Volume Knob on My Stereo

[Absolute]

I have a Panasonic home theater system. The volume seems to be represented by a negative number. For instance, it will display -80dB, and then, after I increase the volume, it will turn into -35dB. Does anyone know why this is done? Nearly every audio system I’m seen does this.

[X_Slayer_ALE]

I’d try to explain but its been so long and I cant anymore

heres the link to read:

http://arts.ucsc.edu/ems/music/tech_background/TE-06/teces_06.html

Decibels are designed for talking about numbers of greatly different magnitude, such as 23 vs. 4,700,000,000,000. With such vast differences between the numbers, the most difficult problem is getting the number of zeros right. We could use scientific notation, but a comparison between 2.3 X 10 and 4.7 X 10 to the 12th is still awkward. For convenience, we find the RATIO between the two numbers and convert that into a logarithm. This gives a number like 11.3. As long as we are going for simplicity, we might as well get rid of the decimal, so we multiply the number times ten. If we measured one value as 23 hp and another as 4.7 trillon hp, we say that one is 113dB greater than the other.

The usefulness of all this becomes becomes apparent when we think about how the ear perceives loudness. First of all, the ear is very sensitive. The softest audible sound has a power of about 0.000000000001 watt/sq. meter and the threshold of pain is around 1 watt/sq. meter, giving a total range of 120dB. In the second place, our judgment of relative levels of loudness is somewhat logarithmic. If a sound has 10 times the power of a reference (10dB) we hear it as twice as loud. If we merely double the power (3dB), the difference will be just noticeable.

[The calculations for the dB relationships I just gave go like this; for a 10 to one relationship, the log of 10 is 1, and ten times 1 is 10. For the 2 to one relationship, the log of 2 is 0.3, and 10 times that is 3. Incidentally, if the ratio goes the other way, with the measured value less than the reference, we get a negative dB value, because the log of 1/10 is -1.]

[Skammer]

Let me be the first to say…

“… this one goes to 11.”

[bilgerat]

It’s because your receiver is showing you the amount that the volume is being attenuated (lowered) from its reference level (0dB). So if you set your receiver to read 0 you would be hearing the audio at the level the sound engineer mastered it.

[PumiceT]

It’s showing the RESISTANCE. Zero being no resistance, or full volume. 80db(?) being your highest resistance or no sound. 80db seems a bit low, since CDs typically have a dynamic range of 96db+… hmm… maybe your receiver just doesn’t have quite the dynamic range as others. With the right speakers, and no EQ, you should be able to use 0db without fear of damaging anything. Volume / power is hardly the damaging factor: distortion is.

To say 0 is the level the engineers wanted you to hear it at is a little… umm… well… wrong! There is no reference volume level. (That would be like saying there is a specific size screen you’re supposed to watch a certain film on.) His speakers will certainly alter the volume level anyway, as some are more efficient than others. Zero is simply meaning that the sound is being routed from the source to the amp without being reduced (by the volume knob anyway, EQ is another story).

[bilgerat]

Where did I say that it had anythig to do with that you’re “supposed” to hear? I said that it was the level that the sound engineer mastered it at. Please don’t read what isn’t written.

Besides, the engineer’s speakers have no relevance as to the signal level that is being recorded. One is input the other output.

At 0dB on your receiver, you should essentially be playing the signal as it was recorded…not attenuation and no gain applied.

[Q.E.D]

Many stereo systems are calibrated in Volume Units (VU) 0dB is the highest level (but what that level actually is is dependant upon the system designers).

Here is a link that might help. The relevant info is near the bottom of that page.