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by Alan Lofft (bio)
Former editor of Sound & Vision and Audio Magazines

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Read related articles:

Home theatre Basics: Buying A DVD Player

Home theatre Basics: Home theatre Components



How to Create a Seamless Soundstage
Got a problem getting a smooth, seamless soundstage from your left main speaker across the center channel to the right speaker? Does much of the image seem collapsed into the center? First, carefully adjust the center-speaker distance and level in your receiver's setup menu. Many enthusiasts run the center too loud. Adjust the center level loud enough so dialogue intelligibility doesn't suffer, but no louder. Try placing your main speakers so their front panels are even with the center channel, with the center channel further back, if possible (wall-mounting it behind the TV is another alternative). If the three main channels form a gentle arc facing your couch, with the center speaker the furthest away, you should experience a significant improvement in the forward soundstage.

How to isolate annoying background hum

Hum lurks there, in the background, omnipresent. As long as the music or movie is playing, you can forget about it, at least until a quiet passage occurs, then there it is again: HUMMMMMMM! Be gone, bad hum, you think. But, like a bad odor at the back of the fridge, it takes some dogged persistence to track it down and eliminate it.

First, let’s define it: Hum is a steady low-frequency noise, usually at about 60 Hz or 120 Hz, that results from voltage differences between true “ground” (what you’d get shoving a copper pipe into the ground) and the “ground” of your receiver’s chassis, or any components connected to it. When this situation occurs, it’s called a “ground loop,” and it’s darned annoying. Here are some tips to banish hum.

First, isolate it. Power up all the components in your system. Do you hear hum from every source (DVD, VCR, CD, TV, etc.) or only from one source? Say you hear it on the VCR input. Try reversing the VCR’s AC plug in the wall outlet. (Sometimes the polarized prongs don't let you do that). Did the hum go away?

While you’re at it, check your powered subwoofer. Turn it on (with no cables attached) and listen for hum. Reverse the AC plug in the wall if you hear any. Now reconnect the sub to your receiver or amp. If the hum is gone, you’ve triumphed! If not, disconnect the RCA jacks of all the components connected to your receiver or preamp, including the line-level cable from the “Subwoofer Output.” Is the hum still present? If it is, reverse the AC plug for your receiver or amp in the AC outlet. If the hum is gone, but only recurs when you reconnect one particular component, then reverse that component’s AC plug.

Finally, if all else fails, your cable-TV system (or satellite dish and decoder) may be the culprit. Disconnect the cables feeding your TV, VCR(s), a set-top cable box, or a satellite decoder. If the hum disappears (and you don’t use a dish) complain to the cable-TV company. They may have to run a copper rod into the ground outside your house or run a ground wire to a metal cold-water pipe.

If nothing else works, and you’ve isolated the hum to the cable-TV feed, build an isolating transformer. Buy two 75-ohm to 300-ohm cable transformers for a few dollars each, and connect the two pairs of 300-ohm “pigtails” together. Now insert it between the incoming cable-TV feed and the 75-ohm input terminal on your cable box or your TV. That should, finally, put all hum to rest, blocking it from entering your system.

How to Find the Best Place for Your Subwoofer
Want to crawl around on your hands and knees like our four-footed friends? It may strike you as a bit odd to do this in the pursuit of smooth, deep, and even bass, but it’s really the best technique to find the ideal spot for your EP125, EP175, or EP350 subwoofer. (Still, I wouldn’t advise doing it within sight of family or friends.) For that matter, this low-profile approach works for any subwoofer. And you’ll only have to heft your subwoofer twice.
Here’s how:
Move your subwoofer as close as you can to where you sit. If it’s a chair, move the chair aside and place the sub where the chair was. If it’s a couch, slide the couch temporarily out of the way and put the sub about where you usually sit.
Play a DVD with lots of low-frequency effects or a CD with plenty of deep bass, the kind that really kicks your sub into motion.
Now the action. Get out the kneepads and crawl about the room in the general area where you were thinking of locating the sub. Go several yards in each direction--near the wall, out from the wall, towards a corner, away from the corner, and so on--while you listen for smooth and extended bass response.
At some locations, the bass may seem really exaggerated and boomy. In other spots, it may almost disappear. Pick a location somewhere between these extremes. That’s it! Mark the spot (no, not like a dog or a wolf would!), then move the subwoofer into that position. Now put the furniture back.

Test the technique by playing the same deep bass selections, only this time sit in your favorite chair (where the subwoofer was). The deep bass should sound just like it did at the place where the sub now sits.

You see? It works. And I hope you noted any dust bunnies while you were at it.

How to optimize subwoofer levels

It's confusing. In most home-theatre setups, your Dolby Digital/dts A/V Receiver has a menu for setting the levels of all your speakers, including an adjustment for the Low Frequency Effects (LFE) channel. This determines the strength of the electrical signal fed to your subwoofer's built-in amplifier. But there's also a volume control on your subwoofer, right?

So where do you set each control?

To keep your receiver's LFE output level from overloading the input stage of your subwoofer amplifier, and to keep noise levels below audibility, adjust the receiver's LFE/subwoofer output level to "0 dB", and leave it there. When you do your level checks, start with the sub's volume control at about the 10:00 a.m position, then use that control to set or trim your final subwoofer level. And of course you may have to vary it somewhat depending on which source you're watching or listening to--CD, DVD, VCR, or off-air TV. However, except for some bass-heavy CD or DVD programming, the sub level shouldn't require much re-adjustment.

How to repair Scratched CDs and DVDs - at home
CDs and DVDs are remarkably resistant to casual scratches and gouges but sooner or later everyone has a disc that causes a CD player to skip, or, in the case of DVDs, show odd video artifacts. When a scratch prevents the laser beam from reading data, both CD and DVD players have built-in digital circuits with lots of redundancy to correct for "drop-outs." These correction circuits search for and replace missing data until eventually the damage exceeds the CD player’s ability to electronically compensate for the scratch. That’s when the machine skips.

Check to see if a scratch is beyond repair by holding a CD up to the light. If you can see light through the scratch, forget trying to fix the CD. Scratches on the upper label surface are impossible to repair. But on the shiny playing side of the disc, a quick polish with any liquid auto wax will often fix minor scratches. Apply a few drops of the liquid wax to the damaged area, then wait for it to dry to a haze. Carefully buff away the haze with a soft cloth or cotton ball. Don’t buff in a circular motion around the CD - do it across the disc. It’s easiest if you put the disc on an old towel on a flat surface to do the work.

You can buy special CD/DVD commercial polishes and scratch removers, of course, but I’ve found that liquid auto wax is just as effective. If scratches are too deep, there isn’t much to be done, although in the case of CDs, there are noticeable differences from one player to another in the sensitivity to damaged discs.

Spring Cleaning Those Noisy Controls

Unlike automobiles, most solid-state electronics--receivers, amps, and preamps--function beautifully for years with little or no attention. But sooner or later, you may notice some of the controls on your receiver or preamp will become noisy or "staticy" when you rotate them. The volume control is the big culprit but it’s common enough for balance and tone controls to get noisy as well. Selector switches or pushbuttons may become intermittent from time to time. This condition may show up in as few as two or three years and it’s commonplace in components that are five years old. After 10 years or more, it’s unusual to find any electronic device with controls that are free of noise or static.

It’s mostly a result of oxidation of the internal metal moving parts within the potentiometer or switch, but dust certainly gums things up as well. You needn’t think these parts are wearing out. They’re not. They just need cleaning and de-oxidizing. And what better time than the advent of Spring to clean those controls? There are special sprays intended for exactly these chores. The contact cleaners I’ve found effective include ProGold GxL and Cramolin Special Spray, both from Caig Laboratories (, and Stabilant 22. Another similar product is Tweak. I’ve tried RadioShack’s TV Tuner and Control Cleaner, but I’ve found its cleaning effect is very short-lived, whereas the other cleaners will keep controls noise-free for years before you have to do them again.

The trick is to get at the noisy control. You have to disconnect your receiver or preamp and remove the bottom plate and perhaps the metal enclosure. These sprays come with a tiny tube that let you insert the end in any opening in the offending control. A quick spritz is sufficient. Do it while you rotate the control back and forth. Some selector switches may have a mechanical link from the front panel to an actual switch mechanism elsewhere inside the preamp or receiver. Just follow the link and spray briefly into the mechanism while you operate the switch. That’s it.

Improving Center Channel Intelligibility

Although most conventional forward-firing speakers don’t direct their audio frequencies as narrowly as a flashlight beam, they still are directional to a degree, depending on the frequencies of sound. Very high treble is quite directional, and plenty of midrange sounds, where most voices reside, are as well. It’s easy enough to demonstrate this effect by just standing in front of your center speaker and walking well off to either side, or "off-axis," as it’s termed. You’ll hear the midrange and highs become less detailed and voices become a bit dull.Detail and intelligibility are among the prime requirements of any center-channel speaker. If you seem to have trouble understanding movie dialogue, first increase the volume of the center channel with your receiver’s speaker setup menu, and then try these remedies:

If the center channel is on top of a big TV, it may be well above the height of the seating area, so get a couple of rubber doorstops (one Axiom owner used hockey pucks) and wedge them under the speaker base at the rear so the front of the speaker fires directly towards the listening area. Axiom’s center channels have broad horizontal dispersion, but it’s always a help to have the speaker aimed toward the listeners. And if your center speaker is on a shelf beneath the TV, angle it upwards towards the seating area. In large movie theatres the center channel is behind the center of the screen and carefully horn-loaded to direct the dialogue over a broad horizontal angle and a narrow vertical one, to avoid sound bouncing off the ceiling, which can inhibit clarity. Likewise don’t position a center channel more than 18 inches above the TV display or recess it in any way on a shelf in an entertainment unit. Move it forward and angle it downwards.

The Listening Room: Reflection and Absorption

In the quest to get smooth, well-balanced sound reproduction in our homes, the one component we often ignore is the listening room itself. When speakers are accused of being "too harsh or too bright" or "too dull," it’s often the reflective or absorptive traits of the room’s furnishings and décor that are shaping the speakers' sound rather than any intrinsic problem with the speakers.

The majority of loudspeakers designed for home listening have their tonal balance adjusted so they’ll sound smooth and natural when heard in living rooms that are "typically" furnished: rugs or carpet on the floor, upholstered furniture, curtains of some sort, and bookcases on at least one wall.

But in rooms with tiled floors, with walls of exposed glass and bare brickwork, an otherwise well-balanced speaker may have too much midrange and treble energy bouncing about the room. With midrange and treble sounds, these surfaces react like mirrors and light, reflecting the high-frequency energy from a speaker.

A treble control or equalizer can be of some help, but a better approach is to add some area rugs, curtains and perhaps a wall hanging or two to break up and absorb some of the high-frequency energy. Upholstered furniture helps a lot, and hutches and bookcases will break up and dissipate sidewall reflections. The thicker the carpet and underpad, the more the absorption of reflected treble and midrange energy. Taming the reflections of a bare room can go a long way to getting that ideal balance of deep bass, midrange, and smooth highs that we all want from our speakers.

Basic TV Picture Calibration

This is a very basic guide to getting a better picture from your TV set. We’ll save the elaborate setup, which requires a test disc, for a later edition of the newsletter. Your TV may have different names for the controls, such as Sony's habit of calling Contrast 'Picture', but the procedure remains the same.

No matter what the age of your TV, the first thing you can do is determine if there is an automatic circuit that controls flesh tones, and turn it off. While these circuits are a convenience, they automatically convert any colour that approaches Caucasian skin tone to a uniform shade of peach. This introduces fundamental inaccuracy in reproducing all the other colors in the spectrum. So find that control and turn it off. You may have to occasionally adjust the Tint (hue) control for skin tones when you change channels, but in my view that’s a small sacrifice to make in order to achieve fidelity of every other color.

The next step is to calibrate contrast (white level), black level (brightness), hue (tint), saturation (color), and sharpness. Most manufacturers set up new TV sets for an extremely bright, contrasty picture. They do this so the sets will look good in bright, fluorescent-lit stores where customers will choose the TV set with the brightest, high-contrast picture as being the “best.” Start by turning down the colour (saturation) control so you’re looking at a black and white picture. Now adjust the Brightness control so you can still see detail in white areas. Then play with the Contrast (white level) control so that blacks are truly black but there remains a bit of detail visible in shadow areas. You may have to go back and forth between these two controls until you get a satisfactory black and white picture. Now you can adjust the sharpness so you get sufficient detail but not so much that any video noise or grain is obtrusive.

Next, turn up the colour (saturation) so colors are natural and vivid but not excessive. Finally, readjust the Tint (hue) so the skin tones look natural. If you have done this successfully, your set should properly render the full range of human skin tones from ebony black, through chestnut, to dusky hues and every shade of pink.

Video Connections

In the old days, hooking up your TV was simple. You connected an outdoor antenna to an "antenna" input on the TV, or a cable-TV connector with an adapter to the same input.

But as TV sets and the sources and delivery of video signals have become more sophisticated and varied (DVDs, satellite dishes, HDTV, videotape, and digital signals), so have the connections. Nowadays, there are four types--composite, S-video, component and digital--with the first three being the most common. If you have an aging VCR, it likely has a composite video connector, typically a single RCA jack. It’s called "composite" because it combines the colour and luminance (brightness) portions of the video signal into one signal, so you only need one cable. But that combining of brightness and colour portions lessens the video quality somewhat, so a new connector was introduced in the 1980s. The S-video jack ("S" stands for separated) keeps the luminance and chrominance (color) information separate, and this connector will usually yield significantly improved picture quality (compared to a composite connection) from sources such as DVD. The S-video connector also uses a single cable and a special plug.

Greater improvement is possible with DVD images by using a component video connection. Component video further separates the colour and brightness information, using three cables from which the TV set extracts the red, green and blue components that make up the picture (plus the brightness or luminance). This type of connection must be used for TV displays and DVD players that have progressive-scan capability, and typically there are three separate RCA jacks. For high-definition (HDTV) video signals, a wide-bandwidth component-video connection is required.

The latest video connector found on some recent HDTV sets is pure digital, called either FireWire, iLink, IEEE 1394 or a DVI (Digital Video Interface). These keep the video signal in digital form until it reaches the TV display.
Your TV display and DVD player must each have compatible connectors in order for you to benefit from the potentially improved picture quality. If your DVD player has component-video output jacks but your TV lacks them, then you can’t realize the benefits until you get a new TV that has component-video inputs. If all your equipment has S-video connectors, then use them.

Home Theater Wizard