Speaker efficiency vs. power requirements

Yes, I think the flaw is starting with the 'efficiency' of 90db, and thinking of this as the base number for dynamic range.

So, a 90db speaker, with 100 watts will do 100 db, and 110 db with 1000 watts. Dynamic range will be from 0 (no current to speaker) to 100 or 110, respectively.

With the logic in the quote above, speaker efficiency is taken out of the equation, as it uses the speaker's efficency as the dynamic range 'floor.'

Your source is ok, I guess, its just said things in a kinda stupid way. This topic has been covered before. Every 10db increase is a doubling in SPL (sound pressure level, and I would call this loudness, colloqually (I know its spelled wrong)) and perceived loudness. 80db is twice as loud as 70db. 90db is 4x as loud as 70db (2x2=4). It takes ten times (10x) the power to double the SPL. So if you can play 90db with 1 watt, then 100db will take 10 watts,110db will need 100 watts, and 120db will need 1,000 watts. Got it. OK. So the first 4 sentences of your source are OK; its just said really weird.

He gets confused on the 5th sentence, or at least I am. If we need 60-70db dynamic range, well, to my knowledge, a bit limited, a 90db efficient speaker already has that dynamic range. It can play 90db with 1 watt so it can do 70db with even less power. What he's done is added the 60-70db onto the 90db to give a dynamic range of 150 to 160db. And from there it appears to be ok mathematically, yes you'll need 1,000,000 watts into a 90db efficient speaker if you expect it to play 150db loud. Thankfully, there are speakers w/ 100db efficiencies and higher, so we can make up for power with sensitivity/efficiency. And there's little reason to go beyond 120db because you'll start getting hearing damage. The 6th sentence is a no-brainer and his first five sentences are a little dumb, it he's just trying to support #6. Just disregard the last sentence (#7). As far as I know, loudness, i.e. how loud the system can play, is dynamic realism, the system can go from really really loud to quite. And the amount of power is in direct relation to how loud it plays once the system efficiency is taken into account. Hopefully, I'm not wrong on anything or I'll have confused you more trying to unlearn, relearn, unlearn, etc.

I may have screwed up in my previous post. But I don't want to think about it anymore. Try this.

Based on a 90db efficient speaker.

Desired SPL Needed Power
90db 1 watt
100db 10watt
110db 100watt
120db 1,000watt
130db 10,000watt
140db 100,000watt
150db 1,000,000watt
160db 10,000,000watt

And that would give you a dynamic range of 160db, and it'll probably kill you along the way!

Hello great information and thanks for the input - just to clarify - the information I posted at the top is NOT my conclusion. This is however what *I* was told by someone who claims to know this stuff. As I pondered the statement, I grew unsatisfied with the logic and chose to post for discussion.

To clear some things up for some of you:
The mention of 90db is in regard to the speaker efficiency. I believe this number was selected since it was the rating of my speakers.

Another couple questions to further enhance this discussion:

1) Given the rated efficiency of a speaker - how does the Ohms rating effect power requirements? For example, a 90db speaker at 6Ohms.

2) Depending on which speaker, isn't it true that different frequency requirements may have more or less efficiency at varying ohms? What does this do to the overall power requirements?

And to top it off, what about impedance?