One more query - when one talks about power when it comes to AVR/speaker combo - what does one mean? Does having more power equate to maintaining same SQ at even higher volumes? Or is it something else? I am not someone who'd like to listen to high volumes, ever. What should someone like me look for when evaluating speakers.
When one is talking about a move there are lots of dynamics involved. For one, you are driving 6 channels of sound in a 5.1 system. In addition, special emphasis has to be given to the front and centre channels as nearly 75% of sound is sent to these channels.
Most speaker have a minimum and maximum wattage specifications. The minimum wattage refers to the power the amplifier must supply before the speaker even wakes up or grunts. The maximum wattage refers to power at which the speaker will start distorting.
Let us say you have speakers with specification such as, say, 30 to 100 watts. If you take a amplifier that can deliver a maximum of 50 watts, the amplifier will be stretched all the time, At it's maximum volume, the amplifier has just 20 watts over the minimum of the speakers capacity. When there is sudden peak in sound signal (a crash, a bomb, an explosion or something similar), the amplifier will not be able to deliver the extra power needed to deliver the peaks. Secondly if you keep increasing the volume, the amplifier could start distorting and clipping quite easily. In many home theatres I have seen that it is difficult to hear regular dialogues. You increase the sound, and when a peak arrives you hear distorted sound. So you keep fiddling with the volume control ceaselessly.
On the other had, if you have an amplifier with a power output of say 120 watts, it will be able to drive the speakers easily. and have ample power in hand to handle dynamic peaks in the sound signal.
In a well designed room and system, you need never to increase the volume beyond, roughly, 1/3rd the amp's power. At 75dB of SPL in your sitting position, you should be able to hear the whispered dialogues clearly, and at the same time, not cringe when a explosion happens.
Another advantage of having ample power is the capacity of the amplifier to clearly differentiate between different sounds and deliver them realistically. One example I give often is from the movie - Gladiator. In Chapter two, when Maximux races down the hillside on his horse, his dog runs ahead of him and the camera focuses on the dog for a few seconds. How many of you have heard the laboured breathing of the dog coming from the centre channel, over and above all the noises of war coming from all the other speakers? Another movie I have recently fallen in for special sound effects is The Haunting
. A good system must make you hair stand on end. There are many such examples.
SQ for a movie sound is not about amplitude. It is about clarity of dialogues, good delivery of music, and the creation of environment that the director so badly wants you to experience.