Speaker sensitivity and amplifier wattage

Question? Seeing I hardly ever listen to my system above about 90db peaks…Does anyone know, if say for example, a 90 db sensitivity loudspeaker @1w/1m ever requires a amp to go beyond the first watt in order to reach that 90 db rating because of the dynamic range variations in the music? Or can and does the speaker require more bursts of power to reach the 90db spec? I know listener/speaker distance beyond 1m is a factor… but for simplicity’s sake,we will just say 1m average db rating.


Yes, for two reasons. First is musical transients, especially in the lower frequencies. Second is your room will not be like the anechoic chamber the speakers were measured in.

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Also you are probably sitting further away than 1m or you should be for proper imaging.

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Thanks guys. So… speaker specs are rather disingenuous when it comes to real numbers needed to make any type of subjective determination on power needed to drive them? So 1w/1m is not a legitimate spec?

Not disingenuous. Complicated.
Good source for useful information: https://www.passlabs.com/press/loudspeakers-lament
I used to have a 3 watt class A amp. It sounded great with my 100db speakers. But my 25 watt class A amp at the same listening levels sounded better. And now my 250 watt amp sounds much better. All at surely no more than a couple watts average at my listening levels. This stuff can drive one crazy.

Well I suppose it is not representative of normal listening but you need to have some standardised way of comparing speakers and this was what was decided on. It may be accurate for near field/studio listening so that may be why it is used.

It’s just a standard, that allows one to compare apples to apples.

The spec is very useful within limits. It is meant to compare the relative efficiency of one pair of speakers to another. It is standardized across the industry, and therefore can be used to compare across brands.

Unfortunately, as with most specifications the temptation is to read too much into the specification. The efficiency is measured in a controlled laboratory type environment. The real world has too many variables to mention here, all of which affect how the speaker will act in your room with your system.

Paul is correct when he says speakers are the hardest components to predict how they will work/sound in a particular situation.

Speaker purchasing is, in my opinion, the most affected area of the industry when it comes to the lack of brick and mortar dealers, and the growth of internet marketing.

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Thanks everyone for the replies…

So, I can take it that the 1w/1m spec is only useful for an across the board generalization used for the benefit of the speaker industry and in reality it takes many more watts to reach and sustain the example of a 90 db sound rating for realistic sound pressure levels in room? Is it because the lower/mid frequencies needed to hit the 90 db spec also need a lot more juice/watts to hit that mark…in order to achieve any realistic level in the sound quality at a 90 db rating?

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You’ve pretty much got it. The 1w/1m spec helps you gauge overall sensitivity of the speaker, but it only tells you so much about how the speaker will behave in-room. Size of the room, choice of music, etc all impact how the speakers will act. If you like listening to classical for instance, some of the dynamic peaks can reach pretty crazy levels (110+ dB). An amp that doesn’t have the power to drive your speakers to that peak will not be doing the music justice.

And when it comes to lower/mid frequencies, they are indeed harder to provide power for because the drivers have to move more mass and more air.

Personally I like having more power on tap than I’ll ever realistically need - it allows the amp to fulfill it’s duty more effortlessly and tends to sound better to my ears. If I wanted to run a low power amp, I’d also shop for high efficiency speakers (96+ dB sensitivity).

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I’m running 95dB/1w/1m 4 ohm speakers with BHK300s pumping 600watts/side. Dynamics are incredible!


And… to throw one more variable at this problem some speakers (ESLs in particular) get harder to drive as frequency increases. Since they are primarily capacitive loads their impedance drops as frequency goes up.

My Sanders speakers are driven by two 900W/channel (into 4 ohms) stereo amplifiers. One for panels and one for woofers with active crossover / EQ. Sounds like an absurd amount of power, but having some headroom never hurts. The woofer amp actually gets pretty warm running in class A/B at sustained higher volume levels.

These Sanders Magtech amps are also quite unusual in that their high voltage DC bus is regulated.

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Thanks all… I felt I had a good understanding of my question presented and the answer for it…but now I see completely through the fog… :sunglasses::grinning:

Keep in mind that most speaker manufacturers do not accurately state performance specifications, including efficiency (gasp). But assuming that the efficiency ratings are accurate it’s painting with very wide brush strokes and leaves out several important factors like setup, room size, and amp being used. You also need to apply a bit of math to arrive at a realistic output number.

First I’d ask how do you know you’re listening to 90 dB peaks? Most sound pressure level meters are “slow” (averaging peaks/dips versus displaying instantaneous peaks/dips), so under reporting the extremes. Live concert peaks range up to 105 dB for jazz, blues, or classical and 110 dB for rock. Instantaneous peaks can range from 10 dB for rock to 30 dB for classical. These are very ball park numbers, based on venue and where the listener is positioned.

The peaks are an important consideration. Overloading an amp will cause distortion (clipping) that try to force the speaker diaphragm to instantly stop and start, which is extremely hard on it and can lead to failure of the driver. To safely listen you must therefore use a more powerful amp or turn it down below concert levels. Note that continued exposure to more than 85 dB will result in permanent hearing loss and possibly permanent pain.

In calculating actual sound pressure levels (spls) keep in mind that having two channels adds 3 dB, but doubling the distance (from the reference 1 meter) subtracts 6 dB, so sitting 13 feet away would drop spls by roughly 10 dB. That translates into the speaker needing to be capable of producing 115 dB for classical/jazz. If the stated efficiency is 88 dB/w/m (a typical manufacturer’s rating) the amp would have to produce 27 dB of gain (115-88).

The relationship between watts and dB of gain is logarithmic (0 dB of gain = 1 watt, 10 dB of gain = 10 watts, 20 dB of gain = 100 watts, 30 dB of gain = 1,000 watts, etc.), therefore 27 dB of gain equals 500 watts per channel (again to safely handle peaks). Note that 32 dB of gain (1600 watts per channel) would be needed for concert level rock music. Most speakers aren’t rated to handle that much power, so your alternatives are to turn it down or switch to more efficient speakers.

Now before you dismiss all this consider that most audiophiles I know do serious listening to jazz/blues at 80 dB average spl (roughly 100 dB peaks) and 75 dB average for classical (up to 105 dB for peaks) - slightly below concert levels. If you’re in a smaller room and sitting closer the power demands also goes down (saving roughly 10 dB). So bedroom listening at concert peaks could take as little as 100 watts for those same 88 dB/w/m speakers.