https://getpocket.com/explore/item/the-s...e=pocket-newtab

Mojo.. you have your work cut out for you to beat that one. ie. how many active LFR's would it take ???

What an interesting article. I knew about Krakatoa but I never imagined it was that loud.

You need 51 active LFRs each fed with 4100 peak Watts.

172dB at 100 miles is 277dB at 3 feet. I made the simplifying assumption that SPL would attenuate by 6dB for each doubling of distance.

One active can produce 126dB at 3 feet given 1 peak Watt.

The SPL at 3 feet produced by n actives is given by:

SPL = 126 + 3*(n-1)

For an SPL of 277dB at 3 feet, solving for n gives 51.

Since each active requires 4100 peak Watts to produce that SPL, over 200KW are required.

I think Ian ought to try it. If he immerses them in Lake Muskoka, he can produce a tsunami.

One acoustic watt is 120 dB - 4 acoustic watts is 126 dB.

If a single Active can deliver 4 acoustic watts, or 126 dB, with 4100 watts of electrical power to the speaker, it would take the same power per speaker through 1 quadrillion actives to hit 276 dB. This is, of course, assuming we are in a 4 pi environment.

Ian's gonna need a bigger factory.

Oh yeah? I've never heard of the term "acoustic Watt". Is that the spawn of an acoustic volt and an acoustic amp?

My number was within the margin of error.

Mojo - each 10 dB increase requires another ten TIMES the acoustic watts:

1 Acoustic watt is 120 dB
10 is 130
100 is 140
1000 is 150
10,000 is 160

SO ... add another 11 zeros to get to 270 ...

1,000,000,000,000,000 Acoustic watts is 270 dB.

Make more sense now?

And admit it - you had plans on taking over North America with 51 actives.

I admit 51 sounded way too practical to be true. I did math without physics like accountants do numbers without business.

I need to understand the theory behind an acoustic Watt. Unlike Ian, I can't study while grilling my tuna and making a stir-fry.

The traditional method for referring to an acoustic watt is per square meter, and it is directly related to the pressure applied. This is why one acoustic watt - which does not sound like much - is powerful to our ears, and lethal to them as well.

Another measurement is across a one meter sphere, which would measure 107.5 dB - think about it, it's a lot more square footage.

While I ponder that, check out my active tuna in walnut natural satin.

Great - now I am hungry to go along with being boring.

Whaaaaaat? What could possibly be more interesting than preaching about acoustic Watts?

Porn.

Audio, primitive implements, camp fires and 40 year old vans are similarly good.

Like

Craig, there's something I'm missing in all of this. It's my understanding as I add a speaker to a system, SPL goes up by 3dB. So if I have an active that gives me 90dB with a Watt at 3 feet away, if I butt up another active that is eating a Watt, at 3 feet away I'll measure 93dB. If I add another, I'll measure 96dB. Is this not correct?

No - you need to double for every 3 dB

If one is 90 dB ... then 2 is 93 ... 4 is 96 ... 8 is 99 ... 16 is 102.

Oh my goodness, that is correct.

The formula for active SPL at 3 feet for 1 Watt electrical power as a function of the number of actives then becomes:

SPL = 126 + 10*log(n)

Solving for n at 277dB, I get 1260E12. That is 1260 trillion actives. Each one needs 4.1 peak kW for a total of 5.2 quintillion Watts. That's one order of magnitude more than all the power produced last year.

Yup - I stopped at 276 dB because it was 150 dB above the 126 dB ... which is 1000 trillion actives. That last dB needs another 260 trillion actives.

As stated earlier, Ian is gonna need a bigger factory!

That being said - it would be cool if 51 actives could have done this. We could have rebooted the Austin Power movies ...

"Give us $1 trillion, or we will play Muskrat Love at 277 dB"

That tune is a new one for me. It ought to be included in the CIA's interrogation manual.

BTW, 277dB at 3 feet away is 200 thousand pounds per square inch!

Obviously you were not around in CBC radio circa 1978~1981 when you could not find a 4-hour stretch where that song was not getting played.

Oh the horror!

I "discovered" music in 1982.

Too bad we can't repro that with only 51 LFR's... I was already planning the get-together trip.

Then again if Krakatoa was rupturing eardrums 40 miles away we might not want to try to reproduce it face-to-face anyways.

I don't think the 25-30dB reduction from a good set of muffs would be sufficient to make that a pleasant experience. Memorable yes, but not in a good way.

Forget muffs. At 3 feet away, you'd need 9 feet thick concrete to protect you from a 2000 Kpsi blast.

makes me think of HitchHikers Guide to the Galaxy - Disaster Area.

https://hitchhikers.fandom.com/wiki/Disaster_Area

Regular concert goers judged that the best sound balance was usually to be heard from within large concrete bunkers some thirty-seven miles away from the stage, whilst the musicians themselves played their instruments by remote control from within a heavily insulated spaceship which stayed in orbit around the planet - or more frequently around a completely different planet.

Right. Aliens blew krakatoa wide open because that's their idea of music.

Muskrat Love doubt it make the CIA list ... now Song Sung Blue on the other hand ...
Try that a 1000 times back to back

After the first two lines, I wanted to ram my skull through my speaker's vortex port.