The subject of Home Theater is fraught with misinformation and conflicting opinions about nearly every aspect of the matter. Most of it boils down to a relatively subjective question of: does it really make a difference? Of course, this often depends on your personal preferences, sensitivity and how well your ears are trained. But, like many other demographics, the audio world is flooded with marketing jargon aimed at steering you toward their product that may or may not be what it claims. Here will discuss 3 of the most commonly proliferated home audio myths: that you need expensive cables, amps with the same power rating will perform the same and speaker size doesn’t affect sound quality.
Myth 1: You Need Expensive Cables
Now, there is a difference between good cables and bad cables, but they are not necessarily directly proportional to expensive and cheap.
So how do you choose a good cable that won’t break the bank?
For speaker cable, one of the most import factors is gauge. And like shotgun shells, the smaller the number the larger the size. Without going through an electrical engineering course, thicker cables offer less resistance to the amplifier than thinner cables. If you think of it like a water pipe, a large pipe allows water to flow easily, where a very small pipe will build up more back pressure with the same amount of water flowing through it. But, this resistance doesn’t really matter until you start getting into longer wire lengths. For example, if you have 6 ohm speakers, an 18 gauge wire can be run up to 24ft before any sound loss would be detectable. So, if your speakers are 5 feet from your receiver, you probably don’t need 10 gauge cables. Although, it is a good idea to use cables a little thicker than you need in case you have strands that break off the ends over time.
The wire material also makes a difference, with the most common being oxygen free copper. However, due to the increasing price of copper, there is an alternative CCA (copper clad aluminum) wire becoming more common. This has an aluminum core with a copper outer skin. Aluminum is not as good of a conductor as copper, but it is considerably less expensive with a minimal performance compromise. That being said, the OFC (oxygen free copper) wire is still the better choice. Some companies make speaker wire out of other materials like silver or even gold, but most of these are more expensive and won’t benefit you sonically. So, you might see some really cool looking thick cables with multiple intertwined cables costing hundreds of dollars; just know that it probably will require your imagination to hear any difference.
Reality
Standard 12 – 14 gauge copper wire should suffice in most applications.
Trivia
Why does the gauge increase as the wire size decreases? The gauge is the number of times the wire is “drawn” through a die. Each time the wire is pulled through the die, the die size decreases. So, a 14 gauge wire was drawn 14 times through a series of dies to make it that size.
Myth 2: 100 watts = 100 watts
Have you ever noticed that two different amplifiers with the same power rating can have vastly different volume output? Amplifier power ratings are one of the most commonly used specs when choosing a receiver. But, like most things in life, wattage is not created equal. Considering that people almost never listen to different receivers before making a purchase, all you have to go on are reviews and specs. But, there are many factors that affect how an amplifier performs. The biggest being the power supply and the power amp section.
The Power Supply
The power supply is the driving force of an amplifier and it consists of three basic pieces: the transformer, rectifiers and capacitors.
The transformer takes the high-current AC voltage from the wall and converts it to a more manageable lower voltage. It’s often called the “heart” of an amp, because it is pumping the power into the amplifier. The size, build quality and materials of the transformer greatly affect the sound and power of the amplifier. Rectifiers then convert the AC to DC power.
Capacitors store energy to be used when power is needed quickly. This of course depends on the source media, but major dynamic changes will utilize these much more frequently. Generally speaking, larger capacitors are better because they can store more energy, but the quality and type can play a big part in the sound.
The Power Amp
The function of an amplifier is to increase the power of a signal. In order to this well and accurately, it takes a lot of engineering and artistry. The amplifier design will not only affect the output level, but also the sound quality. People often don’t realize how much each component filters the signal and therefore affects the tonal quality. There are several types of amplifiers that are divided into “classes.” The most common being class “D” and class “A/B” for home audio applications. Class D amps are much lighter, produce less heat and are more efficient, but they may not produce as warm of a sound. Class A/B is a more traditional amplifier design and is a combination of the class “A” and “B” amp types.
In an ideal world, each of your speakers would be powered with individual (monoblock) amplifiers. But, the more convenient and cost effective way is to use an AVR with multiple amp channels built in. However, a major issue with receivers that have multiple channels is crosstalk. Crosstalk occurs when audio from one channel bleeds into another channel. This would include hearing dialogue from the center channel at low levels in other speakers. This can greatly reduce the spatial separation. Cheaper receivers will have all channels printed on the same circuit board. This configuration is much more susceptible to crosstalk due to proximity. Better amps will have shielding between the channels and the best will also have completely separate boards for each audio channel. This is why the most ideal setup would include completely separate amps for each channel. Heat is another major issue with power. How well the heat is dissipated affects the stability of power output, which is why good amps usually have large heat sinks.
Trying to determine the quality of an amplifier on paper can be a tricky endeavor. Vague or misrepresented specs by deceptive manufactures can cloud the reality of an amp’s abilities. One thing to look for is what the wattage difference is at different ohm ratings. In a best case scenario, if you cut the ohms in half, the amp will have double the power rating (i.e. 100w at 8ohms = 200w at 4ohms). But, most amplifiers will have a lesser difference. This will tell you how stable the power output on the amplifier is.
Another fact to be aware of is that most amplifier ratings are based on using only 2 channels. When you see a 7.1 channel receiver rated at 100w, that’s only using 2 of the channels unless is specifically states “all channels driven.” So, if you are running all 7 channels, that power rating will drop somewhat. With cheaper amps that number could fall down to 80 watts per channel or even less. Make sure to take this into account when you are matching a receiver to speakers.
If you don’t think amplifiers change your sound, just ask a guitar player. Have them crank up a 15w tube amp and then crank up a 15w solid state amp. The tube amp can make your ears bleed (in a good way), while the solid state amp might not even be loud enough to be heard over a drummer. Other than the guitar, the amp is what creates that sweet tone. And there are a plethora of variations. This applies to home audio as well, just on a more subtle level. Your speakers make the biggest difference in the sound of your system, but don’t underestimate the impact of what’s powering them.
Reality
You get what you pay for.
Trivia
The first audio amplifier was invented by an American engineer named Lee De Forest back in 1909. This was the result of another of his inventions, the triode vacuum tube.
Myth 3: Size Doesn’t Matter
There are many different sized speakers out there and many companies that will have you believe that their 2-inch speakers will deliver “movie theater quality” sound in your room. But, no matter how much “magic” is used, you still cannot defy the laws of physics. They will often have a set of small wall mounted speakers with a sub, but these can only produce a fraction of what a full range loudspeaker can achieve.
Sound is literally the physical movement of air. Tiny speakers simply can’t move as much air as a larger speaker unless you have a large array of them, and even then there are limitations. This is why speaker size is generally associated with frequency production. Tweeters are usually around 1 inch, midrange 3-4 inches, woofers 5-6 inches and subwoofers 8-15 inches. As the pitch gets lower, the sound wave gets longer. The wavelength for a 60 Hz tone is about 18.5ft, whereas the wavelength of a sound at 1 kHz is just over an inch. That’s quite a difference!
In order to accurately produce a wide variety of wavelengths simultaneously, you need speakers of different sizes. This is why sound from a 3-way tower speaker (like a Verus Grand Tower) will sound superior to a bookshelf or satellite speaker. Not only is the enclosure larger, providing more resonance, but allowing speakers of different size to focus on the frequencies that they can replicate best will produce a more even sound. A crossover is used to filter and allocate the signal to each of the speaker groups, which is a balancing act all its own. The cabinet, crossover and drivers work as a team to produce clear and even sound (hopefully). But, this is what is basically required to achieve a maximum sonic performance.
Reality
If it seems too good to be true, it probably is.
Trivia
The lowest note ever recorded was produced by a supermassive black hole in the Perseus cluster. It was a B-flat, 57 octaves below middle C. To give you an idea of how low that is, the lowest sound you can hear is 20Hz, which is a frequency 1/20th of a second. The note this black hole produced has a frequency of 10 million years. You might need a bigger sub!