Originally Posted by ryu4000
i'm going get a spl meter and calibrate to 75db just need to know how to do it excatly?
Most people use a calibration DVD such as DVD Essentials
. Its not feasible to use a movie or music to calibrate speaker levels! The quote below is from my Audio Expert
book. If you send me a PM with your email address I'll be glad to mail to the pink noise file mentioned in the text.
Originally Posted by The Audio Expert
REW is great for measuring the response of loudspeakers in a room, but pink noise is simpler and even better for balancing speaker levels. One problem with sine waves is that a small change in microphone placement can give a very large volume change at a given frequency, so moving the mic even an inch or two will affect the reading. However, band-limited pink noise is even better than broadband noise, because it reduces further the change in level versus position by removing the influence of very low and very high frequencies. For your convenience, I created the "pink_noise-400-2000 Hz.wav" file, available on the website for this book. This file contains pink noise, but with frequencies below 400 Hz and above 2 KHz filtered out at 6 dB per octave. For completeness, the file "pink_noise.wav" containing normal pink noise is also available, and both of these files can be looped to play seamlessly for as long as needed. The difference between pink noise and white noise was explained in Chapter 1.
In an ideal surround setup, the listening position will be on-axis for all speakers. In other words, all of the speakers should point directly at your head where you sit. But some people can't do that for whatever reason, and some people have different speaker models for the front and surround speakers. The largest response variations that occur when off-axis or when using different model speakers are at high frequencies. Low frequencies are also highly positional, and moving the measuring microphone even a few inches can change the measured volume a lot when using static tones. So by using noise and omitting high and low frequencies in the noise, leaving only the midrange, SPL meter readings are affected much less by differences in each speaker's low- and high-end response. That is, you're balancing the volume level as it will be heard, with less influence from response differences of the speakers and their placement.
To calibrate loudspeaker volume in a stereo or surround system, you'll send the same signal to each speaker one at a time and adjust each channel’s volume control for the same reading on the SPL meter. Most consumer receivers have a Setup mode to adjust the volume for each speaker, as well as compensate for its distance from your ears, as mentioned in the Surround Monitoring section of Chapter 17. If you don’t have an SPL meter, an omnidirectional microphone plugged into any device that has a record level VU meter works just as well. Again, the SPL meter or microphone should be placed where you sit while listening, pointed straight up to avoid favoring any one speaker.