Explain like I'm five: How much power my speakers actually use.

[Cygnus]

I really don't understand how ohms, amps, and watts work together. Every time I've tried to look up an explanation of these things, they blow my mind.

Could someone please explain this to me, as if I were five years old? My system is in my signature, and I'd like to know how much power my receiver actually uses at quiet, "normal", and loud volumes, on a whole, with my speakers. Perhaps with just front L&R, and 7CH Stereo examples?

Also, what does speaker dB sensitivity actually mean? What does it mean in relation to the volume of my amplifier, or the amount of power used?

Denon AVR-3311CI, rated at 125 Watts (.05%THD) (also, what's Total Harmonic Distortion? Does whatever it is only apply at really high volumes, or is it overall?)

Sensitivity chart:

Fronts: Paradigm Monitor 7's v.6: 96dBCenter: Paradigm CC-190 v.6Room / Anechoic: 93 dB / 90 dB (what's the difference?)
Side Surr: Paradigm Mini Monitor v.6: 92dB
Surround: Yamaha NS-5290: 90dB

 

[SearchofSub]

For starters and to break it down into simple terms you need 2 things for a speaker to put out sound from your source (music or movies from your cd player/bluray player/netflix etc)

1. Speaker
2. Amplifier

The lower the sensitivity of the speakers, the higher wattage power you need fro the amp to run it clean.

Thats basically it.



So if your speakers are rated at 98db sensitivity, you can go for amps that are even 10 watts per channel..

If your speakers are 87db sensitive, you would need amps that are atleast 100 watt per channel.



The lower your speakers sensitiveity is, it is harder for the amp to drive them (so ofcourse you would need higher watt amps), if you get low powered amps and drive low sensitive speakers, it will get distorted bad (the sound will not be clear and sound muddy/ you wont get punches or pops and transperency etc).


now the second part. The amplifiers.

You can go two ways pretty much.


You can get a AVR (audio video reciever) which handles both processing and output of your speakers. usually, this way you wont get a good sound compared to the other option.

which is to get a pre-amplifier thats only job is to process, and an amplifier that is only job is for output. These are called "seperates" because they are seperated. (no sh!t)


Usually the seperates do alot better job of ahndling sound from the source and putting it out through your speakers. Have you heard of Bi-amping speakers? kind of like the same logic.

Better to have different parts made specifically to work certain subjects than one part trying to work all subjects. (comon recievers nowadays)





now the speakers manufacturer rates the speakers imepdence level. Some are rated at 8 (most hifi speakers nowdays) and some are 4.

From my personal experience, the 4 rated speakers always sounded bigger and fuller with more impact than the 8 rated speakers. I have no idea why but perhaps other members can explain that as well.

I am reletevly new to AV so i am sure other members can help you out better but this is just my two cents.

 

[panteragstk]

Think of it in car terms. I know people hate car analogies, but they work for me. A given vehicle has 300hp available. An amp has 300w available. It doesn't take a car all 300hp to get to 70mph in 30 seconds. Same thing with a speaker/amp combo. A speaker will demand the wattage it needs to play at the SPL you want, but it may not need all 300w. Now, on the other hand if the speaker is particularly demanding it may take more than the available wattage to play at a given SPL and the amp clips. Same thing with a vehicle. It may be able to do 0-70 in 8 seconds at its fastest, but throw in a 30 degree incline with a 30mph headwind and the power required to reach 70 in the same time goes up considerably.

Please correct me if I'm wrong.

 

[Alex2507]

Think of it in car terms. I know people hate car analogies, but they work for me. A given vehicle has 300hp available. An amp has 300w available. It doesn't take a car all 300hp to get to 70mph in 30 seconds. Same thing with a speaker/amp combo. A speaker will demand the wattage it needs to play at the SPL you want, but it may not need all 300w. Now, on the other hand if the speaker is particularly demanding it may take more than the available wattage to play at a given SPL and the amp clips. Same thing with a vehicle. It may be able to do 0-70 in 8 seconds at its fastest, but throw in a 30 degree incline with a 30mph headwind and the power required to reach 70 in the same time goes up considerably.

Please correct me if I'm wrong.

So how many gees is my rec'r rated for?

 

[ImcLoud]

That denon and them speakers will work fine...

 

[Steve81]

I really don't understand how ohms, amps, and watts work together.

Try giving this a read if you haven't already:
Understanding Ohm's Law, Impedance And Electrical Phase 101 | Audioholics
I'm not sure if it's suitable for a five year old, but it shouldn't take an EE to parse through it either.

Also, what does speaker dB sensitivity actually mean?

http://www.audioholics.com/loudspeaker-design/loudspeaker-measurement-standard/sensitivity

First sentence:

Loudspeaker sensitivity is a measure of sound pressure level at a given distance when a specific sinusoidal voltage is applied across the loudspeaker terminals.

I'd like to know how much power my receiver actually uses at quiet, "normal", and loud volumes, on a whole, with my speakers.

This little calculator can give you a ballpark idea. I'd stick with "Away from walls" and the anechoic sensitivity to be conservative. It's also got a chart to give you an idea of how loud a particular SPL is.
http://myhometheater.homestead.com/splcalculator.html

 

[Cygnus]

Thanks guys!

One more question. How does one figure out, as SearchofSub did, that x dB sensitivity = x amount of wattage required?

 

[fuzz092888]

Whatever the sensitivity of your speakers is, that's the db you will get from them at 1m with 1 watt of power. Every time you want to increase the the SPL 3db's (which is generally considered the minimum for you to notice) it requires a doubling of power. You also have db loss as you increase distance. Here's a simple calculator.

Peak SPL Calculator

PS there is also a difference between 1w/1m and 2.83v/1m and it has to do with the nominal impedance of the speakers.

 

[anamorphic96]

SearchofSub is not exactly correct in that you will need 100 watts for an 87db sensitive speaker. Depending in the scenario you may only need 10. What also has to be accounted for is how large the room is and how far away the listener will be seated from the speakers. Then we need to know how loud the person listens to the system. There are many variables that go into matching speakers to rooms.

What most people fail to realize is we use much less power than we would like to think. Granted there can be exceptions to the rule. Most people never use more than 10-20 watts during peaks and less than 3-5 watts for the rest of the content.

 

[fuzz092888]

SearchofSub is not exactly correct in that you will need 100 watts for an 87db sensitive speaker. Depending in the scenario you may only need 10. What also has to be accounted for is how large the room is and how far away the listener will be seated from the speakers. Then we need to know how loud the person listens to the system. There are many variables that go into matching speakers to rooms.

What most people fail to realize is we use much less power than we would like to think. Granted there can be exceptions to the rule. Most people never use more than 10-20 watts during peaks and less than 3-5 watts for the rest of the content.

If things took as much power as some people would have you believe, I'd never be able to run all my equipment off of 2 15amp circuits, but I do and they never trip even though I can hit about 115dbC easily.

Obviously it also depends on the speakers and levels, like Gene's Status monsters need a little bit of oomph behind them to get everything out of them.

 

[anamorphic96]

With my Denon 1911 I can hit 104db at my listening distance of 11' with 90 watts according to the calculator. My speakers are 85db sensitive.

Considering I only hit peaks in the low to mid 90's I'm in ok shape for power.

 

[Ampdog]

Cygnus,

OK, as Fuzz ... indicated, the answer to your last question is in point 1 of that reference. Sensitivity and efficiency is related, only sensitivity also involves the angle of radiation of the loudspeaker.

But as you might have picked up by now, the answer to your original question is not at all easy; the reason being that the intensity of music varies all over the show. Thus there is not really such a thing as matching maximum loudspeaker output to maximum amplifier output. How to view this? If it will help: Music has a low average/maximum energy content. That means that the average energy in music might be some 10% of that of the peaks, which is where one does not want overload resulting in distortion. Also as mentioned previously, hearing acts in a logarithmic fashion. Thus if you need 5W for a small room/cubicle, you will need a 50W for a larger room and 500W for a small hall, other things remaining equal. Furthermore the definition of the maximum rating for a loudspeaker is not standard. (What is certain is that a sustained input, say a sine wave, at the stated maximum rating will burn most drivers out within minutes.)

So where does that bring you? Only within a vary vague area I fear. As was said a 100w+100W stereo amplifier should comfortably deal with a large room with normal efficiency loudspeakers (say some 89 dB) - unless you are hearing challenged or do not mind becoming so! But again keep the log law in mind ! Do not even stress over amplifier output choices of less than factor 2 output rating. (That is 3 dB in technical terms, a quite small increment in loudness.) You could have some difficulty in immediately preferring a 300W amplifier over a 100W model on the basis of maximum available output. Logically that also translates to requiring double the amplifier power for every 3 dB that the loudspeaker sensitivity goes down (again other things like room acoustics remaining the same).

 

[Ampdog]

[Apology for some repitition above; folks reply so fast that when the phone rings, immediately one is 4 posts behind!]

 

[panteragstk]

So how many gees is my rec'r rated for?

I knew someone would do it. I bet it can pull at least .000000000001.

 

[monkish54]

3db's (which is generally considered the minimum for you to notice)

Audible Difference in Sound Level Blind Listening Test

1db difference is actually the minimum the average person can hear. If I concentrate I can hear the difference. The 3db test I get 10/10 every time without the least bit concentration. I think the point where it becomes harder for me to detect is around 1.5-2db. Try it out!

 

[Cygnus]

Thanks for all of the info! This is why I love Audioholics!