How loud is it???

Question

Can anyone tell me how loud 400 RMS please. I am buying a new stereo and the one that I like the look of and am thinking of getting says it has 400 watts total RMS and having no idea whatsoever about technical stuff like that i dont know how loud this would be at full volume?????

Answer 1

400W RMS is a decent amount of power, and will be plenty loud enough.

Always look for the RMS value as "PMPO" is meaningless.

Answer 2

Hi Mate. This is actually a good question. A lot better then the normal "Where can I find free mp3's" that are found on here.

First thing.

1) 400w RMS refers to the average total load the amplifier can sustain. For a home stereo it is quite a lot...so I suspect what you are actually looking at is a home cinema system. Otherwise you are going to get 200w RMS per channel, and that is normally considered daft and dangerous for home use. If you split the power over 5 channels you get 80w RMS, which is more reasonable.

2) In terms of percieved loudness it is quite tricky to rate, because there are so many factors that affect how we hear sound.
The first problem is the conversion of Watts to dB. the Db is just a log relationship of power, and itself has no meaning. the dBW inplies a power.

so in this case dBW = log (400/1). I don't have my calculator with me to work this out for you. And the above equation is for a milliWatt. So you will actually need to divide by 100 instead of 1 to compensate the gain factor between a mW and a W.

And lastly loudness also depends on how close you are to the speaker or source. In most situations a doubling of the distance loses around 1/2 of the percieved level.

Answer 3

'Watts' do not measure how loud something is.
'Decibels' measure how loud something is.

There are too many variables to give you a direct answer to your question.
A well built, high quality amp with decent cables, running into high efficiency speakers, will sound phenomenally loud at 400 watts.
A poorly built, low quality amp with cheap cables, running into low efficiency speakers, will sound utterly feeble at 400 watts.

Additionally, how is that 400 watts measured? Yes, the RMS figure is the industry standard, but many companies still quote it at 10% THD (total harmonic distortion), to make them sound more powerful than they really are. My guess is, that your "400 watt" amp is rated at 10% THD.

The correct figure is 0.1% THD - you can actually HEAR the distortion when it gets to 1.0% THD. So in reality, your amp is probably around 100 watts total power (i.e. 50 watts per channel).

Since you refer to a 'stereo', rather than a hi-fi amplifier, I'd say you are looking at complete cheapo system for less than £500, rather than a top quality amplifier (over £3,000). If that's the case, the 400 watts you have seen quoted is utterly meaningless...

Answer 4

Root Mean Square is the real power of the device so 400W is a very, very powerful amplifier. A 30W amp is enough to drive a couple of speakers reasonably well.
PMPO (peak music power output) is the retail way of making amplifiers sound better with bigger numbers.

Answer 5

That will be very very loud!
Look for a figure around 30 to 50 for the average house.