General Forum

Re: Beolab 5 power output

bayerische — Wed, 05 Nov 2008 14:11:28 GMT

Again something I didn't know!

This site is awesome!

Re: Beolab 5 power output

Craig — Wed, 05 Nov 2008 14:01:41 GMT

Christian:
To my knowledge a 10 A fuse does not blow immediately if you draw more than 10 A from it. In fact, IIRC, you can draw 12 A for half an hour, 15 A for couple of minutes and 20 A for a couple of seconds, before the fuse blows.

Correct, a few years ago at work we had a problem at work where we were blowing one of the main fuses. It was rated at 630 Amps, the distribution board had a built in Amp meter. We found it would have to run at around 1200 amps for around 20-30 mins before it would blow. It could run at around 800 for around 90 mins.

Craig

Re: Beolab 5 power output

Puncher — Wed, 05 Nov 2008 13:54:42 GMT

bayerische:

Christian:
To my knowledge a 10 A fuse does not blow immediately if you draw more than 10 A from it. In fact, IIRC, you can draw 12 A for half an hour, 15 A for couple of minutes and 20 A for a couple of seconds, before the fuse blows.

Sounds like a long time... What's the idea with a 10A fuse then?

Christian is correct - a fuse blowing time is a function of the Inverse of the current squared (as current squared is proportional to heating of the fuse element).

Re: Beolab 5 power output

bayerische — Wed, 05 Nov 2008 13:33:07 GMT

Christian:
To my knowledge a 10 A fuse does not blow immediately if you draw more than 10 A from it. In fact, IIRC, you can draw 12 A for half an hour, 15 A for couple of minutes and 20 A for a couple of seconds, before the fuse blows.

Sounds like a long time... What's the idea with a 10A fuse then?

Re: Beolab 5 power output

Christian — Wed, 05 Nov 2008 13:28:08 GMT

To my knowledge a 10 A fuse does not blow immediately if you draw more than 10 A from it. In fact, IIRC, you can draw 12 A for half an hour, 15 A for couple of minutes and 20 A for a couple of seconds, before the fuse blows.

Re: Beolab 5 power output

bayerische — Wed, 05 Nov 2008 11:49:45 GMT

Thanks to Mika and David for making me wiser.

OK, so the amps work in a different matter than the normal transistor stage which apparently "idles" at full power all the time. The ICE amps will only draw the current when needed. Opposite of my Pathos amp that drew almost 1kW whether I was listening at 40dB, 90dB or didn't listen at all.

This was interesting and educating. But still the fact remains, that if it was possible to run the speakers at the amps limits (2500W) per speaker for a longer (say several seconds) and they would draw the whole 5000W the fuse would blow, unless I have a 25amp fuse .

The old wirings would probably melt, and I would have a fire inside my walls.

Re: Beolab 5 power output

Russ — Wed, 05 Nov 2008 11:48:59 GMT

Before jumping into the B&O universe, I spent about 12 years in high-end car audio (yes there really is such a thing!) Dave is, of course, quite correct...but allow me to see if I can simplify the issue for us all.

Most tweeters, egardless of 'style' don't use more than about 20watts to achiecve continuous full volume output,,the rest is dissipated as heat (one hopes, otherwise...'poof1'). And indeed most folks listening at home, at reasonable levels probably rarely exceed 40 watts or so, if that, on a continuing basis...so where is the need for all of the power the BeoLab 5 can produce? Dynamics.

There is an apocryphal story that many years ago, doing research (as teaching engineers are wont to do), a certain Doctor Bose ofr the Massachusetts Institute of Technology, discovered that to accuratle reproduce the sound a pair of scissors makes when cutting into a piece of paper would require approximately 4000 watts! Not for very long, mind you...milliseconds at most...but nonetheless...there we are.

Imagine what might be needed to reproduce a finger-snap...or a snare drum!

The immense power available to the BeoLab 5 is not really intended to produce hours of jet-engine level pink noise...it is intended to reproduce the micro-dynamics present in live performances at believable levels.

But not to worry about your fuse box.

We're talking milliseconds.

Re: Beolab 5 power output

Puncher — Wed, 05 Nov 2008 10:47:30 GMT

Dave Moulton:
VERY briefly:

In the US, where mains voltage is 110, 2500 Watts (per speaker) draws approximately 23 amps of current. IN THEORY, a 20 amp breaker would trip when such a current was called for. So, the question is a valid one.

In order to fulfill the call for 2500 Watts of electrical power (drawing those 23 amps of electrical current), the speaker must maintain a current reserve, and ONLY provide 2500 Watts for VERY brief periods, until that current reserve is exhausted. This is the purpose of the large transformers provided - to maintain sufficient current reserve for such brief power demands.

In music, such calls for power happen with extreme transients, which will typically be 20 dB (100 x power) greater in amplitude than the on-going level. That said, I suspect the on-going power consumption of 1 Watt total output (divided among 4 amps in the speaker, remember) is probably something like 85 dB SPL at 1 meter from the front of the speaker. This would mean that 1 kWatt would yield 115 dB SPL, and 2.5 kWatts will yield something like 119 dB SPL, which sounds about right, based on my measurements.

The implication is that the maximum average level (for ONE speaker @ 1m) would be about 100 dB SPL, if we kept 20 dB of headroom. with the occasional transient peaking 20 dB above that. (In reality, we often have less than 20 dB headroom.)

This is where it begins to get a little trickier. Two speakers combine to create an amplitude of about 4 dB greater (104 dB SPL), and room gain (the additional level caused by the room folding energy back into the space) adds approximately another 6 dB, so two speakers will yield a level of about 110 dB SPL with peaks much greater than 120 dB SPL in a typical small or medium-sizd room. The factory gently claims an upper limit of about 108 dB SPL average at 3 meters in stereo, playing music in a reverberant room.

Back to the question of current, at an average level of 20 dB less than full power for two BeoLab 5s, the power will be 50 Watts continuous, for a current draw of about .45 amps, with brief surges up to several amps. This will be yielding, as noted above, a continuous level of approximately 105-110 dB SPL, which is more than enough for all but the most obstreporous parties! And it's not likely the trip the breakers!

I hope this helps!

That's what I meant!

Re: Beolab 5 power output

Dave Moulton — Wed, 05 Nov 2008 10:43:53 GMT

VERY briefly:

In the US, where mains voltage is 110, 2500 Watts (per speaker) draws approximately 23 amps of current. IN THEORY, a 20 amp breaker would trip when such a current was called for. So, the question is a valid one.

In order to fulfill the call for 2500 Watts of electrical power (drawing those 23 amps of electrical current), the speaker must maintain a current reserve, and ONLY provide 2500 Watts for VERY brief periods, until that current reserve is exhausted. This is the purpose of the large transformers provided - to maintain sufficient current reserve for such brief power demands.

In music, such calls for power happen with extreme transients, which will typically be 20 dB (100 x power) greater in amplitude than the on-going level. That said, I suspect the on-going power consumption of 1 Watt total output (divided among 4 amps in the speaker, remember) is probably something like 85 dB SPL at 1 meter from the front of the speaker. This would mean that 1 kWatt would yield 115 dB SPL, and 2.5 kWatts will yield something like 119 dB SPL, which sounds about right, based on my measurements.

The implication is that the maximum average level (for ONE speaker @ 1m) would be about 100 dB SPL, if we kept 20 dB of headroom. with the occasional transient peaking 20 dB above that. (In reality, we often have less than 20 dB headroom.)

This is where it begins to get a little trickier. Two speakers combine to create an amplitude of about 4 dB greater (104 dB SPL), and room gain (the additional level caused by the room folding energy back into the space) adds approximately another 6 dB, so two speakers will yield a level of about 110 dB SPL with peaks much greater than 120 dB SPL in a typical small or medium-sizd room. The factory gently claims an upper limit of about 108 dB SPL average at 3 meters in stereo, playing music in a reverberant room.

Back to the question of current, at an average level of 20 dB less than full power for two BeoLab 5s, the power will be 50 Watts continuous, for a current draw of about .45 amps, with brief surges up to several amps. This will be yielding, as noted above, a continuous level of approximately 105-110 dB SPL, which is more than enough for all but the most obstreporous parties! And it's not likely the trip the breakers!

I hope this helps!

Re: Beolab 5 power output

Puncher — Wed, 05 Nov 2008 10:29:42 GMT

tournedos:
Puncher:

Average continuous input power, at normal listening levels, in a "normal" room may well be around the 40-50W region. There is nothing contradictory here.
I came up with another way to visualize this. Say you have a "conventional" amplifier with a 2x80W rating. When was the last time you routinely kept the volume higher than halfway (meaning something in the ballpark of 2 x 5-10W power output, given the logarithmic nature of audio power)? Not in my flat you don't
I believe the 40W is the idle power consumption of the Beolab 5 when it's "on" (and that's very little for an amp with this amount of reserve). All music power will be on top of that, but with much greater efficiency than "normal" linear amps.
Last winter I sold my old Pioneer A-9, rated at 2 x 110W as I recall. Its maximum input power was rated at 820W!

............... or you could say that a 5KW PA system would suffice for a live band in a small college-type venue of several hundred people - certainly louder than you'd tend to listen at home

Re: Beolab 5 power output

tournedos — Wed, 05 Nov 2008 10:01:04 GMT

Puncher:
Average continuous input power, at normal listening levels, in a "normal" room may well be around the 40-50W region. There is nothing contradictory here.

I came up with another way to visualize this. Say you have a "conventional" amplifier with a 2x80W rating. When was the last time you routinely kept the volume higher than halfway (meaning something in the ballpark of 2 x 5-10W power output, given the logarithmic nature of audio power)? Not in my flat you don't

I believe the 40W is the idle power consumption of the Beolab 5 when it's "on" (and that's very little for an amp with this amount of reserve). All music power will be on top of that, but with much greater efficiency than "normal" linear amps.

Last winter I sold my old Pioneer A-9, rated at 2 x 110W as I recall. Its maximum input power was rated at 820W!

Re: Beolab 5 power output

Puncher — Wed, 05 Nov 2008 09:34:18 GMT

I really don't see a question - the speakers can play at exceptionally high SPL's with very, very low distortion - the amps have huge reserves of power to ensure distortion free transients.

Average continuous input power, at normal listening levels, in a "normal" room may well be around the 40-50W region. There is nothing contradictory here.

Re: Beolab 5 power output

Santiago — Wed, 05 Nov 2008 09:32:42 GMT

bayerische:
Yes, the specification poster of the speakers speaks of a nominal consumption of 40W per speaker, which I can believe and imagine, since usually you are not listening at full volume, but rather a comfortable background level.

I've listened my 5.1 full B&O (BL2+2xBL1s+2xBL3s+avant) at full volume (72) several times during long time in the last 7 years; and those almost 3.000watts of audio power are ALL plugged in only ONE standard plug in the lounge, with a standard fuse that NEVER has blown

in addition in this same plug/fuse are also connected: HDR2, 2xDVD players, 1VHS, 6x60w lights,1 LC2, 1DVD-controller, and finally the BS9000.

However, some other fuses in my home blow out sometimes (iron, toaster, microwave, electric oven and heater, etc...)

So bayerische, don't worry for your home plugs and fuses and push your BL5s to maximum if you want

Re: Beolab 5 power output

tournedos — Wed, 05 Nov 2008 09:32:42 GMT

bayerische:
I'm wondering how it's possible for my Beolab 5's to have a combined maximum output of 5000W.
I mean at what point will 5000W or 2500W per speaker be necessary?
I read somewhere that the ICE amp. is about 95% effective, which is incredible, but that would still mean that it would need to get from the mains 5250W total in order to produce the 5000W?

Well, the Labs don't have an inbuilt nuclear power generator or something, so they will definitely get all (and then some) of the output power from the mains outlet. That maximum output would require a signal that loads all amplifiers to the max - if you use your Labs for listening music instead of driving vermin out of the county or something, most of the power would be taken out from the bass amps. Then again music is peaks and not sine wave test signals, so the average power used would be way less again. I'd be suprised if driving two Lab5's to the clean limit with real music would add to more than 2 kilowatts, or something like the power consumed by your coffee brewer.

No normal mains in a home will be able to give 5250W. The fuses and probably cables will burn up before that...

From now on, I will switch to Finnish mode since I don't know the electrical regulations elsewhere (I do know that they are completely different in, say, UK).

Currently the maximum fuses you can have feeding a wall outlet is 16A if they are wired with at least 2.5 mm2 cabling (1.5 mm2 wiring can be used after a 10A fuse). That would give a maximum continuous power you can pull from a socket 230V * 16A = ~3.7 kilowatts. This should be more than enough - the household fuses are usually of the slow type (to allow for startup peaks of motorized appliances like vacuum cleaners, washing machines etc) meaning you can even momentarily exceed the maximum current.

The "digital" amplifiers in the Labs are far more efficient than common linear amps, and so they can run at the 40W nominal power at idle and put out the kilowatts in an instant when required. But all the power has to come from the wall plug - the ratings in the picture seen above are real electrical power, nothing imaginary.

Re: Beolab 5 power output

PhilLondon — Wed, 05 Nov 2008 09:21:49 GMT

bayerische:

Right, but power is equal to Joule?

As wikipedia says, power is expressed in Watt, not Joule, A Watt is equal to joule per second.

Distance (meter) is not the same as Speed (meter/second), right?