amplifiers separately (conveniently called "separates"), the best value comes from receivers that have the amplifiers built in. Most include five or six channels of amplification to cover the five full range channels in 5.1 and 6.l recordings, some even offer enough power for 7.1. The quality of these amplifiers will make a significant impact in the overall performance of your speakers. We discuss this in a little more detail in the Product Recommendations section. A good digital receiver/processor will cost you anywhere from $300 to $1000 depending on the extra functionality and quality of the amplifiers and processing components.

The Definitions:

DTS
"Digital Theater Systems" - a multi-channel (5.1) digital audio encoding format created by Digital Theater Systems. The DTS format was introduced in theaters in 1993, with Steven Spielberg's blockbuster movie Jurassic Park . In addition, the DTS format has been applied to home CD's, Laser Disks, and DVD's. DTS audio, as used in DVD-Video's and CD's, is compressed approximately 3:1 from PCM recorded with a sampling frequency of 96 kHz and a 20-bit sampling size. DTS is capable of encoding PCM with a sampling frequency up to 192 kHz and 24-bit sampling size.

Dolby Digital
5.1 multi-channel surround format consisting of discreet front left, front center, front right, rear left, rear right, and a low-frequency-effects (LFE) channel. Dolby Digital is compressed approximately 12:1 compared to PCM.

MPEG1
MP3 is the audio coding format defined by the International Organization for Standardization (ISO) as part of the MPEG-1 Audio Layer-3 specification. MP3 has become a popular audio compression format on the Internet and computers.

MPEG2
AAC is the audio coding standard defined by the International Organization for Standardization (ISO) as part of the MPEG-2 specification. Declared an international standard in April 1997, MPEG-2 AAC builds upon and extends the popular ISO/MPEG-1 Audio Layer-3 (MP3) audio coding format. Compared to MP3, AAC provides higher quality music with approximately 30% storage space or bandwidth. AAC provides up to 48 audio channels and sample rates up to 96 kHz.

AAC
AAC is the audio coding standard defined by the International Organization for Standardization (ISO) as part of the MPEG-2 specification. Declared an international standard in April 1997, MPEG-2 AAC builds upon and extends the popular ISO/MPEG-1 Audio Layer-3 (MP3) audio coding format. Compared to MP3, AAC provides higher quality music with approximately 30% storage space or bandwidth. AAC provides up to 48 audio channels and sample rates up to 96 kHz.

SACD
Super Audio CD (SACD) is a technology for high resolution multi-channel digital audio recordings proposed by Sony and Philips. SACD albums must contain one layer with the "Direct Stream Digital" digital encoding format which requires a SACD capable player. "Direct Stream Digital" encoding will be able to provide a frequency response from DC to 100 kHz with a dynamic range of 120 dB. Stereo SACD players have 2 outputs and can play stereo recordings. SACD albums can optionally contain a second layer encoded with the CD-format (PCM at 44.1-kHz/16-bit) in stereo allowing compatibility with existing CD players.

SACD Multichannel
Super Audio CD (SACD) is a technology for high resolution multi-channel digital audio recordings proposed by Sony and Philips. SACD albums must contain one layer with the "Direct Stream Digital" digital encoding format which requires a SACD capable player. "Direct Stream Digital" encoding will be able to provide a frequency response from DC to 100 kHz with a dynamic range of 120 dB. Multichannel SACD players have 6 outputs and can play 5.1 or 6 channel audio. SACD albums can optionally contain a second layer encoded with the CD-format (PCM at 44.1-kHz/16-bit) in stereo allowing compatibility with existing CD players.

D2D
Products that have pure digital signal paths for their digital audio or video signals. The signal must stay in a pure digital form at every stage and not pass through any analog to digital or digital to analog converters. If the device contains an audio amplifier it must be digital amplifier. If the device is a signal source like a Digital Video camera, DVHS recorder, satellite receiver or a CD,DVD, MP3, or AAC player it must have a digital output so the audio or video signal can be preserved in its digital format. If the device is a digital amplifier it must have a digital input so the audio signal can be introduced in it's digital format. If the device is a digital video monitor it must have a digital input so the video signal can be introduced in it's digital format. If the device has fully pure digital signal paths for all its signals it can use the simpler D2D Rating. If it only has pure audio or video it should use the D2D Audio or D2D Video rating.

A2D
These products are Hybrid analog and digital. The signal path in the device is partly analog and partly digital. If the device is a digital amplifier it is only equipped with analog inputs. If the device is a signal source like a Digital Video camera, DVHS recorder, satellite receiver or a CD, DVD, MP3, or AAC player the digital signal is converted to analog before it is presented to the digital amplifier or digital output. These devices are inherently impure because the digital input or source signal must be converted to analog before it can be output or amplified digitally. Many devices labeled Class T have this Hybrid A2D rating because the Tripath amplifier chips they employ only have analog input capabilities and are therefore inherently NON Pure.

D2A
These products are Hybrid analog and digital. If the device is a signal source like a Digital Video camera, DVHS recorder, satellite receiver or a CD, DVD, MP3, or AAC player they do not have digital outputs. They are only equipped with analog audio outputs. Since these devices have digital signals that can only be used in an analog form they are inherently NON Pure.

A2A
Products that are totally analog. They have analog inputs and analog outputs. The signal is not digital at any point in the signal path.