Watts! How many do we need?

Current and output impedance are important as well. Paul from PS Audio gives a good explanation here.

 

@dogearedaudio 

My point was that I have seen systems so expensive, so complicated and striving for so much power and scale that they become unmanageable for the owner.  They're often difficult to listen to as well.

Point taken. But in this context we are talking about modern power amps/integrated amps that put out high-current, 300 wpc plus into a pair of small to medium size speakers. And in the case of Harbeth's, were designed/voiced for SS. 

Conversely, I'm hoping to put together a much lower powered tube system again when circumstances allow it, but maybe with some vintage Tannoy's or similar. (I owned a 35wpc Raven Audio Osprey that was oh so sweet sounding - I miss it)

No question both high-power and low-power strategies can sound fantastic when the synergy is right. 

Sanders has a vast knowledge I have some of his amps and speakers they are great.  As stated power is volts x amps.its the transients that take alot of watts.its the clipping that causes damage to speakers.it is well known esl take alot of power but big cone speakers do also. Some speakers are efficient that's why the reference 1 watt produces spl sound pressure level. As a standard to compare. There has to be some relationship to reference to be marketable.i have read some high powered amps don't play well at low volume but I have not experienced it. The class d amps are getting better and have alot of watts for lower price.they are put in many speakers these days.i like big speakers because I have the room.the huge watts bring them alive.i have alot of esl and planars from many decades.alot of speakers are putting ribbons in now.some of them have 32 ribbons each and require lots of power.paul mcgowen put a 1k watts each speaker into each of his irs v woffer tower they have 6 each colum.enjoy what you have and the music.stay healthy

@bigtwin Your explanation was super helpful, thank you! It's why it's worth coming here....

Your speakers are not as hard to drive as sensitivity of 85-86 db. You don’t deep under 5-6 ohms. Big speakers like Wilson’s that are dipping into the 1.6-1.5 ohm range need a way more powerful amp even if they have a 91db sensitivity.

Digital metering with a peak hold function is more accurate than physical meters.

P=I squared R or V squared/R It is hard to get away from the fact that current and power are extremely closely related. You know an amp has an adequate power supply if it doubles down to 2 ohms. 

There is no such thing as too much power. How much power is adequate depends on the speaker and listening habits of the individual. Since every 3 dB doubles the power requirement power requirements increase dramatically with volume. To get bass at realistic levels and depth always requires a lot of power especially if room correction is utilized, in the thousands of watts. 

From my experience with solid state, current was the primary determinant if the amp was up to the task, the more the better. From my tube amp experience, it is far, far less important. So I went from high current 350 wpc solid state to 70 wpc tube amplification and my system sounds so much better it is amazing. It is a high quality amp… I am sure there is a difference between 70 wpc with an inexpensive light weight tube amp and a good one.

@ghdprentice 'Current' in the way you describe it above has little or no meaning. You might want to read this article which explains why.

@jfrmusic If you need over 100 Watts to make your speaker really sing, you have a problem- the speaker might be criminally inefficient unless you are in a very large room. The more power you need, quite often the harder it is for the amplifier to sound like real music. Most higher powered amps I've seen simply don't, although they are pretty good at sounding like electronics.

I need 1 to 2.  My amp puts out up to 4.5.   Lots of headroom.

Jerry

Hi @atmasphere,

Thanks for your comment, but I am pretty sure I understand current and how it relates to solid state amplifiers performance characteristics. Sorry, but the article you refer to is so poorly written as to escape making any sense to me, hats off to you if you can understand the techno babble, with a bit of some kind of marketing. I am familiar with ohms law.

 

In the 70’s the power measures of peak watts and then RMS watts were shown to be grossly inadequate. This is when current came into the discussion. This is also when the first high current designed amplifiers were created. The first was the Threshold s series. I purchased the s500 after amp after amp failed to adequately power my speakers. The s500 would produce over 2.5 amps into 8 ohms and much more into lesser resistance. My next amp was a Pass x350 which would develop over 5.5 amps. This I found very amazing as I used an arc welder that produced 6 amps on constructing steel prototypes for work in the mid seventies. Anyway, through these and other high current amps I have used over the decades showed it to be a very positive guide to the solidity and resilience of solid state amplifiers.

I have a bunch, and I’m thinking I use almost all of them. 1000 each in my Legacy IV 2 Amplifier. It runs the Legacy Focus SE’s Mains. 600 each in my 5 channel Legacy IV 5. It runs my Side Phantom’s and Rear Deco's plus the Center Marquis. All are Legacy. Not sure about the 4 subs I have. They are Legacy Foundations and have 1000 each. I invite folks over and we play video Concerts. I try to keep the system humming at 113-115 DB with my Tripplet meter. It’s better than a true live concert. The punch is unbelievable. Favorite is the Eagle’s Farewell tour. Just killer. We are 10 feet back from the soundstage. 65-inch Sony Q-Led does the video. System never heats up, and we always play the entire two-hour concerts. Can lay your hand on the Amps and they are barely warm. Sometimes we pause as I get questions about the system and its impossible to talk. But I USE my system.

He more the better.

there is an openness, a feeling like sleeping in birthday suit,

an ease to the sound, smooth, no clipping, no mumbled distorted passages, 

the amps don’t work too hard, they will,sail along n cruise control doing what they do best.

 

I’ve had small amps, med, large, and,now I’ve learned,when you want to my e air with ease, you need the,power.  
 

sure a 6 w with 991w1m will work, but when you want to rock, you,can’t. 
 

 

Anyone that listen at 113-115db are either def or stupid, or if doing it routinely maybe both?

If you are not def, is it then something you aspirer to be ?

Why would a music lover try to intentionally destroy one’s hearing?

As older we get our hearing for most people deteriorate and unfortunately for many it hinders their ability to function 100% in social gatherings and for some people they choose to redraw a bit from social life.

Also as it is now, there is nothing you can do if getting tinnitus which even is a much bigger problem.

i worry about the younger generation that blast music into their ear canal’s with in-ear headphones, I am guessing that most of them will have big hearing/tinnitus problems before they are 50!

 

Thanks for your comment, but I am pretty sure I understand current and how it relates to solid state amplifiers performance characteristics. Sorry, but the article you refer to is so poorly written as to escape making any sense to me, hats off to you if you can understand the techno babble, with a bit of some kind of marketing. I am familiar with ohms law.

@ghdprentice I'm going with 'apparently not' in this case. The reason, which is pointed out in that article, is that current does not exist without Voltage and the two together make power according to this formula, which is quite simple:

1 Amp times 1 Volt = 1 Watt.

This means that if the amp can make the power, it has the current also. So it makes no difference if the amp is tube, solid state or class D.

When there is talk about current, absent of power, then its nonsense. For example, quite often solid state amps are advertised as having lots of current; not picking on anyone in the industry but I've seen '80 Amps' advertised many times.

Since Power is also (through algebra) equal to Resistance times Amperage squared, let's give the 80 Amps the benefit of the doubt and set Resistance to 1 Ohm. Thus the power is the Amperage squared. In the case of 80 Amps, that's 6400 Watts. To my knowledge there are no amps offered to high end audio that make that kind of power: Amps that make current beyond the power they also make do not exist.

If you think otherwise you are engaging in a myth. That is why I linked the article.

I like the simplicity and purity of the SET. But I also prefer inefficient planar magnetic speakers (Magnepan 0.7 which is all quasi-ribbon because pure ribbons are too fragile). I let a globe 45 SET transformer couple to an 833A run at 1000 Volts and Hammond output transformers. This does not push it to high wattage, but easily drives such speakers well below audible distortion and is as loud as any concert hall.  

@atmasphere  , is it watts that drive the speaker?  (I know that if I put the + & - lead of my vm on the corresponding speaker posts. I get an AC volt reading which varies depending upon volume level.)  But if it is watts that drive the speaker, and every watt is equal to every other watt, what is it that makes speakers sound different with different amps?

Two Futtermans at 135 watts each.

Altecs are 101 db efficiency, 16 ohms.

The can play twice as loud as I could ever tolerate.

see

theaudioatticvinylsundays.com

@atmasphere  There is actually a high end audio amp that can make 6,000 watts RMS into 2ohms the Dan D'Agostino relentless 1600. 

is it watts that drive the speaker? (I know that if I put the + & - lead of my vm on the corresponding speaker posts. I get an AC volt reading which varies depending upon volume level.) But if it is watts that drive the speaker, and every watt is equal to every other watt, what is it that makes speakers sound different with different amps?

@immatthewj Watts drive the speaker. But most speakers are designed to be ’Voltage driven’. "Voltage driven’ is a short hand phrase that basically says the amp, while making power, should be able to act as a Voltage source, which in turn means that the amp can make the same Voltage regardless of load. You are familiar with what this looks like already: if the amp can double power as the speaker load impedance is halved, then its a Voltage source.

So the short hand can be confusing. However Voltage does not exist without current being present and vice versa. So in the end Watts are actually driving the speaker.

The reason amps sound different is how they make distortion on a particular speaker. Our ears convert distortion (harmonics) into tonality in the same way that harmonics of musical instruments define the tonality of those instruments. The ear is particularly sensitive to higher ordered harmonics (the 5th and above) since it uses them to tell how loud a sound actually is. But those harmonics can be masked from causing tonality if the 2nd and/or 3rd harmonic is high enough- this is why SETs seem to sound so musical despite having a lot more distortion (including higher orders) than any other kind of amp; the 2nd and 3rd harmonics are masking the higher orders.

Solid state amps often have much lower amounts of distortion overall, but the higher orders are not masked, causing the amp to sound brighter and harsher.

The most musical amplifiers are those that make very low amounts of distortion (SETs are typically 10% at clipping so they are right out) and that distortion will be the 2nd and /or 3rd harmonic, enough to mask any higher orders.

@invalid Yes, that’s true. But they advertise that pesky current thing on their website- take a look (and click on 'specifications').

Now lets do the math:

Giving the amp the benefit of the doubt, we set the speaker load impedance to one Ohm. Using the Power formula thus the Power the amp makes is the current squared. This amp does not make 160,000 Watts! They claim 6000 Watts into 2 Ohms, so the current flowing at that time is only 54.77 Amps... and if it doubles power into 1 Ohm (which it probably can do but not to full power) it would be double the current or only 109.54 Amps.

Obviously that current spec is something entirely different!! Most likely its 400Amps that flows when the power supply is shorted out for 10mS. So its really a measure of the capacitance in the power supply rather than the current that the output section can produce.

I finally bought kit with power meters and I use between .6 and 6 watts most of the time and it takes some kille rock to get the meters bumping up against 60w...So why did swapping out a 301 wpc source for a 600 wpc source make so much of a difference regarding dynamics and resolution at low volume? I really want to know.

For the Harbeths, the Accuphase is way more than enough - watts and current.

The reason is the relatively flat impedance curve of the Harbeths pose a nice, easy load for the Accuphase to drive.  Not that the Accuphase needs that easy load, with a damping factor of 800!

@jfrmusic not sure about OP question.. Accuphase P4600 (congrats, it’s a good amp!) has output power indicators, which should help you to determine if you reach limit and need more Watts!

@westcoastaudiophile

That is my exact question. The meters never exceed 1 watt. Some here have said they are not accurate and don’t record peaks but I have them set to freeze at peaks. 

@jfrmusic Accuphase output meters are accurate, you drive y’r amp at very low power, accordingly to Accuphase design P4600 is a class A amp till ~20W. You may crank it up to the max to see full power range!

@westcoastaudiophile

Where did you see that the P4600 is Class A up to 20W?

@jfrmusic I looked amp spec and schematics. A/B class P4600 increased idle power and number of output transistors to 12 in each channel, matching their A class amps. 20W is estimate of peak power for linear output transistors range, for both channels combined (2x10W)

@westcoastaudiophile

The specs on their site say 6 transistors per channel. Still don’t see how you com to this conclusion. They don’t mention any Class A wattage. 

@jfrmusic 6 transistors / leg, 12 total pnp-npn power devices per channel. I calculated A class wattage using p4600 schematic. 

@jfrmusic spec with design details for p4600 https://www.accuphase.com/cat/p-4600_e.pdf 

@westcoastaudiophile

Yep that's what I was looking at. 6 transistors per channel. Now I would be happy if I was getting 10 watts per channel in Class A. Please direct to where this is noted.

@jfrmusic it was noted here in my post above.. you may ask Accuphase support and update us on their  detailed spec details for this AB amp design! 

Ok I’ll send them an email. They’re very responsive

@weatcoastaudiophile

Still don’t understand how you calculated your number from those specs but you were on the money. Here’s the response from Accuphase. 
 

The actual amount of Class A bias for the P-4600 is not a fixed amount and will vary depending on the load of the speaker.  For most speakers it should have around 8W – 10W of class A bias but that could be less for speakers if they have less than 4 ohm impedance.  The exact method for how Accuphase applies bias to its output transistors is considered proprietary information and they do not allow us to publish more than that.

@westcoastaudiophile

As a follow up I guess I’m mostly running in Class A since I have not been able push my meters pass 1 watt. 

@ifrmusic thanks for asking Accuphase support! being advanced analog circuit designer it’s not hard for me to estimate AB class amp linear (A class) range, sorry for not explaining to you all boring details of my calculation, which could be lengthy! 

The success of the Pass 25 and other small-bore tube amps Indicates that's plenty for most applications. But remember this - speakers are current driven devices and benefit greatly from amps acknowledging that fact.

Most modern speakers are less than 8 ohms and so are quite current hungry. Also, loudness is logarithmic, so twice the power is only 3dB louder - a just noticeable difference. To sound twice as loud requires 10X the power. Also remember the limits of your speakers. KEF LS50s 84dB @ 1W/1M and 100W limits means they are limited to 104dB maximum output. A big JBL 4367 is at least 10dB more efficient and will handle 200W peaks for a max output of 117dB.  The KEFs are meant for near field listening only a few feet away, the JBLs meant for a large room with the listener 10-15 feet away, so it all must be worked as a system, not just components in isolation. As for me, my 87dB Monitor Audio S300 7G and a solid 60W amp in my 12X16 room is plenty. In other systems, 200W was just adequate, and in another a 40W tube Mcintosh MC240 was fabulous. Lots of valid answers, just don't ignore physics.

My Speakers are Harbeth C7ES-XD at 86db sensitivity. They are rated at up to 150 watts. Their impedance is 6 ohms with the lowest at 5.8 ohms. So an easy drive. But I've been told they like power. The Accuphase P4600 is rated at 150 watts per channel at 8 ohms and 300 watts at 4 ohms and the amp is probably capable of delivering 225 watts per channel at 6 ohms. I have them positioned in a well furnished carpeted room about 7 feet apart and 30" out from the front wall very slightly toed in. I sit about 8-9 ft from them. I have the meters set to freeze at the highest output and they have never exceeded 1 watt so far. Now I don't listen at some of the levels some of you do. My sound pressure meter never exceeds 75 db and is mostly between 60 and 70 db. If the meters are accurate I'm in Class A all the time and the amp is not breaking a sweat.

atmasphere wrote:

If you need over 100 Watts to make your speaker really sing, you have a problem-the speaker might be criminally inefficient unless you are in a very large room.

I would agree, but practically speaking it’s hardly as much low efficiency as it is a difficult load caused by the passive crossover. A lot of amp power can be wasted here, sometimes forcing even several hundred watt and PSU-sturdy amps to their knees. Making matters worse though we mostly see the combination of low efficiency and difficult load, whereas conversely the combo of high efficiency and easy load - not least via active configuration and higher impedance - will make a given amp sound substantially better for a given SPL.

Low eff. in addition to difficult load is a sonic bottleneck that to some can’t be ignored, while to others it’s the only thing they know. To my ears it’s not unlike listening to speakers covered by a blanket - the music just never really frees.

The more power you need, quite often the harder it is for the amplifier to sound like real music. Most higher powered amps I’ve seen simply don’t, although they are pretty good at sounding like electronics.

That’s a popular notion, and I assume not without merit, but as you implicitly indicate there are exceptions. Both due to the specific amplifier design and because my actively configured high efficiency speakers - i.e.: high eff. in the entire frequency range, incl. the subs - present such an easy load to the 3 similar amps, each of them frequency limited to their respective driver segments and independent of the others’ load, the amps are given ideal working conditions and seeing their potential more or less maxed out.

To explain: a 625W amp (8 ohms) given only a ~620Hz on up signal driving a 111dB horn/compression driver combo coupled directly to its terminals with a close to pure ohm load will be cruising along with very low distortion - even at deafening levels. If it’s already a good design, and it is, it will see its performance envelope fulfilled in a way no passive, low efficiency speaker iteration with a single amp covering the entire frequency range can equal.

As others have said, meters, even digital ones, are s-l-o-w. Even on digital recorders, the meters are too slow to see "transient peaks", which is one reason manufactures recommend recording with the "peaks you do see" topping out at -12dB. This allows enough headroom for those transients such that no clipping or compression takes place.

So yes, having more watts can be a good thing - as long as the slew rate of the amp is capable of keeping up with the music and offering those louder transients that might last less than 1/100th of a second, such that the music sounds as "real" as possible.

So, when you are looking at meters, you are more or less looking at what the continuous output power is, averaged over a significant fraction of a second, therefore yes, you will see that most of the time the amp is putting out 1W to 10W at even "loud" volumes. 

Most of the time, I'm using 1-2w listing to the radio. If I want to rock out, or make the house vibrate I use around 50-60w this is out of a 200w amp. At 100db (system can do well over 100db without clipping) at 60w, there will be 100+w peaks.

Since it takes double the power to produce 3db gain, it's good to have all the power, and use it when you want it. Generally a 200w amp will sound better at 50w, then a 50w amp at 50w. Plus staying that far under the amp's peak power produces much cleaner power to the speakers. 

Most of the time, we will all be happy with a 20w amp, but I would never buy anything under 100w

Anyone that listen at 113-115db are either def or stupid, or if doing it routinely maybe both?

If you are not def, is it then something you aspirer to be ?

Why would a music lover try to intentionally destroy one’s hearing?

As older we get our hearing for most people deteriorate and unfortunately for many it hinders their ability to function 100% in social gatherings and for some people they choose to redraw a bit from social life.

Also as it is now, there is nothing you can do if getting tinnitus which even is a much bigger problem.

i worry about the younger generation that blast music into their ear canal’s with in-ear headphones, I am guessing that most of them will have big hearing/tinnitus problems before they are 50!

Don’t get out much, do ya? Lots of folk go to a monthly concert. And they are played in the 113-115 range. Many times, much more than that. You think all those thousands of listeners at the live performances are going deaf? It better hurry up if it’s going to affect me. I’m almost 70 and have been around loud race cars my entire life.... (And a dash of music). You sound boring! But enjoy life however you want it, I know I have enjoyed the heck out of mine.

https://youtu.be/q_-Z0ZVXWZg

https://youtu.be/6O9r_1gnpg0

 

There's nothing like a well designed class A amplifier to bring out the best  performance in your speakers.  I once owned an original Bedini 25/25 that was a nice match with my 15 ohm Rogers LS3/5A's.  It was also supposed be a great match for the original QUAD ELS 57.  The Bedini 10/10 was also a good choice for the ELS 57.  One of the best sounding and most powerful class A amplifiers that I have ever heard is the Classe Audio DR3VHC. It was one of Classe Audio's first products when David Reich was running the company. 

My advice, take it or leave it:  is to note what the speaker manufacturer recommends as a minimum power recommendation into the 8 Ohm load of the speaker, then note what the minimum (not nominal) impedance is, then double down the recommended power for each halving of impedance e.g. 10 Watts into 8 Ohms, 20 Watts into 4 Ohms, 40 Watts into 2 Ohms, etc.. When faced with a non-standard impedance, drop down to the lower standard amplifier rating, for example for 3 Ohm minimum speaker load go to the 2 Ohm standard amplifier ratings unless the amplifier manufacturer offers non-standard ratings (such as the Benchmark amps). Using that as a minimum power need. While room size and desired output levels will actually determine how much power one will need, as a general rule of thumb for most people, in most rooms will most probably be better suited by doubling the manufactures minimum power recommendations into that minimum impedance as noted above for satisfactory results. The important thing is actual power into that lowest impedance. I don't recommend relying on so called "stable into X load " claims, as that only means the amp won't go into osciallation when presented with that impedance. it is not a guarantee of power output or distortions levels into that load. Don't be swayed by manufacturers, dealers, etc., annecdotal suggestions; let them put it writting. Using the above considerations can go a long way towards preventing speaker damage, and offering satsifying sound.

 

.  

If you want to know accurately and in realtime how much power your amp is  consuming then look into purchasing Emporia Smart Plug with energy monitor (on Amazon).

The Emporia Smart Plug allows you to monitor the energy use realtime and control most appliances from anywhere with the Emporia App on your mobile

 It takes very accurate reading every second (resolution of 0.1W) and you can see all the peaks and troughs on a graph and even download the data in a spreadsheet!

@rshank64 
 

I have noticed that with my McIntosh MC7200 amp (non autoformer) and ADS 1590/2 speakers, 2 watts on the meters will almost burst my eardrums. No technical observance here, just noticed this bit of info when listening to all kinds of music in my room. 

watts are watts, a watt will do the same work regardless of how its derived.

amp topology, power supply type, amount of components in the circuit, speaker efficiencies, etc. will make differences. as long as your not clipping the amp, putting the amp into harm i.e. oscillating, etc. should all be similar as far as power requirements for a given speaker. Probably much lower then most would like to admit.

Bragging rights, power wars, room size and volume, etc. seem to be more an issue. don't get me started on "oh its hi current" well of course, because its low voltage. Power=Current x Voltage after all. 

 

nitrobob wrote:

Anyone that listen at 113-115db are either def or stupid, or if doing it routinely maybe both?

If you are not def, is it then something you aspirer to be ?

Why would a music lover try to intentionally destroy one’s hearing?

Such levels isn’t the goal nor point of having a high SPL-capable amp-speaker system domestically - not to me, that is - but rather that the ability here pays off at lower levels and to have the desired max. peak levels reproduced cleanly and wholly effortlessly. Referring to my own context above it’s about "super cruising" (aviation term) at any desired SPL, but also and not least that such a system is of a very different physical stature compared to most typical home speakers, and that in itself is a major aspect sonically. Few seem to realize this.

A speaking of which: for some reason many audiophiles almost feel offended or put off by the prospect of very high SPL capability in a speaker setup, concluding that it automatically means blowing off your ears at concert levels and being of a very young or immature mindset, contrary to the sophisticated, experienced 60+ years audiophile who sips at his glass of (expensive) red wine while savoring the soprano voices of Delibes’ Lakmé opera at 65-70dB’s from his low efficiency high-end speakers.

Well, what can one say other than throwing back the ’inexperienced’ accusation at those who don’t know any better here.

As older we get our hearing for most people deteriorate and unfortunately for many it hinders their ability to function 100% in social gatherings and for some people they choose to redraw a bit from social life.

Also as it is now, there is nothing you can do if getting tinnitus which even is a much bigger problem.

i worry about the younger generation that blast music into their ear canal’s with in-ear headphones, I am guessing that most of them will have big hearing/tinnitus problems before they are 50!

Absolutely agree.

Don’t get out much, do ya? Lots of folk go to a monthly concert. And they are played in the 113-115 range. Many times, much more than that. You think all those thousands of listeners at the live performances are going deaf? It better hurry up if it’s going to affect me. I’m almost 70 and have been around loud race cars my entire life.... (And a dash of music). You sound boring! But enjoy life however you want it, I know I have enjoyed the heck out of mine.

I only just turned 50 some 3 years ago, and it’s been over 20 years since I last treated myself to a very loud, large and "unfiltered" amplified concert experience (Depeche Mode’s Exciter tour, which almost got the better of me). Since then I’ve protected my ears hysterically at such large scale and very loud concert events, and I now mostly attend live acoustic, classical concerts.

Boring? Not in the least, but who am I to tell a seasoned race car junkie with a splash of music exposure to boot.

Boring? Not in the least, but who am I to tell a seasoned race car junkie with a splash of music exposure to boot.

Yea, I’m serious. Here is my in car camera view of one of the thousands of passes I’ve made in the last 25 years of driving one of these things. Loud? Most certainly. But I like music loud also, when its called for.

https://youtu.be/FsYMv_JXPzI

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That’s cool man!!! Loud as hell!