How to buy ... a surround sound home theatre system
- — 10 September, 2006 22:00
Thinking about getting yourself a home theatre system to match that big widescreen telly you bought last year? You’re not the only one. Walk into any electronics chain store and you’ll see shelves lined with home theatre systems of all varieties from every conceivable manufacturer. How do you choose which one is best for you? You could go on price alone and pick the cheapest one you can find, but chances are you’ll quickly become dissatisfied with that ‘bargain’ as you discover the shortcomings of poor sound and low-end features of a system manufactured in such an inexpensive manner. Your best bet is to spend a little more and get something you’ll be pleased with for longer. To do that you need to arm yourself with a little knowledge so you don’t find yourself on the back foot as you enter the store.
What is surround-sound?
The concept of surround-sound is a simple one: it aims to help put you in the centre of the action by placing speakers all around you. Movie theatres introduced surround-sound many years ago but it was the advent of Dolby Digital in the early 1990s that truly changed the way we experience movies. Dolby Digital uses six independent channels of sound (usually referred to as ‘discrete’ channels in home theatre circles) to power six separate speakers, encircling the listener with sound. The real revelation for consumers came in the mid-90s when the new DVD format brought Dolby Digital sound into the home. Relatively cheap home theatre systems consisting of a DVD player, a combined multichannel amplifier and surround-sound processor (a device we call a receiver) and six speakers soon started proliferating as more and more movies were released on DVD.
DVD is the creation of a consortium of electronics manufacturers that includes Sony, Philips, Matsushita (Panasonic), Toshiba, Pioneer, JVC and others. It wasn’t an easy relationship to begin with. Two factions were working on competing high-density CD formats and it was only pressure from a group of powerful computer companies led by IBM that prevented a VHS vs Betamax-style format war. It seems the unbridled success of the DVD format hasn’t taught these companies anything about the benefits of collaboration, however, since two factions, headed by Sony and Toshiba, are again working on two competing formats for the next generation of home entertainment. Sigh.
How many speakers do I need?
The six speakers in a basic home theatre system consist of five full-range speakers and one dedicated bass speaker called a subwoofer. This setup is referred to as ‘5.1’ sound (the ‘.1’ being the subwoofer). Today you can have more than six speakers, and some receivers will even support 10.1 surround-sound. Since we’re concentrating on the basics here we’ll stick with the default standard that is 5.1.
So, getting back to our six-speaker (or 5.1) setup, we find three front speakers including a front left, front right and a centre speaker. It’s these three that produce the bulk of the sound you’ll hear during a movie and of these it’s actually the centre that does most of the work. It handles virtually all dialogue and a healthy chunk of the rest, too, making it the most important speaker of all six. The other two front speakers, the left and right, are responsible for a lot of the ‘slam’ factor in movie sound and will provide ambient effects most of the time before bursting to life when there’s action or music. Along with the centre speaker, it’s this front ‘wall’ of sound that you’ll hear most during a movie.
Frequency response: A measure of the range of frequencies that can be reproduced by a speaker, from lows to highs, and the evenness of their reproduction. For example, you might see something like this: 40Hz to 20KHz, +/-3dB. That means low frequencies from 40Hz (cycles per second) to high frequencies up to 20,000Hz (the approximate upper limit of human hearing) are reproduced with no more than 3 decibels of deviation from perfect accuracy (‘flat’ response).
The part of all this that is worth paying attention to is the low-frequency limit. For most music and many movies outside the action and sci-fi genres, a lower bass limit of 50Hz will do. Pushing the bass down to 40Hz will ensure that you never feel seriously deprived. And if you get it down to 30Hz or below, you can feel some pretty bone-rattling effects.
The two rear or surround speakers provide ambient noise to help create a believable sound field. They also provide directional cues to help give the sensation of sound moving around the viewer. You’ll find things like chirping crickets, zinging bullets, wind blowing and other noises that’ll have you instinctively looking over your shoulder during the movie.
Because the rear speakers carry a lighter workload than the others, manufacturers often use smaller speakers to make them easier to hide away in a busy living room. In theory it’s ideal to have identical speakers for all five to give the most balanced audio experience possible, but this is rarely practical.
Deep, powerful bass is the hallmark of modern blockbuster movies and in a home theatre system it’s up to the subwoofer to provide those really big bangs that rattle your windows. If you’ve opted for a home theatre system that uses small, easy-to-manage satellite speakers then your subwoofer becomes even more important, since it will have to produce virtually all the bass in your system.
There are two types of subwoofer to watch for, active and passive. Active subs have their own dedicated amplifier built into the subwoofer enclosure and are the preferred option since they don’t require any power from the main amplifier, only a line out signal. A passive sub relies on the main amplifier’s power and is plugged in using speaker wire instead of an RCA-style cable.
In addition to speakers there are two other essential elements to a home theatre system — the DVD player and the receiver. Many all-in-one systems combine these two devices into one unit, which is great for reducing cable clutter and making setup ultra-easy, but not so great when it comes time to upgrade and you want to replace just one component. They do, however, offer a decent amount of bang for buck and are particularly useful if you have limited space, so don’t write them off if you see one that otherwise fits the bill.
The heart of a home theatre system is the receiver, which acts as stereo, home theatre processor, radio tuner and video switcher. High-end systems may use separate components to do all of this, but for most of us there’s a receiver at almost all price points to suit our needs. The idea is that you plug your TV into the monitor output of your receiver and then plug everything else into the receiver. You could have your game console, VCR and DVD player all plugged into the receiver so you can control what’s on your TV at any one time simply by pressing a button on your receiver’s remote. That’s why the back of a receiver seems, at first, to be an unholy mass of different-shaped sockets. Thankfully, you most likely won’t need to use half of them, but it’s better to have room to plug more devices in later than not enough.
If you’re buying a one-box system, your speakers should already match the receiver perfectly. If you have a choice, however, then make use of the knowledge of the salesperson to match the speakers to the power rating of the receiver. Depending on your room size you should find that 50w to 150w per channel should give more-than-adequate output from your receiver. Speakers should have an operating range supplied by the manufacturer so ensure your receiver falls somewhere within this. Also ensure the impedance rating of the speakers (measured in ohms) matches that of the receiver. Impedance is the electrical resistance in speakers. If impedance is high the speaker draws less current so is easier for an amplifier to drive. Low impedance requires a more powerful amp. If you buy 6-ohm speakers and run them on an 8-ohm receiver, you could damage your amplifier. Any salesperson will be able to find out the impedance for you, and if they can’t, find someone who can or find another store!
If you have a TV that uses component video connections make sure the receiver you buy has component video switching to get the most from your system. If your TV has the slightly lower-quality S-video socket you should be fine since almost every receiver will have S-video inputs and outputs. Composite is the lowest-quality connection and should be avoided if possible.
HDMI and DVI
HDMI and DVI are new, all-digital methods of connecting your display to your DVD player/receiver and they’re slowly gaining a foothold in mainstream electronics. More and more plasmas, LCDs and projectors are using one of these two input options and they provide the best-quality video signal. If you find a system you like that features HDMI or DVI video output then mark it down as a big plus on your shopping shortlist.
Listen: When it comes to evaluating sound, there's no substitute for your own ears. The quality of a system's speakers will make or break its performance, and you can't gauge that from specs or descriptions alone. Take your own discs so that you can listen to material you're familiar with. And even if you intend to use the system only for movies and TV, include some music CDs. They will make it a lot easier for you to spot problems with tonal balance.
Push the subwoofer: Calling Arnie! Here's where you will need a DVD, preferably a noisy thrill-fest. Find a scene with some heavy bass action and see how the system's subwoofer holds up when you really crank it. You want one that won't wimp out on this sort of material at the volume levels you like to hear.
Check component construction: A general rule of thumb (and barring any dubious efforts by unscrupulous manufacturers) is that the heavier a speaker or component, the better the quality. It means they’ve used better-quality materials in the construction of the speaker casing which has a positive bearing on the quality of sound. Give a speaker a good rap with your knuckles and see what sort of sound it makes. A hollow ringing isn’t good. A solid thud is. Try and avoid plastics. The same can be said of the receiver: if it’s heavy, chances are they’ve used a bigger power transformer inside the amp to provide a steady flow of power to the speakers.
Don't hesitate to go digital: Even if all you've got right now is a VCR and a ten-year-old TV, chances are you're going to wind up sooner or later (probably sooner) with a DVD player or HDTV that will really benefit from Dolby Digital decoding in the sound system. It's not a big premium anymore.
Look before you leap: Take a good, hard look at the room where you plan to use the system. What has to go where, what can go where, and how big can it be and still fit? There's no point in paying extra for a 7.1-channel system if you've got no place to put the two extra surround speakers, for example. If cabinets are involved, make measurements and carry them with you. A small pocket tape measure can be very handy.
Don't get caught up in numbers games: One thousand watts into crummy speakers is just really loud, bad sound. And 20 surround modes is 17 too many if you're going to use only three of them. Stay focused on good sound and ease of use.
Get to know the remote: A poorly laid-out remote control is a pain. How easy is it to find critical buttons (volume, pause, mute, channel and so on) in the dark? How comfortable is it in your hand?