Going to 7.1-Channel Surround Sound

Almost everyone loves surround sound, (except for an eccentric actor whom I know who actually prefers mono!) and what’s not to love? Our ears are on each side of our head, canted forward, but we hear sounds from every direction with almost equal precision. For that reason multi-channel sound reproduction is intrinsically more realistic and believable. But how many surround speakers are required to present a plausible illusion of the real thing?

While Dolby Digital 5.1 (six channels total, including the subwoofer and two discrete surround channels) is the current standard for the digital audio component of digital TV and HDTV and has been the reigning surround format for more than ten years, there are increasing numbers of movies available that utilize the “extra” two back surround channels that define 7.1-channel surround sound.

For newcomers, “Dolby Digital 5.1” consists of three main front channels (Left, Center and Right), the center used to anchor movie dialog and/or vocalists; two surround channels (Left Side, Right Side) and one dedicated Low Frequency Effects (LFE) channel, more commonly known as the subwoofer channel, intended to handle deep bass effects below 100 Hz, hence the “.1” designation of 5.1.

So how is it there are now two additional channels (Left Rear, Right Rear) offered on virtually every current surround-sound receiver?

The short answer is realism: dating back to early experiments in the 1930s by Bell Lab engineers in New Jersey, the more channels of discrete separate channels of sound used to record and reproduce music and sound effects, the greater the realism of the auditory experience. All Bell Labs could manage back then was three channels at the front, but even so engineers and listeners considered three channels “essential” to convey the realism of a live broadcast of the Philadelphia Orchestra piped via three telephone lines to an auditorium a few miles away.

Leap forward 80 years, and digital recording technology makes it comparatively easy to add extra surround channels to the existing Dolby Digital 5.1-channel broadcast standard. The introduction of Blu-ray High-Definition disc technology with its huge storage capacity enables discrete channels of sound moving to 7.1 and even greater numbers. Tomlinson Holman, one of the early pioneers with George Lucas of THX sound systems in cinemas demonstrated a 10.2-channel system that I heard a number of years ago at the Consumer Electronics Show in Las Vegas, and he continues efforts to popularize that system. Even Dolby Lab’s latest “lossy” algorithm, Dolby Digital Plus, enables up to 13 discrete channels of sound. The more popular “lossless” Dolby TruHD and dts HD Master Audio systems contained on many Blu-ray discs permit 8 channels of sound with no sonic compromises.
All About Immersion

What are the benefits of adding the two extra rear surround channels to achieve 7.1, and what circumstances would justify the upgrade? The benefits are greater surround envelopment, depth, and “immersion” in the surround effects field, both for movie effects and for musical ambience, plus much improved surround coverage for various listeners seated throughout the room.

One requirement for 7.1-channel surround is sufficient space behind your couch and listening area—at least 5 feet or more. If your couch is jammed up against the rear wall or you have a comparatively small room of less than about 2,100 cu. ft. (length x width x height), the addition of two rear surround speakers will not likely add significant improvements in envelopment, especially if you are already using Axiom’s QS8 or QS4 “multi-polar” surround speakers. However, if you have the space behind the listening area to play with, and/or your room is medium to large sized (especially so-called great rooms and family rooms), four surround speakers will deliver noticeably improved surround envelopment and coverage for all viewers in different seating locations.

While the great bulk of movie soundtracks (including all SACD and DVD-Audio music discs) are mixed in 5.1 channels, there are increasing numbers of movies (the Harry Potter movies and other movie “spectaculars”) mixed in 6.1 and 7.1 channels, including a surprising number of games. But the real justification for upgrading to 7.1 is the sophistication of smart decoding algorithms from Dolby Labs, dts, and Logic7 (the latter exclusive to Harman-owned companies).

Among its many virtues, Dolby Pro Logic IIx (DPLIIx) as well as earlier versions has the ability to extract or interpolate extra surround data from a standard 5.1-channel mix or even from stereo sources, and re-direct that information to both side and rear surround channels, all of which will increase the sense of depth and precision of the surround experience. (Don’t confuse this process with the “seven-channel stereo” option offered on many AV surround receivers. While pleasant, it only parcels out two-channel stereo among all the speakers in a system.)
Reasons to Believe

No matter how you look at it, there are persuasive reasons to consider upgrading to 7.1 channels with its four surround speakers. Incidentally, there is nothing fake or phony about electronically extracting surround data from existing 5.1 or even 2-channel stereo soundtracks. Just two microphones in a conventional stereo purist recording will pick up all kinds of out-of-phase information, which commonly characterizes ambient surround data, so re-directing those sounds to the sides and rear is really just placing them where they would occur in a dedicated elaborate multi-microphone recording array.

On the road to 7.1 channels, both Dolby Labs and dts previously introduced extended surround formats that use 6.1 channels (a single rear center speaker is utilized besides the left side and right side surrounds), namely Dolby Surround EX 6.1 and DTS-ES 6.1, respectively. The presence of these formats on some DVDs needn’t confuse you (you may even have a 6.1-channel setup already) because both Dolby and DTS processors (and Logic7) will redistribute the surround information to a 7.1-channel setup so long as your AV receiver contains the necessary seven amplifier channels.
Type of Surround Speaker

Finally, the still-debated (except by owners of Axiom multi-polar QS8 surrounds) subject of what type of surround speaker is required for the extra Left and Right rear surround channels continues to surface, in part because of some control-room monitoring setups for SACD and DVD-Audio recordings, where conventional forward-firing surround speakers were used in the back channels. While there are still some who recommend forward-firing speakers for the back surrounds, I’d point out that the original development of dipole, bipole and multi-polar surrounds was to increase diffusion and envelopment in the surround field to simulate the presence of 8 or 10 surround speakers in a large cinema. As such, the Axiom QS8 (or QS4), with its top and bottom-firing woofers and angled dual tweeters comes as close to the ideal for both ambient sound field generation without giving up the specific directional cues sometimes found in movie soundtracks and multi-channel music recordings.
By Alan Lofft of Axiom Audio

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Room Modes and Dealing with Them

The boundaries of a room create what is known as room modes. Room modes accentuate or elevate the frequency response. In many instances certain dimensions work together to create very strong elevations in certain bass frequencies. When this occurs the listeners perception is one of a reduced midrange and soundstage. Very frankly, if you don't get the bass right, nothing ever comes together very well. Contrarily, once the bass is right everything else gets much easier.

The basic function of the PARC is to equalize bass anomalies in the room, commonly referred to as room modes. The most prominent bass anomalies occur when two parallel walls (or floor and ceiling) excite a particular frequency (an axial mode). The distance between the two walls determines which frequency is excited. The most problematic, or highest amplitude, is generally ½ of a wavelength between two walls. The way to calculate the distance is:
½ * speed of sound / distance between walls = Frequency

The speed of sound is ~1130 feet per second (room temperature, sea level). Thus a room with 17 foot spaced walls would have a frequency bump at:
565 / 17 = 33.2 Hz.

This is considered the first mode between those two walls. The second mode is for a full wavelength, which would be at 66.4 Hz. The third mode would be at 3/2 wavelengths, or 99.6 Hz. Each mode has lower amplitude than the previous mode. However, imagine a room where the length is 2 times the width. In this example 34 feet long. The first mode for that room is at the same frequency of the second mode of the width, or 66.4 Hz. When modes combine like this the problem is compounded, and the bass can become very bloated and distorted.

Even at Rives Audio we recommend reducing any bass anomalies as much as possible before employing the PARC; the less electrical equalization the better. However, overdamping a room, or filling it with bass traps can be impractical, expensive, and may not lead to the best sounding environment. The PARC employs the highest grade components and shortest signal paths possible. The goal is to make these alterations to compensate for bass problems with as little effect as possible on anything else in the audio chain.

The PARC operates between 18 and 350 Hz. It attenuates ONLY, there is no gain in the PARC. The purpose is to reduce the frequencies caused by room excitation and elevation in those bass frequencies.There are three bands per channel. These three bands were originally designed to compensate for the 3 parallel surfaces in most rectangular rooms (side to side, front to back, and floor to ceiling). However, they can be cascaded or used in a variety of settings to best suit the room.
1st Axial 2nd Axial 3rd Axial
Height 70 Hz 140 Hz 210 Hz
Width 35 Hz 70 Hz 105 Hz
Length 23.5 Hz 47 Hz 70.5 Hz

For each band there are 3 settings: frequency, width, and attenuation. Frequency is the center frequency that will be attenuated. It is represented in Hz. Attenuation is the dB in attenuation. The number is positive, but the function is reducing the amplitude at that frequency by the dB shown on the display. The range is from 0 to 18 dB. If it is set to zero, then no attenuation is employed. Width is expressed by a Q factor. The Q factor is expressed as:

Center Frequency (Hz) / Width of Frequency (Hz)

Thus the higher the Q the wider the band of attenuation. The width is expressed at 3 db below maximum peak.

parc_graph1.gif

As an example a Center Frequency at 100 Hz, with a width of 25 Hz, would have a Q of 4. Also, Q can be expressed in terms of Octaves. One Octave doubles the frequency. Keep in mind that Frequency is a log function of Octaves, so a center frequency of 100 Hz with a width of one octave is not exactly 100Hz, it's slightly less than 100Hz. In our example of 100 Hz center frequency and a width of 25Hz, the relative octave width is approximately ¼. The Q factor is inversely proportional to the octave width. This is not important, unless you are a musician and more comfortable with octaves. All instructions for set-up will be relative to Hertz, and the Q factor.

The width will change depending on what types of walls, floor, or ceiling you have. In general hard, rigid surfaces, such as concrete, will exhibit a high Q factor, whereas sheetrock on wood studs will exhibit a low Q factor. The lowest Q factor the PARC can produce is 1, which is slightly more than one full octave. This is much broader than we ever anticipate using. The narrowest Q factor is 10, which also corresponds to approximately 1/10 octaves. This entire method is far more comprehensive, accurate, and well suited than the traditional graphic equalizer. Only a parametric can compensate naturally and bring the frequency response, including phase back into balance.

Once the PARC is set up and calibrated the bass response will be near flat. The result will be better bass definition, but also a perceived increase in clarity throughout the midrange and even high frequencies.

Adding the PARC can bring back the clarity and reference quality sound your system deserves.

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Understanding the Differences between HDMI Versions

HDMI has changed versions so many times it's been hard to keep up for most people. We've talked about the versions as part of other articles and documents, but it seemed fitting that we'd formulate and maintain a definitive document outlining the changes in a straightforward and easy-to-digest manner for all concerned.

Hopefully this article helps you understand the format differences and aids in your ability to discern what features are important to you as you shop for HDMI-equipped products.

HDMI 1.0

Release date: December 2002

Specs:

* Single-cable digital audio/video connection with a maximum bitrate of 4.9Gbps.
* Supports up to 165Mpixels/sec video (1080p at 60Hz or UXGA)
* 8-channels of 192kHz/24-bit audio (PCM)

Abstract: The original HDMI v1.0 spec was and remains sufficient for most purposes. The reason is that it is a solid backwards-compatible format that can , through PCM audio handle all of the high definition audio formats present today. The key is having a player that can decode these native HD audio formats to uncompressed PCM. DSD and DVD-audio cannot be natively sent over HDMI 1.0. What HDMI 1.0 fails to do, is account for additional bandwidth provided by Deep Color (10- 12 and 16-bit color depths). It also does not support the new xvYCC color space.

Practical Issues and tips: Most CableTV set-top boxes use HDMI 1.0. The maximum output for this spec is 1080p at 60Hz with 8-bit color depth. Regardless of any display of higher version of HDMI you may have, the source will always limit the maximum bit-depth potential. An HDMI 1.0 device can still pull 8 channels of uncompressed PCM audio and as is perfectly fine for most users.
HDMI 1.1

Release date: May 2004

Specs:

* Added support for DVD Audio
* Slight mechanical and electrical spec changes

Abstract: HDMI 1.1 simply added the ability for the system to transmit DVD-Audio signal over the cbale form the player to the receiving device. If both devices are rated to v1.1 then a DVD-Audio signal can be sent and received. Please note that by "DVD-Audio" we mean the high resolution audio format, not the audio present on a typical DVD disc.

Practical Issues and tips: HDMI 1.1 is very common and was the first spec to hit the mass market apart from CableTV set-top boxes. Many AV receivers came out with this spec and are fine for handling DVD-Audio and uncompressed PCM audio.
HDMI 1.2

Release date: August 2005

Specs:

* Added DSD (Direct Stream Digital) support, allowing native transmission of Super Audio CD (SACD) content at up to 8 channels
* Enabled and acknowledged an HDMI Type A connector for PC-based sources
* Permitted PC sources to use native RGB color-space with the optional ability to also support the YCbCr color space for consumer electronics applications
* Mandated that HDMI 1.2 and later displays support low-voltage sources such as those found with PCI Express technology (the current display interface standard for PC video cards)

Abstract: HDMI 1.2 was the biggest jump since the introduction of HDMI. It really brought the PC market into focus and was developed and announced so as to compete better with the emerging VESA DisplayPort standard. For those still clinging to their universal DVD players, HDMI v1.2 finally delivered the promise of a true one-cable solution for all current high-definition audio sources.

Practical Issues and tips: If you want to utilize a fully native universal DVD player without converting the SACD to PCM then HDMI 1.2 is required. We've found that if the player does a good job at conversion, however, v1.2 isn't always that important.
HDMI 1.2a

Release date: December 2005

Specs:

* Fully specified Consumer Electronic Control (CEC) features, command sets, and compliance tests
* Minor changes to CEC (Consumer Electronic Control) spec

Abstract: This incremental change clarified one of the earlier promises of HDMI, Consumer Electronic Control - a feature that promised "smart" interoperability between components. Unfortunately, this wasn't exactly standardized across the board and, as a result, nearly all manufacturers products only interface within their own brands. Of all things, this is the most disappointing failure of HDMI to-date.

Practical Issues and tips: This is a common format for manufacturers using CEC. There is no practical reason to prefer 1.2a over 1.2. If you don't intend to use the native DSD signal from an SACD player via HDMI, v1.1 is just as good as 1.2 or 1.2a.
HDMI 1.3

Release date: June 2006

Specs:

* Increased single-link bandwidth to 340 MHz (10.2 Gbps)
* Optionally supports 10-bit, 12-bit, and 16-bit "Deep Color" per channel (over one billion colors) up from 8-bit
* Allowed the use of xvYCC color space (previously just sRGB or YCbCr)
* Incorporated automatic audio "lip" syncing capability
* Supported output of native Dolby TrueHD and DTS-HD Master Audio streams for external decoding by AV receivers
* Made available a new Type C "mini" connector for devices such as camcorders
* Added gamut Metadata transmission capability
* Added Reference Cable Equalizer mandate to high frequency displays to recapture degraded copper cable signal

Abstract: To be plain, this update was a complete disaster. First of all, nobody asked for HDMI 1.3, except perhaps the companies behind the new high definition audio formats. Of course TrueHD and DTS-HD, the lossless audio codec formats used on HD DVDs and Blu-ray Discs could be decoded into uncompressed audio by the players. This makes 1.3 irrelevant for audio. What made HDMI 1.3 such as disaster was the increased bandwidth requirements - which hit an already suffering cable market with new requirements for digital signal transmission. Before HDMI 1.3, it was almost impossible to get a non-active copper HDMI cable to pass 1080p at distances greater than 50 feet. After HDMI 1.3, with the addition of Deep Color, that distance shrank to less than 20 feet, causing industry-wide failures on installed cabling systems.

Expensive active solutions started coming on-board to alleviate some of the problems within several months but even today there is a large amount of consumer confusion regarding cable certification and how far a signal will travel over copper cables. The spec also mandated that HDMI 1.3-compliant displays (sinks) which took advantage of high frequency content (Deep Color) must implement built-in cable equalization to help compensate for cable losses through copper cables. Thanks to several companies dedicated to certifying their products for specific distances, this issue is slowly becoming more manageable. The first product on the market with HDMI 1.3 was the PlayStation 3 gaming console.

Practical Issues and tips: HDMI 1.3 is a requirement for Deep Color support or use of the new xvYCC expanded color space. If high definition audio is important to you, you still may not need v1.3 if your player can decode the native HD audio formats into uncompressed PCM audio. This uncompressed audio, up to 8 channels, can be sent over HDMI 1.0.Typically, 24p support coincides with v1.3, however this is nothing more than coincidence of when both format and spec came into popularity.

HDMI 1.3a

Release date: November 2006

Specs:

* Cable and Sink modifications for Type C
* Source termination recommendation
* Removed undershoot and maximum rise/fall time limits.
* CEC capacitance limits changed
* RGB video quantization range clarification
* audio control commands added to CEC and commands for timer control brought back in an altered form
* Concurrently released compliance test specification included

Abstract: An incremental change, v1.3a is mostly an adjustment for manufacturers utilizing CEC features as well as those integrating the new Type C connector (seen only in smaller form factor products and quite rare to-date).

Practical Issues and tips: There is no consumer-focused practical difference between HDMI v1.3a and v1.3.
Summary

We'll be sure to keep this document up to date as soon as any HDMI changes are made and will attempt to clarify any questions or issues raised by readers when going through this list. HDMI seems confusing at first, but if handled well by a manufacturer, the differences can be nearly transparent to consumers. The difficulty comes when selecting budget products that may not implement all of the capabilities needed to maximize the potential of HDMI. In these scenarios it's important to not just pay attention to the version of HDMI, but how HDMI is utilized within the product. For example, HDMI "switching" on a receiver implies that no audio is pulled from the HDMI cable, however if the receiver functions as an HDMI "repeater" then users can expect to pull at least multi-channel PCM audio from the connection.

Stay tuned, because if the past is any indication of the future (and it is) HDMI isn't done yet and will continue to evolve in the years to come.

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Home Theater Set-up Basics 101

Recently, at the Audioholics Showcase Home we've been able to survey some of our neighbors' home theater systems. Despite the fact we don't openly disclose to our neighbors what we do, we've been branded as the "go to" place for any questions related to home theater, speakers and even iPods. Have your builder run 10,000 ft of speaker and audio cable during the framing stage of your house, and the news travels fast among the neighborhood that these guys must know something about home theater.

While most of our neighbors still don't understand what Audioholics is all about, they know that it's a safe bet to come to us with their audio woes. To our surprise we discovered that out of all of neighbors' theater systems we surveyed (nearly a dozen), about 90% of them didn't even have a digital connection between their DVD players and receivers and 100% of them didn't even bother with level calibration or proper bass management setup!

Here are some basic tips we offer for Audiophytes wanting the most from their theater systems:

* clip_image004_172.jpg Properly wire your speakers to your receiver. Use consistent polarity from each speaker to the receiver [red = (+), black = (-)]. Connect the appropriate speaker to the designated speaker terminals in the back of the receiver (ie. your front left speaker should connect to the front left speaker input in your receiver)

* Use the right cables to connect your sources (ie. DVD player, cable box, etc) to your receiver.

References:

Basic Audio & Video Set-Up Guide

Receiver Setup and Connections

DVD Player Setup

Setting Up Your Home Theater System - Basics

Audio & Video Connections Guide

Cable Principles

* Properly set up your speaker system (speaker placement, bass management, etc)

References:

An Easy Solution To Subwoofer Calibration

Bass Management Basics - Settings Made Simple

Home Theater Speaker Layout - An Essential Guide

Subwoofer Placement Guidelines

An Important Note About Volume Controls:

Most modern AV receivers' volume controls don't operate on a 10 point incremental scale where 0 is mute and 10 is full on. Instead they operate on a more precise, usually ½ dB, scale where the larger the negative number is, the lower the volume will be and 0dB is usually very loud and at or near max volume. Remember the volume gets increasingly louder with each clockwise rotation and increasingly lower to each counterclockwise rotation. Always set the volume control to its minimum setting (counterclockwise) when powering up your system for the first time.

A few additional useful tips when planning a Home Theater System:

* Try to avoid placing the primary three front speakers on the ceiling. If they have to be above ear level, angle them down using a device such as the Auralex MoPAD or a proper mounting bracket that can support the speaker.

* Avoid " Cubed" speakers " at all costs. Better sounding speakers with only a modest size increase can be had for the same money or much less. You can also find speakers that integrate better with the aesthetics of your room much more so than those little white or black cubes.

Note: If you already purchased a Cubed speaker system and don't have the ability to return it, make sure you set it up as follows for proper operation.

* Connect all cube speakers to their corresponding connections on the bass module.
* Connect each speaker level connection from the bass module to the corresponding connection on the receiver (ie. center channel to center channel, right rear to right rear, etc)
* Connect an RCA level cable from the sub out of your receiver to the sub in of your bass module
* Set all of the speakers to "Large" in the receivers bass management and the subwoofer to "Yes".
* When in doubt, consult your dealer or the manufacturer.

* Invest in basic calibration gear such as a Radio Shack SPL Meter and Avia Test Disc. Having these tools will ensure more accurate calibration that you simply cannot achieve with just your ear.

* Purchase your equipment from a competent and authorized dealer. If all else fails, solicit their help in setting up your home theater system. Spending your hard earned cash on all of this gear is futile if it isn't properly setup and configured.

Apply the same measures of properly caring for and operating your home theater equipment like you do when you purchase a new car or swimming pool for your home. Doing so will ensure years of carefree listening and viewing enjoyment which can come close to or often exceed the experience you have at your local Cineplex. Now all you need is a pop corn machine and some reclining chairs and you're all set.

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Setting Up Your First Home Theater Surround System: Do's and Don'ts

by Alan Lofft,
Do find the digital output on the back of your DVD player before you connect any other cables to your equipment. It will be labeled "Optical" or "Coaxial" (your DVD player may have both or just one). An optical digital output uses a fiber-optic cable with a square plastic connector (Toslink) on each end. A coaxial digital output uses a standard shielded RCA cable that plugs into the female RCA jack labeled "Coaxial Digital". Both sound the same. Use only one. An optical cable sometimes helps to avoid "ground loops" (see below). This single digital cable, optical or coaxial, carries all six channels of sound from a Dolby Digital 5.1 or dts movie soundtrack. It will also carry 2-channel digital PCM stereo (that's what the data stream from a CD is called, should you use your DVD player to play your CDs). This digital cable does NOT carry video, only audio. Connect it to a digital audio input on the rear of your receiver.

Next, connect the video.

Decide at the outset if you want to route your video cables through the A/V receiver and then to the TV. Doing it this way has two advantages: convenience when you switch the receiver to watch a DVD, as well as the ability to see the on-screen menu for your AV receiver on your TV screen. If you route your video cables directly to the TV display, it's initially easier to connect, but you won't be able to see the receiver's on-screen menu for setup purposes, and you'll have to switch your TV display from the cable or satellite source to the "DVD Input", which might be called "Video 1". In well-designed AV receivers, routing the video through the receiver does not degrade picture quality so long as the component video inputs are "wideband" to 37 Megahertz (MHz) or greater, which will carry HDTV signals with no losses.

In any case, you must connect separate cables to your DVD player to carry the video signal to your TV display or AV/ receiver and then to your TV display. In most cases, your DVD player will have three different types of video outputs. If your TV and/or AV receiver handles Component Video, use those connections. This will deliver the highest image clarity possible from DVDs. There will be three RCA cables required, color-coded Red, Green and Blue and they are sometimes bundled together. If you have an older TV that lacks component video inputs, use the DVD player's S-Video output (it's a single cable with a multi-pin plug). It's the next best. Finally, your TV may only have a Composite Video input, color-coded Yellow. That will yield a decent picture but not the maximum quality available from a DVD.

Your new HDTV and DVD player may also have HDMI or DVI connectors, single multi-pin cables that keep the video in its digital form, rather than converting it to analog, which is what Component Video connections carry. You can try the HDMI or DVI connectors but you may or may not see any difference in video quality over the component video connections. Use whichever connection yields the best picture on your TV display. Note, however, that some new receivers that offer HDMI switching may not process the HDMI signal correctly so that it will display on your TV.

Don't turn the levels of your surround speakers up too high because you can't "hear" them. You aren't supposed to hear them in the conventional sense; that is, if they're set at the correct levels, the surrounds should not call attention to themselves. Surround speakers are primarily used to deliver ambient effects for the on-screen action or to enhance the musical experience by adding the third dimension of space. Their purpose is to provide subtle envelopment of you, the listener/viewer, in the "sound field" or spatial experience of the place or scene occurring on-screen and to immerse you in the delayed secondary reflections of the space where the musical recording was made.

The surround isn't intended to blast you with precise directional cues except for certain hard-mixed sounds that happen off-screen during gun battles, fights, chase sequences and the like. Much of the time, you may wonder if the surrounds are even on-until say, a rainstorm or outdoor sequence or perhaps a phone ringing off-screen suddenly reminds you of how much realism a surround system is capable of.

Note also that surrounds may not be used for long sequences during a movie. Low-budget independent feature films may have few or no surround effects at all. Big-budget action spectaculars, by contrast, will often make remarkable use of the surrounds to involve you in the action.

Don't run your new HDTV (rear- or front-projection), plasma, or LCD panel at its brightest setting and shorten the life of the set (or the projector bulb). In the A/V business, that's called "torching" the set. The brighter you run them, the shorter the longevity of the plasma panel or the DLP/LCD projector bulb. Besides, you'll generally get much-improved highlight and shadow detail and smoother, more natural skin tones when you scale down the brightness and contrast. And that applies to older CRT (picture tube) sets as well.

Try this simple visual test to determine if you have your video image too bright or contrasty. Look at any white area on the screen during scenes from live TV or a movie. It could be the white shirt or blouse on an actor or TV host. Are you able to see detail within the white areas? If you can't, then you are likely running the brightness too high, which washes out fine detail in bright areas. So lower the brightness and/or contrast. There's a reason why control rooms for TV productions and telecasts are always dimly lit: it's because video images on the monitors look best in a dim or darker room and the greatest range of colors and tones can be displayed.

Don't just plunk down that subwoofer in the nearest corner and leave it there, making rash judgments on its performance before you've taken time to experiment with different subwoofer locations in the room. Subwoofer performance is so dependent on individual room dimensions and placement, as well as the relative position of chairs and couches, that you must experiment. A corner sub location will give you the greatest bass output at the risk of boomy or thumpy deep bass. You can always try a corner first; if the bass is too boomy, gradually reposition the sub away from the corner along one wall or the other. Try the "crawl" test, which you can read about here. It works quite well to determine the optimal placement for your subwoofer in any room.

Don't turn up the subwoofer volume too high so you can "hear" it when you've first connected it. Start with the subwoofer turned all the way down while you play a selection of music (not a movie), then gradually increase the subwoofer volume until you detect the foundation of deep bass. Gradually increase the subwoofer level until it's nicely in balance with the midrange and treble. If you've set it correctly, test it with a movie noted for its low-frequency content and you'll likely find that the subwoofer level is ideal. You may still want to make slight adjustments of the subwoofer level using the A/V receiver's remote control during movies or TV shows. Some directors or sound mixers get bass-obsessed and mix the bass levels too loud, which may be distracting and inhibit dialog clarity.

Look at the controls on the back panel of your subwoofer. There should be a control labeled "Crossover" and nearby it may have a switch labeled "Bypass". In most home theater setups that use an A/V receiver, you will set the crossover control inside the receiver (a default setting of 80 Hz works very well in most installations) so the subwoofer's internal crossover won't be needed. Nor do you want to use it together with the crossover in the receiver. That's called "cascading" crossovers and it's not desirable. So if your subwoofer has a "Bypass," then set it to that position. If the sub does not have a bypass setting, turn the crossover control to the highest frequency setting, usually around 150 Hz. That will effectively remove the subwoofer's internal crossover from the circuit.

With all AV receivers and subwoofers, you'll only need a single shielded RCA coaxial cable from the receiver's Subwoofer Out connection (color-coded purple) to the subwoofers "line-level" or "low-level" female RCA input jack. Don't use speaker cable to connect the subwoofer to an AV receiver. That would only be required for a receiver or amplifier that lacks a subwoofer output jack, e.g., an older stereo receiver or integrated stereo amplifier or a stereo "separates" installation. In those cases, you run two speaker cables from the stereo receiver's left and right speaker outputs to the subwoofer's left and right speaker inputs (they will be labeled "Speaker Level Inputs" or "High-Level Inputs") and then from the subwoofer to your main speakers. For that installation, you would set the subwoofer's own internal crossover. Try about 80 Hz as a crossover frequency.

Don't get too fixated on perfectly "calibrating" the level of each channel so they are identical in a 5.1 or 7.1 system. Balancing the relative channel levels is an excellent starting point, but be prepared to make individual channel adjustments until you get a smooth, seamless blend of front channel music and effects, dialog clarity, and surround effects when they're needed, and just the right amount of subwoofer bass. Note that dialog recording quality may vary quite a lot from one movie to the next, or even from scene to scene in the same movie. Some foreign or independent movies are poorly done, with dialog levels that vary constantly from scene to scene. The regional accents may make matters worse. So don't be afraid to make center-channel level adjustments while you're watching if you have trouble hearing the dialog. That's what the center-channel level control is there for.

Do experiment with the location of your center-channel speaker and its sound quality before you drill holes or string wires. Human hearing is especially acute in the midrange where human voices (spoken and sung) reside, and it's where we notice tiny discrepancies and tonal variations most. Moving the center channel speaker either below the TV or above it or even mounted to the wall may dramatically change the tonal balance of the speaker and greatly influence how well it blends with your front left and right speakers. So play a movie as you try different locations and listen to any tonal changes in the male or female voices of the actors. Pick the location that sounds best and works well with your setup. Some compromises are unavoidable, but a little experimentation always pays off in more natural-sounding dialog and better clarity.

Do set your center channel speaker and surround speakers to the "Small" setting. This will route the deep bass to the subwoofer and/or the main left and right front speakers (if they are set to "Large") which is where the bass belongs. Setting a center to "Large" will inhibit dialog clarity and often add some tonal anomalies that you do not want. The vast majority of center channel and surround speakers do not have deep bass capabilities, nor are they intended to because soundtracks mix the bass to the ".1" subwoofer channel.

Do consider getting a test or setup DVD that will help you calibrate and adjust the surround sound levels as well as the video display. After all, you'll likely spend thousands for the HDTV and home theater system. Spending from $20 to $40 for a test DVD and $40 for a Sound Level Meter will help you get the best out of your entire system. Here are several popular test discs, listed in ascending order of ease of use and complexity of test signals: Sound & Vision Magazine Home Theater Tune-Up (DVDI 0790); Avia Guide to Home Theater (Ovation Software); Digital Video Essentials (DVDI 0712). These test DVDs are mostly sold on-line. Try a Google search for outlets.

Don't panic if you hear a loud deep bass hum when you first turn on your AV receiver, speakers and powered subwoofer together with your TV display. The hum is called a "ground loop" and it's a very common side effect of linking audio, video, subwoofers and cable or satellite TV equipment together. There are specific ways to get rid of the hum and often it's as simple as installing a ground-isolating transformer between the incoming cable-TV feed and your set-top box or TV display. Some cable TV system guys even know what a ground loop is and will install an isolation transformer for you. Occasionally just plugging the powered subwoofer into a different AC outlet in the room will eliminate the problem. In every case, however, all ground-loop hum problems are fixable.

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