[Soundbox]

When you bought a HiFi in the 70's and early 80's it used to tell you the output in Watts RMS. Then came 'music power output' and not to be beaten 'peak music power output' - each doubling up on the first so 2x5 Watts became '40 Watts PMPO'. I remember the stickers with up to 1000 Watts promised!
Now there is no mention of the power at all of average home gear - so what happened? Did people suddenly wise up or did they just not care any more?

[chrisjr]

It's still going on. Though with a slightly different twist.

With surround sound kit, (even from manufacturers you would hope would not play such tricks), it seems commonplace to quote power by driving a single channel only to the max then multiplying by 5 to give the total wattage.

So for example the specs may quote 200W single channel only driven so that means total power output of 1,000W. Or it would but for those pesky laws of physics.

Read the small print at the bottom of the specs and you discover the power consumption is say 350W max. So where do the other 650W come from? The marketing department's imagination most likely. So in real life with more than one channel blasting out you are likely getting just 40-50W per channel flat out not the 200W the headline figure would lead you to believe.

[fmradiotuner1]

My Denon 2310 must be one the better amps as it says 600 watts on the back and does look like it has a decent transformer in.
Its more than enough to drive my other wharfedale xarus speakers.

[soulboy77]

RMS is the worse output measurement invented and really doesn't tell you anything. PMPO is even more of a laugh as is assumes perfect conditons and 100% efficiency which no amp can reach let alone sustain without over stressing the circuitry. The continuous power figure will give a better indication of an amplifier's capability. A true 50W per channel amp is way more than ample for the average room and can easily power higher rated speakers as long as they have decent sensitivity.

Even my old NAD 3020 20W continuous per channel could fill the whole downstairs for parties without triggering the clipping circuitry.

[chrisjr]

Quote:

Originally Posted by fmradiotuner1

My Denon 2310 must be one the better amps as it says 600 watts on the back and does look like it has a decent transformer in.
Its more than enough to drive my other wharfedale xarus speakers.

Not really. It may have a 600W power supply but it claims to be 135W per channel into 6ohms or 945W in total. So still missing a load of watts. Even the 8ohm figure of 105W per channel exceeds the power supply by 135W.

Not as bad as some but still not telling the whole truth.

[chrisjr]

Quote:

Originally Posted by soulboy77

RMS is the worse output measurement invented and really doesn't tell you anything. PMPO is even more of a laugh as is assumes perfect conditons and 100% efficiency which no amp can reach let alone sustain without over stressing the circuitry. The continuous power figure will give a better indication of an amplifier's capability. A true 50W per channel amp is way more than ample for the average room and can easily power higher rated speakers as long as they have decent sensitivity.

Even my old NAD 3020 20W continuous per channel could fill the whole downstairs for parties without triggering the clipping circuitry.

RMS has the distinct advantage that it is a recognised method to measure power in AC circuits. Not perfect but at least if two manufacturers quote RMS into the same load impedance and distortion level the figures are pretty much comparable.

It is surprising just how little power an amp might be poking into the speakers at normal listening levels. It could be in single figure watts per channel in a typical living room.

[Nigel Goodwin]

Quote:

Originally Posted by soulboy77

RMS is the worse output measurement invented and really doesn't tell you anything. PMPO is even more of a laugh as is assumes perfect conditons and 100% efficiency which no amp can reach let alone sustain without over stressing the circuitry. The continuous power figure will give a better indication of an amplifier's capability.

You appear to have totally missed the point - RMS is the best possible measurement system, as it's easy to measure, absolutely obvious what you're getting, and direct comparisons make perfect sense - exactly what you want for a specification.

As for your 'continuous power figure' - that's what RMS is

The full title would be "Continuous watts RMS, both channels driven, at a specified frequency (or range of frequencies) and at a specified amount of distortion" - RMS tells you everything you want to know.

But power isn't everything, it's rare that you ever run more than a few watts in a normal household situation, the extra power means it copes effortlessly with sudden peaks.

[Chris Frost]

Quote:

Originally Posted by Soundbox

When you bought a HiFi in the 70's and early 80's it used to tell you the output in Watts RMS. Then came 'music power output' and not to be beaten 'peak music power output' - each doubling up on the first so 2x5 Watts became '40 Watts PMPO'. I remember the stickers with up to 1000 Watts promised!
Now there is no mention of the power at all of average home gear - so what happened? Did people suddenly wise up or did they just not care any more?

You don't say where you're looking, but a quick look at the sort of places that sell mass market audio gear such as Currys then I'd say the trend is alive and well: 19 out of 20 items listed on the first page of "Home Cinema Systems & Sound Bars" include absurdly high power ratings that are totally unachievable in the real world.

The uneducated, the wilfully ignorant and the gullible still believe this sort of guff. The trend seems to follow whatever are the hot selling products du jour. So soundbars, iPod docks, HTiBs, shelf systems are all fair game. Quality Hi-Fi separates and AV Receivers are (in general) rated more realistically.