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Old 4th September 2013, 09:21 PM   #1
forr is offline forr  France
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Default Power amps, dynamics and sound levels at home

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CFA Topology Audio Amplifiers

"To handle an uncompressed (or lightly compressed) recording at decent sound pressure levels then huge amounts of power are required and this is expensive. So people accept clipping as a consequence of this. Having good clipping behaviour is a way of mitigating the issue."

At the light of many data I collected on sound levels from many sources, I disagree.

Note : below, pk/avg stands for ratio peak/average.


Famous in France among diyers for his listening and HC dedicated room, Roland Delacroix stated that the highest dynamics he ever exceptionnaly encountered in a record was 68 dB(pk/avg = 34 dB) and told it is almost impossible to handle. Even 52-55 dB (pk/ag = 27 dB) are extremely rare.
Source :
dolby lake process : Enceintes Hi-Fi - Cinetson - Hifi et Homecinema

Pano who is a moderator of this forum has found that the best CDs from the point of view of dynamics have a pk/avg about 22 dB or more.

Source :
What is a good way to measure peak watts I'm using during music?

So we can state that a system able to reproduce dynamics of almost all existing records needs to reproduce a pk/avg of 25 dB without distorsion.

High but still decent average sound levels may rely between 75 dB (at home) and 85 dB (at the recording studio) SPL. This means that the loudspeakers should deliver peak levels of 100 dB to 110 dB at the listening position.
An often quoted target is 105 dB SPL peak.

To my experience, this is far more than most people need for everyday listening.
Assuming at the listening position for a two channel stereo system, a loss of 3 dB from the nominal sensitivity of the loudspeakers, we ended, if they have a nominal sensitivity of 90 dB SPL / 2.83 V at 1m (1 w in 8 Ohm) with the following levels :

81 dB 0.25 W
87 dB 1 W
93 dB 4 W
99 dB 16 W
105 dB 64 W(peak)

This is for a typical two channel stereo system and for SPLs somewhat higher than usual. It does not represent huge amounts of power and there is no reason why an adequately dimensioned amp for this system should ever clip.
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Old 4th September 2013, 09:34 PM   #2
Bigun is offline Bigun  Canada
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I figure you need to ask yourself how often is too often for clipping. A music signal almost looks random, a lot of peaks at low level, very few at high level, vanishingly few at very high level. If it clips rarely - do you care ? I don't. Many compromises are involved in music playback and I am quite happy not to be running 'megawatt' amplifiers.
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Old 4th September 2013, 11:02 PM   #3
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Quote:
Originally Posted by Bigun View Post
I figure you need to ask yourself how often is too often for clipping. A music signal almost looks random, a lot of peaks at low level, very few at high level, vanishingly few at very high level. If it clips rarely - do you care ? I don't. Many compromises are involved in music playback and I am quite happy not to be running 'megawatt' amplifiers.
This is an important question. There are 2 questions/answers and it depends on the type of music.

1 Is it audible? If you clip a kick drum, most people can tell the difference but most don't find it objectionable (apologies to yus Golden Pinnae who object if a gnat sits on your mains cable. There is a LOT of modern music (?) where if the amp clips 50% of the time, even the best ears in the business can't tell the difference.

http://www.aes.org/e-lib/browse.cfm?elib=3793

2 Is it nasty? Unlike the kick drum, if you clip a good recording of a GOOD unaccompanied choir of about 12-20, this is certainly objectionable. Also holds true for good piano.

The choir can clip the best 16b recorders & microphones if recorded simply.

Most commercial recordings don't come anywhere near this cos evil compression is applied. That's for classical. For pop ...
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Old 5th September 2013, 04:05 AM   #4
Bonsai is offline Bonsai  Taiwan
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forr, we surely have to consider speaker efficiency in this discussion. 90 dB seems a typical figure, although I note in a number of tests, many speakers fall short by 1 or 2dB (might be measurement methodology - I dont know).

I did read an article where it was claimed (by Anthony Michelson of Musical Fidelity) that very high powers were required to produce realistic, undistorted levels for orchestral and piano music. I guess here he would be talking about speakers in the 86-90 dB sensitivry range. The output power quoted was 500W to 1 000W - peak of course. This puts us in B&W 800 or Avalon territory. MF also produced a chart to show amplifier power needed to produce a given SPL vs speaker efficiency.

But, back to my original point, we should assess output power on 3 requirements - desired max listening levels in the home, peak music levels on the material and speaker efficiency. The other factor is the listening space.

BTW I am currently using a 15W class A amp, a 100W AB and a 180W (really 250W) class AB driving B&W 703's and on occasion a small pair of very fine Taiwan book shelf speakers. But, I don't listen at realistic orchestral levels (well maybe when my partner is out and I know the neighbors are not around )
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Last edited by Bonsai; 5th September 2013 at 04:07 AM.
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Old 5th September 2013, 04:32 AM   #5
ttan98 is online now ttan98  Australia
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Hi Bonsai,

I notice you built a 15 watter Class A and a no. of Class AB amps, if you compare them can you distinctively distinguish their differences(*) other than power output, I mean sound reproduction. * I mean Class A sound seems smoother(more liquid) and "more" effortless than Class AB. Any other differences you want to write about?
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Old 5th September 2013, 04:41 AM   #6
Bonsai is offline Bonsai  Taiwan
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Some interesting links

Amplifier Power Required Calculator

for 2m from the speakers, 100 dB SPL and allowing for 3 dB of headroom with 89 dB speakers, I need 100 Watts

Here is a discussion at Audioholics

http://www.audioholics.com/loudspeak...er-sensitivity
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Old 5th September 2013, 12:26 PM   #7
ttan98 is online now ttan98  Australia
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Quote:
Originally Posted by Bonsai View Post
Some interesting links

Amplifier Power Required Calculator

for 2m from the speakers, 100 dB SPL and allowing for 3 dB of headroom with 89 dB speakers, I need 100 Watts

Here is a discussion at Audioholics

Loudspeaker Sensitivity Specifications & Measurements Explained | Audioholics
Bonsai

I wonder whether you can answer my post #5, thanks.
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Old 5th September 2013, 07:37 PM   #8
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Default CDs with high dynamic range

Quote:
Originally Posted by forr View Post
At the light of many data I collected on sound levels from many sources, I disagree.
...
Famous in France among diyers for his listening and HC dedicated room, Roland Delacroix stated that the highest dynamics he ever exceptionnaly encountered in a record was 68 dB(pk/avg = 34 dB) and told it is almost impossible to handle. Even 52-55 dB (pk/ag = 27 dB) are extremely rare.
dolby lake process : Enceintes Hi-Fi - Cinetson - Hifi et Homecinema

Pano who is a moderator of this forum has found that the best CDs from the point of view of dynamics have a pk/avg about 22 dB or more.
What is a good way to measure peak watts I'm using during music?
forr, none of those links seem to have lists of the CDs with high dynamic range. I believe you have your own list.

Can you post a TXT file with your examples?

This was of great importance to me in my previous life and I had my own lists of commercial CDs. Sadly, I no longer have my list

The only ones I sorta remember are Simon Rattle's recording of Britten's War Requiem and a very old Holst Planets.

Very little pop appears on this list. Most of of my high dynamic range examples are my own unprocessed recordings.
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Old 5th September 2013, 10:25 PM   #9
forr is offline forr  France
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Default Records are more often clipped than amplifiers do.

There are many freeware tools available for examining the content of digital records from different points of view. They are very informative. It is quite amazing how many records reach FSD. Nobody guesses they contain clipped moments, they do not sound unpleasant at all.
I'll give some references of softwares and records later.
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Old 6th September 2013, 12:48 AM   #10
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Quote:
Originally Posted by forr View Post
There are many freeware tools available for examining the content of digital records from different points of view. They are very informative. It is quite amazing how many records reach FSD. Nobody guesses they contain clipped moments, they do not sound unpleasant at all.
I'll give some references of softwares and records later.
As I said, and investigated formally in the papers I quoted, there is music (??) where even the best ears in the business find it hard to tell if the amp clips 50% of the time.

BTW, that's the music (??) clipped 50% of the time .. NOT that true golden pinnae can only tell 50% of the time.

An example of the choir effect requiring huge peak capability even at modest average levels I mentioned on a commercial recording is the Preston/Hogwood Messiah with the AAM and Christchurch Cathedral Choir.

If you record such choirs yourself, you'll find it very common. Unlike most pop, overload here is obvious and unpleasant.

I look forward to your list of CDs with high dynamic range.
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