Volume Control
Sydney Morning Herald
Monday May 10, 2004
If you are going to get realistic sound from your amplifier or receiver, you need to know what to look for and be prepared to pay for it.
Buying a plasma screen can be a shocking experience for the uninitiated. The price itself shouldn't be a surprise because the advertisements will have prepared you for a price tag of somewhere between $5000 and $10,000.
The shock comes when you arrive at the store clutching your cash and discover what the advertisements haven't mentioned, which is that when you buy a plasma screen, that's often all you'll get: a screen.
If you'd like sound with that you'll need to find some extra cash for an amplifier and a pair of speakers. Faced with the problem of this additional unforeseen expense, and forced to make an on-the-spot decision, most people end up buying the store's cheapest surround-sound package, usually an all-in-one "home theatre in a box" system. Big mistake.
To generate an illusion of reality, the sound has to be big enough to match the size of the image, and low-cost sound systems just can't keep up. It's the same problem that caused the demise of drive-in cinemas, where patrons hung single small speakers from their car windows to hear what was going on. This worked well when movies were based primarily on dialogue, but once directors started producing blockbuster epics that relied more on large-scale screen and sound effects than on dialogue, those little window-mounted speakers just couldn't keep up and the drive-ins closed.
The first step in creating big sound is making sure your amplifier or home receiver has enough power. In an average-to-large room, a receiver rated at 60 watts per channel or more will be more than sufficient. Unlike a two-channel stereo system, where 60 watts per channel means a total of 120 watts for the system, which under some circumstances may not be sufficient, 60 watts per channel from a 5.1-channel home-theatre amplifier or receiver gives a total of 300 watts for the system, which almost always is sufficient. Don't be concerned about minor differences in power output between different brands.
Because there's no Australian standard on how power output should be measured, each manufacturer measures it in a different way. The result is that a unit with a 60 watt per channel output rating may actually be more powerful than another brand rated at 70 watts.
If in doubt, ask if there's an independent test report available or have the salesman play the two and see which sounds the louder. If you're really not sure, pick them up. The heavier of the two is more likely to have the higher power output.
But power output isn't everything. It's good to have a representative selection of sound fields. These are circuits that make it seem as if you're listening to the sound in a stadium, a church or some other building by adding reverberation and echoes to the original.
The idea is to make it seem as though your living room is larger than it really is. Sound fields are often called DSP modes, because they're created by digital signal processors. But don't get too carried away by DSP effects because they don't always work while you're watching movies with Dolby Digital soundtracks, which is most of them.
All receivers will have a Dolby Digital decoder inside, but the most recent models will also have a ProLogic II decoder. This enables you to create a multi-channel sound field from a stereo soundtrack.
This is great for movies, but if you want stereo sound from all five speakers in your system it's better to use a 5CH circuit, which does a much better job of it. Despite the usefulness of 5CH, not all receivers have it.
Many receivers have Digital Theatre Systems (DTS) decoder circuits in addition to Dolby Digital. DTS enjoys a modest level of success in the United States, but DTS-encoded discs are unusual in Australia, so you won't have many chances to use the circuitry.
THX is a little more important. Developed by LucasFilm, THX started life as a process to improve the sound from rear-channel speakers. It was made redundant by the introduction of Dolby Digital but still survives as a licensing system that guarantees a minimum performance level and that receivers carrying the logo will send the correct low-frequency information to THX-standard subwoofers.
The most difficult and most important part of setting up a home-theatre system involves ensuring each of the five satellite speakers is set to play at a certain volume level compared with the others, and all five signals reach the listening position at the same time.
This is particularly important when the rear-channel speakers are closer to the listening position than the front speakers. Because of
this, receivers that allow you to set and store volume-level and speaker-distance information for every speaker in the system are well worth the extra expense.
Denon AVR-1804 AV receiver
Denon has one of the largest ranges of home-theatre receivers. Its new AVR-1804 is packed with features, including Cinema Equalizer to balance the hot high-end sound on many movies. It's a 6.1-channel unit, with a 90 watt per channel rating. The recommended retail price is $1199. Details from Audio Products on 1300 134 400.
Marantz SR-9300
The Marantz SR-9300 6.1-channel receiver is THX Ultra2 certified. It's possible to switch off all video and DSP circuitry, to let the dual-differential digital-to-analog converters go to work on the audio signal. It also has Gyro-Touch tuning. The recommended retail price is $5990.
Details from Qualifi on 1800 242 426.
© 2004 Sydney Morning Herald
Share This