Watts per channel, RMS... overrated?

[Guest105]

Brian... your comments verify what I've thought about high audio quality and low wattage... they are NOT mutually exclusive. In other words, just having lots of watts doesn't automatically imply high audio quality.

His comments may validate your opinion, but they are not correct. Suggesting that there are few speakers requiring significant power to "open up" (whatever that means) is a meaningless statement.

Forget the generalities and the opinions. There are some fundamental physics that apply, and to make an informed decision about how much power you want/need, you should understand those fundamentals. First, there are two primary variables at play in determining how much power you need:

1. The sensitivity of the speakers you are using. Generally measured at 3 feet (or 1 meter), with one watt (or 2.83V of input). A speaker with a sensitivity rating of 88 will put out 88dB with one watt of input, three feet away.

2. The maximum loudness at which you will want to listen to your music, even if only on an occasional basis. I think you said earlier that 70dB sounds pretty loud to you...which is surprising, but each of us has a different tolerance for loudness. Over the years, I've found that most folks listen regularly at 75-85dB....which I think most people would categorize, approximately, as the low and high end of moderate loudness.

So let's assume that you want to be able to crank them up to 88dB at least once in a while. With one watt of output from your amp, using a pair of EPI 150's (sensitivity 87dB) you'll get somewhere around 83dB at a listening distance of 6-8 feet.

Therefore, you'll need almost 4 watts to get to 88dB (each 3dB change requires a doubling or halving of power). And then you'll need around 9-12dB of headroom to minimize clipping of transient peaks (and the distortion that comes with the clipping). This takes you to a requirement of 32-64 watts. Personally, I target a minimum of 12dB of headroom for peaks.

Note that 88dB is considered at the high end of "moderately loud" by most people. Want to crank it up a bit higher for that favorite Stones song? It takes 3dB to make a significant change in loudness, and as noted earlier, each 3dB requires a doubling of power. So, now your requirement is an amp capable of 64-128 watts!

Sure, with the right speakers and listening distance, 10 watts can be plenty of power. With different speakers and listening habits, 200 watts may not be nearly enough.

And at least in my experience, there are no conclusions you can draw about the quality of an amp based on its power rating. There are great 10 watt amps, and great 100 watt amps. However, it is always true that between two amps of equal quality, the one with more power will be more costly. The power supply and related components are among the most expensive elements of an amplifier.

So, you are absolutely correct in your assertion that low power output and sound quality are not mutually exclusive when it comes to amps. Hopefully, though, you now understand that just because this is true, it doesn't mean that power is "overblown" as an issue, or that quality is more important than quantity.

My suggestion is that you first focus on determining how much power you need, then focus on finding an amp that meets those needs while also satisfying your criteria for quality.

EDIT: To clearly address your original question...yes, it appears that you did the math correctly. But as whoaru pointed out, that is your average power requirement. You also need to account for peaks....as I noted above, 12dB is a good target. That will require an amp capable of 80 watts....40 if you drop down to 9dB.

 

[bare]

Wattage is one measure, instantaneous Current capabilty is another
Quality amps of lowish wattage can and do deliver well upwards of 20 amps when the music signal calls for it. Mediocre amps don't even list that in their specs.. but their wattage info is front and centre.
Headroom is the name of the game.
Frankly if using Realistick and EPI .. it isn't of concern.. imo.

 

[Rybeam]

The added wattage seems to have a pressure type effect. More power behind the power if you will. I have found through the years that a system needs at least 40 watts RMS to get what I call a snap in the sound. A quickness and crispness that less watts does not offer.

 

[Guest105]

The added wattage seems to have a pressure type effect. More power behind the power if you will. I have found through the years that a system needs at least 40 watts RMS to get what I call a snap in the sound. A quickness and crispness that less watts does not offer.

Hmmm. I've heard some pretty snappy sounding speakers - very high sensitivity Klipsch La Scalas - being driven by a 14 watt amp. Speaker sensitivity, desired loudness, and adequate headroom for transient peaks...those are the variables. You might need 4 watts, you might need 40, you might need 400.

Low volume levels never sound "snappy" to me...too much loss of dynamics at very low listening levels. And many folks are hearing clipping without knowing it...attributing the lack of clarity and detail to the quality of their amp, speakers or input components, rather than a simple issue of not having enough power.

 

[kermit z]

To the OP, IMHO, you need to do actual comparos to find what you find to sound good. You like your Realistic , and that is great. But by only comparing numbers without actually hearing a more powerful receiver or amp, is missing the point. My lowest powered receiver is a Pioneer SX-550. At 20wpc it was pretty much entry level back in the 70's with the SX-450 being the bottom. It sounds very nice indeed to my ears. It sits on the extras rack because to my ears, higher powered units sound better. Headroom is big. So my SX-1050, which is from the same series, squashes (Literally) the 550 with it's 120 wpc. Does this make the 550 bad? Absolutely not. Now, but for my daily driver, more power is better. Does that mean that I use all of the power? Nope.

 

[tnmike1]

I always thought you needed more watts to give more headroom which supposedly is important for big symphonic music and other music where there's lots going on instrumentally

 

[ConradH]

Having enough headroom so the amp doesn't clip on the loudest peaks is the goal. As you turn up the volume the required power goes up substantially, so it's hard to make any general recommendation. It's just too dependent on what you listen to and how loud, plus speaker efficiency. Trying to play the cannon and rifle shots in the 1812 at a loud volume can take hundreds if not thousands of watts. They're brutal! OTOH, so what if the amp clips a couple times every now and then. If 30 watts does the job 99.9% of the time, that might be enough to keep you very happy. In my room, at the levels I listen at, 30 watts is more than enough.

As for quality, I've done DIY amps of 5-10 watts that are as good as anything out there. Commercially, the low powered receivers were BOTL, but some were still very well done. Some were not. You just have to take them on a case by case basis.

An earlier comment about pride or desire eludes me. I like to have a moderately high power amp available, even if I never use its full capability. It makes me happy. So what.

 

[GuyK]

I always thought you needed more watts to give more headroom which supposedly is important for big symphonic music and other music where there's lots going on instrumentally

It's not that there is "lots going on instrumentally" with symphonic music; there are large dynamic peaks with symphonic music. Sometimes 20 db or even more. This is what the headroom is for...being able to produce these peaks without producing a distorted signal. Depending upon the type of music one listens to, this distortion can be quite audible.

 

[hnash53]

Wow... this is great. All of the opinions, though some in disagreement, are welcome... it all serves to enlighten me more about audio... and to think more about what & how I do my "listening."

I don't listen to classical music, symphony music... zip. I listen to mostly instrumental music that leans toward soft rock guitar, new age... dreamy spacey music bordering on ambient. There's not a lot of peaks or large increases in intensity to what I listen to. So, just thought I'd state what kind of music I listen to since that was mentioned several times by other contributors to this thread... and a worthwhile thing for me to consider.

I see the need for more headroom, and I think I get the need for a bit more wattage simply to have in "reserve" to easily handle more volume if I want it, or for the music itself. 30-50 watts per channel would give me that with some to spare versus my 12 watts per channel.

It seems clear that marketing pressures/competition have forced things in the direction of "wattage wars" and the message that "more watts is better...no matter what." That being so, it's likely that in most cases, the units with higher wattage also get better audio components... unnecessary/extra watts likely never to be used but if you want better quality audio, you have to buy the extra watts.

By the way, my listening room would probably be considered "hard" since there's no carpet and only two soft pieces of furniture.. a recliner and a leather couch. Wood floors and oak antiques added to that mix. So there's no much dampening of the sound. But I don't know how that impacts the sound production. It's not a room I can do much to change the sound, so for what it's worth....

Thanks for all the comments. More are welcome... thanks.

 

[Brian]

So, now you can see there are about 2 camps, those who believe you can not live nor have a low power amp of high quality and those who have found very differently. Some even find happiness with a 3-5 watt SET.

I am a might surprised at the lack of understanding by one responder as to what it means for a speaker to open up. A simple concept; it is that point in a speaker's output where there is enough energy for it to deliver clear open open sound as designed. Listen to a speaker starting at no volume. At some point the speaker will begin to sonically open up dynamically, soundstage will increase and the speaker's sound will begin to dial in as it used to need called. Most will find this point without ever thinking about it but will sometimes note that a speaker had to be driven more than another or louder. There is a correlation between the amp and the speaker as most ss amps at some low power point as power decreases have an increase in noise and distortion. A low power amp generally will have a much lower point where this happens than a higher power amp. Again many persons adjust for this without knowing what is happening as they tend to increase the output to where this effect is at its lowest. In a high power amp this point may be as high as a watt or two and hence using it at low levels may be unsatisfying where as a low power amp may hit min at a fact lower power setting. So, while a high power amp may sport some low distortion at max output compared to a low power amp's max power rating, at general listening levels the distortion may be lower from the smaller amp. Some makers used to give figures at max and usually the 1 watt level. Not sure how universal it was or done today. A few makers even showed the graph of noise and distortion so it could be factored into a system design. Now, you may understand why some say the first watt is the one that counts the most.

My comment as to why some may prefer high power amps based on pride was not a dig. It is a fact. As is that some find pride in having a system comprised of a particular brand or having a system that has the sound quality of a $10,000 system that only cost $500 as a result of theft store and dumpster diving or having a speaker with 50 drivers and is larger than some of the newest Toronto condos. It is not that they will or care about driving them into near clipping but just having that particular unit. I am in the camp with certain units such as the pride of owning a Sherwood SEL200 receiver, their answer to the Marantz 18 and 19, McIntosh 1900 and Fisher 500TX. Rare, short production, little know and only 40 watts.

 

[fredgarvin]

His comments may validate your opinion, but they are not correct. Suggesting that there are few speakers requiring significant power to "open up" (whatever that means) is a meaningless statement.

Forget the generalities and the opinions. There are some fundamental physics that apply, and to make an informed decision about how much power you want/need, you should understand those fundamentals. First, there are two primary variables at play in determining how much power you need:

1. The sensitivity of the speakers you are using. Generally measured at 3 feet (or 1 meter), with one watt (or 2.83V of input). A speaker with a sensitivity rating of 88 will put out 88dB with one watt of input, three feet away.

2. The maximum loudness at which you will want to listen to your music, even if only on an occasional basis. I think you said earlier that 70dB sounds pretty loud to you...which is surprising, but each of us has a different tolerance for loudness. Over the years, I've found that most folks listen regularly at 75-85dB....which I think most people would categorize, approximately, as the low and high end of moderate loudness.

So let's assume that you want to be able to crank them up to 88dB at least once in a while. With one watt of output from your amp, using a pair of EPI 150's (sensitivity 87dB) you'll get somewhere around 83dB at a listening distance of 6-8 feet.

Therefore, you'll need almost 4 watts to get to 88dB (each 3dB change requires a doubling or halving of power). And then you'll need around 9-12dB of headroom to minimize clipping of transient peaks (and the distortion that comes with the clipping). This takes you to a requirement of 32-64 watts. Personally, I target a minimum of 12dB of headroom for peaks.

Note that 88dB is considered at the high end of "moderately loud" by most people. Want to crank it up a bit higher for that favorite Stones song? It takes 3dB to make a significant change in loudness, and as noted earlier, each 3dB requires a doubling of power. So, now your requirement is an amp capable of 64-128 watts!

Sure, with the right speakers and listening distance, 10 watts can be plenty of power. With different speakers and listening habits, 200 watts may not be nearly enough.

And at least in my experience, there are no conclusions you can draw about the quality of an amp based on its power rating. There are great 10 watt amps, and great 100 watt amps. However, it is always true that between two amps of equal quality, the one with more power will be more costly. The power supply and related components are among the most expensive elements of an amplifier.

So, you are absolutely correct in your assertion that low power output and sound quality are mutually exclusive when it comes to amps. Hopefully, though, you now understand that just because this is true, it doesn't mean that power is "overblown" as an issue, or that quality is more important than quantity.

My suggestion is that you first focus on determining how much power you need, then focus on finding an amp that meets those needs while also satisfying your criteria for quality.

EDIT: To clearly address your original question...yes, it appears that you did the math correctly. But as whoaru pointed out, that is your average power requirement. You also need to account for peaks....as I noted above, 12dB is a good target. That will require an amp capable of 80 watts....40 if you drop down to 9dB.

Excellent post. Power is certainly not overrated, it's more that people don't understand it's fundamentals. Power and current are two very important fundamentals.

 

[musichal]

Excellent post. Power is certainly not overrated, it's more that people don't understand it's fundamentals. Power and current are two very important fundamentals.

Yes, but he left out a third variable just as important as speaker sensitivity and maximum loudness - the venue. The bigger the space the more power you need, consider two extremes, small office vs outdoors, for instance. I also found his reply pretty good, too, but I noticed he forgot this factor.

 

[tnmike1]

Regarding power and watts I recall Cary Audio had a tubed single end triode amp that put out 5 watts and critics raved about how it sounded. Thing was though it was driving highly efficient Klipsch speakers

 

[fredgarvin]

Yes, but he left out a third variable just as important as speaker sensitivity and maximum loudness - the venue. The bigger the space the more power you need, consider two extremes, small office vs outdoors, for instance. I also found his reply pretty good, too, but I noticed he forgot this factor.

That's certainly true.

 

[WaynerN]

Sadly, Congress passed a law requiring stereo power amps to be rated as follows: watts RMS per channel, both channels driven, with a distortion rating at max power output. This, as I recall, part of a consumer protection act. The problem was that there were no standards back in the day and several companies were using non-standard power ratings, like IHF (Institue of HighFidelity), or worse, peak power. Those numbers had no comparison values at all. Early Marantz receivers followed the true RMS rating, and this is why many people are so surprised at the apparent power these vintage receivers had, compared to multi-channel receivers today.

I think Congress truly tried to get a corner on specifications, but that seems to have all gone away with the advent of multi-channel amplifiers. I heard a big name brand receiver the other day that was suppose to have 100 WRMS per channel, but it sounded as if it had about 10.

Other factors also come into play such as dynamic headroom, damping factor and so on.

And the plain fact is that no law can quantify all the perimeters of how an amp sounds or how that relates to specifications. In this day and age of buying sight unseen equipment over the internet, wouldn't it be nice to trust a set of specifications? But alas, this just isn't reality. And as many have chimed in here, its a matter of synergy with the chain of equipment (speakers, cable, preamp, sources) that is the final governing body.

Power ratings, therefore, is a tool but not the final answer to any amplifier's performance. (no intention to be political here, just trying to show that attempts were made to rectify the situation (unsuccessfully)).

 

[Guest105]

Yes, but he left out a third variable just as important as speaker sensitivity and maximum loudness - the venue. The bigger the space the more power you need, consider two extremes, small office vs outdoors, for instance. I also found his reply pretty good, too, but I noticed he forgot this factor.

You might note that I addressed distance as a variable which plays into the power equation.

On a related note...I'd like to know what speakers are being driven satisfactorily with .04 watts?

 

[gslikker]

There was a nice FTC paper about a discussion on the internet, BUT THEY TOOK IT AWAY, since apparently the FTC rule has changed.

So what about this distortion.....

Look at this

http://www.ecfr.gov/cgi-bin/text-idx?SID=6992667adb0b97c6fd6d3ad03ba0ab21&node=pt16.1.432&rgn=div5#se16.1.432_13

Apparently, some audiogon member saved some info from the discussion pdf, read it in the middle of this page.
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1200430667&read&keyw&sae+mark+iii&&st9100


You get an idea how thoughts are.



Depending on how you read, using more than 12.5 % of your wattage of 2 channels driven continuously, from your home theatre system, you may be happy it does not blow up?

Said in a short way, your watts are about the same watts as before the old FTC rules.
Good names for these watts would be "consumer-watts" or "optimistically-enhanced watts" or whatever is my opinion.

The text not available on the original place is still to be found by google http://www.gpo.gov/fdsys/pkg/FR-2000-12-22/html/00-32392.htm

To be able to see how it is in the consumerwatts world, just sit down and take a good reading! I find this quite amusing. (or sad, whatever you want)

 

[Gang-Twanger]

Too much over thinking on this!
Shouldn't take to long to find out if you like it clear and louder than you already have!
As for me the more Watts that I can have under anyone's definition RMS/PMP/Whatever Scale you know,the more the better but really to each his own as always.Running Tubes at 1-2 Watts with the high efficiency speakers (98-102 DB's) is plenty loud yet not so efficient speakers (80-90 DBs) need more power period depending on how loud one likes or needs? Trail & Error?

I usually just have it at background levels, which is why I've aimed for a big sound at low volume levels, but if the neighbors aren't around, I do like to crank it up. The old Wharfedales fatten up with just a little bit of volume, and if you can get it into that sweet spot, that's where they "stop being polite... and start getting real". But even in those cases, I doubt I'm pushing more than 3-4wpc. My Fisher 800C is only 30wpc stereo, and that's more than enough for my speakers in all but the biggest rooms. More watts would only result in more hearing damage. I don't get anywhere near their peak volume (Right now they are effortlessly-breathing Fats Domino songs... I just fiddled with the mid and tweeter volume adjusters, just for a change... I bet the old Altecs are great with his music as well).

I'd like to get some power meters (like LED or something) that I can run between the receiver and my speakers so I can assure perfect channel-balance without having to use my ears (Many Fisher owners know what I'm talking about... That combination power switch/volume knob is a quirky bastard... I've gotten used to it enough that I can level it out by ear using a familiar piece of music, but it would be a lot better to have a pair of LED power meters wired into the chain out by my W90's).

 

[HTWillie]

I'd like to get some power meters (like LED or something)...so I can assure perfect channel-balance without having to use my ears...

My 24x7 rig has separate volume controls for left and right. I use an SPL meter app on my phone while playing radio station static to get them even again after fiddling with them.

 

[titanstats]

On a related note...I'd like to know what speakers are being driven satisfactorily with .04 watts?

My Model 14s are not super-sensitive, but unless both my amp's meters are totally buggered, they sound pretty good around that level. This, from a guy who was just bitching about low powered units!

Don't get me wrong guys, I know all about the dance between source, speakers, amps, and volume, but OP's original question had really nothing to do with this. He was suggesting that he'd get better sound with a lower-powered RS receiver paired with some not-so-efficient EPIs; that's just never gonna happen.

The other overlooked part of buying a bit more power is in long-term saving of money and sanity -- you can run pretty much any pair of speakers (regardless of efficiency) that you wish to try without having to go out and buy a new amp.