RMS, Music Power, Continous Output etc....

[Blacksabbath25]

RMS ratings tend to be considered the benchmark, but sadly they are of little use, they can be so easily manipulated. in fact very little of what the manufacturer gives you is any use at all.

The most useful rating is probably 'peak power', ie the output that an amplifier can sustain without clipping. Sounds simple but specifying the load conditions and the time period that the peak power can be sustained is difficult. Ideally you want an amplifier that can sustain it's peak power for the duration of that peak, then do it again a few fractions of a second later, very difficult to specify and even harder to measure.

Not sure what rms figures you have seen which are manipulated. If the specifications give an rms figure for 8ohms, 4ohms and 2ohms (which they usually do) this gives a good indication of power, especially if the power doubles as the impedance halves. Very rarely do you see manipulated figures from Hi-Fi manufacturers; in most cases the amplifiers exceed their specification when tested.

Which is itself a form of manipulation....! Everyone knows that 'Naim watts' are more powerfull than 'ordinary watts'.

Mostly the figures are manipulated by not being complete. Many mainstream amplifiers are now quoting power into 6 ohms, not 8 ohms as was once considered the norm. They may well deliver the rated power into an 8 (or6) ohm resistor, but a real world speaker like a B&W where the impedance drops to 3.2 ohms?

Similarly, how long can they maintain this power? Driving heavily compressed music into a difficult low impedance speaker is quite difficult, many mainstream amplifiers will not cope well under these conditions even though the actual continuous power delivered by the amplifier is way below it's specified continuous power ratings. The power ratings are of little use in these examples.

How can manufacturers get away with this? Simple, in my first post I showed how little continuous power is required by most systems most of the time, as long as the amplifier is only called upon to produce such power, remember 1 watt into an average speaker may produce 87dB spl, already very loud, they will be absolutely fine.

But in more demanding system? Low sensitivity speakers, low impedence speakers, heavily compressed music, a bit of bass boost, higher than average playback levels and pretty soon the amplifier that was doing so well in the previous paragraph is now hideously out of it's depth.

The important thing for anyone coming to this hobby for the first time is to understand how few watts are needed most of the time and how many are required the moment we ask a system to 'do a little more'.

or just buy a abrahamsen amp and problem solved !*biggrin*

The Upgraded Abrahamsen is all about the power supply, it's no secret, just rather expensive.

Yet the Abrahamsen is 'only' 70 watts, amplifiers with the same rating (measured, not claimed) can be had for around one third of the price.

As a user, perhaps you would care to explain why your amplifier is so much better than those of similar power at a much cheaper price?

i did when i first got it *smile*

 

[davedotco]

RMS ratings tend to be considered the benchmark, but sadly they are of little use, they can be so easily manipulated. in fact very little of what the manufacturer gives you is any use at all.

The most useful rating is probably 'peak power', ie the output that an amplifier can sustain without clipping. Sounds simple but specifying the load conditions and the time period that the peak power can be sustained is difficult. Ideally you want an amplifier that can sustain it's peak power for the duration of that peak, then do it again a few fractions of a second later, very difficult to specify and even harder to measure.

Not sure what rms figures you have seen which are manipulated. If the specifications give an rms figure for 8ohms, 4ohms and 2ohms (which they usually do) this gives a good indication of power, especially if the power doubles as the impedance halves. Very rarely do you see manipulated figures from Hi-Fi manufacturers; in most cases the amplifiers exceed their specification when tested.

Which is itself a form of manipulation....! Everyone knows that 'Naim watts' are more powerfull than 'ordinary watts'.

Mostly the figures are manipulated by not being complete. Many mainstream amplifiers are now quoting power into 6 ohms, not 8 ohms as was once considered the norm. They may well deliver the rated power into an 8 (or6) ohm resistor, but a real world speaker like a B&W where the impedance drops to 3.2 ohms?

Similarly, how long can they maintain this power? Driving heavily compressed music into a difficult low impedance speaker is quite difficult, many mainstream amplifiers will not cope well under these conditions even though the actual continuous power delivered by the amplifier is way below it's specified continuous power ratings. The power ratings are of little use in these examples.

How can manufacturers get away with this? Simple, in my first post I showed how little continuous power is required by most systems most of the time, as long as the amplifier is only called upon to produce such power, remember 1 watt into an average speaker may produce 87dB spl, already very loud, they will be absolutely fine.

But in more demanding system? Low sensitivity speakers, low impedence speakers, heavily compressed music, a bit of bass boost, higher than average playback levels and pretty soon the amplifier that was doing so well in the previous paragraph is now hideously out of it's depth.

The important thing for anyone coming to this hobby for the first time is to understand how few watts are needed most of the time and how many are required the moment we ask a system to 'do a little more'.

or just buy a abrahamsen amp and problem solved !*biggrin*

The Upgraded Abrahamsen is all about the power supply, it's no secret, just rather expensive.

Yet the Abrahamsen is 'only' 70 watts, amplifiers with the same rating (measured, not claimed) can be had for around one third of the price.

As a user, perhaps you would care to explain why your amplifier is so much better than those of similar power at a much cheaper price?

i did when i first got it *smile*

I've been away, can you point me at the right thread?

As an old 'electro' fan I am very interested.

 

[Jota180]

RMS ratings tend to be considered the benchmark, but sadly they are of little use, they can be so easily manipulated. in fact very little of what the manufacturer gives you is any use at all.

The most useful rating is probably 'peak power', ie the output that an amplifier can sustain without clipping. Sounds simple but specifying the load conditions and the time period that the peak power can be sustained is difficult. Ideally you want an amplifier that can sustain it's peak power for the duration of that peak, then do it again a few fractions of a second later, very difficult to specify and even harder to measure.

Not sure what rms figures you have seen which are manipulated. If the specifications give an rms figure for 8ohms, 4ohms and 2ohms (which they usually do) this gives a good indication of power, especially if the power doubles as the impedance halves. Very rarely do you see manipulated figures from Hi-Fi manufacturers; in most cases the amplifiers exceed their specification when tested.

An amplifier exceeding the manufacturers rms into 8 Ohm claim is a bit of a con trick so they can say their amp doubles in power whent he impedence halves to 4 Ohms.

For example. A manufacturer claims their amplifier delivers 100 watts into 8 Ohms and 200 watts into 4 Ohms therefore the implication is it's really potent as it doubles it's power as impedence halves but when tested their amplifiers actually puts out 117 watts into 8 Ohms and 200 Watts in 4 Ohms. It's not really doubling as impedence halves.

The manufacturer, by deliberately understating the 8 Ohm rms figure, gives the impression their amp doubles it's power as the impedence halves which is a manipulation in anyone's books.

 

[Blacksabbath25]

RMS ratings tend to be considered the benchmark, but sadly they are of little use, they can be so easily manipulated. in fact very little of what the manufacturer gives you is any use at all.

The most useful rating is probably 'peak power', ie the output that an amplifier can sustain without clipping. Sounds simple but specifying the load conditions and the time period that the peak power can be sustained is difficult. Ideally you want an amplifier that can sustain it's peak power for the duration of that peak, then do it again a few fractions of a second later, very difficult to specify and even harder to measure.

Not sure what rms figures you have seen which are manipulated. If the specifications give an rms figure for 8ohms, 4ohms and 2ohms (which they usually do) this gives a good indication of power, especially if the power doubles as the impedance halves. Very rarely do you see manipulated figures from Hi-Fi manufacturers; in most cases the amplifiers exceed their specification when tested.

Which is itself a form of manipulation....! Everyone knows that 'Naim watts' are more powerfull than 'ordinary watts'.

Mostly the figures are manipulated by not being complete. Many mainstream amplifiers are now quoting power into 6 ohms, not 8 ohms as was once considered the norm. They may well deliver the rated power into an 8 (or6) ohm resistor, but a real world speaker like a B&W where the impedance drops to 3.2 ohms?

Similarly, how long can they maintain this power? Driving heavily compressed music into a difficult low impedance speaker is quite difficult, many mainstream amplifiers will not cope well under these conditions even though the actual continuous power delivered by the amplifier is way below it's specified continuous power ratings. The power ratings are of little use in these examples.

How can manufacturers get away with this? Simple, in my first post I showed how little continuous power is required by most systems most of the time, as long as the amplifier is only called upon to produce such power, remember 1 watt into an average speaker may produce 87dB spl, already very loud, they will be absolutely fine.

But in more demanding system? Low sensitivity speakers, low impedence speakers, heavily compressed music, a bit of bass boost, higher than average playback levels and pretty soon the amplifier that was doing so well in the previous paragraph is now hideously out of it's depth.

The important thing for anyone coming to this hobby for the first time is to understand how few watts are needed most of the time and how many are required the moment we ask a system to 'do a little more'.

or just buy a abrahamsen amp and problem solved !*biggrin*

The Upgraded Abrahamsen is all about the power supply, it's no secret, just rather expensive.

Yet the Abrahamsen is 'only' 70 watts, amplifiers with the same rating (measured, not claimed) can be had for around one third of the price.

As a user, perhaps you would care to explain why your amplifier is so much better than those of similar power at a much cheaper price?

i did when i first got it *smile*

I've been away, can you point me at the right thread?

As an old 'electro' fan I am very interested.

http://Abrahamsen 2up review Right ok had 2 days with this lovely amp of mine the abrahamsen 2up I got it Thursday morning it came well packed and I got it safely without any issues . Bulld quality is amazing with the 2up it's well made nothing plastic on this amp it's all metal construction with 2 brass nobs for volume + input selection , led display in a light blue easy to read display , remote control is very 1970s feel to it all metal finish the bonus was that it works the controls of the marantz CD player which was a bonus for me as I do not have to use 2 remotes only the one . It's a very heavy amp 16kg the back of the amp you have your normal connections for CD player options are balanced inputs XLR or for phono's RCA you can use unbalanced which for me at this time is Aux input useing phono's the rest of the inputs are DVD input not sure why that's on there and some others that I can not think off . Speaker binding post are made out of gold very high quality there are 2 only for the L+R channels there is an input for home cinema I am not sure if this are pre -outs or not ? Sound quality is amazing over the marantz and not saying that the marantz was rubbish or it did a bad job because it's a lovely amp which I will be keeping . The abrahamsen was worth getting I did take a little bit of a risk on buying this amp without demoing first which is important to do so kind of went on gut feeling which did payoff for me The soundstage is very open a lot more then the marantz the sound is very clean and warm not clinical which I hate . you can pickup detail on a songs which I have not picked up before and I no the songs in side out . Guitar stings being plucked , symbols crashes were you can hear the after affects of the crash on the symbols this was the kind of level of detail I was looking for fine detail which even though the marantz is good it could not match that kind of detail . Music separation amazing you hear the instruments separately they are not all blended together like they are with the marantz vocals and instruments have separation with the abrahamsen . Bass is well controlled , fast deep when it needs to be it's like you getting 3 kinds of bass heavy bass , light bass , vocalists bass but separate when the song calls for anyone one this kinds of basses or all 3 but controlled . I found that the treble end on my speakers are more open high sounding like the singer is 6ft but used to be 5ft singer with the marantz Pros Good bulld quality , very clean and natural sound of instruments , great instrument separation , very detailed , great sound stage , warm sounding , a sound that is not tiring remote control works the functions of the marantz CD player Cons No phono stage , no tone controls , you can not bi wire if you wanted too as there are only 1 set of speaker posts , if your useing phono's for the CD player then your input choice is Aux , DVD , tuner inputs so you will have this on the display even though your useing cd , no co- axe , optical inputs unless you have a CD player with balanced inputs then you can use the proper input for the CD player then the display will read cd Was it worth buying yes well worth £899 was it a side ways move no way the abrahamsen amp is in a different class from the marantz and I class it as a good and proper upgrade and recommend one to anyone who's thinking of buying one

 

[davedotco]

Though it doesn't address my question.

Why does a 70 watt amplifier such as the Abrahamsen comfortably outperform mainstream amplifiers with a similar 70 watt rating? I am not talking about underspecified amps, but amps that are genuine measured 70 wpc, so what makes the difference.

 

[gisgillen]

Thanks for all your replys, not sure how the discussion between davedotco and Vladimir was relevant?! but it was fun to read! Sorry to say it was all far too technical for me. Think I`ll stick with my assumption that RMS and continuous power (egontoast) is what I should be looking for. So, just to summarise. My B&W XT4`s sound excellent with my Denon AVR 700AE (80 watts RMS per channel) but I`m a bit scared to turn the volume too high....when I got them a couple of weeks ago the amplifier broke at high volume...but this was due to the fact I wound the speaker wires around instead of threading them through the hole (my stupidity) and there came some sort of short circuit. The amp has since been repaired and all again is fine. I was so relieved the speakers were ok!! Can I turn it up??? How high?? The speakers in the `what hifi´ review are said to love high volumes. Thanks to you all.

 

[tonky]

I see what you mean DDC -But Blacksabbath certainly prefers the sound quality of it compared to his previous marantz 8005 which is what mainly counts I suppose. Large power supply? - I can't explain it though.

tonky

 

[Blacksabbath25]

Though it doesn't address my question.

Why does a 70 watt amplifier such as the Abrahamsen comfortably outperform mainstream amplifiers with a similar 70 watt rating? I am not talking about underspecified amps, but amps that are genuine measured 70 wpc, so what makes the difference.

outperform is a bit strong of a word but I would say with the 3 amps I have owned the abrahamsen does things the same but with better control of the bass and handling of speakers because of the big power supply which I think some of the smaller amps struggle with the sound is coming across a lot clearer then the marantz amps do I think there's less distortion in the abrahamsen then the marantz amps but this would have to be proven by testing which I do not have the no how to do I can only go by what my ears tell me but between the marantz pm8005 and the abrahamsen it's close I just get that little bit extra not in watts but in sound quality and even though the abrahamsen is 70 watts it plenty of power in loudness it feels the room with sound but as you know it has a big power supply which I think it matters as I have an amp that will manage the peaks and the lows of a song with no issues which as you know some speakers Evan if they say 8 ohms they could drop two 2 ohms . Sorry not very good at explaining this but it's worth the £899 and glad I got one

 

[eggontoast]

An amplifier exceeding the manufacturers rms into 8 Ohm claim is a bit of a con trick so they can say their amp doubles in power whent he impedence halves to 4 Ohms.

For example. A manufacturer claims their amplifier delivers 100 watts into 8 Ohms and 200 watts into 4 Ohms therefore the implication is it's really potent as it doubles it's power as impedence halves but when tested their amplifiers actually puts out 117 watts into 8 Ohms and 200 Watts in 4 Ohms. It's not really doubling as impedence halves.

The manufacturer, by deliberately understating the 8 Ohm rms figure, gives the impression their amp doubles it's power as the impedence halves which is a manipulation in anyone's books.

i don't think this ever happens, I certainly haven't seen any specs like this.

Driving the 8 ohm load is 'easy', getting it to double into 4 is where the merits of an amplifier can be gauged, it indicates how big the psu is. Most mainstream manufacturers amplifiers like Arcam, Marantz, Rotel, Musical Fidelity, Naim etc, which I have measured, always meet their specs bang on. NAD amplifier are always conservative with their figures in my experience.

IME if you find a manufacturer has specs in rms, din or continuous ratings, they will meet those specs. If other terms like music, peak or some other unit of power has been used, it's likely to be a POS and best avoided.

 

[Electro]

Though it doesn't address my question.

Why does a 70 watt amplifier such as the Abrahamsen comfortably outperform mainstream amplifiers with a similar 70 watt rating? I am not talking about underspecified amps, but amps that are genuine measured 70 wpc, so what makes the difference.

A 1000va transformer , around 100 amps or more peak current delivery, 100,000uf capacitance , 12 output devices and almost unlimited transient power so it is very unlikely that it will ever clip with even with the most demanding speakers or music, stable into loads down to 0.5 of an ohm .

Vladimir calculates the figures below are also relevant but you will be able to shed more light on that than I can *scratch_one-s_head*

In your case 560Wpc RMS in 1 ohm transients. In 20ms transients the 300J PSU can deliver total of 15,000W.

Probably sounds better than most 70 watters too. *biggrin*

 

[Vladimir]

PSU:

E = ½ * C * V² = 0.5 * 0.1F * 80V² = 320J

P = E / t = 320J / 0.02s = 16,000W

Power output:

70Wpc in 8 ohms, 140Wpc in 4 ohms, 280Wpc in 2 ohms, 560Wpc in 1 ohm.

12 output devices with max 150W each = 1,800W RMS max (900Wpc).

I relly can't think of a loudspeaker that will completely drain that PSU in the 70W Abe regardless of impedance drop and phase shift in transient peaks. It's limited to 70Wpc in 8 ohms because of the small heatsink. You can't push all that power constantly like you would with large touring amps, but for music at home it will do brilliantly.

 

[Blacksabbath25]

PSU:

E = ½ * C * V² = 0.5 * 0.1F * 80V² = 320J

P = E / t = 320J / 0.02s = 16,000W

Power output:

70Wpc in 8 ohms, 140Wpc in 4 ohms, 280Wpc in 2 ohms, 560Wpc in 1 ohm.

12 output devices with max 150W each = 1,800W RMS max (900Wpc).

I relly can't think of a loudspeaker that will completely drain that PSU in the 70W Abe regardless of impedance drop and phase shift in transient peaks. It's limited to 70Wpc in 8 ohms because of the small heatsink. You can't push all that power constantly like you would with large touring amps, but for music at home it will do brilliantly.

there's plenty of power I thought I would have to add a power amp to the abrahamsen but do not need to as it goes as loud as I want it too but not sure what it's knocking out at 50 on the volume is that 50 watts ? As I used to use the marantz around the 10 o'clock or 11 o'clock volume is that about the same .

 

[Vladimir]

I doubt 50 indicates watts. It's likely 50% on a logarhytmic scale. Even when loud you are probably not using more than just few watts. Only in transients the speakers will draw more power.

Also they probably have different input sensitivity.

 

[Andrewjvt]

It was either that or hiking. It's a bit nippy outside.

Do you live again?

Where do I live?

I know its europe somewhere. Or am i being nosy? Just curious as to the hiking

 

[Vladimir]

It's no secret on the forum. I'm in Macedonia, South-East Europe.

 

[tonky]

Where did you learn such good english? - if you don't mind me asking

regards tonky

 

[Vladimir]

School, travel and work mostly. Hollywood brainwashing too probably.

 

[Jota180]

An amplifier exceeding the manufacturers rms into 8 Ohm claim is a bit of a con trick so they can say their amp doubles in power whent he impedence halves to 4 Ohms.

For example. A manufacturer claims their amplifier delivers 100 watts into 8 Ohms and 200 watts into 4 Ohms therefore the implication is it's really potent as it doubles it's power as impedence halves but when tested their amplifiers actually puts out 117 watts into 8 Ohms and 200 Watts in 4 Ohms. It's not really doubling as impedence halves.

The manufacturer, by deliberately understating the 8 Ohm rms figure, gives the impression their amp doubles it's power as the impedence halves which is a manipulation in anyone's books.

i don't think this ever happens, I certainly haven't seen any specs like this.

Driving the 8 ohm load is 'easy', getting it to double into 4 is where the merits of an amplifier can be gauged, it indicates how big the psu is. Most mainstream manufacturers amplifiers like Arcam, Marantz, Rotel, Musical Fidelity, Naim etc, which I have measured, always meet their specs bang on. NAD amplifier are always conservative with their figures in my experience.

IME if you find a manufacturer has specs in rms, din or continuous ratings, they will meet those specs. If other terms like music, peak or some other unit of power has been used, it's likely to be a POS and best avoided.

This does indeed happen and the figures I quoted were taken from a test done by an American HiFi review.

 

[davedotco]

Thanks for all your replys, not sure how the discussion between davedotco and Vladimir was relevant?! but it was fun to read! Sorry to say it was all far too technical for me. Think I`ll stick with my assumption that RMS and continuous power (egontoast) is what I should be looking for. So, just to summarise. My B&W XT4`s sound excellent with my Denon AVR 700AE (80 watts RMS per channel) but I`m a bit scared to turn the volume too high....when I got them a couple of weeks ago the amplifier broke at high volume...but this was due to the fact I wound the speaker wires around instead of threading them through the hole (my stupidity) and there came some sort of short circuit. The amp has since been repaired and all again is fine. I was so relieved the speakers were ok!! Can I turn it up??? How high?? The speakers in the `what hifi´ review are said to love high volumes. Thanks to you all.

To some extent the point of the argument was to show that the specified power rating, be it rms, peak or whatever is all but meaningless in itself. To make real sense of it you need to know a little about how things work to give context and some experience to work out what this means to you and your setup.

To put this simply, an amplifier may produce 80 watts into an 8 ohm resistor, a perfect, easy load, but produce far less power into a 'real world' loudspeaker whose load is far from easy. Mostly the ability to drive complex loads is a function of the power supply size and quality, hence the frequent mention of the Abrahamsen amplifier which has a 70 watt rating but a power supply bigger than most AVRs boasting 5 x 150 watts rms (or more).

This brings us on to the subject of volume and how far you can turn things up. The first thing to understand is that the setting of the volume control is no indicator of the power actually being used.

For most people, most of the time, 50-80 watts is ample power, way more than they will need but the moment you ask a system to do a little more then power requirements increase exponentially.

Speakers with a low sensitivity, a 'difficult' impedance curve, music with a wide dynamic range (classical and acoustic music generally) can easily be clipping the amplifier at quite modest levels, low dynamic range (most moderm pop, rock, dance etc) use up masses of continuous power which can be easily made worse by adding a bit of bass boost for example.

Generally you have to use your ears and your common sense. If, it sounds very loud and is starting to sound harsh at around 11 o'clock, then that is the maximum you can use for that type of music.

 

[gisgillen]

Hi again. I`ll try and finish here!!! So for my B&W XT4`s, which apparently need power. The Cambridge Audio Topaz SR20 at 100 watts RMS per channel and 500 euros new (here in Finland) or the Harman Kardon HK 3770 at 120 watts RMS per channel....(and this is in my town) at 450 euros, which includes a 25% discount?? Others have been suggested but are much too expensive..Naim, Exposure, Roksan... Would there be a vast improvement over my Denon AVR-700AE (80 watts RMS per channel). Thanks to all of you, your help has been invaluable...albeit a bit technical for me! PS I do play LP`s and they both have a phono input and the radio is useful. And PPS!!! I would like to know the model of my old B&W`s from the 70`s, how do you attach photos? I`m not great at this lark!

 

[MeanandGreen]

Personally this is what I look for regarding power output.

The power output figure should ideally be quoted as continuous power output at the amplifiers lowest THD, both channels driven across the whole audible frequency range with the impedance load of the speakers I choose to use.

For example my NAD C326 BEE...

Continuous output power >50W at 20hz - 20khz, <0.009% THD at 4 ohms and 8 ohms, both channels driven.

IHF peak power (around 20ms) 100W at 8 ohms, 150W at 4 ohms, 200W at 2 ohms.

I know this is enough for my needs with a pair of 8 ohm 90db/w/m speakers. When being very silly I peak at about 2 watts output.

I personally find NAD spec sheets more informative than anyone else's.

 

[Andrewjvt]

Personally this is what I look for regarding power output.?

The power output figure should ideally be quoted as continuous power output at the amplifiers lowest  THD, both channels driven across the whole audible frequency range with the impedance load of the speakers I choose to use.

For example my NAD C326 BEE...

Continuous output power >50W at 20hz - 20khz, <0.009% THD at 4 ohms and 8 ohms, both channels driven.?

IHF peak power (around 20ms) 100W at 8 ohms, 150W at 4 ohms, 200W at 2 ohms.?

I know this is enough for my needs with a pair of 8 ohm 90db/w/m speakers. When being very silly I peak at about 2 watts output.?

I personally find NAD spec sheets more informative than anyone else's.?

?

 

Total disclosure power. Also spec the dynamic short burst power