Question about sound levels

[jsteinhauer]

When setting up surround speakers, you adjust the level of each speaker independently of the master level, in such a way to optimize the sound at the listening position. Does it matter what you have these relative levels set at, so long as they match the position, or will you have a different result with say, your speakers all set at -5 to -10dB and turning your master volume up to 29dB versus having them all set at +5 to +10dB and only turning you master volume up to say 9 or 19dB?

[MouseRider]

For theater sound, the volume known as the "Reference Volume" is defined at 105db peak signal from all channels.

What that means is when your preamp/receiver is set to 0db attenuation, the peak sound pressure coming from each of your speakers should be 105db at your listening position.

Most calibration tones on discs and built-in are usually set to be at -30db, so if you are using an SPL meter to measure the sound pressure from your speakers, they should all read 75db.

You can get one of these meters pretty cheaply at Radio Shack.

If you do that and set your receiver/preamp to 0db attenuation, you will be listening to the soundtrack at the levels it was mixed in the mixing theater.

Depending on your room setup, this might be too loud but once you have it calibrated, you can lower the volume and your receiver/amp will do it proportionately.

Some lower-end receivers don't indicate proper attenuation levels but use an arbitrary "volume number" instead, if you have that problem, you'll have to pick a number and stick with it and hope the your system has a volume scaling system that is equivalent to the log scale of db.

[cawgijoe]

What Mouserider said.......just to add....the Radio Shack SPL meter is worth every penny....go buy one now.......also.....you may find depending upon your speakers and proximity of your seating to them.....not all rooms are ideal.....that the center channel speaker may have too low of a volume...I had to compensate by uping it's output a notch or two.

[clyon]

You know 105db is in the danger area don't you?

http://www.lowertheboom.org/trice/safedblevels.htm

[MouseRider]

When it comes to the center channel, as cawgijoe described, there is a situation in Dolby encoded materials called "Dialog Normalization" which sometimes can make matters worse.

Dolby, in the wisdom, decided (they do have their reasons but you can agree or disagree with it) to apply a -4db attenuation to the dialog soundtrack.

Due to that, there will be instances that people say that they can't hear the dialog and turn up the volume then something explodes and the whole neighborhood wakes up.

What you can do here is increase the center channel by 4db, so calibrate to 79db instead of 75db, for those Dolby stuff with dialnorm and you'll nullify it.

[MouseRider]

Originally Posted by clyon

You know 105db is in the danger area don't you?

http://www.lowertheboom.org/trice/safedblevels.htm

That's the standard and remember, 105db is peak not average.

It's also why calibration tones are at -30db so you don't go deaf calibrating your system.

You'll probably be even more shocked to hear that audio CDs are not mixed to a peak reference volume.

[T-Town Oil]

Originally Posted by clyon

You know 105db is in the danger area don't you?

http://www.lowertheboom.org/trice/safedblevels.htm

i think that is earplug level according to OSHA

[jsteinhauer]

Very helpful. I'll pick up a meter when I get around to it. I suspect, then, that the autocalibration feature of the receiver is setting the relative levels of my speakers based on 105dB peak (though I can't be sure without measuring myself), and I don't think it works terribly well, since it has done some funky things.

Is it important to have the receiver level set at 0dB when you do the calibration? Or, is it simply relative?