Wattage for Stereo and Home Theaters Explained

Wattage, watts-per-channel (wpc), power, and power-handling are all terms that get thrown around a lot at stereo and home theater stores.  With all the talk of watts and power, one would naturally think they're pretty important.  And power is certainly an important measure of how a given receiver or amplifier will perform.  But if you don't understand what your salesperson means when she says "power" or "watts", you may well buy something that's less than ideal. This Hub seeks to explain what watts and power mean in the stereo and home theater world, and how to weigh watts and power against other factors that go into making a good purchase and getting the best value for your money.

Wikipedia defines a watt as:

"By the definitions of electric potential (volt) and current (ampere), work is done at a rate of one watt when one ampere flows through a potential difference of one volt.^[1]

1W=1V×1A

In other words, a watt is a measure of work. In the case of stereo and home theater systems, the work being done is moving the drivers (tweeters, midrange, and woofers) back and forth inside your speakers. The power to do this work is supplied by an amplifier. This amplifier is either inside your receiver, or in its own cabinet. Take a look at the schematic below, showing all the different ways an amplifier can be packaged into a stereo or home theater. You can click on the image to see a larger view.

If you've been into a stereo or home theater (HT) store, you've probably heard that watts matter. The higher in price you go, so go the watts. The best pieces are sometimes three or even four times more powerful - in terms of watts - than the least expensive gear. So how many watts do you need? Not as many as most of today's equipment manufacturers would have you believe, unfortunately.

It's no conspiracy theory, just business. Many of today's manufacturers are owned by private corporations or private equity funds: dispassionate, financially-minded managers with a beady eye on the bottom-line. They study customers' willingness to pay for certain packages of features, combine those results with the imperatives of their long-term technology and new-product release schedules, and design products based on these results, and the vagaries of current prices of different metals. Finally, they add in whatever cost-cutting measures they think the market will tolerate, and violá!

Most of the basics that customers require - such as Dolby 5.1 Surround - are relatively inexpensive. So manufacturers use wattage to differentiate the top of the line from the bottom. This has led to the inexorable creep of more and more watts of power packed into receivers, amplifiers, and powered subwoofers. Meanwhile, workmanship slowly creeps downward, as engineers game the measurements (distortion, for example) to create the appearance (on paper) of good sounding gear, for as little cost of goods sold as possible. After decades of this, most new equipment, and almost all of what you'll find at a big-box store, is of low quality and FAR OVERPOWERED.

it is hard to blame the manufacturers for this trend. After all, it's much more difficult to explain why using gold-plated contacts is better than aluminum - and even harder to get customers to pay for gold-plated when the next product on the shelf boasts so many more watts for the same price. So cost-cutting goes largely unnoticed.

One of the most common ways is to have different components share parts. For example, if two channels (or five channels) all share the same amplification components (transformers, transistors, etc...), then the amp can produce more "watts per channel" but use less copper wire. Another cost-cutting measure is to have many speakers share one crossover, which is one of the reasons for the deluge of all-in-one systems.

So the next time you're in a big-box store, or at one of the direct-marketing manufacturer's mall outlets, ask yourself: how do i find out which one of these receivers uses the most gold in their contacts? Or if not gold, how much to the contacts weigh? You may well find you can't find that information. That should tell you just how powerful the concept of wattage has become, and how little you can find out about the quality of the equipment.

Know this: with any two pieces of equipment at a given price, you are trading watts for quality. Watts either cost money or quality, every time. Obviously, therefore, it's important to know how many watts you need for your room, right? Right. Go into a store, and you're likely to hear something that's true: more wattage in general often results in better sound. But it would be more correct to say that more wattage of a given quality sounds better in general. There's that pesky quality thing again! You see, not all wattage is created equal. To see one reason why, let's return to our example of component-sharing. Don't forget to click the image to enlarge it! :)

So is it always bad to share components like transformers?  No, it isn't.  But it can be, especially when you consider all the things a good stereo or home theater should be: it should sound good, and be flexible enough to sound good in your next home.  Perhaps you think it should be upgradable - I certainly do.  Many people want their stereo to work without trouble for twenty years, or not fade, chip, or fall apart.  And these are just a few of the things a good stereo "should" be. 

Since cost-cutting is everywhere, and your stereo has to be so many things to be a "good stereo", you really never know when some cost-cutting measure is going to jump up and bite you in the buns. 

That's why I recommend buying the highest quality gear you can afford, and buy only the power you truly need.  I also recommend taking at face value the claim that "high quality" watts from a product such as a Krell, Rotel, Adcom, or Carver amplifier will provide more power than "low-quality" watts from a receiver from a company like Sony, Yamaha, or Onkyo.

So how many watts do you need for your stereo or home theater?  Well, unfortunately, it depends.  Here are the things that affect your power needs the most:

• Speaker Efficiency: some speakers are very efficient, which means they make a lot of sound on only a few watts.  Other speakers need a lot of power to make the same volume of sound.  Hallmarks of efficient speakers are ports (holes) in the cabinets, large paper cones, and horn-loaded tweeters.
• Room Size: the larger your room, the more power you'll need to fill it, all else equal.  For a room 18 feet by 18 feet, with 9-foot ceilings, you'll want a stereo with at least 25 watts per channel with efficient speakers, or 40 watts per channel with non-efficient speakers.  Think those numbers are low? They're not.  You simply do not need a stereo where you only turn up the volume to "3".  Oddly, take a look around and that's what most people have.  Interesting, no?  That 200 watt-per-channel Sony you got from the electronics store could power a P.A. for a large church...how did it end up in your living room?
• Type of music: if you listen to music loud, you'll need more power than the guy whose ears hurt at the slightest hint of decibels, obviously.  Also, rock, reggae, and rap are not only bass-driven styles of music, but listeners to these often like to boost the bass relative to the rest of the music.  If that's you, you'll need speakers to make the really low frequencies, and the wattage to match.  Again, for that fabled 18 x 18 - foot room, an extra 125 watts or so for bass reinforcement should be plenty.

*** A Note on Wattage, Bass, and Subwoofers: I am a believer in bass, and powered subwoofers.  There are four powered subwoofers in my home theater: two are wired into my Left & Right Channels post-preamp, and reside under their respective front speakers.  The other two produce the Dolby 5.1 subwoofer signal, and are placed under my two rear surround speakers.  Major wattage is needed to make good, clean, low bass.  I also like powered subwoofers because they take significant load off of the main speakers and amp, making them far more musical in the mids, low-mids, and highs. 

Once you recognize that most gear is overpowered, you'll notice something annoying: it's hard to find a quality component without all those unnecessary watts! The top-of-the-line in a big-box store is always jam-packed with wattage. But why pay for it? And you know you are paying for it. What to do?

The thing to do is go upscale - not to the top of the line in the big-box store, but to the bottom of the line at the audiophile store. Here's why (remember to click the image to enlarge):

While stepping up to the "low-end of the high-end", you score a significant upgrade in quality, and have the right amount of power.  But there's a way to get even more value for your dollar: buy used vintage gear.  Here's why:

The technology behind the best amplifiers, pre-amplifiers, and, to a lesser extent, speakers, hasn't changed much in fifty years.  Sure, technology allows manufacturers to do more with less, but since when has that translated into value for the customer?  No, the reason new equipment comes out year after year is because it must.  Companies must sell new equipment every year, but even the cheapest Sony will last twenty years, 80% of the time.  The new gear has WAY more power than vintage stuff, but we already saw why all those watts don't mean much.

There's another reason buying vintage is a good idea: Every year, hundreds of new products come to market.  Some of them will prove to be of poor quality - filled with cost-cutting measures that cut too close for comfort.  But some will prove to be elegant compromises of function and cost, and rise over the decades to legendary status.