Absinthe & Cookies (a bit bitter, a bit sweet)

Home Theater gotcha's

This is for people who are considering or actually buying/receiving a small home theater setup for the Christmas holiday. (It is NOT intended for those very experienced home theater buffs. :) ) Usually at this time of year, the stores are flooded with a veritable plethora of "Complete Surround Sound Systems" aka "Home Theater in a box" items. All of these 'systems' usually boast fairly impressive specifications with decent styling and color schemes. On top of that, they also have reasonable (ok, somewhat reasonable) price tags to match. All in all it sounds like a good deal all around. At least that is what one would think.

Since I have been in the hobby of Audio for some 20+ years I thought I would shed some light on the dark side of Home Theater. This is the side that most manufacturers don't want you to know about. Certain little "tricks" that are played with specifications etc.

So to begin:

1) Power Rating: This is the number that most people look first when looking at a home theater system. More specifically: How many watts per channel and how many channels. The most common specification out there is (7 x 100) or 7 channels at 100 watts per channel. Sounds impressive doesn't it? This is why that spec is usually labeled rather prominently on a Home theater in a box ( HTIB) system. After all 7 x 100 looks much better that 7 x 50, right?

This is the most prevalent "trick" out there. It may come as a surprise ( or not, depending on your view of manufacturers ) but the combination of lax standards and advertising allows a great deal of "hot air" in the power specification.

To start, let us look at a little bit of electrical theory. There is a little number called efficiency. Put simply it is a percentage, it means how much power can you output from what you input. The efficiency is a number that is between 0 and 1. No one would market a device that is 0 percent efficient ( really, who would buy such a thing, and why would you if you could?). No one can market a device that is 100 percent efficient ( since there is nothing made that is 100 percent efficient...yet). That leaves us with a device that is less than 100%. For most of these HTIB's it is FAR below 100%. (This is based on the fact, that most HTIB's have a Class AB amplifier and not the more exotic Class D-Class H designs. If you don't know what that means, don't worry). A good rule of thumb is approximately 50% efficiency. Keep that figure in mind as we continue, if you would.

The next time you look at a HTIB, look at the power spec then look at the physical unit. Rather the BACK of the unit itself. In an area near the power cord there should be some information regarding how much power it draws. Either something like "Power 400 Watts" or " 3.3 A @ 120 V". The first is self explanatory, the second needs some translation. 3.3 A means 3.3 Amps and 120 V means 120 volts. To get the number of watts multiply 3.3 by 120 which comes to 396. So the power drawn is 396 watts.

Remember our efficiency number? Multiply that by the power drawn and you get the amount of USABLE power available for the system. So 400 watts X 0.50 = 200 Watts. Now that is 200 watts TOTAL power. With most HTIB systems there are 5 or 7 speakers including a subwoofer. Assuming 5 speakers ( and disregarding the subwoofer for now ) that gives us about 40 watts per speaker ( or channel ). A far cry from the 5 x 100 spec that we referenced earlier isn't it?
Now you may be wondering how the heck the manufacturers get away with that kind of advertising. The answer: Lax standards and no real policy from the FTC on surround sound systems ( at least not yet ). That said try to find a system that has at least 30-40 watts of Real power per channel and about 50 watts or more for the subwoofer. The subwoofer usually has its own power draw spec so you can use the above method on it as well.

2) Connectivity capability. Many HTIB's advertise that they can connect other equipment, Vcr's, Tivo, cable box etc. Again, we need to check the BACK of the unit to determine what can truly be connected. Some units have connections for only 1 item, while others can only connect units of the same BRAND as the HTIB itself-usually through a proprietary connection cable. ( at an additional cost of course ). Checking never hurts!

3) Speaker connectivity. Some HTIB's, usually the cheaper ones, have their speakers prewired with color coded connectors. Although this makes for easy connection, you are limited to the speaker wire length when placing the speaker
( 25' is NOT that much for placement options ). Try to stick with a system that uses standard wire connections, because if you ever break the supplied wire, or want to place the speaker further away, you can always buy more wire.

4) Expectations. Last but definitely not least. DO NOT expect a HTIB with a price tag between 400-1000 dollars to sound like the system that your audiophile friend has when listening to music or watching movies. The audiophile probably spent over 1200 for the amplifier ALONE, not to mention the speakers, the DVD player and the Cd Player and the powered subwoofer ( that alone runs from $500 and up ). A HTIB is not a replacement for a full blown Home Theater rig.

Now having said all that you probably think I am dead against the HTIB's, right?
Actually no. Within their limitations these little systems can introduce you ( or the gift recipient ) to the idea of having your own little cinema at home, in a very nice and fun way. The trick is to (as always) do the research and ask questions and then when shopping, look at the unit, both front and back. Staying away from the no-name brands that only appear at this time of year is also a good idea. Another thing is this. Some HTIB's have wireless surround speakers. Although a cool idea, the technology is not really there yet.

That pretty much wraps it up and I hope it answered a few questions. Happy shopping!

Posted by Bob at November 28, 2006 12:53 PM | PROCURE FINE OLD WORLD ABSINTHE