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Watts and Home Theater – Myth vs Reality

  • 7 min read

What makes your home theater sound good? There is a big myth that the more watts your home theater system has the louder it can get. However, that is only partially true. Wattage output is just one factor in determining how good your system will sound in a given space. 

When shopping for home theater receivers, soundbars, or all-one-systems, wattage output is always hyped in promotional materials as the main draw. You are led to believe that the number of watts will be the determining factor as to how loud and how well your system will sound. 

The number of watts an amplifier can dish out is one factor that contributes to sound quality, but those promoted numbers are often misleading. You need to look past just the watts. 

Watts and Volume

What Watts Numbers Tell and Don't Tell You

Continuous Sustained Power

Watts and Sound Level Changes (Dynamic Headroom)

Watts and Audio Frequency

Distortion

Noise

Speaker Impedance

Speaker Sensitivity/Efficiency.

Speaker Power Handling

Watts, Speakers, and Enclave Audio

Watts and Volume

The first thing we have to get out of the way is how watts affect how loud your system gets.

In order to double the volume, an amplifier needs to output ten times the power to produce it.

This means that an amplifier that can output 100 Watts isn't going to be significantly louder than an amplifier that can output 150 watts. Watts and Volume have a logarithmic relationship, rather than a linear relationship. 

Most of the time (under normal home theater listening conditions), an amplifier outputs just 1 to 10 watts across most frequencies for a comfortable listening experience. Extreme low frequencies require more power to produce a desirable listening level but you may not need as much as you think. 

What Watts Numbers Tell and Don't Tell You 

When a manufacturer claims an amplifier outputs a specific number of watts-per-channel (WPC) it doesn't always mean it can output that wattage continuously or across all audible frequencies. How a manufacturer states their wattage output claim makes a difference.

Here are some ways amplifier wattage output is “measured”.

  • One Channel Driven: This means the manufacturer measured the wattage output on just one channel at a time. When you see an amplifier rated at “X” number of Watts per channel with one channel driven, it doesn't tell you how many watts it produces in the real world when 5 or more channels are used. With 5 or more channels used, the power output could be as much as 30 to 40% less. 
  • Two Channels Driven: This means wattage output was measured with two channels running at the same time. This may provide a more accurate number than the single-channel measurement, and is traditionally used to measure power output for stereo amplifiers and receivers, as only two channels are used, but it’s often used in wattage output specs for home theater receivers.
  • All Channels Driven: This means wattage output was measured on 5 or more channels (depending on the system) at the same time. Logic would suggest that this provides an accurate measurement of wattage output for a 5 or more channel home theater receiver or system, but it isn't used (or promoted) often. 

The wattage output specifications as stated in the categories above don’t tell you the other factors you need to consider. 

Continuous/Sustained Power

If the wattage output is stated using the terms FTC, RMS, or Continuous (ie: 100 WPC RMS) it means that the amplifier should be able to output that much power over long periods of time. 

The term RMS is technically not the same as Continuous Power, but for real-world applications, it’s close enough and manufacturers often use the term RMS and Continuous to represent the same thing with regards to amplifier power output. The FTC (Federal Trade Commission) may also be referenced. The FTC controls the standards for measuring amplifier power output.

However, despite the above standards, manufacturers often drift into the more misleading territory by using non-standard terms such as PMPO (Peak Music Power Output). When you see an outrageous claim of 1000 WPC PMPO, this means the amplifier can only output those watts for a fraction of a section. PMPO doesn't tell you anything about how much power an amplifier can deliver on a long-term basis, or even for a few seconds or minutes, so it is a useless specification to consider for a home theater or any audio setup.

Watts and Sound Level Changes (Dynamic Headroom)

Sound levels constantly change throughout musical recordings and movies. This means that sound reproduction over listening time is dynamic. Sound levels will also vary depending on the content. For example, a person talking doesn’t produce as much sound as an elephant trumpeting would. Sound levels (Volume, Loudness) are measured in decibels (dB).

Dynamic Headroom refers to the ability of an amplifier to increase power rapidly for short periods of time when sudden or dramatic increases in sound levels occur in music or movie content such as a crescendo in an orchestra or an exploding bomb.

Similar to sound level, Dynamic Headroom is measured in decibels (dB). If an amplifier can double its power output capability when needed without added distortion, it has 3dB of dynamic headroom. However, doubling the power output does not mean doubling the volume. As mentioned previously, to double the volume from a given point, an amplifier has to increase its power output by a factor of 10.

Watts and Audio Frequency

Another problem when focusing just on watts is whether it was measured using one frequency (such as a 1kHZ test tone), or across the total range of human hearing (20Hz to 20Hz test tones). 

Just because an amplifier can deliver 100 watts at a single frequency such as 1kHZ, doesn't mean it can deliver that power over a wider range of frequencies. Higher frequencies need less power and lower frequencies need more power relative to the overall volume level.

Note: The human voice frequency range is about 100 to 3000Hz for male singers and 200 to 4000Hz for female singers.

Distortion

The quality of the amplifier isn't only reflected in wattage output and how loud it gets. An amplifier that produces excessive distortion at loud volume levels is unlistenable.

It doesn't do you any good to buy a receiver or home theater system with a 100WPC amplifier if at high volume levels the sound is distorted. 

For example, an amplifier might have a stated distortion rating of .01% (which is extremely low) at 50 watts, while another amplifier might have a distortion rating of 1% (which is borderline acceptable) at 100 watts. An amplifier with a stated distortion rating of 10 percent at “X” watts would be unlistenable.

Distortion in audio specifications is commonly referred to as Total Harmonic Distortion (THD).

When you consider both power and distortion, clean sound is better than louder sound.

Noise

Another thing to consider with regards to sound quality is how much actual sound you hear from the content as opposed to background noise. This is expressed as an amplifier's Signal-to-Noise Ratio (aka S/N). This is also stated in terms of decibels. The larger the number, the cleaner the sound. This means if the S/N is 90db, that is less noisy than 80db. 

However, it must be pointed out that noise is not only present in an amplifier, but also in the actual content. For example, a Vinyl Record typically has an S/N of 70db, while a CD has an S/N of 100db. 

Speaker Impedance

An amplifier doesn't work alone to produce sound, loudspeakers need to be connected in order for you to hear anything. 

When checking amplifier wattage output specifications, the amount of power output is also determined by the impedance of the speakers you are using. Impedance is the "pipe" that allows power to flow from an amplifier to the speaker.

Most commonly, amplifier wattage output ratings are tied to a speaker impedance of 8 ohms. If you connect speakers with a 4-ohm impedance, it forces the amplifier to double its power output continuously to the speakers. If the amplifier doesn't have enough continuous power output that 4-ohm speakers may require at a specific volume level, you can damage the amplifier. 

Some amplifiers can work with both 8 and 4-ohm speakers, but most are optimized for use with 8-ohm speakers. Amplifier specs usually provide this information. Even if your amplifier can be used with both 4 and 8-ohm speakers, it is not advisable to mix speakers with different impedance ratings in the same system.

Speaker Sensitivity/Efficiency

In addition to impedance, Speaker Sensitivity/Efficiency also comes into play. 

A speaker will produce sound when fed adequate power from the amplifier. If two speakers with different sensitivity are fed the same amount of power via the volume control, a speaker with higher sensitivity will play louder than a speaker with lower sensitivity. 

If a speaker has a sensitivity of 91dB it will play louder with “X” number of watts than a speaker with an 88dB sensitivity rating. To hear the 88dB speakers as loud as the 91dB speaker, you need to increase the volume by 3dB, which requires an amplifier to output double the power.

Speaker Power Handling

Along with Speaker sensitivity/efficiency, you also have to consider both the minimum power input from the amplifier that is required for the speaker to produce sound as well as the maximum power input it can handle without distortion or damage. This will vary according to the specific brand/model of speaker and may be labeled as Max Input Power or Power Handling.

Watts, Speakers, and Enclave Audio

As you can see from the above sections, the world of amplifier specifications can be very deceiving, especially when you take all the factors (in addition to watts) that go into getting a good listening experience from a home theater setup.

Enclave Audio doesn't publically promote detailed specs for its CineHome II or CineHome Pro wireless home theater systems as they don't follow the practice by many manufacturers of pushing high-wattage specs as a deceptive marketing tool. 

Enclave Audio systems are totally integrated. Each speaker (and subwoofer) in an Enclave system is custom-designed with a speaker driver(s) supported by its own amplifier. The speaker/amp combination is specifically powered and tuned with the correct impedance, maximum speaker efficiency, and both minimum and maximum power handling characteristics. The systems use the least amount of amplifier power needed, which sufficient Dynamic Headroom to provide a clean and powerful listening experience. 

In addition, the CineHome pro is THX certified in the I/S (Integrated System) Plus Categorywhich is perfectly suited for home theater room setups where the viewing distance from the screen is usually 6 to 8 eight feet. Enclave Audio also provides the option of adding multiple subwoofers should that be needed or desired. 


Enclave Audio provides all the settings needed to fine-tune each individual speaker and whole system output levels for your specific room characteristics via its Mobile App for iOS or Android, CineSync, or Roku TV Ready features.

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