[Brian Walsh]

If I use the following numbers in that Crown s/sheet:
* 3.5m distance
* 80dB average level
* 83dB speaker sensitivity
* 0dB headroom

I get 6w.  Obviously this is a steady-state reading.

But 2,100 times this power to cope with transients which are 10 times as loud ... sheeech!!         I think my assumptions are wrong somewhere!  Mebbe a more "real world" figure is only 5 times?

What multiplying factor does that produce?

About 210 watts, which makes sense: ten times the power gives a 2:1 SPL ratio.

I created a spreadsheet to do the math. Give it a try, and use the goal seeking feature to back solve. Click here for the link.
 

[andyr]

I created a spreadsheet to do the math. Give it a try, and use the goal seeking feature to back solve. Click here for the link.
 

Hi Brian,

I clicked on the link - your s/sheet is very neat and appears to give me a result of 2 watts required to deliver 80dB from my line-source speakers at my 3.5m listening distance ... did I drive it correctly?   

Does this mean I theoretically have about 100 times the power in reserve (if I have a 200w amp driving my bass panels)?  So if ten times the power gives a 2:1 SPL ratio, I have a 4:1 SPL ratio "available" for transients??   

But maybe in terms of the apocryphal reproduction of "a glass breaking on tiles" - which we are assuming will give a realistic, life-like representation of live music - it is not so much the theoretical steady-state SPL ratio capability which is key, it is (as Russell D suggested) more how much instantaneous (undistorted) power the amp can deliver in an instant - ie. for 20 msec, 10 msec and 1 msec??   

I suspect this depends on amp topology as well as how good its PS is ... and still we come back to the question of what is the amount of headroom required ... 4:1? ... 10:1?      

Regards,

Andy

[JLM]

It seems that the calculator is based on a single channel/speaker and anechoic conditions, so the results are conservative.  (It comes from a producer of big amps, duh.)

Don't mistake dynamic limitations of speakers for ultimate spl.

These are the numbers I use for average/maximum in home spls (this is painting with a very wide brush and I'm an old fart):

Classical    75 dB/105 dB
Jazz          80 dB/100 dB
Rock        100dB/110 dB