Audio purists will say a sound signal is a sound signal and a speaker should simply reproduce that signal without modifying it in any way. After all, high fidelity means highly faithful to the original. But when it comes to the audio content of movies and music there are typically some dramatic differences in the content itself. So even though the “Do no evil” concept of speaker performance is valid, the demands on speakers can differ greatly between most music and movies. You can check out 2 ohm vs 4 ohm speakers if you need the best speakers.
Let’s take a look.
If you are really into music and visit sites like www.musemantra.com, you might know that music usually contains a broad range of frequencies from bass to treble. But unless you’re a pipe organ aficionado or a hip hop fanatic it’s rare to find much energy below 50Hz. Although there are some instruments that generate lower tones (i.e. piano – 28Hz, pipe organ – 16Hz, double bass – 41Hz, 4 string bass guitar – 41Hz) these tones aren’t present musically all that often.
Movie special effects, on the other hand, frequently include very deep frequencies and often at very high volumes. Think of the footfalls of the T-Rex in the Jurassic Park films, explosions in any number of action films, earthquakes, and even outer space battles where entire planets explode. Just as a quick aside, if these outer space battles were actually to take place they would happen in silence because there isn’t any medium to transmit sound! And just for the record, there wouldn’t be any fire either, because there’s no oxygen in space.
In films both the frequency range, especially in the bass, and the dynamic range (the difference between the softest and loudest sounds) typically exceed those found in most music. In order for speakers to accurately reproduce cinema content they’d often have to play louder and deeper than the same speakers playing music.
In general you should be able to use the same speakers for music and movie reproduction. But for movies you’d want to make sure they can deliver high dynamic range. For instance, compact mini- monitors with efficiency ratings of around 85dB (@1 watt, 1 meter) would be a marginal choice for a surround system as they will undoubtedly lack dynamic capability. A better choice would be higher efficiency speakers like tailgate speakers and powerful amplifiers. At the same time you’d want to ensure the speakers can deliver clarity at both low and high volumes.
Dialogue clarity is critical to surround system performance. Arguably, the single most important speaker in the system is the center channel. Choose wisely, using one that is dynamic, clear, detailed and capable of playing at the levels needed.
Cinema systems should always include one or more high performance subwoofers. They can be built into the main speakers or separate, but unless your main speakers can produce thunderous levels of truly deep bass, they should be considered critical to system performance.
The THX certification program is a valid attempt to standardize these performance requirements. Even if you aren’t using THX certified equipment, understanding the THX requirement and goals would be beneficial to anyone who designs and installs home theaters.