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I posted this a while back in a different thread, but the info might be useful here too.The real problem is that the audiophile for the most part has no idea the power is an exponential function as a factor of voltage swing. Exponential functions are definitely not intuitive.In any event, if you have two speakers who's input sensitivity is 3 dB apart, the less sensitive one needs double the amplifier power for the same acoustic output. If the speakers are 6 dB apart, the less sensitive one needs four times the power, 9 dB apart needs 8 times the power, and so on. A 3dB difference in sound levels is pretty much established as a difference anyone can easily hear, but not a large difference. It also requires twice the voltage swing to generate 3dB more output.Power equals RMS voltage SQUARED divided by load resistance. However apparent loudness is much better defined by RMS voltage rather than power. Peak V x .707 quantity squared divided by 8 in general.For example our 200W/Ch Fet Valve 400R will swing 60 V peak, our 300W/Ch Fet Valve 600R will swing 70 V peak (both into an 8 ohm load both channels driven in phase). That is a 10V voltage difference. However that is about a 100 Watt power difference. The apparent sonic loudness capability is much more in line with the voltage output difference (about 10 percent more) not power difference (50 percent more).Note that measuring power into 4 ohms is a cheap way of doubling your power ratings (do the math) as long as the amplifier under question can supply the necessary twice the current needed for the low impedance load.As an aside, in the real world, "gas milage" is also a non intuitive based exponential number. Your car's gas economy is much better served by considering "gallons per one hundred miles" than gas mileage. How important is it to improve your gas mileage by 10 miles per gallon? Not much if you are going from 40 MPG to 50 MPG, you are only saving one-half gallon per one hundred miles. But from 10 MPG to 20 MPG, that saves 5 gallons per hundred miles. Do the math! Makes me wonder why truckers drive so fast when they would save hundred of dollars with of gas on every long distance trip if they just stuck to 50 mph or so and the reduced drag with save them more than they would realize. Again, do the math, its just simple algebra.Frank Van AlstinePS Yes I know that watts by themselves are not an end-all measurement, the quality of these watts (or preferred, volts) are probably even more important. But at least the data above should help clear your head a bit.
not anymore. with a bullet.
The part converting Watts to the IMO more appropriate measure of dBW is good, but otherwise that paper makes the same basic mistake the Crown calculator does - assuming that all the sound is the direct field response from one loudspeaker. In small rooms, there is significant SPL contribution from reflected sound.Though there is a material difference: the Crown calculator is targeted towards people who may actually need to know how much power is needed for a given SPL from a loudspeaker of a given sensitivity outdoors, but here it is simply misapplied to small rooms by someone who doesn't know any better. The authors of that paper, however, should know better.Since "the factual basis" (as the paper snottily puts it) of SPL falloff with distance from the source is completely wrong in the context of a small room, Claimed "Scientific facts" (again, to use the paper's rather schmucky language) are "scientific false," because of the authors' blithe disregard for context. But hopefully nobody's going to take my word for it, and instead people who are properly skeptical of my assertions will do a simple test. Walk from the speaker to the listening position while something's playing, and observe the SPL falloff as you move away from the speakers on an SPL meter. JL Audio offers a free SPL meter for iPhones that is adequate to this task. Perhaps there is a similar app for other ecosystems. No calibration or anything is required, as the absolute SPL value is unimportant.
Anand, if you have scope you could look at output of your amplifier while playing back some very dynamic material and watch for clipping of the waveform on peaks.Scotty
Yep. I suspect there is a lot more (very short term) clipping going on than folks realize when playing back music. With modern digital recordings, the dynamic swings can be significant. That is one thing that tube amps provide which adds to people enjoying their sound (soft clipping).
Not for the last several decades, you mean.
Who cares what Theta (or anyone else, for that matter) thinks about? Class D amps are "Cheap as Chips" to make compared to other types of amps, so sure, a whole host of manufactures are going to jump on the bandwagon. Much better profit margins. No new news there. Just because you don't agree with the fact that there is a section of the audiophile market that thinks Class D is sonically inferior to other topologies does not make them snobs. What do you care what they think, anyway? If YOU like it, and think it's great, fine, by all means, feel free to express that. Casting negative dispersions on people who disagree with you serves no one, and in fact, takes away ones credibility. After all, once you get past certain basic physics, it's ALL subjective as to what sounds better. Besides all that, it's off topic. The topic is how many watts does one need for playback.
I've never heard one audio-freak say "Man, what I need is less watts."Get the very most of the very best watts you can afford. Your speakers, whatever they may be, will thank you for it.Have fun,Jerry
Disagree. The Crown calculator is as good as any other tool, even for the home user. It sets a worst-case set of boundary conditions. If a room has a lot of dampining (rugs, furniture, etc), it gives one an idea of how much power you may require. The type of music one listens to makes a BIG difference. If you listen to compressed music,(including rock/pop), then yes, you likely need less watts. If however, you listen to a lot of heavy symphonic type music, then you NEED a bit more power to capture the dynamic contrasts without distortion/clipping, Maybe vinyl is dynamics limited (it is), but good SACD/Blu Ray recordings from a digital source are not.
It kind of depends on the vinyl. Does anyone remember the Telarc 1812 Overture recording.Scotty
Couple of thoughts........First, the calculator. The calculator tells me I only need one watt to hear my music at 87dB from 2.6 meters away. I don't know if that is with one speaker or two, in an anechoic chamber or my living space, but since the calculator knows what's best for me and it gives me a worst case scenario, then I must have seven too many watts.So why did the little two watt 45 amplifier not suffice? I really wanted that little amp to be all that I need. Damn.Second, digital audio. Sure the format has a huge dynamic range capability, but if you make a lot of recordings you will notice that most music, even great sounding music, only has about a 20dB dynamic range. The mastering engineers make it that way so we can all enjoy it. And it sounds just fine that way.
Thank you for the analysis and constructive criticism. Given that I have a pair of mains speakers plus 3 subs, I guess I should turn off the subs and 1 speaker while playing a recording of my choice, then move from 1m away from the speaker to my listening position (about 3.3 m). Then I'll record the difference in SPL. Does that sound reasonable?Best,Anand.
Just because you don't agree with the fact that there is a section of the audiophile market that thinks Class D is sonically inferior to other topologies does not make them snobs.
