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SPL, rated power, and sensitivity question

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Posted on January 9, 2022 at 19:07:38
psn
Audiophile

Posts: 56
Location: Houston
Joined: January 6, 2007
 Looks like there are three important levels with music. Which one corresponds to the speaker sensitivity for determining clean levels with respect to the amp's rated power?

- average
The time duration basis for average is not standardized; average is used to describe whole albums, single songs, and as indicated using a SPL meter set to "slow", what appears to be about one second or two of accumulation.

- peak
The basis for peak is standardized, based on male announcer voice from radio long ago. It appears to be timed about the rate of individual syllables, about 1/5 second. This is the "fast" setting on a SPL meter.
This is also the standardized level of monitoring playback in the recording studio during the mixing mastering balancing engineering process (because it is also the anticipated most common level of playback by the consumer). Historically since the 50s, this playback monitoring peak level is 85dB.

- instantaneous
These are too fast to appear on the SPL meter, the leading edge transients of instruments.
If I recall, both Klipsch and Joppa state that these are +13dB above peak - there must be a technical paper with which both were familiar.

According to databases of recordings, the distribution of peak over average (dynamic range) is pretty much a normal distribution with a mean of +12dB.

So for typical popular music... a 25dB range.

average <---12dB---> peak <---13dB---> instantaneous

When determining the usable range of amplifier power we hope to get the whole range (ex., 25dB) under the amp's rated power (below rated distortion)... and for some listeners' music preferences they will need a bit more, maybe approaching 30dB.

However with a single frequency sine wave, the musical versions of average, peak, and instantaneous are all the same level.

Assuming all the above is correct... :)

Should a speaker sensitivity be considered the instantaneous level in order to prevent the transients from distorting? It appears that most are considering the sensitivity figure as the fast peak, which is technically correct for test sine waves, but with music signal, using that as the "top" level under the distortion threshold looks like the +13dB transients will be well into distortion.

For example, fitting 25dB under the rated power of a 100 watt amp:

instantaneous will be close to 100 Watts
peak will be close to 5 Watts
average will be close to 1/3 Watt)

 

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RE: SPL, rated power, and sensitivity question, posted on January 10, 2022 at 03:13:06
brush001
Audiophile

Posts: 60
Location: ON. Canada
Joined: January 2, 2011
 Remember a big factor is the room, how far back you are sitting to.
The level you listen to as well.
Some people never listen at concert level others may want to turn it up once and awhile
Lot of speakers are in the sensitivity range of 85-90db.
So going out on a limb here if you have modest amp say 20-30 watts RMS you might be looking more at say higher sensitivity speakers direction
There is calculators around like the Crown one and others I am sure
If people are into home theatre and listen at high levels then some smaller bookshelves or even larger may get stressed at high listening levels.
Not sure on going on further into the maze lol

 

RE: SPL, rated power, and sensitivity question, posted on January 10, 2022 at 07:39:26
G Squared
Audiophile

Posts: 8487
Location: Washington, DC Metro Area
Joined: November 16, 2004
Contributor
  Since: May 23, 2023
 In modern HT set ups, a lot of the burden is shifted to purpose built subs that can pack the punch and the system "spares" the front, center, rear... speakers from over extension.
Gsquared

 

RE: SPL, rated power, and sensitivity question, posted on January 10, 2022 at 16:02:18
6bq5
Audiophile

Posts: 4387
Location: SF Bay
Joined: August 16, 2001
 I am not completely sure I understand your question-

Having said this, there are two other factors that significantly impact all of this:
1: speakers and Room interaction: to both the comments above, having satellites and a powered sub take a considerable load off the main amp - and the regularity/irregularity can set the speakers free or box them in with resonances and room artifacts that can make it great on paper but sound like s^&$t
2: what are you listening to - Vinyl?, R2R tape?, Broadcast radio?, CDs? MP3? and How are you listening? is this a 'main' rig for critical listening to hear all that the artist and Recording Engineer want to convey?, or casual music to live by?

I think your comment at the bottom about power employed is spot on.
Having used many different amps in different rooms with different program material, bearing that table in mind could help to wring the best from a system.
Happy Listening

 

RE: SPL, rated power, and sensitivity question, posted on January 10, 2022 at 16:50:06
Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002
 "Remember a big factor is the room, how far back you are sitting to."

In open space, out doors with no structures or anything for the sound to bounce off of around, there is a 6db loss for every doubling of distance. In a typical living room, with typical speakers there is no loss with distance because the reverbrant field starts at about one meter so if your speakers are rated at say 92db 1W 1M and of course you have two of them and two amps so the sounds adds. Two speakers rated at 92db with one watt going into each gives 95db. Two watts each gets you 98db and so on.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Free chart for all of you , posted on January 11, 2022 at 07:45:59
merdy
Audiophile

Posts: 1625
Location: New paltz,ny
Joined: July 25, 2001



From real life engineers

Silence is golden duct tape is silver

 

RE: Free chart for all of you , posted on January 11, 2022 at 08:58:34
psn
Audiophile

Posts: 56
Location: Houston
Joined: January 6, 2007
 6bq5,

1: speakers and room interaction

Paul Klipsch would write technical papers and use the anechoic figures for sensitivity, but use the adjusted indoor room gain figures for consumer specs and advertising. Someone eventually criticized him using these latter figures, claiming they were improper or misleading.

Paul's response was to look into it and agree! He noticed that the old standard of measuring sensitivity at four feet had been changed and made metric by the general industry, changing that distance to one meter (just a bit over three feet)... so he remeasured and corrected the Heritage figures. This was the change from 104 to 105dB/W/m. :)

2: what are you listening to

Yes, critical listening, records only, La Scala speakers, I alternate between two amps, 48 year old Sansui and a 2A3 SET.

merdy,

Nice chart! In particular to my question, I find this part confusing:

"RMS Watts = Amps x Amps x Ohms = True Power"

"Peak Watts = Volts x Amps = Apparent Power"

My calculations show these two are equal. I also find technical people writing that RMS is appropriate for voltage and current, but not for watts...

 

RE: SPL, rated power, and sensitivity question, posted on January 11, 2022 at 11:54:41
mlsstl
Audiophile

Posts: 1079
Location: Midwest
Joined: September 1, 2015
 Particularly for rock/pop music, I don't buy the into the premise that there is a 25 dB range between average volume and instantaneous peaks on recordings.

As noted in another recent post I made, I spent a number of years converting over 1,000 LPs from vinyl to digital using Adobe Audition. This program gives a lot of information concerning average and peak levels. I can't think of a single recording I converted, including a lot of classical, where the average playback level allowed for 25 dB peaks, whether "instantaneous" or just "ordinary" peaks.

Particularly with digital, there is a maximum level that can be recorded. If the live musicians strike a peak louder than that max recorded level, it is either clipped by the recording itself, or is dynamically compressed by a limiter circuit or software algorithm. Even with LPs, the vast majority of them were originally recorded on open reel tape which has a very well defined max record level. And, with both analog tape and LPs, the more limited dynamic range means that is the average level is set too low, you are introducing more of the background noise of tape hiss and vinyl clicks and pops into the music.

Using the volume level bars on Audition, most of the recordings I've seen have an average level that is only 3 to 6 dB down from 0. There may be a few more dB of headroom above 0, but thinking there is 25 dB of range above average is in the territory of fertile imagination.

One observation, a lot of people forget that the dynamic range of any recording includes a lot of portions that are =below= the average level, even if it is only for the fade in/out of a pop recording. So, yes, an LP recording can have 50, 60 dB or more of dynamic range (and digital more than that) but the vast majority of range exists =below= the average playback level, not above.

 

RE: Instantaneous levels: "+13 dB above peak" and "too fast to appear on the SPL meter", posted on January 14, 2022 at 12:43:08
peppy m.
Audiophile

Posts: 2242
Joined: February 19, 2021
 Sensitive horn speaker systems to the rescue ?

 

RE: Instantaneous levels: "+13 dB above peak" and "too fast to appear on the SPL meter", posted on January 14, 2022 at 14:36:12
psn
Audiophile

Posts: 56
Location: Houston
Joined: January 6, 2007
 These folks certainly think there is instantaneous level capacity required above measurable mechanical meter peak level...

Supplement No. 2 to NAB (NARTB) Engineering Handbook (Fourth edition, 1949) NARTB Recording and Reproducing Standards (June 1953)
The NARTB Recording and Reproducing Standards Committee
Neal McNaughten, Chairman
K,R, Smith, Mechanical Disk Subcommittee
W.Earl Stewart, Magnetic Tape Subcommittee

The National Association of Radio and Television Broadcasters
Department of Engineering - A. Prose Walker, Manager
1771 "N" Street, N. W.
Washington, D.C.

https://worldradiohistory.com/Archive-NAB-Engineering/NAB-4th-Edition/Audio%20Recording--NAB-Engineering-4th-Edition.pdf

Footnote 4 on page six (page index labeled 1-3-04):

"It is well established that at least a 10 db margin is required between the sine wave load handling capacity of a system and the level of program material measured by a standard volume indicator. This standard would then contemplate program peaks running as high as a velocity of 21 centimetres per second. This is believed to be approximately the maximum velocity which can be traced without excessive distortion at groove speeds encountered at the inner radius of a 33-1/3 rpm disk. This has also been substantiated by practical experience."

Same page under section Recorded Level 1.80 states the standard for recorded level will be the same VU deflection as a 1,000-cycle tone recorded at a peak velocity of 7 cm. per second.

7 cm/s +10dB is 21 cm/sec

They standardize the recorded level at the accumulation time of the measuring device (mechanical peak meters: VU, SPL, Watts...) set for fast peaks so they match measuring 1KHz produced by 7 cm/s stylus tracing. This places this fast peak level 10dB under the true peak level of 21 cm/s. This standard is designed to set the fast peak meter levels with additional headroom above for the true peaks.

And yes, sensitivity to the rescue... my typical listening at 83dB (fast peak SPL meter) requires 0.05W of power, so 13dB over that is 0.366W with much room to spare. :)

 

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