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Watts and Current - Page 7

post #181 of 227
Quote:
Originally Posted by DonH50 
I have read on here ratios of 20 to 30 dB for movies (100x to 1000x in power) but have no personal data.

Wouldn't a subwoofer and bass management alleviate most of these power requirements?
post #182 of 227
Quote:
Originally Posted by goneten View Post

Wouldn't a subwoofer and bass management alleviate most of these power requirements?

Sort of. Except it just moves the problem to the sub woofer power supply.
post #183 of 227
I don't know but there is quite a bit of dynamic range in the midrange as well. I suspect the loudest sounds and thus most power are in the bass region, but the dynamic range in the midrange is pretty large, too. Think ppp (quiet) to single instruments to full orchestra/band, for instance, and 20 dB change does not seem large. I have taken and seen 'scope shots of drum and cymbal hits where the peaks were easily 10 - 20 dB above the average without the kick drum in play.
post #184 of 227
Quote:
Originally Posted by Glimmie View Post

Quote:
Originally Posted by goneten View Post

Wouldn't a subwoofer and bass management alleviate most of these power requirements?

Sort of. Except it just moves the problem to the sub woofer power supply.

From a systems standpoint this is an useful benefit because it offloads the AVR power amps and power supply and helps keep the equipment cabinet cooler.
post #185 of 227
Hi Arny, glad you could join us. I have a question or two :
Quote:
Arnyk/Jneutron, I have a question for you. smile.gif Sorry to hijack the thread, but it's somewhat related. As far as power requirements go, assuming reasonable speaker sensitivities (87 dB and above) and seated distances (2-3 meters), would you reckon 10 times the average power would be a good and safe bet for dynamic swings in music and/or movie material?

So if an AVR on the test bench using typical sine waves can deliver 80-100 watts at low distortion, which is pretty typical nowadays, using a reasonable speaker sensitivity of 87-90 dB and seated 2-3 meters away, the average power on idle with real world musical signals would be, I assume, a few watts at most?

Sine wave testing is not indicative of real world usage of amplifiers using real world music, but how much additional overhead could you expect with real world music signals? If you could perhaps elaborate more on that, it would be appreciated.

Thanks!

Thanks. biggrin.gif
post #186 of 227
^^ You might find this extract interesting.
post #187 of 227
Given a pair of 87 dB/W/m speakers 12' (about 3 m) away, an SPL calculator says 78.7 dB for 1 W, fairly loud. For reference, a normal conversation runs around 60 dB, so 70 dB is twice as loud and 80 dB is louder than I usually like to listen (for an average level). At 3 W, 83.5 dB SPL; at 10 W, 88.7 dB. 100 W yields 98.7 dB.

See e.g. http://myhometheater.homestead.com/splcalculator.html

I was thinking of the overall dynamic range and crest factors in my previous post; I agree with Arny that at a system level most of the power most of the time is in the deep bass and so a subwoofer is a great help. Look up loudness curves and you'll see it takes a LOT more power in the bass region to sound as loud as a midrange signal.
post #188 of 227
Don, so then you think it's a good idea to have at least 10 times the average power for dynamic peaks assuming you have a subwoofer in the chain?
post #189 of 227
Quote:
Originally Posted by goneten View Post

Don, so then you think it's a good idea to have at least 10 times the average power for dynamic peaks assuming you have a subwoofer in the chain?

10 times the power is 10 dB more power. I generally use 20 dB or 100 times more power in my estimates. Just being generous!

Having a subwoofer decreases the average power sent to speakers in the system that are set to "small" by the bass management system.. It probably does not change the peak-to-average ratio.
post #190 of 227
Quote:
Originally Posted by arnyk 
10 times the power is 10 dB more power. I generally use 20 dB or 100 times more power in my estimates. Just being generous!

Oh okay, it's just that I've read previous posts from you where you mentioned 100 watts as being, in a way, generous, using reasonable speaker sensitivities and seated distances. Your previous replies on power requirements have given me the impression that you don't agree with the use of dedicated power amplifiers over AVRs, but you're free to change your mind whenever you want. biggrin.gif
post #191 of 227
Quote:
Originally Posted by goneten View Post

Quote:
Originally Posted by arnyk 
10 times the power is 10 dB more power. I generally use 20 dB or 100 times more power in my estimates. Just being generous!

Oh okay, it's just that I've read previous posts from you where you mentioned 100 watts as being, in a way, generous, using reasonable speaker sensitivities and seated distances.

You've read right and perceived what I wrote as I intended. I'm not against being generous like this when in fact most AVRs have such similar power ratings around 100 wpc that you don't have a lot of choice. ;-)
Quote:
Your previous replies on power requirements have given me the impression that you don't agree with the use of dedicated power amplifiers over AVRs,

Again, you've read right and perceived what I wrote as I intended.

I agree with the use of dedicated power amps when they are needed. It is just that they aren't needed nearly as often as they are installed. ;-) Also a ton of people seem to be buying dedicated power amps that actually aren't enough more powerful to make a worthwhile difference even if they are needed. There is at least one multichannel power amp that appears to be no more powerful than most of the AVRs that it seems intended to replace. Some upgrade!
Quote:
but you're free to change your mind whenever you want. biggrin.gif

It's just a matter of clarification. ;-)
post #192 of 227
Quote:
Originally Posted by A9X-308 View Post

^^ You might find this extract interesting.

I know the RLJ recording mentioned, and up until lately it was in fact the most dynamic recording I've ever found and stayed at the top of my list for about 20 years. It is a >99.99% worst case object for a test.

I don't have a problem with that, but this needs to be understood by the reader when he is standing up to run right out and buy a 15 KW power amp. ;-)

The choice of listening levels Cordell used was probably a subjective judgement. He wanted to make a point. Its a demo, not science.

AFAIK nobody knows for sure what levels the RLJ album was recorded at. It is a studio recording and may well been done done using classic multitrack techniques. That means that there never ever was a live performance that matches up with it so nobody knows for sure or ever has experienced the exact acoustic levels that it was recorded at. Therefore, Cordell's judgement and preferences are part of this evaluation and as objectivist as he tries to sound, his demo is as about as subjective as it gets.

More to the point almost nobody throws on a CD and listens to it at live levels for fun and relaxation. We all back off, at least a little most of the time.
post #193 of 227
Quote:
Originally Posted by goneten View Post

Don, so then you think it's a good idea to have at least 10 times the average power for dynamic peaks assuming you have a subwoofer in the chain?

Like Arny, I would personally shoot for around 20 dB, but bear in mind the average power level most people use is far less than they think. It is not that hard to get 50 - 100 times the average power level (17 - 20 dB headroom) in most systems today. In the 60's and 70's, yeah, but today even midrange AVRs exceed 100 W output.

I do not recall the frequency range of the AES tests and have no hope of finding the reference paper in any reasonable amount of time, unfortunately. But, if memory serves, it was not focused on the deep bass by any means -- most systems back then would not reproduce below 30 - 40 Hz.
post #194 of 227
Quote:
Originally Posted by DonH50 View Post

Given a pair of 87 dB/W/m speakers 12' (about 3 m) away, an SPL calculator says 78.7 dB for 1 W, fairly loud..l.
I think they are using 6 db fall off for doubling of distance. If that is the case, that applies to open space and large auditoriums according to hyperphysics.
post #195 of 227
Quote:
Originally Posted by arnyk View Post

I know the RLJ recording mentioned, and up until lately it was in fact the most dynamic recording I've ever found and stayed at the top of my list for about 20 years. It is a >99.99% worst case object for a test.

...
And, by the numbers, what is the dynamic range of this recording, regardless of how it was recorded. Thanks.
post #196 of 227
Quote:
Originally Posted by CharlesJ View Post

Quote:
Originally Posted by DonH50 View Post

Given a pair of 87 dB/W/m speakers 12' (about 3 m) away, an SPL calculator says 78.7 dB for 1 W, fairly loud..l.
I think they are using 6 db fall off for doubling of distance. If that is the case, that applies to open space and large auditoriums according to hyperphysics.

Yes. The calculator actually has fields to include boundary effects but I did not include them -- my room is heavily treated and I tend to use the worst-case assumption anyway.

Hyperphysics -- I thought that dealt with worm holes and warp drives? smile.gif
post #197 of 227
Quote:
Originally Posted by DonH50 
Like Arny, I would personally shoot for around 20 dB, but bear in mind the average power level most people use is far less than they think.

I know this is a difficult question to answer, but what do you think is the average power level for most people, in most typical situations? biggrin.gif 1-3 watts?
post #198 of 227
Quote:
Originally Posted by CharlesJ View Post

Quote:
Originally Posted by arnyk View Post

I know the RLJ recording mentioned, and up until lately it was in fact the most dynamic recording I've ever found and stayed at the top of my list for about 20 years. It is a >99.99% worst case object for a test.

...
And, by the numbers, what is the dynamic range of this recording, regardless of how it was recorded. Thanks.

If memory serves, its dynamic range is about 73 dB.

That's from noise floor to peak level. I don't recall what its average level is.
post #199 of 227
Quote:
Originally Posted by goneten View Post

Quote:
Originally Posted by DonH50 
Like Arny, I would personally shoot for around 20 dB, but bear in mind the average power level most people use is far less than they think.

I know this is a difficult question to answer, but what do you think is the average power level for most people, in most typical situations? biggrin.gif 1-3 watts?

In that range.
post #200 of 227
If we assume 3 watts is the average power for an average guy, as a hypothetical, then you need 100 times that for dynamic swings in the most demanding material. So that's 300 watts. What type of SPL levels are we talking about here? wink.gif Surely it's well above reference level 105 dB SPL? Let's assume for the sake of the discussion an 87 dB sensitivity speaker and you're seated 3 meters away, which I would imagine is the typical seated distance for many people.
post #201 of 227
Quote:
Originally Posted by goneten View Post

If we assume 3 watts is the average power for an average guy, as a hypothetical, then you need 100 times that for dynamic swings in the most demanding material.

I guess this is the new math. I agree with a range of 1-3 watts and now the average of 1-3 watts is 3 watts.
Quote:
So that's 300 watts.

No, in the real world its more like 50-100 watts.
Quote:
What type of SPL levels are we talking about here? wink.gif Surely it's well above reference level 105 dB SPL?

Same trick, again. Reference level is 85 dB, and the 20 dB peaks-to-average ratio gets you to 105 dB peaks.
Quote:
Let's assume for the sake of the discussion an 87 dB sensitivity speaker

Same trick again. 87 dB is towards the low end of efficiency. 90 dB would be average.
Quote:
and you're seated 3 meters away, which I would imagine is the typical seated distance for many people.

Finally, an actual average number!
post #202 of 227
Quote:
Originally Posted by arnyk 
No, in the real world its more like 50-100 watts.

Could you please explain how you calculated that 50-100 watts figure? Thanks.
post #203 of 227
Quote:
Originally Posted by arnyk 
Same trick, again. Reference level is 85 dB, and the 20 dB peaks-to-average ratio gets you to 105 dB peaks.

Yeah but when I say 105 dB reference level obviously you know I'm referring to peaks, not an average level. smile.gif
post #204 of 227
The math and on-line SPL calculator link are in post #187. here is the relevant extract:
Quote:
Given a pair of 87 dB/W/m speakers 12' (about 3 m) away, an SPL calculator says 78.7 dB for 1 W, fairly loud. For reference, a normal conversation runs around 60 dB, so 70 dB is twice as loud and 80 dB is louder than I usually like to listen (for an average level). At 3 W, 83.5 dB SPL; at 10 W, 88.7 dB. 100 W yields 98.7 dB.

See e.g. http://myhometheater.homestead.com/splcalculator.html

As I said in a later post, I did not include any room gain so those are conservative numbers. Also, 12' is actually about 4 m, not the 3 m you stated, so even more conservative. 1 W would be pretty loud to me given the parameters in the example. There are many variables and you must be the one to decide how much power you need for your speakers, room, listening habits, etc.

Another example: at 12' (about 4 m) using 90 dB/W/m speakers and assuming the speakers are near a wall (but not in a corner) then the SPL calculator says:

1 W = 84.7 dB (that is a louder average than I would normally listen)
10 W = 94.7 dB
100 W = 104.7 dB

Same speakers at 10' (hair over 3 m):

1 W = 86.3 dB
10 W = 96.3 dB
100 W = 106.3 dB

I would say for the parameters given 100 W is a reasonable power requirement. The relationship is logarithmic. Every doubling in power will increase the volume (SPL) by 3 dB; every 10x increase in power adds 10 dB to the SPL. You can play with the numbers as you wish. 1 dB increase is not noticed by most people listening to music or movies; it takes about 3 dB to be a noticeable "bump" in volume. An increase of 10 dB is perceived as about twice as loud in the midrange.
post #205 of 227
Quote:
Originally Posted by DonH50 
As I said in a later post, I did not include any room gain so those are conservative numbers. Also, 12' is actually about 4 m, not the 3 m you stated, so even more conservative. 1 W would be pretty loud to me given the parameters in the example. There are many variables and you must be the one to decide how much power you need for your speakers, room, listening habits, etc.

So if the amplifiers aren't clipping at your particular volume level then you're home free - ie you have enough power? How do you calculate room gain into those figures? I'll take a look at the calculator. Thanks.
post #206 of 227
Quote:
Originally Posted by DonH50 
1 W = 84.7 dB (that is a louder average than I would normally listen)

So in your case, if 84.7 dB is louder than your average SPL then the actual power required for you could be several hundred milliwatts. If 60 dB is a conversation type volume then twice as loud (70 dB) would probably be quite loud as a continuous volume. If I calibrate my system using pink noise at 75 dB (-30 below full scale), I generally don't listen at 0, as my reference point. It's loud! However I normally listen anywhere between -8 to -15 from reference.

So if I listen at -15 from reference that would put me at around 60 dB as an average. Correct me if my math is failing me. So for me, seated at 3 meters, using a 90 dB sensitive speaker would require significantly less than 1 watt to achieve my average levels. If I only ever listen at between -15 to -8 from reference then I'll have more than enough power with a 100 watt receiver (assuming it can deliver 100 watts).
post #207 of 227
Quote:
Originally Posted by DonH50 
The relationship is logarithmic. Every doubling in power will increase the volume (SPL) by 3 dB; every 10x increase in power adds 10 dB to the SPL.

Your figuring leaves out the effects of compression. At levels over 95-100db many speakers are only putting out 1 or 2 db for a doubling of power and reach a state where electrical power in has no effect on acoustic power out at all - ie the speaker acts like a glorified heat sink at that point.
post #208 of 227
Quote:
Originally Posted by OllieS View Post

Quote:
Originally Posted by DonH50 
The relationship is logarithmic. Every doubling in power will increase the volume (SPL) by 3 dB; every 10x increase in power adds 10 dB to the SPL.

Your figuring leaves out the effects of compression. At levels over 95-100db many speakers are only putting out 1 or 2 db for a doubling of power and reach a state where electrical power in has no effect on acoustic power out at all - ie the speaker acts like a glorified heat sink at that point.

This article:

http://sound.westhost.com/articles/pwr-vs-eff.htm

Shows that driver thermal compression does happen but perhaps less severely. Higher driver efficiency generally means less thermal compression.

When a driver puts out only 2 dB more with a doubling of power that may sound dire, but it the driver had zero thermal compression, it would still put out only 3 dB more.

That's only 1 dB of compression, which will be clearly audible under ideal conditions, but just that.
Edited by arnyk - 7/18/13 at 4:14am
post #209 of 227
Quote:
Originally Posted by OllieS View Post

Quote:
Originally Posted by DonH50 
The relationship is logarithmic. Every doubling in power will increase the volume (SPL) by 3 dB; every 10x increase in power adds 10 dB to the SPL.

Your figuring leaves out the effects of compression. At levels over 95-100db many speakers are only putting out 1 or 2 db for a doubling of power and reach a state where electrical power in has no effect on acoustic power out at all - ie the speaker acts like a glorified heat sink at that point.

Good grief. Yes, and a whole lot of other things, but I was trying to answer the question without introducing a whole lot of other issues. And, they are not "my" figures, I am just reporting the numbers that particular SPL calculator supplies; not sure anything but a design program figures out the compression, and most people do not have speaker parameters to plug into such a program anyway. The SPL calculator (that one and others) provide at least some guidance to people who just want to play around and who do not have engineering degrees.

Besides this is veering off the original discussion of Watts and current anyway...

@goneten -- Play around with the calculator and you can see where the numbers end up without doing the math yourself. For the record, it is not "my case" -- my speakers are far less efficient but also not the type of speakers most folk have (low-impedance and low sensitivity planar magnetics, Magnepans). i was simply trying to show a few examples bounded around the conditions you stated.
post #210 of 227
Quote:
Originally Posted by DonH50 View Post


Hyperphysics -- I thought that dealt with worm holes and warp drives? smile.gif

It might but then I didn't read everything they have wink.gif

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
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