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A Primer for Home Theater Newcomers


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#1 of 89 OFFLINE   Vince Maskeeper

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Posted March 10 2002 - 02:37 AM

Welcome to the HOME THEATER FORUM, the premiere discussion forum for the hobby and obsession of Home Theater.

As part of our "HT BASICS" area, some of the established members of the forum have all pitched in and created a basic primer of information all newcomers to the hobby should know. This set of posts should help you get acquainted with all the basic concepts involved with this hobby-- and answer some of the more common questions that people have.

This set of tips has been compiled "on the fly"- so while you can simply read it from beginning to end, I have compiled a table of contents to organize the posts into a logical progression to help you make your way through the information.

It is advised that you take a minute and read the topics in the order I have presented them below. I'm sure after finishing, you will find that have a much greater understanding of the technology and the ideology that goes into the hobby of home theater. It might answer some of your questions, and might help you realize some new questions.

See you on the forum!

Vince Maskeeper


Table of Contents

I. General Concepts

What is Hometheater anyway? by Mike Knapp
Home Theater Means Accuracy & Calibration by Jay Mitchosky
What the heck is a DVD? by Vince Maskeeper
Who Invented DVD? by Adam Barratt
What the heck is a Laserdisc? by Vince Maskeeper
HDTV Overview by Ray Melnik
What is a PVR- Personal Video Recorder? by Greg_R
Music Listening as Part of Your Home Theater by Mike Broadman
What are DVD-A and SACD? by Jagan Seshadri
What is a DAD disc? by Philip Hamm
DVD vs. CD, they look the same by Adam Barratt
DVD vs. VHS, why we need DVD by Nate Anderson
Why DVDs are letterboxed by Vince Maskeeper
Why Some DVDs aren't letterboxed by Adam Lenhardt
Common Film Aspect Ratios by Michael Reuben
What is Region Coding? by Adam Lenhardt



II. Software Concepts & Specifics

Anamorphic DVD by Michael Reuben
Dolby Digital Audio Format by Adam Barratt
DTS Audio Format by Dan Brecher
Dolby Prologic and Prologic II by Chris Tsutsui
Older Surround formats vs. modern 5.1 / 6.1 formats by Patrick Sun
A 7.1 surround sound format by Jeff Kleist
What is the difference between MATRIXED and DISCRETE audio channels? by Vince Maskeeper
THX - is this an audio format? by Dan Brecher
Layer Change Pause, Dual/Single Layered DVDs by Chuck Mayer
HD-DVD: High Definition DVD by Jeff Kleist
A complete guide to Laserdisc {GREAT INFO} by Rachael B
Why are some CDs so much louder than Other Cds? by Vince Maskeeper
The Criterion Collection, and its purpose by Paul Dalmaine
Ugly Fire Streaks in Saving Private Ryan? by Jeff Kleist
Getting the most out of your audio and video with a calibration DVD! by Vince Maskeeper
Great sounding DVDs to show off my system by Ash Williams
Great looking DVDs to show off my system by Jesse Leonard
Why won't this DVD play? by Jesse Leonard
Special Edition DVD vs. Bare Bones DVD by Nate Anderson
Easter Eggs on DVD by Keith_R
Why are DVDs released on Tuesdays? by Jeff Kleist


III. Hardware Concepts & Specifics

If I buy a 16x9 wide screen TV, will I get rid of the black bars forever? by Vince Maskeeper
16x9 vs. 4x3 - Which type of equipment setup should I select? by Neil Joseph & Cees Alons
Understanding Basic Hardware by Chris Matson
General Hookup Tips by Steve Berger
Different Video and Audio connection cables and types by Chella
Why receivers have video ins and outs by Neil Joseph
Options for Routing Audio & Video by Ted Lee
Digital Audio: Optical Connection vs. Coax connection by Neil Joseph
Purposes of 6 channel inputs and outputs on HT equipment by Vince Maskeeper
Not Able To Get DTS Audio? by John Garcia
Why is CD and TV so much louder than DVDs- Did I hook it up wrong? by Vince Maskeeper
DVD setup with 16:9 TVs by William K F
Amplifiers & Preamplifiers by Cees Alons
Why You Need So many Speakers by Ted Lee
Do I really need a subwoofer?? by Cees Alons
More on the purpose of Subwoofers and how to connect by Neil Joseph
Can I use bookshelf sized speakers for my HT? by Ted Lee
Where am I supposed to put all these speakers? by Ted Lee
Speaker Positioning and Aiming by Neil Joseph
Dipole Type Speakers by Andy W
Why is my subwoofer/speaker humming? by Greg_R
Line conditioners and surge protectors by Bill Kane
So where do I put all this stuff? by MarcVH
Color and Video Signals by Cees Alons
Displays: Color Decoder, Red Push, Grayscale by ThomasL
Front Projection - How do I select one for my needs? by Neil Joseph
Universal Remote Controls by Ted Lee
An Overview of Calibration and Reference Level by Vince Maskeeper
Universal and Hi-Rez (DVD-A and SACD) Player FAQ by Brian L

IV. Shopping, Buying, Choosing

Buying speakers from some guy in a white van by Vince Maskeeper
How to decide what to buy (best bang for the buck) by Max Knight
More advice on picking components by Greg R
Choosing the right Speaker Wire by Chris Tsutsui
Choosing Speakers by Jeffrey Forner
Isn't Bose the best? by Jeffrey Forner
The truth about Nuance Speakers by Michael Hein
Advice on Auditioning and Shopping by Robert Gaither
More Auditioning Tips by Jim DiJoseph
More Auditioning/Shopping Tips by Elbert Lee
More Shopping Tips- Discount vs. Audio Specialty Shops by George King
Budgeting for HT, what you need by Adam S
Specific Components Suggested by Robert Gaither


V. Advanced Concepts & DIY Topics

Using a computer in you home theater: An introduction to HTPC by Vince Maskeeper
What is a BFD and do I need one? by Brian Fellmeth
Bi-wiring & Bi-Amping Speakers by Vince Maskeeper
Speaker Wiring and Connections by Earl Simpson
What's an OHM? by Charles J P
Should I consider a Do It Yourself speaker or subwoofer project? by Brian Fellmeth
Speaker Designs and Methodology by Kerry Hackney
More Speaker Designs and Methodology by Earl Simpson
DIY Subs: Understanding Powerhandling by Rudy H
Amplifier Wattage and how it relates to speaker output by Dustin B
Crossovers: Basics and Advanced by Dustin B
How to Solder by Marc Rochkind
What is the Chroma Bug? by Cees Alons



-Vince


(revised 7/07 by Mike Frezon)
Need an introduction to home theater? Check out our FAQ and Primer!!

#2 of 89 OFFLINE   Vince Maskeeper

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Posted March 10 2002 - 02:44 AM

DVDs are widescreen (letterboxed), and widescreen is better!


Many first time DVD buyers notice that DVDs are mostly in the "widescreen" or "letterboxed format", which have balck bars at the top and bottom, and they wonder why.


Well, next time you go to your local movie theater, take a close look at the movie screen. You'll find that modern movie theater screens are actually a rectangular shape (they are much wider than they are tall).

[c]Posted Image[/c]

Modern movies are shot in such a way that the shape of the picture is a rectangle. While you watch a movie in the theater, take note of how WIDE the movie picture is.


Now, when you get home - take a look at your TV set. Your TV set (if it's a regular TV) is basically square shape. It's not that wide rectangle you saw in the theater, it is closer to a perfect square.

[c]Posted Image[/c]



Now- In order to make the rectangle movie picture you saw at the movie theater fit in your square tv, one of these two process is usually used:

1) The studio cuts off the sides of the rectangle picture and make it a square (obviously losing picture area from the original film). This is called PAN & SCAN, and it is probably what you're used to if you watch movies on VHS or on Cable TV. You might have seen the warning "THIS FILM HAS BEEN MODIFIED TO FIT YOUR SCREEN"-- they are letting you know they've cut off big pieces of the rectangle to make it square.

2) The image is zoomed out a little. This allows your set to fit the full width of the rectangle inside the square TV shape, but leaves unused areas at the top and bottom (letterboxing). You see black bars because you are seeing the full width of the rectangle, which leaves no picture for the top and bottom of your square shaped TV.


In order to truly create the THEATER in your home (which is the basic goal of Home Theater)-- it is important to present the film as it was originally intended. The only way to respect the film and present it as the director composed it, is to display it without cutting off parts of the picture. Thus, we have widescreen DVDs.


The proper way to show widscreen films without cutting off the sides of the picture, is letterboxing.


This respect for the original shape of the film is often referred to as OAR, which means presenting a film in its original aspect ratio.

In other words: OAR means presenting the film including the entire picture the director intended you to see. The Home Theater Forum is officially PRO-OAR.

Aspect Ratio is just the term for what shape the movie is in.


You can learn more about widescreen and the importance of letterboxing here (check out the first one for an excellent animated example):

http://www.ryanwright.com/ht/oar.shtml
http://www.hometheat...home/wsfaq.html
http://www.widescreenadvocate.org/
http://www.thedigita....reenorama.html
http://www.widescreen.org/
http://www.widescreenmuseum.com/

-Vince
Need an introduction to home theater? Check out our FAQ and Primer!!

#3 of 89 OFFLINE   Michael Reuben

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Posted March 10 2002 - 03:03 AM

What are some common aspect ratios?

Books can be (and have been) written on the history of aspect ratios in motion pictures. But let's keep this basic. In the early days of cinema, movies were roughly the same shape as a standard TV screen, which is about 1.33:1 (which means that the screen is 1.33 times as wide as it is tall). The shape of a standard TV is also sometimes described as "4:3". The terms "4:3" and "1.33:1" are used interchangeably.

Fifty years ago, studios were going broke because theater patrons were staying home to watch TV. So they embarked on a campaign to give theatergoers something they couldn't get at home. That's when movies got wider.

Today, the vast majority of films are framed for one of three common shapes or "aspect ratios":

1.66:1: This is much more common than Europe than in the U.S. When a film is transferred to DVD in this aspect ratio, it will have very small black bars on a standard 1.33:1 TV screen.

1.85:1: Very common in the U.S. Films transferred to DVD in this ratio will have somewhat larger black bars, but still less than a third of the available space on a standard TV screen.

2.35:1: This very wide aspect ratio used to be found primarily in epic adventures, but today it has become common for all sorts of films, even intimate domestic dramas like the 2001 Oscar contender In the Bedroom. Films on DVD in this aspect ratio will have very large black bars, roughly 40% of the available display area.

There's another aspect ratio you may have heard about, 1.78:1. It's not from film. Instead, it's the official aspect ratio for high-definition TV. You may know it by its other designation: 16:9. DVDs have a special connection with the 16:9 format, which is the next subject to address.


What are "anamorphic" DVDs?

Many widescreen DVDs feature what's called "anamorphic" enhancement. You can't always tell by looking at the DVD cover, because the studios don't have a standard format for listing this feature. Often it's referred to as "enhanced for 16:9". Sometimes you'll see "enhanced for widescreen TVs". And often there's no mention of it at all (e.g., most DVDs from Columbia Tristar).

The following explanation of anamorphic DVD is one from the vaults. It was written by former HTF admin Rob Gillespie, and it's the best short explanation of the subject I've ever seen.

Rob's explanation talks about "scan lines". "Scan lines" are what make up the picture on your TV screen. Your TV draws 480 visible scan lines across the screen 30 times every second to "paint" the video picture you see. When films are presented in widescreen, some of those lines have to be used to draw the black bars, which is something of a waste. DVDs offer a way to make better use of those scan lines, and that's what anamorphic enhancement is all about:

Quote:
An anamorphically enhanced DVD spreads the image over more scan lines, increasing the resolution. Where do these extra lines come from? Well, on a normal letterboxed transfer, they are the space used for the black matting bars. If you play such a transfer on a standard 4:3 TV, the image appears tall and thin.

OK so far?

When an anamorphic DVD is played back, obviously the image needs to be restored to it's correct proportions. There are three ways this can be done.

On a standard 4:3 TV, the 'squeeze trick' can be done. This consists of entering the service mode and reducing the vertical size of the viewable picture until the proportions are correct. You're basically doing the same adjustment that's possible on computer monitors. On most European and very few American TVs, there is a proper '16:9' mode which does the squeeze trick at the touch of a button.

On a 4:3 TV without doing the 'squeeze', the DVD player must be set to '4:3' within it's setup menu. This forces the player to 'downconvert' the anamorphic image by removing some of the scan lines. This plays the image back at the correct proportion, but obviously loses some of the original resolution. It can also introduce unwanted artifacts, especially on scrolling credits etc.

On a widescreen TV, if the correct screen mode is used, the anamorphic image is stretched laterally, restoring it to the correct proportions.
Right.

The aspect ratio of the film itself is completely independent to the above. On an anamorphic DVD, the AR can be anything above 1.78:1.

OK?

A normal 'widescreen' DVD presents the film in it's proper aspect ratio (eg. 1.85:1, 2.35:1 etc) but does not include the anamorphic enhancement. This means the image is spread over fewer scan lines, dropping the resolution somewhat. This will play back fine on a normal TV without adjustment, but will obviously have the 'black bars' top and bottom depending on the AR. If played on a widescreen TV, the set must be put into the correct picture mode (on Sony's, it's usually 'Zoom', but varies with other makes).

Phew.

For further information, try here:

http://www.thedigita....c/welcome.html

http://www.dvdfile.c....anamorphic.htm

M.
COMPLETE list of my disc reviews.       HTF Rules / 200920102011 Film Lists

#4 of 89 OFFLINE   Jay Mitchosky

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Posted March 10 2002 - 03:52 AM

Home Theater Means Accuracy & Calibration!

Make Video Essentials or Avia and a Radio Shack sound pressure level (SPL) meter a mandatory purchase when you set up a home theater. It's more than just plugging in a bunch of boxes. The goal is to faithfully recreate to the extent possible the theatrical experience. That means setting audio and video levels relative to recognized standards. It only takes a short time to make these basic adjustments but makes all the difference in the world.

For video, colors will be more natural and vivid and the overall image will offer more punch and snap. You will see greater amounts of detail and richer, deeper levels of black. Images will no longer have that blown out, desaturated look like you see on the showroom floor.

For audio you will realize a better balance between each channel. Dialogue won't be obtrusive or lost in the mix. Surround effects will serve to enhance the presentation rather than distract from it. Low frequency effects will not overpower the rest of the soundtrack.

For a fraction of the money you spent on your hardware (and probably software) you can invest in tools that will make movies look and sound closer to the way they were originally intended. And these tools will be appropriate as your home theater evolves.

See also:
A Quick Overview of Home Theater Calibration by Vince Maskeeper
"The computer had attained consciousness, only to reject it, claiming it was too unstable an operating system."

#5 of 89 OFFLINE   Cees Alons

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Posted March 10 2002 - 05:44 AM

All those amplifiers in a HT

Audio signals come from a source (CD player, DVD player, VHS player), then go to a processor to have it divided for multichannel output (Dolby Surround, DTS, Dolby Digital). Then go to pre-amplifier to get some corrections and make it a standard level (also may have treble and bass regulated- as well as overall volume level), then go to (power-) amplifiers who produce power (voltage times current), so it can drive a speaker and make a lot of noise.

If the pre-amplifier and the amplifiers are combined (together with a processor and a radio-tuner as well), it's called a receiver. This is the most common solution in a HT. Therefore, if the power-amplifiers are not all inside a receiver, but apart, that's called separates.

In the old days, when multi-channel audio (except stereo) wasn't common (at least not the "coded" form), there already were integrated amplifiers - of course they still exist, there are many audio freaks around - meaning the pre-amp and the power-amp were together, and generally two of them to form an audio stereo combination.

#6 of 89 OFFLINE   Cees Alons

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Posted March 10 2002 - 06:26 AM

Colour signals

Video signals undergo a terrible form of compression: all those infinite frequencies of the visible color spectrum are represented by only three different colors (frequencies)! The reason they can get away with that, is that it's based on the physiological peculiarities of the human eye. We simply don't see the difference!
The information about the three colors at any moment is called the video signal.

To broadcast the video signal so it could be picked up in our homes, they had to group the colors together and the coding technique was called NTSC. Soon some problems became obvious, especially variable color shifting during transmission through the air. But by then all American TV sets were able to decode NTSC-signals - and nothing else. In Europe they didn't have color broadcasts at the time, so they could come up with a solution: a different way of coding the video signal, which was called PAL. As a result, all TV sets in the US, Canada and Japan can now only decode NTSC signals. All sets in Europe (except in France and Russia) and Australia can decode PAL, and recently most of them NTSC as well.

The digtal nature of the data on DVD made it less desirable to try and code the data as either NTSC or PAL. Instead, they kept the three colors separate, but they used a trick (had been used before): of two colors they record the signal strength and the third value is the total strength of the colors (the brightness). Thus you can easily compute the third color, while in practice a signal is present that can be used in older B/W devices.

To serve older color TV-sets, the DVD-player is able to combine the colors into either NTSC (America, Japan) or PAL (Europe, Australia), and this signal is called the composite color signal. It's less desirable, because immediately after it has just been combined, the TV set will have to split it up again (as it always does) with something called a "comb-filter". The quality of the resulting color image is heavily dependent on the quality (price!) of the comb-filter.

Better use the recorded information, called S-Video (US) or S-VHS (Europe). If your monitor (TV-set or projector) has S-Video input, this is a huge improvement over composite!

Some DVD-players (and all DVD-drives inside PC's) can compute the pure three-color information themselves. This is often called RGB-signal or component signal. In fact the latter term is a bit inaccurate here, because the S-Video is a component signal as well!

You will understand that using the RGB-signal may offer a slight improvement over S-Video (if the decoder is good), but certainly not as much as going from composite to S-Video!

#7 of 89 OFFLINE   Cees Alons

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Posted March 10 2002 - 07:14 AM

Do I really need a Subwoofer?

No, you don't need anything. But then if you don't have anything you won't see or hear much when seated in your HT.

Well, if you're on a budget, or if you need some more time to decide better, you can postpone the subwoofer: that way you can start your HT-experience now, and you will be happily surprised the day you get one!

Why have a sub?
The human ear can hear frequencies starting as low as 20Hz (lower frequencies can hardly be heard - but you can feel them in your chest!). And those terribly low frequencies add tremendously to the drama of the soundstage. No explosion, or earth-quake without them. And they add a foreboding tension to any scene. So they are heavily used in modern films.

On DVD they can be recorded, and the special channel containing them is called the effect-channel, or more accurately: the Low Frequencies Effects (LFE-) channel. It's the "1" in "5.1" (or in "7.1"). Receivers and decoders have an output that is meant to be fed to a special low frequency speaker the (generally having it's own amplifier: active) subwoofer.

Then some guys remembered an older technique. Because you cannot hear where low frequencies exactly come from, you don't have to produce them exactly at the spot of the different audio channels. They used that in older stereo equipment, so they could have less expensive L- and R-speakers, and have all lower frequencies of both channels sent to one subwoofer (located under the couch, or so)!

That's brilliant: now we already have the LFE-sub, we can use it to reproduce the very low frequencies of the other channels as well! No need to buy five extremely expensive speakers (ha, no, not extremely)! All decoders and receivers now have something added called bass-management: you can define any channel you want (often all of them) as small (meaning: no frequencies lower than approx. 80-100Hz), and the decoder (receiver) will send it's bass to the LFE-channel!

So now you know what happens if you add a sub later: you will acquire the possibility to hear the LFE-channel AND you will severely improve your total frequency range. If you were on a budget in the first place, your other channels won't be too good at very low freqs, isn't it? Well, they don't have to be.

#8 of 89 OFFLINE   Dan Brecher

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Posted March 10 2002 - 10:32 AM

As you may already know, the encoded audio information on DVD is digital- meaning the sound has been translated into computer data. When audio is turned into this "digital data", there are several ways it can be written. Much the same way you can express the message "PEACE ON EARTH" in dozens of languages (English, French, Korean, etc)- you can translate audio into DATA using many different systems.

Some computer users might be familiar with formats like MP3 or WAV-- these are simply different ways of expressing audio in the form of computer data. In the wide world of audio, there are literally hundreds of ways audio can be turned into data, or "encoded". Each format has it's own advantages and disavantages.

In the world of DVD, we have essentially 2 major formats for digital audio: one is called Dolby Digital and one is called DTS...



What's to know about DTS?

It is very likely various components within your home theatre (your DVD player for example) sport the DTS logo on the front panel somewhere, but what does this mean? Well, DTS, like Dolby Digital, is another delivery format for digital surround sound (predomenantly 5.1 based) in both movie theatres, and in our homes.

In 1993, Steven Spielberg's Jurassic Park was the first ever movie to carry a DTS (Digital Theatre Systems) soundtrack. A short number of years after it's theatrical launch (which has now seen DTS installed in over 20,000 movie theatres worldwide) the first laserdiscs to carry DTS sound were released to much acclaim, and of recent years much of the home theatre world has been able to embrace a growing amount of DVD releases sporting an optional DTS soundtrack.

As you begin to learn more about the DTS format you're likely to want to ask a number of very common questions, and there are essentially three key questions newcomers are often itching to ask. It is best we tackle each of these one at a time;


1) Why don't all DVDs support DTS soundtracks?

No doubt you have by now noticed, or will come to notice, that not all DVD releases sport the option of a DTS soundtrack. Why is this?

It first needs to be understood that Dolby is the set "standard" for audio on DVD. DTS is an optional format, and frankly, some studios still don't see it as a format that has a wide enough user base to warrant the extra costs of mastering an additional soundtrack for a DVD.

What one must also understand is that the space to encode material on a DVD is far from limitless, and DTS takes up space, more space than Dolby Digital. The additional space DTS requires can often prove problematic when it comes to producing a DVD, and when there is a desire to offer a number of supplements on the disc (not to mention the best video transfer possible) the inclusion of DTS can sometimes be seen as a burden and not a valid enough adition to warrant compromise of a disc's visual presentation. The DVD releases of X-Men and Star Wars The Phantom Menace are among those known not to have included an optional DTS track for this very reason.


2) Ok, so I understand that in some cases the addition of an optional DTS soundtrack is not seen as entirely feasible, even by the studios that support it on DVD, but why don't some studios even support DTS on DVD at all?

Well, again we must return to the fact that some studios just still don't see DTS as a format that has a wide enough user base in the home to warrant the extra costs of mastering an additional soundtrack for a DVD.

Paramount is pretty much the one remaining major studio to have never put out a single DVD that carries an optional DTS track. With them in their lack of DTS support are Warner Brothers, who did in fact issue special editions of Twister, the first three Lethal Weapon movies and Interview with a Vampire with DTS soundtracks on DVD a couple of years ago, though have done no more since. Finally, of the big studios, there is MGM, who have thus far only released one DVD with a DTS track option (Ridley Scott's Hannibal).

The studios that continue to pledge continuing support as and when they see possible? 20th Century Fox, Dreamworks, Universal, New Line Disney. The likes of Anchoy Bay and Criterion continue to show their DTS support on a number of titles.


3) So, am I hearing the stories correctly? Is DTS better than Dolby Digital?

This is the most common question of all, and one you will never get a definitive answer to, especially if you decide to openly ask the varied opinions of a membership as large as that of the Home Theatre Forum.

A lot of the time it is said that it's simply not worth even bothereing to compare the DTS track to the Dolby Digital track on the same DVD, and this is mainly due to the fact that a majority of DTS tracks we are given on DVD are mastered from alternate source material to that of the Dolby counterpart. Why is this? Well, one could imagine this is done to follow the DTS philosophy of presenting the best delivery of a film's original sound mix possible. Why not just source the Dolby track from the best materials possible then you may ask, and that remains one of the killer questions...

A number of DTS tracks on DVD to be mastered from alternate source material over their Dolby counterparts include Saving Private Ryan, Gladiator, Jurassic Park & Se7en.


Listen with your own ears, only you and you alone can decide upon your preference. Simply sit back, turn up the volume and take full advantage of the beauty of being given the choice of Dolby and DTS soundtracks on an ever growing number of DVDs.

For more information on DTS, its history and the growing list of titles available on DVD with DTS soundtracks, visit the official DTS Website

#9 of 89 OFFLINE   Adam Barratt

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Posted March 10 2002 - 11:19 AM

As you may already know, audio information on DVD is stored digitally. Sound is an inherently analogue medium, so must be converted into computer data (long strings of 1s and 0s) before this can take place. Much as the message "PEACE ON EARTH" can be translated into dozens of spoken languages (English, French, Korean, etc.) this sound can be translated into data using many different languages or 'formats'.

Computer users might be familiar with formats such as MP3 or WAV -- these are simply different ways of expressing audio in the form of computer data. In the field of digital audio there are numerous ways audio can be turned into data. Each format has its own advantages and disadvantages, but the goal is always the same: to reproduce the original signal as accurately as possible within the limitations and constraints imposed on each format.

In the world of DVD, there are two primary 'multichannel' (that is, more than the conventional one to two audio channel) formats. One is called DTS (Digital Theater Systems) and the other is called Dolby Digital. DTS has been discussed above, so I will focus on the most common format, Dolby Digital.


What is Dolby Digital?

Dolby Digital is an audio compression system introduced to theatres back in 1992 for the film Batman Returns. In late 1995 the system made its appearance on LaserDisc, DVD's immediate predecessor, with the release of Clear and Present Danger. It first appeared on DVD in late 1996 (in Japan), and early the following year in the US.

Dolby Digital is a very flexible system, allowing anywhere from 1 to 5 full-range audio channels with an optional 'LFE' (Low Frequency Effects, or bass) channel for each variant. Dolby Digital also consumes very little 'space' (data) on a DVD, and a typical Dolby Digital 5.1 soundtrack requires less than a third of the space required by a CD's two channels. This small size leaves lots of space for multiple soundtracks, extras, or better video.

Dolby Digital soundtracks can be so small because they are 'compressed', much like a computer .zip file (but in this case 'AC-3'); although unlike a computer's compression system some audio information is 'thrown away' to save additional space. This may sound bad but this information shouldn't be audible so makes little to no difference to the system's overall sound quality.

Dolby Digital 2.0 is the most common use of the format, the '2' indicating the number of full range channels and the '0' indicating the lack of an LFE channel.

Dolby Digital 2.0 is usually used to present stereo soundtracks on DVD, which can additionally be recorded in Dolby Surround (a technique that squeezes four audio channels into two, and is intended to be processed by a Pro Logic or Pro Logic 2 decoder).

Dolby Digital 5.1 is the second most common use of Dolby Digital on DVD, presenting five full-range audio channels and an LFE channel. Three of these channel are arranged across the front soundstage (left, centre and right) and two across the rear soundstage (left surround and right surround; Dolby Digital Surround EX adds an additional back-surround channel blended into the two surround channels). The LFE channel is directed to a subwoofer, or if one is unavailable to a system's main speakers.

Other variants such as Dolby Digital 4.1 are much less common, appearing on a few DVDs such as Big Trouble in Little China. Dolby Digital 4.1 usually indicates three front soundstage channels and a single surround channel that is fed to both surround speakers.

Along with PCM audio (the same kind of audio used by the venerable CD) Dolby Digital is one of DVD's audio 'standards', which means every DVD must contain either a Dolby Digital or PCM soundtrack. Any type of Dolby Digital will do, even a mono Dolby Digital 1.0 soundtrack.

Because Dolby Digital soundtracks are so much smaller than PCM soundtracks, most DVDs include a Dolby Digital soundtrack rather than PCM.

Adam

#10 of 89 OFFLINE   Patrick Sun

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Posted March 10 2002 - 11:47 AM

Going from Dolby Surround to 5.1 audio


Dolby Pro Logic, the dark ages

The advent of 5.1 audio allowed for a more viable and pleasing home theater movie watching experience over the older Dolby Surround sound tracks that relied on 2 channels of audio, decoded by a process known as Dolby Pro-Logic to create 4 channels of audio: Front-Left, Front Center, Front-Right, Mono-Rear-channel (usually split into 2 channels, but possessing the same audio information in each). Receivers and processors with Dolby Pro-Logic decoding would do all the work.

Dolby Pro-Logic would basically take the 2 channels (the left and right channels usually from a source like a VCR or LaserDisc player) and create the 4 channels in this manner: The Front-Center channel was produced by taking the signal common to both the left and the right channels and steering them into the Front-Center channel. The new Front-Left was the left channel information that wasn't common to the right channel, the new Front-Right was the right channel information that wasn't the common to the left channel, and the rear channel as created from out of phase audio from the combined left and right channel.

Sounds convoluted, right? It also SOUNDED convoluted when it was played back as well.

Dolby Surround was an audio presentation that was problematic in the bleed through from either of the 2 channels into the 4 channels. Most of the time, the center channel seem to get all of the audio information, leaving the front-left and front-right channels with little to do. It did not create a realistic enough surround sound environment for home theater enthusiasts like you!

Then DVDs were invented. Yay!



5.1 Channel Audio, the modern era

To achieve the surround sound environment of a movie theater, a majority of DVDs today come with audio that allows a receiver/processor that is capable of decoding a single digital audio track (usually encoded as Dolby Digital 5.1, sometimes dts 5.1) that comes from the DVD player, into 5 discrete channels of full range audio, and a .1 discrete channel that is limited to bass frequencies and is known as the Low Frequency Effects (LFE) channel.

So, now you will see this number "5.1" everywhere you look around here. It means an audio format that has 5 main speakers (regular left and right like a normal stereo system- and added to that a center speaker to go between the left & right speakers. And then you have two surround speakers that go behind you for surround effects)-- and you have the .1 speaker which is the special channel for just bass.



The receiver or processor handles it all

Receivers can be thought of as the control center of your home theater. It contains amplifiers to power your speakers, it allows you to switch from source to source for audio and often video, it allows you to adjust many HT setup parameters, and it processes digital audio tracks and splits them into discrete channels of audio for the speakers.

Processors do the processing of the digital audio tracks. Processors can be either standalone, or built into a Pre-amp. If they feed a pre-amp, the discrete channels of audio are connected from the processor to the pre-amp in the form of cables with male RCA jacks on each end. These cables are referred as "InterConnects", and to get good performance, choose a shielded cable rated at 75 ohms, these are the same type of cables that will be referred to as Digital Coax cables later in this article.

As long as you select the right input on the receiver/processor so that it knows which input to process, you're almost home free in getting 5.1 audio.

Most pre-amps with built-in processors are referred to as Pre-Pros because they do everything a receiver does with the exception of supplying the power for the speakers (you'd use separate amps to power the speakers).

Receivers will take in the digital audio input from the DVD player, and process it, and direct the 5.1 discrete channels of audio to the proper amplifier channels, which will power the proper speakers. The 5 main channels feed the following placed speakers: Front-Left, Front-Center, Front-Right, Rear-Left, and Rear-Right. The .1 channel is fed into a subwoofer, and requires amplification from the subwoofer to play the signal back properly (some Powered Subwoofers are powered by a self-contained amplifier onboard, other Passive subwoofers require a separate amplifier to power it).

Along those same lines, a processor will take in the input signal, process it, and produce 5 discrete channels of full range audio, plus the .1 LFE channel. Sending the 5.1 discrete audio channels to a Pre-amp (via InterConnects) will allow you to adjust the levels of each channel in case you need to lower or boost a channel to provide a more cohesive sound environment (this can usually be done with a receiver as well). Then the "corrected" audio channels are sent to amplifiers which are connected to the properly placed speakers.



Hooking up the DVD player for digital sound

That about covers the Receiver/Processor side. Let's turn our attention back towards the start of all this mess, the DVD player:

So, you have 2 types of connections from the DVD player:

1. A cable that has RCA jacks on each end (refered as a Digital Coax cable, which sounds fancy, but the main ingredients are that each end is terminated with RCA male connectors, and the cable itself needs to be a shielded 75 ohm rated cable to ensure proper operation/connection/impedance matching between the DVD player and the receiver or processor).

2. A cable with a small square-ish plug on each end, and the cable itself is made of a fiber-optic material. Sometimes this is known as a TOSLink cable.

The majority of the digital output from a DVD player will be the TOSLink variety. But there will always be some players that have the digital Coax RCA output as well. They offer the same functionality.

It is essential to get into the DVD player's setup settings and select what digital output stream you want your player's digital audio output to output. Consult your player's manual for the proper setting (usually it is called the Digital bitstream, rather than PCM, which is for CD playback for the most part).

When the receiver/processor processes the digitial audio signal and produces 5 full range channels and the LFE channel, the channels are mixed by the makers of the DVD's audio tracks so that when played through properly positioned speakers in a HT setup, the 5.1 channels of audio will produce a surround sound environment that envelops the viewer/listener all around them, and creates a more believable setting for the contents of the DVD, whether it be a film, a music concert, and documentary, etc.



So what the heck is 6.1?

As you check out your options for obtaining 5.1 audio in your home, you'll come across 6.1 audio, and the simple fact of the matter is that there are a few DVDs that include digital audio tracks that will allow the receivers/processors that can handle the 6.1 digital audio tracks and produce not only the usual 5.1 discrete channels of audio, but also the Rear-Center audio channel for a more complete 360 degree enveloping surround sound setup in your home. To get 6.1 capability, it'll mean looking for a new receiver/processor that can handle those DVDs encoded with 6.1 audio.

The 3 main flavors of 6.1 audio are:

Dolby Digital EX Surround

dts ES Surround

dts ES discrete surround

The first two types use a matrixing system to "encode" a 3rd rear channel inside the audio for the regular two. On these tracks there are really still only 2 real "discrete" encoded tracks-- but they are created in such a way to make a 3rd (the rear center) able to be extracted using signal processing. Like the center and surround in pro logic (which are extracted from processing a simple stereo file)- a processor is able to take the audio signal and extract a rear center channel from an compatible signal.

For the DVDs with a DD EX compatible 6.1 track, there's USUALLY a flag set in the bitstream which will tell the 6.1 decoder to activate and extract the extra rear matrixed center channel from the 2 rear channel information (however- this decoder feature can also be activated manually).

In addition to these matrixed systems- DTS offers a "discrete" 6.1 channel configuration that is (happily) backwards compatible with current 5.1 DTS decoders. Again- in this case, a flag is present to tell a compatible 6.1 DTS system to play back the audio track in 6.1.

In addition to this formats- There are receivers/processor that do faux multichannel processing which uses DSP to extract even more extra channels from a surround track. There are even forms of EX processing that are different from the Dolby or DTS EX processing, which use similar DSPs to extract a rear center channel from a 5.1 signal (see the OUTLAW 1050 receiver for an example of this).

Unless you have to have the latest and greatest in surround sound formats, it's not paramount in choosing receivers/processors that include 6.1 processing, and 5.1 audio is good enough for most HT enthusiasts. But, sometimes: the more, the merrier!

The following is an up-to-date DD-EX & DTS-ES encoded movies listing
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#11 of 89 OFFLINE   ChrisMatson

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Posted March 11 2002 - 05:55 AM

Basic Hardware

Here are some real basics:

The Receiver is the brain of the entertainment system. The receiver will process sound from the various audio sources (DVD player, TV, VCR, Cable, Satellite, Internal Tuner, etc...) and send the sound to speakers you connect to the receiver. You can use the receiver to switch video sources (i.e. select the desired connected video input from the receiver to display on your TV) but the receiver does not alter the video signal in any way. Good entry level receiver begin in the ~$300 range.

The Speakers are connected to the receiver. For music, you will generally use only the left and right or Main speakers. The Mains are also used for movie soundtracks and surround sound for processing sounds to the left and right of the screen, like a car driving by. For movies and other audio sources for which you want surround sound, you will use a Center Channel speaker, which is mainly used for dialogue in movies and TV. The center channel actually produces most of a movie soundtrack. The rear Surround Speakers reproduce directional sound effects, like a helicopter flying around or other "ambient" sounds. A Subwoofer produces the low bass for music and movies. Speakers and subwoofers vary greatly in price. I suggest buying good speakers as you can afford them, beginning with mains.

The TV has the demanding task of producing images for TV and video sources. You can hook up video sources directly to the TV (Component is best, then S-Video, then Composite, then RF cable) if you have enough inputs. Alternatively, as mentioned above you can route video sources through a receiver. It may be better for the "newbie" to have at least a 27" TV with S-video input and a 16:9/anamorphic mode. Such TVs should be in the ~$750 range.

#12 of 89 OFFLINE   Max Knight

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Posted March 11 2002 - 06:20 AM

How to determine the best speaker/amplifier/receiver for $xxx?

This question comes up a lot. When it comes to sound, there is rarely a best anything than everyone can agree on, because what "sounds best" can be very subjective. To answer this question for yourself (the only one who really matters in this case!) take (at least) the following steps:

1. Define a feature set that you feel you MUST have.
2. Define a feature set of nice-to-have features.
3. Set a budget.
4. Determine a list of components which fit your minimum feature set and hover around your budget.
5. Ask opinions (and search for past posts) on the specific models in your list.
6. Shorten your list down to three candidates.
7. LISTEN
8. LISTEN AGAIN
9. Make up your mind and go for it!
Max Knight
----------
Lacking fins and tail
the gefilte fish swims with
great difficulty.

#13 of 89 OFFLINE   Ted Lee

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Posted March 11 2002 - 10:19 AM

Why do I need so many speakers?

Today's typical home-theater consists of at least five (5) speakers plus an optional subwoofer. Here's what each speaker is for.

Mains (left/right)
These are the speakers you are probably most used to. For regular two-channel (stereo) playback, these are the speakers you are going to use. In HT, these speakers help provide localization and "off-screen" effects. So, if someone throws a plate off to the left of the screen, you'll hear that plate break in your left speaker.

Center Speaker
A very important speaker for HT. Considering most of what you hear will come from the center channel, it's importance cannot be understated. Imagine if I was talking to you right now. Where would my voice come from? Obviously, it would be coming directly from me. Almost all of the dialog you hear in a movie comes from this speaker.

Rears (left/right)
These speakers are mostly utilized for localized or diffuse/ambient type sound effects. Imagine if a plane or helicopter flew "over" your head. The sound would start in the front and finish in the rear. It feels as if the plane actually flew over your head and behind you. Or, imagine it's a rainy scene...you'd hear the sound of the rain and thunder coming from all around, including from behind you...just like it would be in the real world.

Subwoofer
Many HT systems/speakers are great at reproducing mid-to-hi frequencies, but they're not so good at reproducing that chest-pounding thump you get when you're at the theater. Speakers have to work pretty hard to get that kind of thump. That's where the subwoofer comes in. It'll help provide for a deeper sense of bass when needed. Remember that really big explosion in the theater? With a sub, you'll get closer to that sensation at home! Remember, you can always add a sub later.

Some other things to consider about speakers

Timbre Matching
This is the term used to describe a set of speakers that are sonically matched to eachother. This is very important to ensure that you get the same "type of sound" out of every speaker. Imagine a motorcycle in your left speaker...as it moves towards the center the sound starts changing...by the time it gets to your center speaker the motorcycle now sounds like a moped! That's not good HT. Ensuring that your speakers are timbre-matched will ensure a good sonic imagine throughout your room. Many companies now offer HT speaker packages with similar drivers in them...those will definitely be timbre matched.

Listening
One of the most often asked questions is, "How good is this speaker?" That is something you will have to decide for yourself...remember...no one can tell you what sounds good to your ears. You absolutely must listen to as many speakers as you can...then...decide for YOURSELF what sounds good. When auditioning speakers, remember to bring music/movies that you are familiar with. Also, remember that they will sound different once you get them home. Make sure your retailer will take them back or exchange if necessary.
 

#14 of 89 OFFLINE   Jeff Kleist

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Posted March 11 2002 - 10:32 AM

WHAT'S 7.1?

On some recievers, there is an extra port for the rear surround channel which let's you create a more immersive experience by making the center channel sound more open by adding another speaker. No true home 7.1 digital surround system is available, nor is likely to be in the near future.

For there to be a "true" 7.1 format, there would have to be real discrete 7.1 encoded masters... and currently for HT, there are not (SDDS can offer this for theatrical, but not for the home).

There are several "7.1" formats (including the Onkyo 7.1 and Lexicon's excellent Logic 7 system)... but all these are creating matrixed channels from an existing discrete set of 5.1 or 6.1 signals.


ISN'T HD-DVD GOING TO SUPPLANT DVD IN A FEW YEARS?

Not likely. At this time less than one half of 1% of US homes have a digital/HD television, and these numbers are unlikely to grow astronomically any time soon. We are a minimum of 7 years for them to even seriously start on production of discs, and probably closer to 10 or 12.

Remember, the studios have spent the last 5 years putting a HUGE amount of their catalog out on DVD, and they're still missing some of the major, most desireable ones. Do you really think they'll sabotage their sales with a new format so soon?

#15 of 89 OFFLINE   Greg_R

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Posted March 11 2002 - 11:14 AM

How do I pick out components for my Home Theater?

There are a couple of things you might consider:
1) How durable is the product?
2) Does the product support the features I want?
3) What about looks / aesthetics?
4) Cost?
5) Do I like it?

Once you've determined #1->#4 for a product, you need to wade through the thousands of A/V products out there and find ones that meet your criteria. Searching this and other forums is a good way to get a list of potential candidates.

Once you have your list, go out and audition the item. This means bring CDs & DVDs to the dealer. The reason for this is that you want something familiar that you can take to various dealers for comparison. Ideally, you'd like to listen to each component in your own room (room acoustics play a huge part in the final system sound). Make sure the store has a $$$-back guarantee so you can return any equipment that doesn't work out.

Finally, do you like what you purchased (and not because someone told you it was a good system)? Many components of HT are very subjective and a lot boils down to personal preference & room acoustics. It's your money, so make sure it's your decision...

#16 of 89 OFFLINE   Dustin B

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Posted March 11 2002 - 06:14 PM

How does a watt relate to the output level (SPL) of a speaker
(or "why watts can be meaningless without context").

First off SPL stands for sound pressure level. Remember that term, it is used a lot around here. It is a basic measure of how LOUD something is.

SPL is measured in a unit call the decibel. Decibels are a logorithmic scale not a linear scale. ie a doubling of the output level is a 3dB increase while a factor of 10 increase in output level is a 10dB increase (if it was a linear scale, a factor of 10 increase would be a 30dB increase). Bottom line is the higher on the scale you go the larger the difference between the levels.

For a person to easily perceive a difference between the intensity of two sounds they need to differ by approximately 3dB. To percieve a doubling of the intensity, two sounds need to differ by approximately 10dB.

With this info you are ready to see how a watt relates to a speaker's output. A speaker has a sensitivity rating. This rating is given as dB/W/m. This number can range from the low 80's to some very efficient horn loaded speakers with ratings over 100. For the purposes of this explanation lets assume we have a speaker with a sensitivity rating of 91dB/W/m. This means that with one watt of power applied to the speaker, measured one meter away from the speaker, you should read a SPL level of 91dB.

Now remember the dB scale definition above, to increase the output by 3dB we have to increase the input power by a factor of 2. So it would go something like this:

dB - watts
91 - 1
94 - 2
97 - 4
100 - 8
103 - 16
105 - 32
108 - 64
111 - 128
114 - 256

Now as you can see power requirements for a meaningful increase in output go up very very quickly. It also becomes obvious that the difference between a 80watt and a 100watt per channel amp is not going to be all that great. Finally you can also see that a 91dB/W/m speaker will require half as much power as an 88dB/W/m speaker to reach the same output level.

Now there is one other thing you have to consider. These numbers are only valid if you are listening 1 meter away from the speaker. Very few people listen to there speakers at a distance of one meter. However, you can apply the same sort of rule to distance. Every doubling of distance will cause a 6dB decrease in output. So listening to our 91dB/W/m speaker at a distance of 4 meters (about 13') the scale changes to this:

dB - watts
79 - 1
82 - 2
85 - 4
88 - 8
91 - 16
94 - 32
97 - 64
100 - 128
103 - 256

Now it won't quite drop this much as room gain will increase the level a bit, but it's the jist of it all. The watt is meaningless without also considering the speaker being driven and the room the speaker is in.

Also, don't take this as meaning higher efficiency speakers are always better. Only use the sensitivity ratings as an indication of how much power you will need to effectively drive the speaker. Listen to the speaker to determine whether you like it or not. But don't forget about the power handling rating. It is a guide line for how much power the speaker can take. Short bursts above this power rating won't damage the speaker. In fact it can be a good thing to have more power available than the speaker can handle since amp clipping (running out of power) is much more harmful to speakers than over driving them. Amp clipping gives no warning, but over driving your speakers makes them sound bad warning you to turn it down. Still, do remember running a speaker continously above its' rated power handling will eventually damage it.

As a side note. Also remember the watt rating on an amp isn't always an accurate one. Things to watch for are amps that give their rating at 1khz instead of from 20hz-20khz. Amps that give THD numbers higher than 0.1 in their power rating. Amps that don't specifiy all channels were being driven when this power output rating was obtained. Amps that rate into 6ohms but say not to drive 6ohm speakers. So as an example take these two specs:

1) 110W at 1khz, with 0.7%THD into 6ohms (on the front of the box they also claim 110Wx5 and in the manual say not to drive 6ohm speaker with it)
2) 70Wx5 (all channels driven) from 20hz-20khz, with 0.08THD into 8ohms (manual says you can drive 6ohm speakers)

2 should actually have 70W for each channel. 1 if measured under the same conditions as 2, will in all likely hood have less than 40Wx5.


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#17 of 89 OFFLINE   Bill Kane

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Posted March 12 2002 - 01:47 PM

WHAT IS A POWER OR LINE CONDITIONER/SURGE PROTECTOR?

Many people incorrectly describe these boxes as the same thing, but there's no argument that it's just good peace-of-mind insurance to use a SURGE SUPPRESSOR on our electronic gear.

Surge protectors alone -- virtually every one under $100 --DO NOTHING TO IMPROVE your sound and picture beyond an AC noise filter. They should be neutral, and, like a good physician, first do no harm to your listening signal.

We'll talk about "power conditioners" later.

Surge protectors range from $19 at an office supply store to hundreds of dollars. Ideally, these can act as more than just extra-plug power strips. Some feature outlets for high-current amplifiers and delayed power-on for monoblock amps; coax pass-thru terminals for CATV and satellite; plus telephone lines. Most $60-$350 surge protectors use MOVs (metal oxide varistors). These are designed to FAIL when taking a huge hit. They are sacrificial. But surge suppression ALSO may be cumulative, little ones each day, until a utility outage or electrical storm comes along. These high-voltage surges are of very short duration, but can peak to 5,000 volts or higher. Hundreds of these surges enter your home every day through the wiring. They can either burn out an electronic component instantly, or, more likely, gradually degrade its performance.

IF MOVs eventully blow and hopefully save the gear, these units can be returned for free replacement.

Consider your personal experience with your electric utility (rock steady, grid brownouts, daily flickers) and geographic-related storms (lightning prone), as well as how many components you have, when you decide on how large a surge protector you may need. TVs, satellite equipment, DSS systems, VCRs, DVD and CD players, stereo receivers and cable modems ALL need surge protection. Telephone lines (computer) and coax cables going into your equipment need to be surge-protected.

Monster consumer units use MOVs and the company has upgraded its 2001-2002 line. Panamax has a new 2001-2002 line that still use larger MOVs, and like the rest will clamp off overvoltages and undervoltges with "SurgeGate" circuits and hopefully keep working.
Tripplite,
AR and Belkin also are widely available under $80. Most of these units provide ~ 50dB EMI/RFI AC line noise filter, and call it a "line conditioner." In addition, people often regard the big-$$$ replacement warranty, but it's not a deal-maker; it may be a chore to collect and it may be required that one applies for homeowner insurance FIRST.

A common method to judge these plug-in units is by the Joule rating. The Joule rating of any MOV is a measure of the amount of energy it can absorb at one time without failing. Anything above 2,000 joules is regarded as good (edited for 2003).

Here's a link to How Stuff Works on Surge Suppression

If nothing else, buyers should only accept a surge protector that says it's "U.L. 1449 Listed." This standard cuts a lot of the hype away.

HERE is a link to some under-$100 units posted from AUG '02.

A totally different, non-MOV technology is used by Brickwall (an industrial company discovered five years ago by audiophiles, and whose business now is 50 percent audio sales). Units start at $149 2-outlet and range up to 10 outlets. The ADCOM 315 and 615 units ($250 and $395 MSRP) are 8-outlet models that license this technology.Furman offers a pro level unit (designed for entertainment industry) with 8 outlets with protection for power-line related transient voltage, noise and wiring faults, $399 MSRP. This non-MOV technology is termed Series Mode and currently is the highest level of surge/spike protection for those who need or want it.

Some amplifiers (aside from audio/video receivers) have their own built-in protection and should not be connected to anything beyond the wall outlet; the manufacturers typically provide this instruction.

Ultimately, one can add a WHOLE-HOUSE SURGE PROTECTOR as a first line of defense to protect every appliance in the home. HERE is an explainer from an Oregon power company. These units can go behind the electric meter or on the main breaker box.

But nothing will protect you from direct lightning strike.
If you are able, unplug your sensitive equipment, including satellite boxes, when electrical storms threaten your home.

Now, what is power conditioning and do I need it?

It depends. Ideally, we want a steady 120-volt to 117-volt pure sine wave electrical feed. But voltage will drop when adding more current draw, besides neighborhood power grid fluctuations. Audiophiles claim they can hear improved sound and see better picture quality from various power line conditioners, but in many cases, it takes high-end gear to detect it.

But I Read That Surge Suppressors May Limit Current
In some tests, when amps are DRIVEN HARD, the ability of the line filter and surge protectors to supply the needed power may diminish, blunting transients, compressing the bass, reducing dynamic range and blurring sonic images. If amps are not driven hard, then you likely won't have a problem. There are surge units that come with two high-current outlets designed to overcome "current limiting."

But I Read That I May Be Getting "Dirty Power"

In North America, the idea that there is something fundamentally flawed with AC power from the wall is overstated. Most AC power is fairly well regulated and generally free from noise. The power supplies in our equipment will filter any small noise spikes and bypass most RFI to ground. If power utility voltage is not constant, then buying a voltage regulator can make up for flucuations between 80V and 140V. These power conditioners that are voltage stabilizer/regulators are much more costly, and usually work independently of any surge suppressor.

There are other devices for "balanced power," something regular electricians often don't know about. They often are recommended for systems with persistent ground potential hums.

B-P-T is a big player. BPT units claim surge protection with two types in combination: MOV & Avalanche. Equi=Tech also is highly-evolved and far from budget-priced.
PS Audio , Richard Gray's Power Company and Tice Audio also sell specialized power conditioners.

#18 of 89 OFFLINE   Mike Broadman

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Posted March 13 2002 - 03:11 AM

What About Music

You're starting to get into home theater movie watching, but you're also a music lover. How does all this fancy technology impact your listening?

Sharing the equipment
When acquiring your audio equipment, keep in mind that it will be used for music as well as movies. Use CDs to test speakers. Like your musical tastes, your sound preferences are subjective and will differ, sometimes dramatically, with others. For example, a hard rock fan may place more emphasis on the subwoofer and the over-all "oomph" of the sound. A classical listener might concentrate more on the high and mid range, and focus on sharpness and clarity. A discriminating jazz listener will look for a certain timbric quality.

The good news is that you can start enjoying your music as soon as you hook up, calibrate, and configure your HT without spending an extra dime or performing any additional installation. Most, if not all, DVD players can play CDs. This is great if you don't want to or can't afford to buy a CD player, or just want to keep the number of components to a minimum. However, a DVD player lacks many features common to CD players, such as multi-disc changing (though some DVD players do have the ability to store more than one disc), shuffle and random play, track programing, etc. Most DVDs also cannot play CD-R and CD-RW discs.

Even by just using a DVD player, you will notice a dramatic improvement in sound by using your new speakers.

CD source equipment- CD player
For the hard-core music lover, the DVD player will probably not be good enough to listen to music. You'll want to get a seperate CD player- they are, after all, designed specifically for music output.

There are, of course, many different kinds out there. Like any piece of equipment, figure out what you "need," what would be nice, and how much you can spend. Options to consider:

1. Ability to play newer high-fi sound formats like DVD-A and/or SACD (see below).
2. Multi-disc changing capability. Some players only store one disc at a time. Some can store 3, 5, or 10, allowing you to listen to tracks from multiple discs. There are also changers that can store hundreds of discs, providing the convenience of keeping whole chunks of your music collection, if not all of it, in the player at all times, resulting in juke-box-like functionality.
3. Ability to play other non-CD formats, ie, recordable discs and MP3.
4. Extra options and features: track programming, title display, etc.
5. General build quality and look. You may find two players that do exactly the same things, yet are considerably different in price.

Hi-resolution, multi-channel and new digital sound formats: the next generation of home music listening

One of the things a HT owner can enjoy in many ways is multi-channel surround music. This is one of those hot-button issues that HT enthusiasts disagree on. Some people like the idea of being immersed in the music and using all of their speakers to create a concert-like listening experience. Some feel that if a recording was done in stereo, it is more proper to listen to it in stereo, and that since we have two ears, two channels is the best way to hear music. Also, they may feel that the novelty of surround music is gimmicky.

Your receiver should come with the ability to allow you to select surround modes. While listening to a CD, you can, for example, select "stereo," which sends the two channels to your main speakers (left and right front), and some bass to your subwoofer. This is standard. You may also be able to select "Pro-Logic," which distributes the two channels to all of your speakers. While it is certainly your choice, I highly recommend against the latter. Music that is designed for 2-ch suffers a lot when you try to force it to play through 5 channels.

However, there is material out there that is designed for multi-channel listening.

Two new musical formats have entered the market for the audiophile to enjoy and spend money on.

1. DVD-Audio
Using the same compression on music that DVD uses, this allows for a higher bit rate and more informaton to be stored on DVD-Audio than on CDs. It also allows for multi-channel sound.
DVD-A seems to benefit greatly from the multi-channel soundtracks. Many DVD-A discs come with a DVD-A surround track, a DVD-A stereo track, and DVD track, which allows you to play the disc on a standard DVD player, but will not give you as good a sound as using the DVD-A tracks.

To play DVD-A, you need a compatible player. Often, folks use the same player for both DVD-A and DVD.

2. Super Audio CD (SACD)
This format, invented by Sony and Phillips, is a higher-end version of CD, with the ability to produce a much larger frequency range. Like DVD-A, SACD supports multi-channel music. However, there seem to be very few SACDs with multi-channel tracks on them.

SACDs themselves come in many different forms. Almost all have an SACD 2-channel track. This is the real reason to get SACD, as it is the most common way of listening to SACD. Some have multi-channel tracks. Some have both, allowing you to select which one you want to listen to on your player.

Players come in many different forms as well. SACD/CD players are as varied as the CD player discussed above. There are also DVD players that play SACD. For a large sum of money, you can find a player that plays DVD, DVD-A, and SACD.

Because of the cost, many people end up having to choose either SACD or DVD-A. Both formats have their defenders and detractos. Going by the software, it seems that DVD-A is banking on multi-channel while SACD is emphasising high-end stereo listening. IMO, the best way to pick which format to go into is by looking at what music is available for each. After all, what's the point of buying SACD player if all of your favorite music is released on DVD-A?

3. Other high-end music
Even without SACD and DVD-A, there are still all sorts of ways to enjoy music that is not on CD. A tape deck or turntable will allow you to take out your dusty old music collection from the attic. DTS discs and HD-CDs are yet other musical formats that, while not particularly popular, allow you to hear music in a different way just by using your DVD or CD player.

Music-related DVDs add another music listening experience to your HT. Lots of concert DVDs are being released. You get to see a band perform in excellent visual quality, while enjoying superior audio. Like movie DVDs, a concert DVD can have mutliple sound tracks, including stereo, DD5.1, or DTS. Surround sound mixes on these can vary from cheesy and gimmicky to immersive and sublime.

#19 of 89 OFFLINE   Jim DiJoseph

Jim DiJoseph

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Posted March 13 2002 - 06:20 AM

Audition equipment in person, when possible, and be patient!

A frequent question that people ask is, "Which speakers are the best?" As with many of the different aspects of Hometheater, the perceived quality of certain components can be extremely subjective. Take some time to research your new hobby, and then venture out into the world to perform a test run in person. You may find that your tastes do not demand some of the high prices that the higher end equipment commands. On the other hand, you may find that you simply cannot live without the absolute best. In either case, take time to go through all of the motions. One thing you should try to avoid is purchasing the first device or system that you demo. You may discover after only a few short weeks that you need (want) to upgrade already. Be patient. Soon you will be enjoying the absolute best hometheater that is tailored just for you. Enjoy!
Remember...no matter where you go, there you are.

#20 of 89 OFFLINE   Dustin B

Dustin B

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Posted March 13 2002 - 06:45 AM

What is a Crossover?



****Basics****

A crossover is probably the most important part of a speaker. A bad crossover design can cause a speaker that uses the best drivers in the world to sound like crap. An extremely well executed crossover network however can enable some very inexpensive drivers to sound excellent. The intracacies of crossover design are way over my head (and certainly not all that helpful in a newbie document), but a basic understanding of what a crossover is and what it does can help immensely with understanding home theater.

In a loudspeaker (like your home stereo speakers) you almost always have more than one driver (components making the sound).

In a "two way" speaker system you have a tweeter (usually 0.75" or 1" in diameter) and a woofer (usually 4"-8" in diameter). The tweeter is used to cover the higher frequencies sounds while the mid/woof is used to cover the lower frequencies.


*The crossover is what makes the tweeter only get high frequencies and the mid/woof only get low frequencies.


A crossover consists of two filters. A high pass (HP) filter and a low pass (LP) filter. When you combine the two you have a crossover.

A HP filter allows higher frequencies to pass through it while attenuating lower frequencies and is therefore connected to the tweeter (makes sense right: a High Pass filter only allows HIGH freq to PASS though).

A LP filter allows lower frequencies to pass through it while filtering away higher frequencies and is therefore connected to the mid/woof (again: a Low Pass filter only allows LOW freq to PASS though).


What is defined as lower frequencies and higher frequencies is defined by the guy who designed the filters. The designer will choose a frequency based on the tweeter and woofer components being used in the speaker. Above this point will be the higher frequencies (that get sent to the tweeter) and below this point will be the lower frequencies (sent to the woofer).




****Advanced****

To understand the finer points of a crossover it also helps to know what an octave is. An octave, most basically, is a doubling of audio frequency. So when you see someone complain about subwoofers not being able to play the first octave, they usually mean 16hz-32hz. The next octave is 32hz-64hz, the next is 64hz-128hz etc. Although depending on what scale definition you are using, the particular frequency ranges that make up an octave differ.

It is very important to understand that the choosen crossover point frequency mentiond above is not a brick wall divider.

Lets say the choosen crossover point was 2000hz. This does not mean that the tweeter plays the frequencies from 2001hz and up and the mid/woof plays the frequencies below 2000hz.

It means that below 2000hz the HP filter will start to filter off the lower freq at a specific rate. The farther below 2000hz you go the more the signal will be filtered away.

The LP filter is the reverse. Above 2000hz the LP filter will start to attenuate the high freq signal at a specific rate. The farther above 2000hz you go the more the signal will be attenuated.

The rate and shape of this filtering will be determined by the "type" and "order" of the filter.

There are a bunch of different names for the types, but they aren't overly important to this discussion. If you get into speaker construction and design, you'll want to check out the DIY/ADVANCED area of this forum to get tips on crossover types.

The order of the crossover is how steep the slope is (how quickly it filters away audio). A first order filters the signal gradually as you move away from the crossover point, while a 4th order filters much more drastically.

Anyone interested in the specifics: A first order filter will attenuate the input signal 6 dB/octave. Second order at 12 dB/octave. Third at 18 dB/octave. Fourth at 24 dB/octave and so on.


The neat part is, that given how the dB scale works, when you have a tweeter with a HP filter and a mid/woof with a comparable LP filter the frequencies where the filters overlap (freq that both drivers are playing) will be filtered in such a way that you get an even level across the entire frequency range the two drivers are capable of!

Posted Image

Now this is a little bit of an over simplification, the filters won't both use 2000hz. The HP will start to attenuate a little above 2000hz and the LP will start to attenuate a little below 2000hz so that the two filters will sum correctly. The frequency quoted as the crossover point, is usually the point at which both sides are down by 3dB.

No speaker will play a perfectly flat 85dB from 20hz-20khz. It will uaually be +/-3dB over some frequency range (not necessarily 20hz-20khz, could be from 48hz-22khz). There is also a lot of other things the filter design takes into account. It accounts for the size of the speakers baffel and the layout of the drivers on the baffel. It accounts for oddities in a drivers frequency response. It will also account for differences in sensitivity between the drivers. And likely a few other things I'm not even aware of.

So that's a two way speaker. What about a three way. Well a three way just has two crossovers. It has a HP attached to a tweeter. A HP and a LP attached to the midrange driver and a LP attached to the woofer. There are also 4way speakers, and I'm sure some fool somewhere has designed higher way speakers.

You may have also seen speakers listed as 2 1/2 way. What this means is that you have a 2way speaker with a HP attached to a tweeter and a LP attached to a mid/woof. But you also have a second mid/woof or woofer with another LP filter. This second LP filter will start to attenuate higher frequencies at much lower frequency than the first LP filter.
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