Sorry, mis-typol. volumn is -12 for DTS.

KWOK

Gonk speaks thusly:
"Well, if you calibrate two different systems to the same reference level (so that they both produce a 75dB test tone when the volume is set to 0, for example)... you should get the same SPL levels when the volume controls are in the same position."

Sure, that makes very good sense. The flip side, as you say, is that without equalizing the callibration like that, different systems will have comfortable volume settings that are all over the map. Doesn't really make sense to ask "what's your volume level for movies"?

I think we're saying the same thing.

You do raise a point I've wondered about though: is the db volume 'scale' really linear as suggested? If system A produces 75db test tone at "0", and system B produces 75db test tone at "-10", should we expect them to still be the same at A=-10, B=-20? The reason I wonder has to do with system calibration; and trying to decide how important it was to do the level cal's at or near typical listening volumes. If the db scale is truly linear, then it shouldn't matter at all.

And yeah, you're right, the Crown amps are enjoying an easy life of leisure these days; well deserved after years of much harder concert duty.
Can you say dynamic headroom boys and girls? ;-) The only one that get's a workout is probably my sub amp, driving what I think to be a 2ohm load (bridged amp driving 2 4ohm drivers in parallel).

Redrob,

Audio is logarithmic. Every +6dB is twice as loud, and every -6dB is 1/2 as loud to the ear.

If the display is showing actual dB changes, then lets say:

System A: 0 = 75dB
System B: -6 = 75dB

When we turn System A to -6 and System B to -12, each has gone down 6 dB, and thus is half as loud as before. Also since we know the calibration amount, if the display is dB accurate than we know they both will be at 69dB.

Also with your sub amp. 2 @ 4 ohm drivers in parallel are a 2 ohm load. When bridged, the amp sees half the load, so you are giving the amp an effective 1 ohm load. Good thing it is a Crown, few other amps could survive that.

Yeah, redrob, I think we are saying the same thing - we can eliminate some variables from the equation by using consistent calibration techniques, but there are other variables (particularly things like the movie being watched and the individual's preferences) that will insure that we don't all get the same answer.

As for the question of the decibel scale, it gets complex pretty quickly. The scale is actually logarithmic, which makes acoustical analysis all the more interesting, but for the sake of this discussion the answer is yes - if I calibrate at 0 and you calibrate at -10, then my -10 and your -20 would be equivalent (all we've done is move the "zero" point). This all reminds me - I need to go through some recent seminar notes and update my technique for HVAC acoustical analysis. Maybe in a couple weeks...

At the risk of further complicating the already complex, I've read in psychoacoustic research that for listeners to report one audio stimulus (most likely a single tone in lab situations) as "twice as loud" as another there must be a 10-decibel difference in terms of power delivered to the transducer (probably earphones). If that relationship holds for real-world listening situations, "twice as loud" as a 1-watt average power level to the speakers will be 10 watts, "twice as loud" as that will be 100 watts, and 99.9% of us can't afford "twice as loud" as that.

Very true. A 10dB increase is considered "twice as loud" but requires ten times as much power to generate. Doubling your power input yields a 3dB increase.

Actually when you do the math, it comes out to 6dB being twice or half as loud. It does require 10x the amount of power though. gonk is also correct that 3dB is double the power.

If that doesn't make sense, just remember that this is all logarithmic. It is based on curves. Each additional dB is more than the previous. Here is an article with way more info than you may have ever wanted.

But either way, even if calibrated differently, the two systems could be correlated volume-wise if we know what the two calibrations used are. If I set up with 0 on the display set to 60 dB speaker output and someone else set 0 to 80 dB output, then setting their system to -20 dB on the display should reasonably match my system's volume. What is really pertinent about this is that this will be the case if the 990's display is measured via dB and not some other arbitrary system. As long as we are comparing dB to dB adding and subtracting reasonably works.

I haven't run back through the math, but every source I've seen that relates perceived loudness (not actual power level) to decibel increases equates 10dB to a doubling or halving of loudness. Here's one summary that I've seen on more than one occasion:

• 1dB: Imperceptible Change
• 3dB: Barely Perceptible Change
• 5dB: Clearly Noticeable Change
• 10dB: About Twice as Loud
• 20dB: About Four Times as Loud

I'm not saying that these values equate to actual sound power (or intensity), but they are pretty widely-used guidelines for how people perceive changes.

Wife is gone for 6 days time to find out what loud really is with this combo.

Hmmm- armed with this new info, and looking at the back-end of my system:

http://tinyurl.com/rd6kz

I'm just not sure how I'm go about trying to get 10X the power; when I decide it needs to be twice as loud ;-).