Watts! How many do we need?

@ghdprentice  I assume it makes a great deal of difference on the individual speaker you are using.  I've always heard there is a difference between "tube" watts and SS watts.  On this very sight I have read that tube watts are roughly 3 times as powerful as SS watts.  To this end I've found this lengthy article penned by Roger Sanders to be quite interesting.  Especially as I am driving a set of SoundLab Majestic 745's.  Cheers.  

https://sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors

This is a portion of the text taken from Roger Sander's white paper on amp power requirements.  I found it to be very interesting and it appears to be pertinent to this discussion?  Take it away Roger:

"To see what is going on with an amp when playing music only requires an oscilloscope.  These are very fast (the slowest ones will show 20 MHz) and will clearly show amplifier peak clipping when music is playing.  A meter is too slow to do so.  A 'scope is cheap (you can get them for $100 on eBay all day long).  So you don't have to take my word for what I am about to explain.  Feel free to get your own 'scope and examine your system's performance.

You simply connect the 'scope across your speaker or amplifier terminals (which are electrically the same), adjust the horizontal sweep as slow as you can while still seeing a horizontal line on the screen.  Don't go so slowly that you see a moving dot.

Now play dynamic music at the normally loud levels you enjoy.  Adjust the vertical gain on the 'scope so that the trace stays on the screen.

As music plays, you will clearly see if clipping occurs.  The trace (which will just be a jumble of squiggly lines) will appear to hit an invisible brick wall.  It will appear as though somebody took a pair of scissors and clipped off the top of the trace.  That's where the term "clipping" comes from.

If you see clipping at the levels you like to listen, then you are not using a sufficiently powerful amplifier to play your music cleanly.  Your system is compromised because your amplifier will have compressed dynamics, sound strained, lose its detail, and have high levels of distortion.

The 'scope will be calibrated so that you will know the voltage at which clipping occurs by observing the grid lines.  If you know the voltage and the impedance of your speakers, you can easily calculate the power.

Power is the voltage squared, divided by the impedance.  So if the 'scope measures 40 volts at clipping, and you are driving 8 ohm speakers, you know that 200 watts are being produced at clipping -- and this is insufficient power for your particular system because it is clipping.

You will find that conventional, direct-radiator (not horn-loaded), magnetic speaker systems of around 90 dB sensitivity, require around 500 watts/channel to avoid clipping.  More power is needed in larger rooms or if you like to play your music more loudly than most.

The key point I'm trying to make is that audiophiles usually are using under powered amplifiers and are therefore listening to clipping amplifiers most of the time.  When an amplifier is clipping, it is behaving (and sounding) grossly differently than its measured performance would suggest. This is because we always measure amplifiers when they are operating within their design parameters -- never when clipping.  A clipping amp has horrible performance, so attempting to measure it is a waste of time.

In other words, we usually listen to an amplifier when it is clipping and we measure it when it is not.  This is why amplifiers sound so different than their measurements would imply.  It is not that measurements are wrong, it is simply that we are listening and measuring different conditions.

It is essential to understand that when an amp is clipping, it will sound quite different than when it is not clipping.  It is also important to realise that different types of output devices (tubes vs. transistors) clip in very different ways, so sound quite different when they are clipping.

Finally, it is important to realise that an amp does not instantly recover from clipping.  It takes several milliseconds for its power supply voltage to recover, for it to recharge its power supply capacitors, and for its internal circuitry to settle down and operate properly again.  Therefore, even though an amp may only be clipping on the musical peaks, it will not immediately operate properly at average music levels where it is not clipping."

I suspect that most of us are not aware of how our amps are truly performing?  I for one have never attached an oscilloscope to my equipment.  

The full article can be found here:

https://sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors

@mlsstl  I'll be the first to admit how little I know about much of this hobby.  I believe what Sanders is trying to get across is the fact that many people are oblivious to the fact their amps may be clipping and are under powered, and that their system could sound even better with a higher powered amp?.  I suspect you don't need to be playing at excessive volume to be stressing an amp.  I think, and correct me if I'm wrong, that the load the speaker presents to the amps has a lot to do with it.  I owned a pair of Acoustic Zen Crescendo Mark ll.  When you look at the impedance graph, that speaker is almost a flat line at 6 ohms.  Extremely easy on your amp.  My current speakers are the opposite.  Dipping as low as 1 ohm which is a punishing load.  Luckily my amps are stable at 1 ohm.  In summary, I found the Sanders article very interesting and will assume he knows a lot more about this than I do. I don't think it ever hurts to read the lengthy papers written by the designers and builders.   Cheers, 

@immatthewj   Actually, all watts are the same.  There's a scientific calculation that defines a watt.  It's all the other stuff that makes the difference.   

@immatthewj   I think that Sanders covered this question fully in his paper?  

Beyond my paygrade.  We should all buy and listen to what we like.  There is no one right answer when it comes to amp power.  As pointed out in several comments, which I agree with, there are many factors that determine the proper combination of equipment.  I can only say that with my speakers, a low powered amp is not that correct equipment.  Cheers.

@immatthewj  Scroll up about 15 posts and you will see I pasted a potion of the paper and included a link to the full paper.  Sanders does a good job explaining the perceived difference in tubes and SS, and why many systems may be underpowered.   Once again, I am assuming he knows what he is talking about after designing and building amps and speakers for decades.   For me anyway, he calls into question all the members who claim only fhe first watt is important and that 50 watt amps are all you need.   Read the whole paper and tell me what you think.  Cheers. 

@dogearedaudio   You are correct that Sanders is speaking about ESL for the  most part.  I listened to your attached file.  Very interesting.  I would suggest you could start at the 25 min mark as he doesn't really get into the meat of the subject before that.  Incredibly knowledgeable guy.  Kind of funny how many of the amps his own company produces are in the 50 - 100 watt range when 5 watts is sufficient for 95% of speakers and 99% of listening rooms (I think I got that right).  Anyway, a good listen for sure.  I liked his comment that we should all start by choosing our speakers first and then work backwards to the right amp.  Maybe that's why I liked the Sanders paper as I am running very large panel speakers.  Cheers.