Understanding watts and dB in my system

Hi all!

I apologize if this has been beaten to death already but I’ve never paid that much attention to power in my system. I have a pair of M700s driving bookshelves… so the Pre’s always at like the lowest tenth of what it can do.

But anyway, I am curious about upgrading my speakers in the next year or so. This Powerplay deal has me more curious about all the power numbers that I haven’t paid much attention to!

So if I understand correctly, when a speaker spec sheet reports 92dB efficiency this means that 1 watt gets me that 92db, and I would need 100watts to hit 112dB and 1000 watts to hit 132dB?

I guess this is where I get confused because realistically I never even listen to music at 92dB… but surely this doesn’t mean that I expend less than 1 watt per channel by listening to music below 92dB, does it?

Is there a general rule of thumb between what your amp power to speaker efficiency should be?

And also, what’s up with the impedance. If a speaker says “nominal impedance: compatible with 8 ohms” does that mean it is an ‘8ohm speaker?’

Thanks for taking the time to read!

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Uum, it depends on your viewpoint yet from a strictly engineering perspective, you’re right about the wattage vs. the output level. It just misses the point, which is linear region and headroom.

We want tons of excess wattage that we don’t use to ensure what we do use stays within the linear operating region of the amplifier and never approaches the maximum power output. Think of it like having a very powerful 427 cubic inch engine so you car drive to the supermarket without ever concerning yourself with struggling to get in front of another car or quickly shifting lanes (I had a VW bug once that when I wanted to pass a slow moving truck I had to wait for a hill and calculate enough time to make my move without some speedier car roaring up behind me).

Headroom and linearity. That’s what we’re after and you cannot have too much of that.


You got the best answer!
Also, in your example, it is 92 dB @ 1 watt @ 1 meter.
So if you are 2 1/2 -3 meters away from your speakers, the dB level will drop a bit.

Sound pressure drops 6dB with each doubling of distance.


This SPL Calculator (from listening position) may be of interest

I have been using this app to assess the dBs for safe listening:


As others have suggested, directly or indirectly, the speaker’s sensitivity specs are the barest minimum guideline, because you have no idea how they’re measured other than knowing the mic is typically one meter away. You don’t know anything about the signal itself, you don’t know anything about the environment in which the measurement is made. Even if you did, it’s a virtual certainty those conditions are nothing like the real world. To listen at your preferred levels, you could be utilizing less power or more power than the spec’d “first watt.” But what’s critical is that music is dynamic, and its demands on the amplifier are constantly changing, sometimes drastically, and the amp needs the resources to provide those short-term surges. I used to think that once you’ve passed a certain threshold in amp power, any extra is wasted money - but since I got my M700s, I’m convinced that there is no practical threshold in available power you should shoot for - that the easier it is for an amp to meet the music’s demands, the better quality sound you get, even in non-demanding passages or at low volume. Since getting these amps, I’ve struggled to articulate the difference the power makes in the sound quality overall. But it’s real and recognizable in how smooth, detailed and lifelike the sound is. And to get it, you need as much high-quality amplifier power capacity as you can afford.

That’s my opinion, anyway.


Thanks everyone. I’ve appreciated all your insight!!

I also use that app. Usual listening upper 60’s to mid 70’s. Occasionally hit mid to high 80’s. Very rarely above 95 & has read a bit over 100 only a couple of times. These 90+ levels are during orchestral peaks & are of relatively short duration.

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I started to pay attention after a hearing assessment that showed some decline. The doctor said I am about 5 years ahead of my peers (on the downward curve). I ceased using closed headphones and ear phones for good. Once in a blue moon, I use my open AKG K1000 headphones with their dedicated amp. Also, when listening to the main system, I have learnt where my volume should be for my favorite tunes.