dB (volume) vs. watts

[herbu]

I've read that an increase in volume 6dB takes twice the power from your AVR or amp. Is that true?

On my system, an increase of 6dB makes a pretty small noticeable difference. -60db is soft... -24dB is fairly loud, but reasonable. That doubles the power 6 times. If -60db is using 10w, then -24dB is using 640w, and reference 0dB doubles that 4 more times and uses OMGw! My amp produces 200wpc.

I don't understand. Something doesn't add up.

 

[fuzz092888]

3db indicates a doubling of power. The db reading on your receiver isn't what you think it is. What that is telling you is how far below reference volume you are, not the in room SPL. At full reference playback your system (if calibrated properly and capable) will be capable of playing 85db average levels and be able to play 20db peaks. If you want to actually roughly calculate how much power you're using you need an SPL meter and need to measure the sound pressure levels at your listening position. This also starts to take into account the sensitivity of your speakers. If your speakers are 88db/1watt/1meter. It means you only need 1 watt to produce an SPL of 88db at 1 meter away.

Look up the sensitivity of your speakers and play with this and it might make more sense.

Peak SPL Calculator

 

[Adam]

Hi. My understanding is that twice the power will yield an extra 3dB, and ten times the power will yield 10dB. I think that most people equate an increase of 10dB as being twice as loud.

Your 0dB point is some reference level (if you ran auto calibration on your system) which is around 80dB. So, -60dB should equate to a sound level of around 20dB wherever you had the calibration mic located.

The thing throwing off your understanding is this: at -60dB, you aren't using 10W/channel. No where near that. If your speakers output, say, 90dB at 1W/1m, then at one meter away from a speaker, it will be 90dB if you put 1W through it. So, 80dB at 0.1W, 70dB at 0.01W...and so on until you get down to the level required for your ~20dB output at the mic location. 20dB at that location is a function of multiple speakers, all of which are probably more than one meter away. So, it's more math - but the short story is that it's much, much less than 10W.

EDIT: I must have started typing right when Fuzz was posting.

 

[walter duque]

I've read that an increase in volume 6dB takes twice the power from your AVR or amp. Is that true?

On my system, an increase of 6dB makes a pretty small noticeable difference. -60 db is soft... -24 dB is fairly loud, but reasonable.

On low volume I notice a very slight (if any) difference in volume increase of 3 db increments. Biggest and most noticeable difference is when I go from 0 db to +3 db and then to +6 db.

 

[Steve81]

I've read that an increase in volume 6dB takes twice the power from your AVR or amp.

As Fuzz & Adam have mentioned, double the power results in a gain of 3dB. Double the voltage results in a gain of 6dB, which also corresponds with a doubling of sound pressure (measured in Pascals) and 4x the power. You can glean a little more about the dB scale with this link:
The Decibel (dB) Scale & Audio Rules 101 | Audioholics

 

[herbu]

Thanks, guys! Your info and links have been most helpful. (I bookmarked the links.) I've seen numerous references to using an SPL meter, but never really considered it. After reading the links, and links within the links, now I think it might be interesting. See a bunch of them in Amazon. Most seem to be between $20-40. Some go lots higher. Does it matter?

 

[fuzz092888]

Thanks, guys! Your info and links have been most helpful. (I bookmarked the links.) I've seen numerous references to using an SPL meter, but never really considered it. After reading the links, and links within the links, now I think it might be interesting. See a bunch of them in Amazon. Most seem to be between $20-40. Some go lots higher. Does it matter?

It depends on your usage. If it's just casual curiosity, then one of those would be fine. The more expensive ones are more accurate at the top and bottom ends, as well as overall.<style id="pageBrightnessCustomCSS">body{zoom:165%;}</style>

 

[Adam]

There are also SPL meter apps for smart phones. Almost surely not as accurate, but not too bad...free...and instant gratification today if you have a smart phone.

 

[fuzz092888]

There are also SPL meter apps for smart phones. Almost surely not as accurate, but not too bad...free...and instant gratification today if you have a smart phone.

Speaking of....there's also one of these. You can do basic measurements as well as get SPL measurements. Definitely not as accurate as other options, but not nearly as expensive either. Great for playing around if you've got a smartphone.<style id="pageBrightnessCustomCSS">body{zoom:165%;}</style>

 

[herbu]

The most expensive one at $250, (Galaxy Audio CM-150), has a freq range of 31.5 - 8kHz. I suppose the 8kHz is fine for the top end, but is 31.5Hz OK for the low end? For HT measuring/playing, I would think the very low floor shaking booms would be below this range. Do you have to spend a LOT to capture them?

 

[Nestor]

The most expensive one at $250, (Galaxy Audio CM-150), has a freq range of 31.5 - 8kHz. I suppose the 8kHz is fine for the top end, but is 31.5Hz OK for the low end? For HT measuring/playing, I would think the very low floor shaking booms would be below this range. Do you have to spend a LOT to capture them?

For that kind of money, I'd look into the Dayton Audio Omnimic or something similar. You get a calibrated mic, measurement software, and test tone discs.

 

[fuzz092888]

Speaking of....there's also one of these. You can do basic measurements as well as get SPL measurements. Definitely not as accurate as other options, but not nearly as expensive either. Great for playing around if you've got a smartphone.

http://www.amazon.com/gp/aw/d/B00ADR2B84/ref=redir_mdp_mobile