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Old 22nd March 2010, 06:26 PM   #1
Mooly is offline Mooly  United Kingdom
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Default So how much power do you really need for domestic listening ?

So just how much power do you need at home... the next time you are wondering whether to build that 500 watt monster amp.

I recently got my hands on a sound level meter (C weighted) and was (pleasantly) surprised at just how low the levels were that I normally listen too. At the listening position around 70db (average level) is plenty for normal listening. The meter shows around 75db peaks (125ms response)

So that got me thinking... if you have CD with test tones at 0db, a little experiment that's easy to do.

You turn the amp up to what is the loudest you would ever normally listen on a music CD. Stop the CD and disconnect the speakers. Now play the test tone and measure the RMS voltage at the amplifier terminals. Make sure your meter reads AC accurately at the frequency chosen... probably around 100hz is best if your test disc has that. Disconnecting the speaker saves your ears and maybe even the amp as many may not like delivering a lot of power continuosly if the heatsinking etc is marginal.

What does that tell us ?

Well the fact the tone is recorded at 0db (make sure it is), means that that is the maximum signal you can ever get from the CD player. No transient in a music program from CD can ever exceed that level. It's cast in stone.
So lets say the meter showed 10volts RMS. We will also assume an imaginary load of 8 ohm (because you actually measured with no load) for these calculations. We assume the amp would maintain it's output when loaded.
So 10 volts RMS across 8 ohm is (10*10)/8 which is 12.5 watts RMS. That implies that an amp rated at that output would in fact deliver all you ask of it, cleanly and with no clipping.

Following this reasoning my "ideal" target amplifier would be around 20 to 30 watts RMS. Once you reach that level then it takes a relatively large increase in power to get a "noticeable" increase in volume. A doubling of power gives a 3db increase which is not as noticeable as you think and certainly not twice as loud. With my speakers which are rated at 90db efficiency for 1 watt, that implies a max peak level of around 102 to 105 db. The average of course would be far lower, and not only that, these measurements are based on 0db or maximum output from the CD player being reached on music program which is unlikely.

So what's your ideal power rating for an amplifier ? How loud do you really listen ?
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Old 22nd March 2010, 06:55 PM   #2
Glowbug is offline Glowbug  United States
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Totally depends on the speakers

On big Altec multicells, you might not need more than a 45 triode amp on the horns...for full-size Maggies, you might need that pair of bridged Crown beasts
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Old 22nd March 2010, 07:20 PM   #3
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Don't forget that you need the headroom for the dynamics, not the steady state level. If your average is 70 dB, you can easily get 85-90 dB peaks so your power requirement may have increased by more than a factor of 10.
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Old 22nd March 2010, 07:22 PM   #4
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It's like a delinquent raper , when you know he's gonna make it again ,he should be evirated not to get compulsed to do that again! Same for amplifier's power-ie listening levels- once you settle down and you know that you won't disturb anyone else like you did in the past (mostly with bad distorting amps )...well,it depends from many things : a certain power reserve might lift your mood sometimes ,you'll never know ....
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Old 22nd March 2010, 07:25 PM   #5
Gyuri is offline Gyuri  Hungary
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Fundamental question, what the neighbours say to all of this!

Gyuri

I pester you again already somewhere else, kind pico!
You know it because I am an ugly, evil, bearded, bald little old man, who got drunk moreover yet,.
no, because of that not so much after all.
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Last edited by Gyuri; 22nd March 2010 at 07:34 PM. Reason: Private message for a friend, excuse me.
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Old 22nd March 2010, 07:27 PM   #6
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by fastbike1 View Post
Don't forget that you need the headroom for the dynamics, not the steady state level. If your average is 70 dB, you can easily get 85-90 dB peaks so your power requirement may have increased by more than a factor of 10.
Yes... but those transients are set by the max output of the CD player (say 2v RMS at Odb) and the setting of the volume control at "your loudest" listening volume.
That's where the rough and ready meter and test CD comes in. At the highest volume I would ever use the peaks would not exceed 105db. They couldn't because that measurement is taken using a 0db test track which sets the max possible level.
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Old 22nd March 2010, 07:31 PM   #7
wahab is offline wahab  Algeria
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I use a 3 channel amp , 2 X 5W + 10W for the basses.
My speakers s efficency is 90db/1W/1m..
This is vastly enough, even for loud listenings levels..
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Old 22nd March 2010, 07:34 PM   #8
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by wahab View Post
I use a 3 channel amp , 2 X 5W + 10W for the basses.
My speakers s efficency is 90db/1W/1m..
This is vastly enough, even for loud listenings levels..
Exactly what I find. Your speakers are the same efficiency as mine too.

And I'm sure your ears appreciate it too...
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Old 22nd March 2010, 07:36 PM   #9
Svein_B is offline Svein_B  Norway
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The method proposed is a nice one to get an indication of power requirement.

However, not all CD's (which you would use to determine your comfort level) are recorded with the same level. You may therefore find that you like to listen to some CD's with the volume control at 11 o'clock, but others at 3 o'clock. This will give drastically different levels when you insert your 0 dB disc.

Type of music, ambient noise, mood, etc may also influence your preferences.

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Old 22nd March 2010, 07:46 PM   #10
Gyuri is offline Gyuri  Hungary
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I agree with the above one totally.
The exact method would be the application of a sound pressure gauge otherwise, in the listener's distance and his head altitude.
Everything else only misleading, and totally system pendant,
including the neighbours.
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