Volume Display on A/V Equipment

[FMTaylor]

I never was very good in Physics. But, why does the volume control go from negative dbs to positive? 0 db is almost unbearably loud for my system.

 

[MDS]

You really should search for this topic...

I am on a mission to help people understand this because it seems to be very confusing for many.

It has nothing to do with physics. It's just a scale. Some receivers use the absolute display and go from say 0 - 80, while others use the relative scale and go from -80 to +whatever. Some, like Onkyo, allow you to choose which scale you want to see. It could just as well be labeled A - Z.

However, the reason the relative scale is popular is because 0 on the scale is a convenient point to use for 'reference' level. [Whether you calibrate to Dolby Reference Level or choose any level you want]. When the numbers are in the negative, you are X dB below your reference level and when they are in the positive, you are X db above your reference level.

That's it. It is no different than using the absolute scale except that the absolute scale isn't as convenient. If you use the absolute scale and choose say 60 on the dial as the reference level, it takes a little more mental math to realize that at 40 you are 20 dB below your reference, whereas with the relative scale you can see at a glance because the dial reads '-20 dB'.

So if you calibrate to Dolby Reference Level where 0 dB on the volume dial yields 85 dB SPL and the dial is on -20, you are listening at 65 dB. [Note that for Dolby Reference Level, the test tone is at -20 dB so if the source you are playing is higher or lower than that, the resulting SPL will be higher or lower].

 

[edwelly]

You really should search for this topic...

I am on a mission to help people understand this because it seems to be very confusing for many.

It has nothing to do with physics. It's just a scale. Some receivers use the absolute display and go from say 0 - 80, while others use the relative scale and go from -80 to +whatever. Some, like Onkyo, allow you to choose which scale you want to see. It could just as well be labeled A - Z.

However, the reason the relative scale is popular is because 0 on the scale is a convenient point to use for 'reference' level. [Whether you calibrate to Dolby Reference Level or choose any level you want]. When the numbers are in the negative, you are X dB below your reference level and when they are in the positive, you are X db above your reference level.

That's it. It is no different than using the absolute scale except that the absolute scale isn't as convenient. If you use the absolute scale and choose say 60 on the dial as the reference level, it takes a little more mental math to realize that at 40 you are 20 dB below your reference, whereas with the relative scale you can see at a glance because the dial reads '-20 dB'.

So if you calibrate to Dolby Reference Level where 0 dB on the volume dial yields 85 dB SPL and the dial is on -20, you are listening at 65 dB. [Note that for Dolby Reference Level, the test tone is at -20 dB so if the source you are playing is higher or lower than that, the resulting SPL will be higher or lower].

What is the eassiet way from someone to calibrate a system to Dolby reference level?

 

[MDS]

The easiest way is to use an auto-setup routine in one of the newer receivers but you can do it manually.

Dolby Reference Level is defined as 105 dB peaks at the listening position (+10 dB more for LFE). The level of the test tone you use determines what number you want to see on the SPL meter to achieve dolby reference level.

The internal test tones of a receiver are -30 dB pink noise. That means that the average level of the tone is 30 dB below 'full scale digital' (0 dB). 0 dBFS is NOT the same as 0 dB on the volume dial! If you use those tones, you want the meter to read 75 dB because 75+30=105. If you were to use the AVIA disc, its tones are at -20 dB, so you want the meter to read 85 dB.

You calibrate by playing the test tones and using the level up and down buttons on the remote or receiver to adjust each channel until the meter reads about 75 dB (+/- 1 dB is about as close as you can get).

Anticipating the logical next question, 'Does that mean that when the volume dial is at 0 dB, I am getting 75 or 85 dB SPL? The answer is: Only if the average level of the source you are playing matches the level of the tone you used to calibrate. In all cases, PEAKS will be 105 dB. A peak is when the digital signal is full scale - the maximum sample value.

So for a real world example, if you used the receiver's internal test tones at -30 dB to calibrate, but are playing a CD with an average level of -10 dB (any modern overcompressed CD) the SPL you get will be 20 dB higher than what you saw when you calibrated. In other words, if you play that CD and take a reading on the SPL meter, it should average 95 dB, not the 75 dB you saw when the calibration was done. The peaks will still be 105 dB because the recording can't exceed full scale digital (95+10 is still 105).

 

[edwelly]

So if I use Avia and a SPL meter, once I deteremine what a constant 85db is, that would be Dolby Reference level regardless of what it says on the volume dial, correct?
Reason I ask is that my AVR stops at 0 db and I wanted to figure out where ref. level actaully is - for no reason other than I want to know

 

[MDS]

So if I use Avia and a SPL meter, once I deteremine what a constant 85db is, that would be Dolby Reference level regardless of what it says on the volume dial, correct?
Reason I ask is that my AVR stops at 0 db and I wanted to figure out where ref. level actaully is - for no reason other than I want to know

Correct, but a question on your volume display. What receiver is it? Are you sure it stops at 0 dB or does it really go to +something but due to channel trim levels set in the positive range, the max number is reduced to zero?

The channel trims work in concert with the master volume control, so if any of the channel levels are greater than zero, the maximum number shown on the master volume control will be reduced.

 

[edwelly]

I have a Sony STR-DA4ES - it goes from -115 to 0db and I hate it... Wish it was easier to understand. I just know what I normally use depending on what I am watching. I was just curious as to to how loud I like it vs. what Dolby Ref. says it sould be.
Last night I watched War of the Worlds (dts) and was more than comfortable on -40 on the ole knob...