Amount of power needed for dynamic peaks?

[F1308]

I guess my two electrical engineering degrees won’t suffice

Well...jet engines have been improved a lot since 1939.
The same goes for radios, amplifiers and the likes...
Google was made by some students sitting right next desk, attending the very same teachers...
And many others, like the Wright brothers decided to discard what previously had been searched [Lilienthal....] building their own test equipment and their own engine... paving their way to success.
And, believe me, I see so many graduates that simply do not understand what they are talking about...There is some lack of true knowledge there. Was learned without a root, without a reason.
Remember NASA was not able to reproduce rocket engines of the Apollo project, bringing astronauts to ISS thanks to Soyuz.

Our youngest son came back home telling very happily he had been learning a lot about plants that very morning at school. At his pretty four years of age, he went on asking us all if we knew which was the most primitive plant on Earth so far.
We gave up, we didn't know, so he smiled and went on saying loudly: it is the fern.

Some good ten minutes later he got close to my wife and said:
Mummy, what does primitive mean...?

 

[waynel]

Well...jet engines have been improved a lot since 1939.
The same goes for radios, amplifiers and the likes...
Google was made by some students sitting right next desk, attending the very same teachers...
And many others, like the Wright brothers decided to discard what previously had been searched [Lilienthal....] building their own test equipment and their own engine... paving their way to success.
And, believe me, I see so many graduates that simply do not understand what they are talking about...There is some lack of true knowledge there. Was learned without a root, without a reason.
Remember NASA was not able to reproduce rocket engines of the Apollo project, bringing astronauts to ISS thanks to Soyuz.

Our youngest son came back home telling very happily he had been learning a lot about plants that very morning at school. At his pretty four years of age, he went on asking us all if we knew which was the most primitive plant on Earth so far.
We gave up, we didn't know, so he smiled and went on saying loudly: it is the fern.

Some good ten minutes later he got close to my wife and said:
Mummy, what does primitive mean...?

What are you trying to say here? Are you trying to discredit education and credentials? Do you disagree with one of my posts? The other poster already admitted it was he who was confused on the issue.

 

[F1308]

What are you trying to say here? Are you trying to discredit education and credentials? Do you disagree with one of my posts? The other poster already admitted it was he who was confused on the issue.

I am simply saying that education improves, that things get better as time passes by, that thoughts are revised, knowledge of things deeppens with time...and that not all graduates are the same...
An that two degrees and four masters grant nothing.

Try this question on as many graduates as you can, please:

Do electrons move from positive to negative or from negative to positive ?

You will have some fun, I promise.

 

[pozz]

Please, be aware you are not taking into account humidity....

The dependence on humidity is a particularly complicated function. In the normal range from 20 to 99% relative humidity (RH), acoustic energy at midrange frequencies is absorbed at the same low rate (0.1dB per 100' of air-path length) regardless of the value of RH. But at high audio frequencies the transmission of sound through the air improves dramatically as the amount of water vapor increases. The following table shows how rapidly the sound is absorbed per 100' of air-path length, at a frequency of 10kHz:

Relative Humidity Absorption:
20% 9dB
50% 6dB
80% 3dB

https://www.stereophile.com/content/humidity-concert-hall-sound-spectral-tilt

This only applies to concert halls or other large venues, which is why they use line arrays and other reinforcement techniques for even coverage and to counteract other things like temperature gradients and wind.

For small rooms, spectrum-based power requirements will be mostly to do with the balance of the program material/signal.

 

[pozz]

This is true. I generally listen to music up-mixed to or in native multichannel, so that gives me some cushion. Although, the THX reference standard says that each speaker should be capable of hitting 105db on its own. So, if one is going for movie theater dynamics, then the calculation should be for a single speaker.



Good point. I need to measure my room(s) specifically for this figure to get a better idea of what I'm working with.


In addition to what other's have mentioned, I also like to add a couple extra subtrations for my calculations.

1. I'll subtract 3-6db for extra safety. Music/Movies tends to sound bad to me if I'm even the slightest bit worried I might damage something. Makes it harder to concentrate and enjoy.,

2. I'll subtract another 3-6db headroom for EQ. This will vary based on room. I'm using about 5dB boost in my worst room(bedroom), and 2dB boost in my best room(living room).

This makes me think I need to get much more powerful amps, and that's even with crazy efficient speakers(101dB). Also shows me just how woefully inadequate most hifi speakers are in terms of being able to recreate live sound or movie theater dynamics with normal amplification levels. I'll probably end up needing to build two separate systems; one for casual listening, and one for "live" listening.

Taking my Revel M105s as an example in my main room. Say I want to recreate the movie theater experience at home. 4m distance.

Low End Estimate(-3dB/double, -3db headroom, -3db EQ):
Starting at 86dB,
-6db for distance(distance doubled twice)
-3db for headroom
-3db for EQ.
I need 31dB of amp gain to reach reference, or ~1,500 watts?

Safer More Moderate Estimate(-4.5dB/double, -4.5db headroom, -4.5db EQ):
Starting at 86dB,
-9db for distance(distance doubled twice)
-4.5db for headroom
-4.5db for EQ.
I need 37dB of amp gain to reach reference, or ~5,000 watts?

So somewhere between 1,500 and 5,000 watts, haha. I think they'd blow up if I fed them that.

Luckily, most of my listening is not that loud, but I do go ham sometimes. That's for if I want movie theater dynamics. Live music dynamics might be even tougher. The live concerts I've been to have had incredible dynamics, though I've never actually measured with a good spl meter. The highest I've ever seen at home in my main room with 5 speakers and 2 subs was ~120db at the end of Overture 1812 when the cannons are going off. Going just by my faulty memory, I'd say the live concerts I've attended were comparable to that, so quite loud indeed.

Unless I've misunderstood, I think you are confusing your input signal with amp power requirements. The calculation is just for SPL at the listening position.

So using the 86dB sensitivity of the Revel M105:

You want to reach 105dB SPL (peak) with one speaker at 4m right? So looking at power requirements of the amplifier:

No adjustments:

• 1.3kW
• +3dB amp headroom: 2.5kW

Using the two speaker adjustment (-3dB):

• 631W
• +3dB amp headroom: 1.3kW

Adding on top the average reverberant room adjustment mentioned by @Sancus (-3dB):

• 316W
• +3dB amp headroom: 631W

 

[DonH56]

I usually send folk to this online calculator as it can account for some room effects: Peak SPL Calculator You can also download an Excel spreadsheet version.

Decide how loud you want to play, for a given set of speakers (nominal impedance and sensitivity in dB/W/m), at a given distance. I usually just run the numbers for the L/R front pair. 80 dB is pretty loud for an average level to me so 100 to 105 dB max is good enough. I have subs for the deep bass where you need much more power to hear at the same loudness as the midrange (see equal-loudness curves). Music peaks are around 17 dB above the average level (from an old AES paper I remember but can't find, trust me or not, find it if you can -- and send it to me!), a factor of 50 in power, so if your average level takes 1 W you're OK with a 50 W or so amplifier. Might as well get 100 W so you have 20 dB (100x in power) headroom over average. Movies have been shown to have 30 dB peaks (1000x the average power) but I figure that's mostly explosions and such where I wouldn't notice a little clipping and am too cheap to buy a bunch of 1 kW amps. Even if I thought the speakers could take that kind of power (doubtful).

All of these are a guesstimate since knowing the impedance over frequency and such is hard, rooms impact the SPL over frequency, etc.

Note, despite marketing blurbs and erroneous manufacturing spec sheets, there is no such thing as "RMS power". Continuous power is average power, the product of RMS current and RMS voltage. Multiplying RMS by RMS does not get you RMS units for the result... All my EE texts and books use the term average power = Vrms * Irms.

Example:

 

[macauley86]

Guys, at what volume level do you listen to music? When I reach average 78 dB with 85 dB peaks, it's plenty loud for my ears and my wife wants to murder me, unless it's Kenny G, in which case other things happen.

 

[waynel]

Guys, at what volume level do you listen to music? When I reach average 78 dB with 85 dB peaks, it's plenty loud for my ears and my wife wants to murder me, unless it's Kenny G, in which case other things happen.

Worse or better than murder?

 

[DonH56]

Guys, at what volume level do you listen to music? When I reach average 78 dB with 85 dB peaks, it's plenty loud for my ears and my wife wants to murder me, unless it's Kenny G, in which case other things happen.

Typically around 65-70 dB or so average for movies, a little more for some music and if I am feeling "loud".

 

[CDMC]

This is true. I generally listen to music up-mixed to or in native multichannel, so that gives me some cushion. Although, the THX reference standard says that each speaker should be capable of hitting 105db on its own. So, if one is going for movie theater dynamics, then the calculation should be for a single speaker.

Ironically this is incorrect, but keeps being restated by authorities that should know better. The reference calibration is not 85db at -20dbfs, but 83 db at -20dbfs IN A LARGE THEATER. It was revised more than 30 years ago.

https://www.digido.com/portfolio-item/level-practices-part-2/

The second part is that you need to adjust the levels based on the size of your listening room. When doing so the proper reference level for most domestic rooms ends up at 76-78 db c weighted per speaker using 500-2000hz band limited pink noise. If you look at most of the home theater guys you will see they constantly say that the reference level it too high and they listen 5-10 db below. That is because even the manufactures and industry gurus that should know better and be discussing it always miss the room size adjustment.

https://www.soundonsound.com/techni...ect-studio-reference-monitoring-levels?page=3

Translating this to usage, for most home theaters, the Dolby/THX reference max level should be 96-98 db per speaker and 106-108 for subwoofers. I find that for music listening on highly dynamic music 105db peaks are not out of the question. For compressed music, peak levels are much lower.

 

[HansHolland]

My example:

At full digital signal and the digital volume control at 0 dB (meaning: it can't get louder) my DAC outputs 2 Veff.
The output of the DAC goes into a signal transformer that lowers the voltage by a factor 2. So, 1 Veff goes into the amplifier.
The voltage gain of the amplifier can be changed between 20 dB or 26 dB. I did set it on 20 dB. 20 dB means a voltage gain of 10 times.
So, I get 10 Veff at the outputs of my amplifier when the analog volume control of my amplifier is full open.
10 Veff is 25 W at 4 Ohm.
In the peak of the sine wave the power is 2 times higher than the effective value. So 50 Wpeak.

And that times 2 (I listen stereo) = 100 W.

But, the analog volume control of my amplifier is fixed at -12 dB (I control the volume in the digital domain). So, the power levels mentioned above are always 16 times lower.

Let's say: I need 2 x 4 Wpeak!

No app/calculator needed to calculate that!

b.t.w. I have a desktop setup. Listening distance is less than 1 meter.

 

[patate91]

Typically around 65-70 dB or so average for movies, a little more for some music and if I am feeling "loud".

Same thing here between 65-70 db. I need more than when I'm doing other things than listening to music.

 

[aac]

Conversely, with highly dynamic music, I find that my average level may be 83 db, but now I am getting peaks of over 100 db. I was curious and measured with REW on a dynamic piece that I was playing above even my normal loud level and shocked to be seeing short peaks of over 110 db. Now we are talking some real power, 400 watts needed to not clip the amp (fortunately my amp puts out 300w/ch into 8 ohms and 600w/ch into 4 ohms), so when turned up, I was right at the clipping point for a pretty big amp with moderately sensitive speakers.

You can't measure like that, as your room will amplify sound a lot more than you think. Use a dBTP meter (decibels true peak) to find out peaks, calculate voltage to your speaker. Power will vary as speakers are complex loads, but you'll have an idea. Ideally you'd connect oscilloscope to check for peaks, but not everyone has one.
Don't use measured SPL for power calculations

 

[dfuller]

Depends entirely on what you're listening to. Crest factor of highly compressed music (e.g. electronic, rock/metal, modern pop and rap) is generally 10-11dB at maximum.

Highly dynamic music (film scores, high dynamic range classical, jazz, etc) might be more like 15-20dB crest factor, but peak level is often lower.

So, figure peaks will need 10ish times the power of your average level... Factor that in with your speakers' sensitivity and you're in the ballpark. I think unless you're listening at massively loud volumes, 100wpc is probably plenty. My Focal Shape 65s are 80w low and 25w high (they're active, biamped) and can get far too loud to comfortably listen to long before the amps run out of steam.

 

[CDMC]

You can't measure like that, as your room will amplify sound a lot more than you think. Use a dBTP meter (decibels true peak) to find out peaks, calculate voltage to your speaker. Power will vary as speakers are complex loads, but you'll have an idea. Ideally you'd connect oscilloscope to check for peaks, but not everyone has one.
Don't use measured SPL for power calculations

If I am understanding correctly, you are saying that in order to accurately measure, I need to take that maximum listening volume and hold it, run whatever I am listening to through software to get the dBTP for what I am listening to, then play back that segment of music while taking the peak voltage (assuming I have a meter that reads that fast or an oscilloscope) to see the peak voltage and confirm no clipping. Once I do all that then calculate the wattage used.

Assuming I understood that correctly, you have massively overestimated my skills and equipment. I don't have software to check dBTP, I don't have a volt meter that will catch peak voltage of a short transient, I don't have (nor know how to use) an oscilloscope. The good news is I could calculate the wattage from the peak voltage (Ohm's law I do understand). Otherwise, you are correct, my method is an estimate at best given the room gain and falloff from the speakers creating what could be a 3-6db change (2x-4x power).

 

[Duke]

Something which is often not factored in, in part because it has not been well studied, is "thermal modulation", or rapid-onset thermal compression, which arises from voice coils heating virtually instantaneously when hit by a peak, which in turn causes their resistance to rise. To a rough first approximation, a 200 watt peak would be like touching the voice coil with a 200 watt soldering iron. (This is a precursor of, yet different from, the more familiar "thermal compression" which arises when motors heat up over time and temporarily lose some of their magnetic flux.)

Floyd Toole had this to say on the topic, in a post on another forum:

"The audibility of power compression in its many variations probably could use some more research to define what is audible and what is tolerable. The magnet heating that you describe is important in pro audio sound reinforcement systems where the loudspeakers are required to work at or close to their design limits for long periods. Such heating and cooling has a very long time constant. This is not the case in most home systems. Although the modification of motor strength through magnet heating is a factor, most of the audible effects are from voice coil heating, which has a much shorter time constant. I just saw a test of a high-end audiophile speaker that in going from an average level of 70 dB (loud conversation, background music) to 90 dB (a moderate crescendo, or foreground rock listening) lost about 4 dB in output over about 3 octaves in the mid-high-frequency range. It became a different loudspeaker at different listening levels." [emphasis Duke's]

If we take the example Toole mentions, and mentally scale up to 100 dB peaks at 3 meters, we can see that THAT particular speaker would compress the peaks severely and probably sound lifeless no matter how much amplifier power we have. Even down at 70 dB average level, what should have been a 20 dB peak ends up only being a 16 dB peak!

My point is, if you really want to preserve all of the dynamic contrast in peaks, amplifier power is only one piece of the puzzle. The thermal modulation characteristics of the loudspeaker drivers is another piece. This is where high-efficiency speakers which use prosound-style drivers have a distinct advantage, as not only do they require far less amplifier power to reach a given SPL, but also their large voice coils usually have much greater thermal mass and therefore do not heat up as rapidly as more conventional "hifi" type drivers. (Note that musicians use dynamic contrast to convey emotion, so when the dynamics are lost, so is some of the emotion.)

Years ago Stereophile did an article which supposedly "debunked" the "myth" of thermal modulation. Their measurement procedure was flawed in that they did not sample the voice coil temperature at the instant of peak power, but rather they sampled voice coil temperature at regular time intervals and then averaged the results. So whatever was happening at the peaks was not captured.

 

[gene_stl]

I am surprised that in four pages of posts there are only three posts by two posters on thermal effects and power handling capacity of tweeters.

The peak to rms ratio is almost irrelevant. The first thing to look at is the power handling capacity of the tweeters. After the above mentioned thermal compression happens if you keep pushing louder the voice coil will unwind itself or the tweeter will burn or punch the diaphragm out due to adhesive failure. These are the only parameters that are important. It is very nice to take advantage of the efficiency increase and damping increase of multi amping. But you also want to make sure you aren't going to cook your drivers. (This in contrast to a high level passive crossover where using too SMALL an amp can blow the speakers by sending clipping into the crossover)

The Crown HiQ net /System Architect DSP software has among its features a smart limiter compressor that is able to take into account the recent history of the signal sent through an amp or driver (it can do both full range or active crossover) and limits more if it calculates that the voice coil is hot. I have not yet studied how it models the thermal behavior of the voice coil, but I think its pretty smart. I think the dBx Drive Rack and Behringer crossover/dsp units may be able to limit too. (Edit: You set the long term power handling rating of the speaker or driver into the software)

There is some max level for each driver. That needs to be available unclipped. But it needs to be then compressed at that level without clipping. A limiter. A smart limiter is even better.

The room volume/size and desired SPL approximate how many drivers you will need. Then you work backwards. Better an amp too big than too small. But if its too big, better have small fuses in the speaker lines. Tweeters for expensive audiophile speakers are very expensive to replace.




I notice that people who minimize the value of education , often have not been willing to subject themselves to its discipline.

 

[restorer-john]

which arises from voice coils heating virtually instantaneously when hit by a peak, which in turn causes their resistance to rise. To a rough first approximation, a 200 watt peak would be like touching the voice coil with a 200 watt soldering iron.

A 200W peak would not be anything like touching the voice coil with a 200W soldering iron.

A woofer's entire voice coil and metal former has considerable thermal inertia and a point source quick (peak) application of heat from a 200W soldering iron sitting at 300 degrees centigrade is a ridiculous analogy.

A tweeter with perhaps a non-metallic former and very thin voice coil windings on the the other hand, would rapidly heat, but they are subject to mere single figure watts in almost all typical musical content.

That doesn't change your point on compression which is very much a valid point. I have numerous small bookshelf speakers which change their character and output in a very audible manner when subjected to elevated listening levels and overall motor assembly heating over a long period. At one point, I attached a thermocouple down the vented pole piece on a speaker's woofer and ran the wires out the port to see how warm the driver got over a long listening session.

That power has to go somewhere and with so little actually converted to sound, the rest goes up as heat.

 

[aac]

If I am understanding correctly, you are saying that in order to accurately measure, I need to take that maximum listening volume and hold it, run whatever I am listening to through software to get the dBTP for what I am listening to, then play back that segment of music while taking the peak voltage (assuming I have a meter that reads that fast or an oscilloscope) to see the peak voltage and confirm no clipping. Once I do all that then calculate the wattage used.

Assuming I understood that correctly, you have massively overestimated my skills and equipment. I don't have software to check dBTP, I don't have a volt meter that will catch peak voltage of a short transient, I don't have (nor know how to use) an oscilloscope. The good news is I could calculate the wattage from the peak voltage (Ohm's law I do understand). Otherwise, you are correct, my method is an estimate at best given the room gain and falloff from the speakers creating what could be a 3-6db change (2x-4x power).

Probably, I was too bad with words.
What you can do is
1)find out dbtp value
2)find out gains of your amp/preamp/volume control
3)knowing your DAC specifications (manufacturers usually give V @ 0 dBFS) calculate voltage at the speaker.
4)if you don't know gains or specifications you can use a voltmeter - use a sine wave generator (be careful) at 50 Hz and measure Vrms at the speaker input and then you'll know relation between digital level and voltage.

You'll need to be careful with calculations as manufacturers and software makers use different definitions of dbfs.

 

[restorer-john]

The first thing to look at is the power handling capacity of the tweeters. After the above mentioned thermal compression happens if you keep pushing louder the voice coil will unwind itself or the tweeter will burn or punch the diaphragm out due to adhesive failure.

Usually what happens is the enamel on the windings bubbles/burns, the former and adhesive fails and the voice coil adjacent windings short and/or the lead in wire solder point melts. Unwinding of a tweeter voice coil is extremely rare and only happens when the VC has detached from the dome/cone and continues to be driven loose in the gap.