'Stereo Expand' Button Channels Wider Sound

May 24, 1986|By George Gascon, Special to The Sentinel

QUESTION: I own a portable AM-FM cassette that has a button called ''stereo expand.'' It does give a very wide open sound and I like it, but how does this vary from regular stereo?

ANSWER: The stereo expand is an electronic process that creates the wide or spatial stereo sound. The most common way is to take some of the right channel signal and feed it into the left channel.

The same is then done from the left to right channel.

Some more elaborate units even add a small amount of time delay to the out-of-phase signal before entering it into the opposite channel.

Regular stereo is made up of independent left and right channel signals without any crossing over of opposite signals.

Q: I recently purchased a JVC KSE-7 equalizer that has seven bands. Is there any rule of thumb as to what frequencies have the most effect on particular sounds that I can use as a guideline?

A: When setting up an equalizer there is no standard method. An equalizer should help you get the sound you like from your stereo in the room where it is located.

Start with each control in the center and make your adjustments in moderate increases or decreases. The list of frequencies below will give you an idea of what to expect when making your adjustments.

-- 50-70 hertz affects low bass frequencies.

-- 140-160 hertz affects a boomy sound to bass frequencies.

-- 350-450 hertz affects a warm and solid sound in midbass.

-- 1,000-1,200 hertz brings vocal or instrumental soloists to the forefront.

-- 2,000-2,500 hertz tends to create hollow or nasal sounds.

-- 5,000-7,000 hertz affects brightness of the sound, most noticeably in cymbals and other high-pitched percussion instruments.

-- 15,000 hertz affects shimmer and openness in the overall sound.

Q: I recently purchased a good used turntable but I'm having trouble setting the arm balance and antiskate controls. I have enlisted a friend's help but things just don't seem right. What do I do?

A: To begin with, the cartridge is what determines the tracking forces required.

You did not mention what type of cartridge you have. If you do not have the proper information, you might check with the local audio stores or send me the brand name and model so I can find out for you. When you have this information, do the following.

Set the tracking and antiskate adjustments at zero. Slide the counterweight back and forth until the arm floats in the horizontal plane. Then turn the tracking adjustment to the proper amount required and do the same to the antiskate control.

If you have any doubt about the settings on your turntable, invest in a tracking force gauge, available at local audio stores. A good tracking force gauge is superior to most built-in gauges on turntables.

Q: Can you explain to me why most movies on TV always start with the people on the screen looking very tall and skinny? Then, when the titles are over, everything seems normal.

A: The reason for the change in the appearance of your picture is because of the incompatibility of movie and television screens.

Those movies made for the theater are usually filmed for wide-screen viewing and have to be narrowed to fit the TV screen.

If the people were not ''tall and skinny'' you would miss a large portion of the titles. The difference in viewing areas of a movie screen and a television screen is the problem. The width of the picture must be compressed in order to fit on the narrower TV screen.

When the titles are on the screen the difference is more apparent, but the picture is reduced to fit the television screen for broadcasting.

Q: How often can I use my audio and video tapes to record over again without losing any quality in sound or picture?

A: Let's start with audio tapes. The recording and playing life of a good quality audio tape should be many years.

The only limits are the physical aspects of the tape: The edges can be be damaged by the tape guides and the pressure pad and liners in the cassette cartridge itself can gradually weaken.

Video tapes do not have as long a life. The high-rotating video heads will wear away the oxide coating on the tapes and therefore decrease picture quality. From my experience, video tape used more than 100 times will show deterioration.

Remember to store all tapes in a cool and dry place as high humidity can cause harm.

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